Abstracts
Contributed Papers (Poster and Oral)
Workshops
Colloquia
ACB Orals
ACB Posters
95th Annual International Conference of the
American Society for Horticultural Science
Charlotte, North Carolina, USA
12–15 July 1998
The Abstracts that follow are arranged by type 42
of session (Posters first, then Orals, Colloquia,
and Workshops). The Poster abstract numbers
correspond to the Poster Board number at which
the Poster will be presented.
001
POSTER SESSION 1A (Abstr. 001–014)
Culture & Management/Nutrition—
Vegetable Crops
Growth Analysis and Performance of Four Sweetpotato Culti-
To determine when a paper is to be presented, vars Under Different Levels of Nitrogen and Potassium
Alicia Nin and Juan C Gilsanz*; Dept. of Horticulture, National Inst. for Agriculcheck the session number in the Program Schedule ture
Research (INIA), Las Brujas “Exp. Est. Canelones, Uruguay, C.P. 90200 Las
or the Conference at a Glance charts. The Author Piedras C.C.3308
The objectives of this work were: Establish the growth pattern of four cultivars
presenting the paper is indicated by an asterisk.
and evaluate different cultivar performance at different rates of fertilization. ‘Morada
Inta’, ‘Kokey 14’, ‘Sandu’, and ‘Lago’ were transplanted in Nov. 1995 and were grown
at 0, 50, and 100 kg/ha of nitrogen and 0 and100 g/ha of potassium. Sequential
samples were done throughout the growth cycle. The parameters evaluated were:
Fresh and dry weight of leaves, stems and roots, stem length, internode distance,
and leaf area. A color foliage evaluation was complimented by foliar analysis
throughout the growth cycle. At the end of the crop cycle, nitrogen and potassium
content and soluble solid levels at the roots were determined. Cultivars differed
most for all the parameters evaluated. Fertilization affected stem length, internode
distance, foliar and root N, color determination, and soluble solid content. Plant,
stem, root dry weight, leaf area, and yield tended to be greater at 100–0 kg/ha of
N–K rate.
HORTSCIENCE, VOL. 33(3), JUNE 1998
443
002
Effect of Nitrogen Fertilization on Yield and Quality of Some
Salad Crops
M.I. Abdalla; M. M.A. Abdalla*, S.A. Abdel-Aal , and I.A. Farag, Assiut Univ.,
Eygpt
The present experiments were carried out at the Assiut Univ. Experimental
Farm during two winter seasons, 1994/1995 and 1995/1996, to study the effect
of nitrogen source and level on growth, yield, and quality of salad crops (lettuce,
parsley, and roquette). Nitrogen sources were urea, ammonium nitrate, and ammonium sufate. Three nitrogen levels, namely 20, 40, and 80 kg N/feddan, in
addition to organic manure (2.028% N), in addition to the control, were used.
Plant height, number of leaves (parsley and roquette), number of non-edible leaves
(in lettuce) were signifi cantly increased with urea followed by ammonium nitrate.
Plant fresh weight, weight of edible part (in lettuce), and total yield/feddan were
signifi cantly higher with urea than ammonium nitrate or ammonium sulfate. The
lowest content of nitrate and nitrite in leaves of the salad crops was obtained with
ammonium sulfate followed by ammonium nitrate, while urea gave the highest
values. Application of organic manure produced plant height, number of leaves
per plant, plant fresh weight, total yield, dry matter content almost equal to that
obtained from 40 or 20 kg N/fed. Nitrate and nitrite content were at their lowest
value when organic manure was used. Plant height, number of leaves, non-edible
leaves, weight of plant and total yield/feddan were signifi cantly increased with
increasing nitrogen rates from 0 to 80 kg/feddan. Using 80 kg N/fed. gave the
highest dry matter, nitrate, and nitrite content.
003
Nitrogen Applications Alter Tissue and Soil N Levels but Not
Postharvest Quality of Boston Lettuce Grown on Ohio Muck
Soils
W.B. Evans* ; Muck Crops Research Branch, Ohio Agricultural Research and
Development Center, Willard, OH 44890
Unreplicated nitrogen rate demonstrations in 1996 indicated that nitrogen
fertilizer rates may reduce storage life and postharvest quality of Boston lettuce
grown on Linwood muck. A fi eld trial using three planting dates, four nitrogen
rates, and six replications was conducted using Boston lettuce cv. Esmirelda.
All nitrogen, phosphorus, and potassium was broadcast and disked-in prior to
planting. The spring planting used greenhouse-grown plugs. The summer and
late summer sowings were direct-seeded. Soil and plant tissue tests were taken
and correlated with fertilizer N rate and yield. In the spring planting, each plot
was harvested at maturity, rather than all at once. Twenty-four trimmed heads
were boxed, hydrocooled, and stored in a commercial cold storage room at 0 to
1 °C. The boxes of lettuce were weighed before and after cooling, and every 24
to 48 h thereafter, until all boxes were deemed not salable. Samples were rated
for soft rot symptoms after the fi nal weighing. The spring planting was the only
one to show signifi cant differences in days to crop maturity among nitrogen rates.
No differences in head weight, weight loss during storage, or number of heads
with rot symptoms were found in the mid- or late summer crops. Wrapper leaf
nitrate levels at harvest increased with applied nitrogen rate. Residual soil nitrate
increased with applied nitrogen in the late summer trial.
004
Effect of Nitrogen Application Rates on the Yield of Head Cabbage, Japanese Eggplant, and Two Distinct Tomato Cultivars
in Hawaii
H.R. Valenzuela*; Dept. of Horticulture, Univ. of Hawaii at Manoa, Honolulu, HI
96822-2279
Little nutrient calibration data exists for the production of vegetables in the
tropics. Replicated experiments were conducted to evaluate the effect of several N
application rates on the yield of head cabbage, Japanese eggplant, an old openpollinated determinate tomato cultivar, and of ‘Merced’‚ a standard commercially
grown determinate tomato hybrid. Data collected included soil nutrient analysis
prior to experiment initiation, tissue nutrient analysis, nutrient sap analysis for
eggplant, canopy dimensions for eggplant and tomato, and marketable yields. Additional data collected in tomato included both laboratory tissue nutrient analysis
and NO3 and K+ determinations, through rapid sap analysis kits, collected during
three crop growth stages, ripened fruit soluble solid determinations, and NO3
determinations at three soil depths conducted ≈2 weeks after the last harvest.
Yields of head cabbage, grown at about 360 m elevation, were not affected by
444
N application rates ranging from 0 to 300 kg N/ha. Eggplant was grown at sea
level in a soil rich in organic matter. Eggplant yields from an 8-month harvest
period were little affected by N rates ranging from 0 to 300 kg• ha–1, except for
a trend toward greater yields with the highest N rates, during the last 4 months.
In tomato, the old OP variety was less responsive to N than the newer tomato
hybrid. Greatest ‘Merced’ tomato yields were obtained with 100 to 200 kg N/ha in
treatments ranging from 0 to 400 kg N/ha. Our data indicate that acceptable yields
are obtained with modest N application rates, and that excessive N applications by
commercial growers may result in nitrate leaching, and in unnecessary fertilizer
application expenses.
005
Influence of Nitrogen and Potassium Fertilization on Yield and
Quality of Carrot
Ricky L. Abrahamson* 1, Larry J. Cihacek1, and Chiwon W. Lee2; Depts. of 1Soil
Science and 2Plant Sciences, North Dakota State Univ., Fargo, ND 58105
The infl uences of various nitrogen and potassium fertilizer levels on the
growth, yield, sugar content, and tissue mineral concentrations of carrot (Daucus
carota) were investigated. Nitrogen (0.0, 7.3, 14.7, 22.0, 29.4, 36.7 kg/ha) and
potassium (0, 4.6, 9.2, 18.4, 27.5, 36.7 kg/ha) were applied to the sandy loam
soil prior to seed planting. Plants were grown without irrigation. The total root
yield was the highest (68.2 t/ha) at a nitrogen level of 29.4 kg/ha. Potassium did
not affect either the total root yield or the number of marketable roots. Root sugar
contents were slightly higher when plants were grown with potassium levels at
18.4 kg/ha or higher as compared to lower K application rates. Root sugar contents
were unaffected by nitrogen levels. The relationships between the leaf petiole sap
nitrogen and potassium concentrations and the shoot dry mass concentrations of
N, K, and other minerals were determined.
006
Evaluation of Nitrogen Sources and Rates on the Yield and
Quality of Sweet Onion
Jorge Arboleya*, Diego Delgado, and Santiago Pieri ; INIA Las Brujas. CC 33085
Las Piedras, 90200 Canelones, Uruguay
During the 1980s, research was conducted mainly for long-day onion, with
limited research on cultural practices for short-day cultivars, in Uruguay. Sweet
onion production became important in Uruguay in 1992. Research was conducted
on cultivar adaptation, sowing time, plant population, transplanting and directseeded methods, irrigation, and plant protection. Onion fertilization criteria were
established for long-day cultivars in the southern region in the 1980s. National
Research Inst. of Agriculture started a study on sweet onion fertilization using
four N rates, 0, 60 120, and 180 kg/ha, and four N sources, urea, ammonium
nitrate, potassium nitrate, and calcium nitrate. Nitrogen was applied into the
soil 40% before transplanting and the remaining 60% in two applications in the
spring. Granex 33 cultivar was transplanted on 27 June 1997 into a soil with the
following characteristics, pH 6.4, P (Bray 1) 44.5 ppm, organic matter 3.3, and
K 0.64 meq/100 g. Beds were separated 1.5 t, with four rows and plants 12 cm
apart. Plant height and leaf color were evaluated. Lack of nitrogen and 60 kg N/ha
showed lighter green colored leaves. Leaf, total plant, and soil samples were collected to determine nutrient status and dry matter production. Bulbing ratio was
measured in 10 plants in each plot. Sweet onion quality was done by pyruvic acid
analysis.
007
Iron Deficiency Chlorosis and Seed Yield in Dry Edible Beans
Grown on High-pH Calcareous Soils
J.W. Gonzales* 1, D.P. Coyne1, and W.W. Stroup2; Depts. of 1Horticulture and
2
Biometry, Univ. of Nebraska, Lincoln, NE 68583
Iron defi ciency chlorosis (FeDC) can cause signifi cant seed yield reduction in
dry beans (Phaseolus vulgaris L.) grown on high-pH calcareous soils. To determine
the effects of FeDC on seed yield, and the effect of Fe-spray as a correction factor
for FeDC, 22 breeding lines/cultivars were planted on high-pH (8.0), calcareous
(3.2–3.5 calcium carbonate equivalent), and low-Fe (1.8–4.2 ppm DTPA) sandy
clay loam Tripp soils at Mitchell and Scottsbluff in western Nebraska. A split-plot
design was used with Fe treatments as main plots and breeding lines/cultivars
as subplots. Three foliar sprays of Fe-EDDHA (2.4 kg• ha–1) were applied at V4,
R5, and R7 dry bean growth stages, during 1996 and 1997. Leaf chlorosis was
measured simultaneously by using a Minolta Chroma-meter (CIE L* a* b* color
HORTSCIENCE, VOL. 33(3), JUNE 1998
space system), a Minolta Chlorophyll-meter (chlorophyll content index), and by
visual ratings (1 = normal green to 5 = severe chlorosis). In 1996 no signifi cant
Fe-spray x line interaction (P = 0.776) and Fe-spray effect (P = 0.884) on seed
yield was observed. Breeding lines showed signifi cant differences in seed yield
(P = 0.0001) with WM2-96-5 being the highest-yielding line (4047 kg• ha–1). In
1997 a signifi cant Fe spray x line interaction (P = 0.029) was observed. The cultivar
Chase without Fe spray (3375 kg• ha–1), and lines WM2-96-5 (3281 kg• ha–1),
WM2-96-8 (3171 kg• ha–1) with Fe spray were the highest yielding entries under
those treatments. Differences in visual ratings after the third Fe spray in 1997 were
signifi cant (P = 0.004) for Fe spray x line interaction. In 1996 visual ratings were
different only for breeding lines. Chlorophyll content index showed a signifi cant
Fe spray x line interaction after the second Fe spray (P = 0.022) and after the third
Fe spray (P = 0.0003) in 1997.
008
Effects of Calcium Fertilizers on Pod Calcium Concentration and
Yield of Four Snap Bean (Phaseolus vulgaris L. ) Cultivars
J.M. Quintana*, H.C. Harrison, J.P. Palta, J. Nienhuis, and K. Kmiecik; Dept. of
Horticulture, Univ. of Wisconsin–Madison, Madison, WI 53706
Four snap bean cultivars were grown during the summers of 1996 and 1997
in Hancock, Wis. Fertilizer treatments consisted on 80 kg of Ca/ha applied as
gypsum (CaSO4• 2H2O) or calcium nitrate [Ca(NO3)2], and the control (no calcium
applied). The experimental design was a randomized complete block with a factorial set of treatments (4 x 3) repeated six times each year. Gypsum was all applied
at planting, whereas calcium nitrate was applied weekly starting 1 week prior to
fl owering for 4 weeks. Yield and calcium concentrations in pods were determined.
The statistical analyses showed no signifi cant effect from fertilizer type on pod
calcium concentration or yield. A strong cultivar effect was detected for both
parameters measured. ‘Evergreen’ ( 5.47 mg Ca/g dry wt ) presented the highest
pod calcium concentration and ‘Labrador’ (4.10 mg Ca/g dry wt) the lowest. No
signifi cant fertilizer x cultivar interactions were observed. Results for pod calcium
concentration remained consistent, even when a signifi cant year effect was found
for both parameters. The results suggest that breeding and selection remain the
most attainable methods to enhance pod calcium concentration in snap bean.
009
Zinc, Manganese, and Iron Fertilization in ‘Spineless Beauty’
Zucchini (Cucurbita sp. )
J. Pablo Morales-Payan*; Dominican HortResearch Group/Sociedad Dominicana
de Investigadores Agropecuarios y Forestales (SODIAF), Dominican Republic
Zucchini (Cucurbita sp.) fruit yield response to zinc (Zn), manganese (Mn),
and iron (Fe) foliar fertilization was determined in fi eld trials conducted in a loamy
clay soil in Nigua, San Cristobal, Dominican Republic. The soil had Zn, Mn, and Fe
contents of 1.2, 8, and 2 parts per million (ppm), respectively. ‘Spineless Beauty’
zucchini was direct-seeded at a distance of 1 m between rows and 0.5 m within
rows. Except for Zn, Mn, and Fe fertilization, the crop was grown according to
recommended practices. Experimental units contained fi ve plants. A randomized
complete-block design with a factorial arrangement (3 x 3 x 3) with four replications was utilized. Micronutrient rates were 0, 1, and 3 kg• ha–1 for Zn; 0, 3, and
6 kg• ha–1 for Mn; and 0, 3, and 6 kg• ha–1 for Fe. Total rates were divided in two
50% rate applications, sprayed in aqueous solution to the crop leaves 15 and
30 days after emergence. Fruit harvest began 40 days after crop emergence and
was performed every other day during 20 days. Resulting data was subjected to
analysis of variance. There were signifi cant Zn, Mn, and Fe interactions, and thus
micronutrient combinations were considered as individual treatments. Treatment
means were separated with the LSD 5% test. Zucchini plants treated with a combination of 3 kg Zn/ha, 3 kg Mn/ha, and 3 kg Fe/ha produced fruit yields 31.5%
higher than control plants. Combinations including higher Mn and Fe rates failed
to further increase zucchini yields.
010
Effect of Boron and Molybdenum Fertilization on ‘Spineless
Beauty’ Zucchini (Cucurbita sp. )
J. Pablo Morales-Payan*; Dominican HortResearch Group/Sociedad Dominicana
de Investigadores Agropecuarios y Forestales (SODIAF), Dominican Republic
The effect of boron (B) and molybdenum (Mo) foliar fertilization on ‘Spineless
Beauty’ zucchini (Cucurbita sp.) fruit yield was studied in Nigua, San Cristobal,
Dominican Republic. Field trials were conducted in a loamy clay soil containing
HORTSCIENCE, VOL. 33(3), JUNE 1998
0.3 parts per million (ppm) of B and no detectable amounts of Mo (detection limit
0.1 ppm). Zucchini was direct-seeded at a distance of 1 m between rows and 0.5
m within rows. Fertilization (except B and Mo applications) and other production
practices were implemented as recommended. A randomized complete-block
design with a factorial arrangement (0, 1, 2, and 3 kg B and 0, 0.1, and 0.2 kg
Mo/ha) with four replications was utilized. Experimental units consisted of fi ve
plants. Fruits were harvested every other day during 20 days, starting 40 days
after crop emergence. Yield data was submitted to analysis of variance. Signifi cant
B and Mo rate interactions were found. Maximum zucchini yields were achieved
when the combination of 1.5 kg B and 0.1 kg Mo/ha was applied. Combinations
containing 3 kg B/ha were toxic to zucchini, reducing yields in nearly 20% as
compared to untreated plants.
011
Response of ‘Spineless Beauty’ Zucchini (Cucurbita sp. ) to
Nitrogen, Phosphorus, and Potassium Fertilization
J.Pablo Morales-Payan*; Dominican HortResearch Group/Sociedad Dominicana
de Investigadores Agropecuarios y Forestales (SODIAF), Dominican Republic
Field trials were conducted in Nigua, San Cristobal, Dominican Republic,
to determine the yield response of ‘Spineless Beauty’ zucchini (Cucurbita sp.)
to nitrogen (N), phosphorus (P), and potassium (K) soil applications in a loamy
clay soil containing 4.3% organic matter, 3 parts per million (ppm) of P, and 155
ppm of K. Zucchini was direct-seeded at a distance of 1 m between rows and 0.5
m within rows. Except for N, P, and K fertilization, the crop was grown according
to recommended practices. A factorial design (4 x 4 x 4) with four replications
was utilized. Rates of N, P, and K were 50, 100, 150, and 200 kg• ha–1, applied as
a side dressing 7 days after zucchini emergence. Zucchini fruit harvest started 40
days after crop emergence and every other day thereafter during 20 days. Analysis
of variance was performed on the resulting data. Results indicate that there were
signifi cant interactions of N, P, and K fertilizer rates on ‘Spineless Beauty’ fruit
yield; therefore, nutrient combinations were considered as individual treatments.
Signifi cantly superior (LSD 5% ) fruit yield was obtained with 150, 150, and 50
kg• ha–1 N, P, and K, respectively.
012
Field Evaluations of Nutrient Absorption Enhancer and Starter
Fertilizer in Bell Pepper
John M. Swiader* and William H. Shoemaker; Dept. of Natural Resources &
Environmental Sciences, Univ. of Illinois, Urbana, IL 61801
In recent years, vegetable growers in the Midwestern United States have
received much advertising information about using the synthetic protein polyaspartic acid (PA) in their fertility management program as a nutrient absorption
enhancer. Supposedly, each long-chain PA molecule acts as an extension of the
plant’s root hairs; and by virtue of its negative charge, attracts nutrients to the root
surface. The result should be a higher level of nutrient uptake, and correspondingly
improved plant growth and crop yields. Subsequently, research was conducted at
two locations, Urbana and St. Charles, Ill., evaluating various combinations of PA
and starter fertilizer in bell peppers. At each site, PA at 0.24 ml/plant banded (5
x 5 cm) in combination with starter fertilizer (114N–240P–160K mg/plant) had a
positive effect on plant growth, increasing shoot dry mass 8% and 11% , respectively, compared to starter fertilizer alone. There was a positive yield response to
PA at St. Charles, but not at Urbana. At St. Charles, fruit production increased
14% , while yields increased 9% by applying PA as a greenhouse transplant soak
(16.4 ml PA/2.0 L water per 512 plants in fi ve applications) in conjunction with
banded (5 x 5 cm) starter fertilizer (114N–240P–160K mg/plant). Tissue analysis
at both locations showed various degrees of nutrient absorption enhancement.
However, the physiological basis for PA-induced increases in plant growth and
crop yields are not clear.
013
Soil Cation Balance Affects Tomato Fruit Color Disorders
T.K. Hartz1*, C. Giannini 1, E. Miyao2, J. Valencia2, M. Cahn2, R. Mullen2 and K.
Brittan2, 1Dept. of Vegetable Crops, Univ. of California, Davis, CA 95616; 2UC
Cooperative Extension
A survey of 140 processing tomato fi elds throughout central California was
conducted in 1996–97 to determine whether soil factors affect the occurrence of
the tomato (Lycopersicon esculentum Mill.) fruit color disorders “yellow eye” (a
halo of yellow tissue around the stem scar) and white core (an abnormal amount
445
of internal white tissue); these disorders render fruit unsuitable for use as
peeled or diced product. All fi elds were planted in ‘Halley’ or ‘Heinz 8892’. Soil
samples (0–30 cm) were analyzed for pH, texture, TKN, bicarbonate extractable
P, and ammonium acetate-extractable K, Ca, and Mg. Ripe fruit were rated for
the incidence (% ) of fruit affected by one or both of the disorders, blended color,
and % soluble solids (SS). Soil K (in meq., expressed as a % of base exchange)
was negatively correlated with the incidence of the disorders, while soil Mg was
positively correlated. Fields with extractable K <2% of base exchange averaged
21% of fruits affected by one or both disorders, compared to only 4% of fruits
affected in fi elds with K >2.5% of base exchange and a Mg/K ratio (meq. basis)
<12. Percent SS was weakly correlated with extractable K, but blended color
was unrelated to any soil factor. In 1997 fi eld trials, both gypsum application (to
displace soil Mg) and K fertilization signifi cantly suppressed the color disorders
but did not affect yield, blended color, or % SS.
014
Canola Seed Glucosinolate Content as Affected by Boron
Availability Under Water Stress
Andrew J. Price* , Barbara Kocourkova, Craig S. Charron, Charles Graves,
and Carl E. Sams; Dept. of Plant and Soil Sciences, The Univ. of Tennessee,
Knoxville, TN 37901
It is hypothesized that soil boron (B) availability is infl uenced by water
stress and affects canola glucosinolate content. This research was conducted
to determine if added B can overcome water stress-induced changes in seed
glucosinolate content in canola. The cultivars Cyclone and American A112 were
grown in a continuously recirculating hydroponic system with modifi ed Hoagland
solutions. The experimental design was a randomized incomplete block. Two
B concentrations and one water stress treatment (maintained with polyethylene
glycol 8000, PEG) were used: 0.04 mg• L–1 B (not water stressed, without PEG),
0.04 mg• L–1 B (water stressed, with PEG), and 0.60 mg• L–1 B (water stressed,
with PEG). Osmotic potential was maintained at –0.1 MPa (with PEG) or 0.05
MPa (without PEG). The 0.04-mg• L–1 B treatment without PEG had signifi cantly
lower total glucosinolates than the 0.04-mg• L–1 B treatment with PEG. This
indicates that at low available B levels, glucosinolate content is increased by
water stress. The 0.04-mg• L–1 B treatment with PEG had signifi cantly higher
total glucosinolates than the 0.60 -mg• L–1 B treatment with PEG. Thus, under
water stress, the higher available B treatment resulted in lower seed glucosinolate
content.
42
POSTER SESSION 1B (Abstr. 015–027)
Floriculture/Greenhouse Management—
Light/Temperature/Growth Regulators
015
Effect of Irradiance on Hibiscus L. Species Flowering
Ryan M. Warner* and John E. Erwin; Dept. of Horticultural Science, Univ. of
Minnesota, St. Paul, MN 55108
The effect of supplemental lighting on fl owering of six Hibiscus L. species
was examined. Plants were grown in a greenhouse at 20 ± 1 °C under either of
two photoperiods, 9-h (covered with opaque cloth from 1430–0730 HR) or 16 h.
Within each photoperiod, four levels of supplemental light were provided using
high-pressure sodium lamps. Total supplemental irradiance levels were: 0, 2, 4,
and 8 mol/day photosynthetically active radiation (PAR), at the apical meristem,
for plants grown under a 9-h photoperiod, and 2, 4, 8, and 16 mol/day PAR for
plants grown under a 16-h photoperiod. Irradiance levels were measured weekly,
with plants being moved to maintain the designated irradiance level at the apical
meristem. Data collected included anthesis date, number of leaves below the fi rst
fl ower, lateral shoot and fl ower bud number, plant height, and fl ower diameter.
Increasing daily light integral reduced the number of leaves below the fi rst fl ower
for some species in one or both photoperiods. Irradiance and photoperiod effects
on lateral shoot and fl ower bud number at anthesis will be discussed. Photosynthetic-response curves and light-response curves with respect to fl owering were
constructed for each species. Response curve variation between species will be
discussed.
446
016
Light Quality Regulation of Gene Expression in Chrysanthemum
L. Zhang1, S. Rajapakse1, R.E. Ballard1, and N.C. Rajapakse* 2; 1Dept. of Biological
Sciences and 2Dept. of Horticulture, Clemson Univ., Clemson, SC 29634
A major part of Clemson light quality research program focuses on understanding the mechanisms of plant growth alteration under spectral fi lters. We
have extended this research to understand the molecular basis for plant height
control by spectral fi lters. From the whole plant research we have found that gibberellins (GA) play a key role in height control under spectral fi lters. However, it
is not clear whether an alteration of endogenous gibberellin levels or a change
in sensitivity to gibberellins is causing the observed effects. Since gibberellins
are a key hormone in cell expansion and fl ower development, an understanding
of gibberellin regulation and metabolism under spectral fi lters is critical for
the control of height and fl owering of plants grown under these fi lters. For the
molecular study, we have selected the gene that code for enzyme GA 20-oxidase,
one of the key enzymes involved in producing functional GAs in the mevalonic
acid pathway. GA 20-oxidase is thought to be a site of regulation of GA synthesis
by the environment. We are currently studying the regulation of the expression
of this gene by light quality using Northern analysis. Results from temporal and
tissue specifi c regulation of chrysanthemum plants grown under CuSO4 fi lters
will be presented.
017
Effect of Irradiance Level and Paclobutrazol on Reducation of
Leaf Damage in Begonia x cheimantha
Beyounghan Yoon* and Harvey J. Lang; Dept. of Horticultural Sciences, Texas
A& M Univ., College Station, TX 77843-2133
Begonia x cheimantha (Christmas or Lorraine begonia) is a popular holiday
crop in Europe, with certain cultivars having outstanding postharvest characteristics. Its commercial production in the southern United States has been limited
by the occurrence of mottled leaf chlorosis and necrosis, apparently due to
environmental stress. In this study, B. x cheimantha ‘Emma’ was grown in the fall
in a glass greenhouse at College Station, Texas, under either 0% , 60% , or 87%
polyethylene shade cloth. Leaf chlorosis and necrosis was very severe on plants
grown in full sun (≈650 mol • m–2• s–1), with slight chlorosis on plants under 60%
shade. Plants under full sun, however, were more compact, fl owered earlier, and
had shorter peduncles with more fl owers than those grown under shade. Reducing
the vegetative long-day treatment period from 7 to 4 weeks had no effect on leaf
damage development. Plants treated with paclobutrazol were shorter and had less
leaf damage than untreated plants. Leaves of treated plants had a relatively higher
concentration of soluble protein, chlorophyll, and enhanced activities of ascorbate
peroxidase (AsA), dehydroascorbate (DHA) reductase, and monodehydro-ascorbate (MDHA) reductase than untreated plants. For Texas growing conditions,
these preliminary studies indicate that B. x cheimantha should be grown under
reduced light intensities, with excessive height and leaf damage being controlled
with growth retardants such as paclobutrazol.
018
Screening Perennial Bedding Plants for Response to Plant
Growth Regulators
Joyce G. Latimer* 1 and Paul A. Thomas2; 1Dept. of Horticulture, The Univ. of
Georgia, Griffi n, GA 30223; 2Dept. of Horticulture, The Univ. of Georgia, Athens,
GA 30602
Perennial bedding plant species were tested for response to single treatments
of Sumagic (0, 15, 30, 45, or 60 ppm), Bonzi (0, 40, 80, 120, or 160 ppm), Cycocel
(0, 750, 1500, 2250, or 3000 ppm) or B-Nine (5000 ppm, applied twice) applied
during greenhouse production in Spring 1997. Plant height of both Chrysanthemum
parthenium and Malva alcea had a quadratic response to Sumagic and Bonzi
rates, with excessive height reductions at the lowest application rates at 4 weeks
after treatment. All rates of Cycocel reduced plant height of C. parthenium and
M. alcea by 33% and 40% , respectively. These species did not establish in the
landscape. Verbena bonariensis was moderately responsive to Sumagic and
Bonzi, but not Cycocel. Application rates of 15 and 30 ppm Sumagic or 160 ppm
Bonzi provided moderate height control without landscape persistence beyond
4 weeks after planting. Leucanthemum x superbum ‘Alaska’ was responsive to
Sumagic and Bonzi, but not Cycocel or B-Nine. Rates of 15 ppm Sumagic or 40
ppm Bonzi provided moderate control without landscape persistence. Plant height
HORTSCIENCE, VOL. 33(3), JUNE 1998
of Monarda didyma ‘Blue Stocking’ had a linear response to Sumagic and Bonzi
rates. Plant height of Rudbeckia fulgida var. Sullivantii ‘Goldstrum’ was reduced
by Bonzi and Sumagic but not B-Nine or Cycocel, with recommended rates of 30
to 40 ppm Sumagic or 160 ppm Bonzi. Treatment of Sedum x ‘Autumn Joy’ with
Sumagic resulted in excessive landscape persistence of growth retardation at all
rates, but Sedum was not responsive to Cycocel. Veronica alpina ‘Sunny Border
Blue’ was responsive to all rates of Cycocel, but growth retardation persisted
through 12 weeks after planting.
019
Lupine (Lupinus polyphyllus) Flowering Response to Photoperiod and Hosta Response to Florel Growth Regulator
Douglas A. Hopper * , Danelle E. Drew, Catherine E. Hudachek, and Lori C.
Rudolph; Agricultural Experiment Station, Colorado State Univ., Fort Collins,
CO 80523
Seeds of ‘Russell hybrid’ and ‘Minarette’ mix lupines were sown in three
experiments on 3 Sept., 10 Nov., and 2 Mar. under long-day (LD). Seedlings were
transplanted on 27 Jan., 11 Mar., and 16 Apr. and moved to natural-day (ND) or
LD (1500 to 0200 HR). Plants were either placed in a 17/13C day/night (DT/NT)
temperature or 22/18 ° C DT/NT greenhouse, and moved monthly to ND or LD
for 32 treatment combinations. Days until visible bud, fl owering, and vegetative
heights were analyzed. ‘Minarette’ formed fl owers more consistently than did
‘Russell hybrids’, indicating that ‘Minarette’ populations tend to fl ower earlier.
Young lupines did not respond to photoperiod, but facultative fl owering was
observed. Foliage height was greater under LD. One-year-old Hosta sieboldiana
and H. ‘Francis William’ were transplanted with one crown and placed in two
temperatures as with lupines. Expt. H1 hostas were placed under LD/ND with
no spray, 500 ppm, or 1000 ppm Florel; Expt. H2 hostas were placed under LD
with no spray, 250 ppm Florel monthly, 500 ppm Florel at 4-, 6-, or 8-week
intervals, or 2500 ppm benzyladenine (BA) sprays monthly (Dec. 1996 to July
1997). H. sieboldiana had more offsets than H. ‘Francis William’, but the latter
had increased offsets with Florel sprays. Both cultivars were shorter with 1000
ppm Florel treatments. BA-treated plants were shorter with more offsets than
Florel-treated plants.
020
Prefinishing Strategies for Flowering Petunia x hybrida
Vilm.
Ryan M. Warner* and John E. Erwin; Dept. of Horticultural Science, Univ. of
Minnesota, St. Paul, MN 55108
Petunia x hybrida Vilm. ‘Purple Wave’ and ‘White Storm’ were grown under
different lighting treatments for different lengths of time at different stages of
development during the fi rst 4 weeks after germination. The objective of the
experiment was to identify the effects of photoperiod and stage of development
on date of anthesis and plant form at anthesis. Seedlings were transplanted from
25-cm 3 “plugs” into 85-cm 3 cell-packs prior to treatment initiation. Plants were
grown under ambient photoperiod (April, St. Paul, Minn.) at 20 ± 1 ° C before
and after treatments. Lighting treatments were 4 weeks of either 9-h ambient light
(SD), ambient light plus 100 µmol • m –2• s–1 continuous light (CT) provided by
high-pressure sodium lamps, or varying combinations of weeks of SD and CT.
After 4 weeks of treatment, plants either remained in cell-packs, were transplanted
into 10-cm pots (one plant per pot), or 19-cm pots (three plants per pot), and
grown until anthesis. Data collected included anthesis date, leaf number below
the fi rst fl ower, lateral shoot number, and fl ower bud number. A single week of
CT was suffi cient to induce fl owering in ‘White Storm’. ‘Purple Wave’ plants did
not fl ower in response to lighting during the fi rst 2 weeks of development. ‘Purple
Wave’ plants grown under CT during weeks 3 and 4 fl owered with a lower leaf
number than if grown in SD for all 4weeks. Consequences of these fi ndings with
respect to prefi nishing seedlings and scheduling crops of different container
sizes will be discussed.
021
Growth and Branching Responses of Portulaca grandiflora to
Foliar Applications of Chemical Growth Regulators
T.J. Banko * and M .A. Stefani ; Virginia Tech, Hampton Roads Agricultural
Research and Extension Center, Virginia Beach, VA 23455
During container production of portulaca, growth of long, prostrate, sparsely
branched stems makes handling of plants diffi cult, and reduces their commercial
HORTSCIENCE, VOL. 33(3), JUNE 1998
appeal. Growers prefer to minimize shoot elongation while increasing branching
to provide a full, compact plant. The objectives of this study were to evaluate
growth regulators for promotion of branching and inhibition of stem elongation.
Container-grown plants ≈21 cm in diameter were treated with sprays of ProShear
(benzylaminopurine) at 62.4, 125, and 250 ppm; Promalin (benzyaminopurine +
gibberellins 4+7) at 125, 250, and 500 ppm; Atrimmec (dikegulac) at 250, 500,
and 750 ppm; and Florel (ethephon) at 250, 500, and 750 ppm. These treatments
were compared with untreated controls in a randomized complete-block design.
Main shoot lengths were measured at 16, 31, and 51 days after treatment (DAT).
Numbers of new shoot breaks were counted 16 DAT. The growth habit, that is,
tendency to grow upright or prostrate, was also evaluated 16 DAT. The most-effective material for retarding primary shoot elongation and for stimulating secondary
shoot development was ProShear. At 16 DAT, 250 ppm ProShear reduced shoot
elongation by 25% compared to control plants. This treatment also increased the
number of secondary shoot breaks by 143% . Promalin increased the number of
new shoot breaks, but it also increased the lengths of all shoots. High rates of
Florel and Promalin caused shoots to grow predominantly upright rather then
prostrate. ProShear, however, caused more prostrate growth as rate increased.
022
Cyclamen Leaf Unfolding Rate in Response to Temperature
Meriam Karlsson* and Jeffrey Werner; Dept. of Plant, Animal and Soil Sciences,
Univ. of Alaska, Fairbanks, AK 99775-7200
Nine-week-old plants of Cyclamen persicum ‘Miracle Salmon’ were transplanted into 10-cm pots and placed in growth chambers at 8, 12, 16, 20, or 24 °C.
The irradiance was 10 mol/day per m 2 during a 16-h day length. After 8 weeks,
the temperature was changed to 16 ° C for all plants. Expanded leaves (1 cm or
larger) were counted at weekly intervals for each plant. The rate of leaf unfolding
increased with temperature to 20 ° C. The fastest rate at 20 ° C was 0.34 ± 0.05
leaf/day. Flower buds were visible 55 ± 7 days from start of temperature treatments (118 days from seeding) for the plants grown at 12, 16, or 20 ° C. Flower
buds appeared 60 ± 6.9 days from initiation of treatments for plants grown at
24 ° C and 93 ± 8.9 days for cyclamens grown at 8 ° C. Although there was no
signifi cant difference in rate of fl ower bud appearance for cyclamens grown at 12,
16, or 20 ° C, the number of leaves, fl owers, and fl ower buds varied signifi cantly
among all temperature treatments. Leaf number at fl owering increased from 38 ±
4.7 for plants at 12 ° C to 77 ± 8.3 at 24 ° C. Flowers and fl ower buds increased
from 18 ± 2.9 to 52 ± 11.0 as temperature increased from 12 to 24 ° C. Plants
grown at 8 ° C had on average 6 ± 2 visible fl ower buds, but no open fl owers at
termination of the study (128 days from start of treatments).
023
Cyclamen Flower Development in Response to Temperature
Meriam Karlsson* and Jeffrey Werner; Dept. of Plant, Animal and Soil Sciences,
Univ. of Alaska, Fairbanks, AK 99775-7200
Commercially plug-produced Cyclamen persicum ‘Miracle Salmon’ were
transplanted into 10-cm pots 15 weeks from seeding and placed at 16 ° C. The
irradiance was 10 mol/day per m 2 during a 16-h day length throughout the study.
Three weeks from transplant, the plants were placed at 8, 12, 16, 20, or 24 ° C.
At the time of temperature change, fl ower buds were fi rst visible. Time to fi rst
open fl ower decreased with increasing temperature to 20 ° C. On average, the
cyclamens grown at 20 ° C required 60 ± 4.5 days from transplant (165 days
from seeding) to fi rst open fl ower. There was no difference in rate of fl owering
for the plants grown at 16 or 24 ° C (74 ± 9.5 days from transplant). Cyclamens
grown at 12 ° C required on average 28 more days and cyclamens grown at 8
° C, 45 more days to fi rst open fl ower compared to plants grown at 20 ° C. There
was no difference in number of leaves per plant (55 ± 14.4). However, the plants
grown at 24 ° C had signifi cantly larger leaves and total leaf area per plant (1060
± 235 cm 2) than plants in the other temperature treatments (585 ± 104 cm 2). The
number of fl owers and buds per plant was 45 ± 10.6 for plants grown at 16, 20
or 24 ° C. Signifi cantly less fl owers and buds were produced by plants grown at
12 ° C (34 ± 7.9) or 8 ° C (17 ± 3.7).
024
Effect of High Temperatures on the Postharvest Flowering of
Specialty Floral Crop Species
Millie S. Williams, Terri Woods Starman* , and James E. Faust; Dept. of Ornamental Horticulture and Landscape Design, Inst. of Agriculture, Univ. of Tennessee,
447
Knoxville, TN 37901-1071
Flower growers experience decreased consumer satisfaction with plant species that cease fl owering during the summer. The objective of this experiment was
to characterize the heat tolerance of four specialty fl oral crop species in order to
predict their summer performance in the different climatalogical regions of the
United States. The effect of increasing temperatures on the duration of postharvest
fl ower development was determined for Ageranthemum frutescens ‘Butterfl y’ and
‘Sugar Baby’, Brachycome hybrid ‘Ultra’, and Sutera cordata ‘Snowfl ake’. Plants
were grown in a 18 ° C greenhouse until marketable with foliage covering the
container and fl owers distributed evenly across the plant canopy. Plants were then
placed in a phytotron to determine their heat tolerance. Temperature set points
of 18, 23, 28, and 33 ° C were delivered serially at 2-week intervals, starting at
18 ° C. Plants were then returned to 18 ° C after the 33 ° C treatment. Immature
fl ower bud, mature fl ower bud, fl ower and senesced fl ower numbers were collected once per week. Sutera ‘Snowfl ake’, and Brachycome ‘Ultra’ had the greatest
fl ower number at the 23 ° C temperature, decreasing in the 28 ° C environment.
Argeranthemum ‘Butterfl y’ and ‘Sugar Baby’ had greatest fl ower number at 28
° C, but fl owers were smaller and of lower quality than at 23 ° C. Flower development of all cultivars ceased at 33 ° C, but when plants were returned to the 18
° C production greenhouse, fl ower development resumed. According to normal
average daily temperatures in Knoxville, Tenn., Ageranthemum frutescens ‘Butterfl y’ and ‘Sugar Baby’ would fl ower until mid-June, while Brachycome hybrid
‘Ultra’ and Sutera cordata ‘Snowfl ake’ would fl ower until mid-May.
025
Effect of Temperature on Cutting Production of 10 HangingBasket Crops
Shi-Ying Wang* , William H. Carlson, and Royal D. Heins; Dept. of Horticulture,
Michigan State Univ., East Lansing, MI 48824-1325
Stock plants of Argeranthemum frutescens ‘Butterfl y’ and ‘Sugar Baby’,
Brachycome hybrid ‘Ultra’, Helichrysum bracteatum ‘Golden Beauty’, Scaevola
aemula ‘New Wonder’, Petunia axillaris hybrids ‘Purple Sunsport’ and ‘Blue Vein’,
Sutera cordata ‘Mauve Mist’ and ‘Snowfl ake’, and Verbena hybrid ‘Blue’ were
grown in glass greenhouses under fi ve different temperatures (17, 20, 23, 26, or
29 ° C) and a 13-h photoperiod. Cuttings were taken two to three times per week.
Total cutting production increased as temperature increased. However, different
varieties showed different temperature response patterns. Cutting production
in Argeranthmum and Brachycome was relatively insensitive to temperature.
For Brachycome, Helichrysum, Scaevola, Petunia, Sutera, and Verbena, cutting
production in the 29 ° C treatment was double or triple that in the 17 ° C treatment.
For all tested species, the highest cutting production was in the 29 ° C treatment.
Although cuttings produced in the 29 ° C treatment tended to have a soft stem,
rooting was not affected by temperature under which stock plants were grown.
026
Stock Plant Environment Impacts Lateral Stem Strength of
Finished Poinsettias
James E. Faust*, Elizabeth Will, and Rob Klein; Univ. of Tennessee, P.O. Box 1071,
Knoxville, TN 37901-1071
Previous work indicated that the cutting source impacted lateral stem strength
of the fi nished poinsettia. The objective of this experiment was to determine the
effect of the stock plant environment on the stem strength of the harvested cuttings. Stock plants were grown in two greenhouses. The night temperature was
maintained at 20 °C in both, while the day temperature was maintained at 30 or
37 °C. Two irradiance levels were maintained with each greenhouse: 50% and
75% shade cloth. Within each irradiance treatment, individual stock plants were
provided 522, 929, or 1451 cm2 of bench space. Stock plants were pinched to 12
nodes, lateral shoots developed, and cuttings were harvested. The cuttings were
propagated, transplanted and pinched. Lateral stem strength was quantifi ed by
dropping the fi nished plants from progressively greater heights and recording stem
breakage. Stem strength increased as temperature increased, irradiance increased,
and as stock plant density decreased. Plants grown in the lower temperature, lower
irradiance level, and higher plant density experienced 34% of the lateral shoots
breaking off at a 30-cm drop height, while 4% of the lateral shoots broke on the
cuttings harvested from the higher temperature, higher irradiance, and lower plant
density treatment.
448
027
GHSIM Developed in Spreadsheet Quattro Pro Simulates the
Interactive Greenhouse
Douglas A. Hopper*; Agricultural Expt. Station, Colorado State Univ., Fort Collins, CO 80523
A computer model, GHSIM, was formulated in Quattro Pro spreadsheet format.
GHSIM was designed having individual pages calculating simulated activities
necessary for greenhouse production. Pages were arranged by alphabetical topics
starting with the “Area” used in the greenhouse. Time advanced by 1 day for each
10 s of real time. The time advance in the program can be paused to make setting
changes interactively. Pest infestation occurred as probabilities accumulated,
and the pest population spread through the greenhouse based on proximity and
density of pests. Pest control was simulated by a pesticide application capable of
partially reducing populations; repeated applications could effectively eliminate a
pest. Crop growth was simulated by iterative acccumulation of biomass using Euler
integration of daily plant growth. The daily growth increment was calculated using
the fi rst derivative of the Richard’s Function. Large pest populations negatively
impacted the daily growth increment, and pesticide applicaions would remove the
inhibition of growth. Additional features proposed include light and temperature
effects on the plant growth rate and accumulated biomass.
42
POSTER SESSION 1C (Abstr. 028–035)
Nutrition—Woody Ornamentals/Landscape/Turf
028
Effect of Phosphorus Applied as a Controlled-release Fertilizer
or Soluble Fertilizer to a Container Nursery Crop
Arleen Godoy* and Janet C. Cole; Dept. of Horticulture and Landscape Architecture,
Oklahoma State Univ., Stillwater, OK 74078-0511
Thirty commercially propagated bareroot cuttings and 30 cuttings with growing
medium around the roots of Halwards’ Silver Spiraea were fertilized with various
phosphorus fertilizers to determine the effect of fertilizer type on P leaching and
on plant quality. The following treatments were applied: 1) 100% controlledrelease fertilizer (CRF) consisting of 22N–6P–14K; 2) 50% CRF consisting of
22N–3P–14K plus 50% soluble fertilizer (SF) consisting of 0N–46P–0K, triple
superphosphate (TSP); and 3) 100% SF consisting of 22N–0P–14K plus TSP
(0N–46P–0K). There was a signifi cant plant by fertilizer interaction for leachate
P content. Cuttings with medium and bareroot cuttings receiving 100% SF had a
higher concentration of P in leachate; while the cuttings with medium receiving
100% CRF and 50% CRF/50% SF had lowest P concentration in leachate. Plants
grown with 50% CRF/50% SF had larger root dry masses compared to the plants
grown in 100% CRF and 100% SF. Plants grown in 100% CRF had the smallest
stem dry masses compared to the other fertilizer treatments. Plants containing
100% CRF had a lower P concentration in the stems compared to plants containing
100% SF and 50% CRF/50% SF.
029
Mulch and Fertilizer Application Method Influence on Plant
Growth in Winter Annual Plantings
R.A. Mirabello* 1, A.E. Einert1, G.L. Klingaman1, and R.W. McNew2; 1Dept. of
Horticulture, 2Agricultural Statistics Laboratory, Univ. of Arkansas, Fayetteville,
AR 72701
A winter planting of pansies, Viola x wittrockiana Gams, was established in
existing landscape beds to determine mulch type and fertilizer application method
infl uences on plant growth. Two cultivars, ‘Bingo Blue’ and ‘Bingo Purple’, were
planted in beds containing four different mulches (cottonseed hulls, cypress wood,
pine bark, pine straw). A split application of fertilizer by three application methods
(granular, liquid, time-release) was applied at planting for plant establishment and
in the spring to encourage new growth. Fertilizer was applied either below the
mulch on the soil surface or over the mulch surface. Cottonseed hulls, cypress
wood, and pine bark delayed soil warming in the spring and the effectiveness of
all fertilizers. The use of time-release fertilizer below all mulches improved growth.
Pine straw allowed soil temperatures to rise and fertilizer to increase plant dry
HORTSCIENCE, VOL. 33(3), JUNE 1998
weight accumulation. Rapid decomposition of pine straw resulted in a 0.55-unit
decrease in soil pH and increases in soil nitrogen and EC values.
030
Effect of Organic and Mineral Mulches on Soil Properties and
Growth of Red Maple
Jeffery K. Iles* and Michael S. Dosmann; Dept. of Horticulture, 106 Horticulture
Hall, Iowa State Univ., Ames, IA 50011-1100
Five mineral mulches (crushed red brick, pea gravel, lava rock, carmel rock,
and river rock) and three organic mulches (fi nely screened pine bark, wood chips,
and shredded hardwood bark) were evaluated over 2 years to determine their infl uence on soil temperature, moisture, and pH, and to quantify their effect on growth
of Fairview Flame® red maple (Acer rubrum L.). Mulch treatments (2.3-m2 plots
of eight mulches and a non-mulched control) were randomly applied to trees in
fi ve blocks. Organic mulches were placed directly on bare ground, while mineral
mulches were underlaid with a woven polypropylene fabric. Soil temperature was
highest and soil moisture lowest under the mineral mulches and non-mulched
control. Soil pH was highest under shredded bark (6.82) and wood chips (6.81),
and lowest in the non-mulched control (6.03). Despite such differences in the
root-zone environments, there were no signifi cant differences in stem caliper or tree
height, but leaf dry mass was greatest for trees treated with mineral mulches.
031
Release of Mineral Elements and Heavy Metals Restrained in
Organic Residues and Their Effects on Physocarpus opulifolius
‘Nanus’ Grown in Containers
Mondher Bouden* and Jacques-Andre Rioux; Envirotron Building, Horticulture
Research Center, Laval Univ., Ste-Foy, Quebec, Canada G1K7P4
The use of waste in ornamental culture seems to be the best optional method
of disposal. However, the amount of available mineral elements in organic residues
is not equilibrated with the mineral needs of plants. In this context, this study
was performed to evaluate the infl uence of fresh bio-fi lters (FBF), composted
sewage sludges (CSS), and composted de-inked sludges (CDS) on the mineral
composition of substrate water solution. Substrates containing 10% of each
organic residues and control substrate (4 peatmoss, 5 composted conifer bark,
and 1 fi ne crushed gravel, by volume) were potted in 5-L containers. An experiment was conducted with Physocarpus opulifolius ‘Nanus’ plants and a soluble
fertilizer 20N–20P–20K (400 mg/L of N). Another experiment was carried out
without plants and without fertilization. In the two experiments, the four substrates
were randomized in a complete block design with six replications. All containers
were watered every 2 weeks until leaching (inspired by the pour-through method
described by Wright, 1986) and a sample of each leachate was collected for
analysis. Growth parameters were statistically analyzed. The content of nutrient
elements in the water solution of substrates with plants and with fertilization was
higher than their content in the water solution of substrates without plants and
without fertilization. However, the content of heavy metals was quite similar with
the two fertilization regimes and was below the undesirable limits. Substrates
amended with CSS released a higher quantity of P, K, S, and Na than substrates
amended with FBF or CDS. Moreover, Physocarpus plants grown in CSS were
signifi cantly larger than those plants grown in the control substrate. The results
obtained in media containing FBF or CDS were similar to those obtained in the
control substrate.
032
Assessment of Biologically Converted Swine Waste as a Fertilizer Source in Container Production
Cindy L. Flinn* 1, Ray Campbell 2, and Ted E. Bilderback3; 1Bion Technologies, Inc.,
Smithfi eld, NC 27577; 2North Carolina Dept. of Agriculture Agronomic Division,
Raleigh, NC 27607; 3Dept. of Horticultural Science, North Carolina State Univ.,
Raleigh, NC 27695
Swine waste (SW), the by-product of North Carolina’s booming hog industry,
is one of the state’s most underutilized resources. Currently, SW is used to grow
coastal bermuda hay, a “disposal” crop with little to no economic value. Use of
SW by commercial growers as fertilizer would reduce the need to dispose of
SW and could reduce the overall input of nutrients into the environment. Our
objectives were to determine: plant growth characteristics of SW, the effects of
SW on leachable forms of nitrogen, and the physical effects of SW in a pine bark
media. To avoid pathogens, we used SW (BionSoil™) that had been biologically
HORTSCIENCE, VOL. 33(3), JUNE 1998
digested as part of a proprietary SW treatment process (Bion Technologies, Inc.).
Liners of ‘Rose Madness’ petunia, ‘Skogholm’ cotoneaster, ‘Girard’s Red’ azalea,
and ‘Wilson’s Yellow’ daylily were planted in 3.8-L plastic pots that contained
one of the following (by volume): 10% SW:90% pine bark, 20% SW:80% pine
bark, 30% SW:70% pine bark, or pine bark (control) amended with 3.6 kg of
23-4-8 controlled release fertilizer (CLF), 3.6 kg dolomitic limestone, and 330 g
micronutrient fertilizer per m3. Shoot dry weights were determined for all species
at harvest. Root dry weights were obtained for cotoneaster and daylily. Leachate
nitrogen and pH was determined periodically throughout the 22-week study. By the
14th week, nitrogen and potassium defi ciencies were identifi ed on plants growing
in SW-amended media. Those treatments were subsequently topdressed with a
corrective application of 9 g of 23N–4P–8K CRF. Generally, SW can produce plants
similar to short-term CRF without the need for supplemental micronutrients or
lime Root biomass was greater in SW media than in the control. A mid-season
application of a N–P–K fertilizer may be necessary.
033
The Response of Bermudagrass (Cynodon spp.) to Microorganisms and Humate Soil Inoculations
J.O. Kuti* 1, S. Gans2, J.C. Hayes2, and W. Tucker2; 1Dept. of Agronomy & Resource
Sciences, Texas A& M Univ.–Kingsville, Kingsville, TX 78363; 2Nature’s Technology Inc., Pilot Point, TX 76258
Effects of soil inoculations of selected benefi cial microorganisms and humate
materials on root mass, shoot growth, and turfgrass quality of a 6-month-old
bermudagrass (Cynodon dactylon L. cv. Tifway) stands growing on microplots in
Kingsville, Texas, were studied. *SuperBio + Humus soil inoculant formulated by
Ag-Technology Inc., was used in this study. Various levels (0, 1/4, 1/2, 1, and 1.5
gallons per acre) of the *SuperBio product were injected into the soil with irrigation
water on weekly basis. Prior to the treatments, fi ve 7.62-cm plugs were removed
from each of the microplot for root and shoot growth analysis. Plug samples were
subsequently taken every 4 weeks after the treatments. While all treatments, except
the controls, showed increase in shoot growth, only 1 gal/acre treatment gave
signifi cant increase in root mass as compared to the other treatments including
the controls. It appears that visual turfgrass quality ratings increased with an
increase in treatment levels.
034
Colonization Potential of Ornamental Plants by Three Vesicular–Arbuscular Mycorrhizal Fungi
M artin Trépanier* and Jacques-André Rioux, Horticultural Research Center,
Envirotron Building, Laval Univ., Sainte-Foy, Québec, Canada, G1K 7P4
Roots of majority of natural shrubs are colonized by many species of vesicular–arbuscular mycorrhizal (VAM) fungi. These kinds of fungi form a symbiosis
with the root system of the plant and give a better water and mineral absorption
(P, Zn, N, Cu, etc.), and a better root disease resistance to the plant. However, the
media usually used in ornemental plants nursery contain no or few mycorrhizal
fungi. For now, new commercial inoculum are available and could be used to get the
advantages provided by VAM fungi. In order to evaluate the potential of ornamental
plants to be colonized, we have inoculated the rooting media with three VAM fungi
(Glomus intraradices Schenk & Smith, Glomus etunicatum Becker & Gerdemann,
and Glomus mosseae Nicol. & Gerd.; Premier Tech, Rivière-du-Loup, Québec). The
inoculum proportion used contained about 1500 propagules/L. After 16 weeks,
near 80% of the 200 species and cultivars tested have shown a colonization by
at least one of the fungi. We shall present here a list of the results.
035
Comparison of Nodular Efficiencies Between Partridge Pea and
Soybean Using Acetylene Reduction
Lisa M. Barry* and Michael N. Dana; Dept. of Horticulture and Landscape Architecture, Purdue Univ., West Lafayette, IN 47907-1165
Legumes are grown as nurse crops in agriculture because they increase soil
microbial life and productivity. Native legumes have potential in ecological restoration to mimic the benefi ts found in agriculture plus they enhance the restored
ecosystem. This study was initiated to compare the growth rates, nodulation
characteristics, and nitrogen fi xation rates of a native versus a non-native legume.
The two legumes were partridge pea (Cassia fasciculata); a native, wild, annual
legume and soybean (Glycine max ‘Century Yellow); a domesticated, agricultural,
annual legume native to Asia. Plants were grown for 11 weeks in pots containing
449
silica sand and received a nitrogen-free Hoagland’s nutrient solution. Beginning
at week 12, plants were harvested weekly for four consecutive weeks. Nodulated
root systems were exposed to acetylene gas and the resulting ethylene amounts
were measured. The two legumes exhibited signifi cant differences in nodule size
and shape and plant growth rate. In soybean, nodules were large, spherical, and
clustered around the taproot while in partridge pea, nodules were small, irregularly
shaped, and spread throughout the fi brous root system. Soybean plants had a
signifi cantly faster growth rate at the onset of the experiment but partridge pea
maintained a constant growth rate and eventually exceeded soybean plant size. In
spite of these observed differences, partridge pea and soybean plants were equally
effi cient at reducing acetylene to ethylene. These results indicate partridge pea has
the potential to produce as much nitrogen in the fi eld as soybean. Native legumes
such as partridge pea deserve further research to explore their use as nurse crops
in agricultural or restoration regimes.
42
POSTER SESSION 1D (Abstr. 036–042)
Management—Wildflowers/Miscellaneous
036
Regulatory Oversight of Natural and Alternative Landscapes
Harold E. Balbach* 1 and Margaret K. Balbach2; 1US Army CERL, Champaign, IL
61826; 2Illinois State Univ., Normal, Ill.
In their attempts to be more environmentally sensitive, many thousands of
homeowners propose, or actually implement, alternatives to conventional lawn
maintenance. In many cases, the perception of “naturalness” incorporates unmowed grasses and forbs believed by the homeowner to be reminiscent of fi elds
and pastures. A previous study of municipal attitudes toward this phenomenon
revealed a wide variety of responses, ranging from laissez-faire, through offi cial
recognition and registration to strict prohibition and vigorous enforcement. The
current expansion of this study focused on larger cities and their suburbs, especially newer subdivisions. In contrast to the general air of tolerance expressed
by many smaller, midwestern towns for alternative landscape plans, provided
they are well-maintained, larger cities and suburbs appear generally much less
tolerant of nonstandard lawn maintenance. Failure to maintain lawn grasses at
a standard height will almost certainly lead to enforcement of lawn maintenance
and weed control ordinances in a majority of the cities surveyed, no matter what
the intentions of the homeowner.
037
Historic Military Landscapes: A Design and Management Opportunity
Suzanne K. Loechl , Gary Kesler, Paul Loechl , Diane Timlin, Geoffrey Burt, Lisa
Duwall , Megan Weaver, and Harold E. Balbach*; US Army CERL, P.O. Box 9005,
Champaign, IL 61926; Univ. of Illinois, Urbana, Ill.
The United States Army has recently recognized the evaluation and management of historic military landscapes as an integral component of cultural
resource management. The process of properly assessing and managing military
landscapes, however, can be problematic due to the need to preserve the historic
character of the landscape, to enhance the military image and to improve quality
of life. In addition there is a desire to implement “… environmentally and economically benefi cial landscape practices on Federal properties… ,” as set forth
in a memorandum from the President. USACERL recently completed an historic
landscape inventory and management plan for Fort Sam Houston, Texas. The
landscape master plan was awarded the Texas Historical Commission’s Award of
Excellence in Historic Architecture. The management plan provides historically and
ecologically sensitive designs that relate to each of the periods represented in the
installations’ historic district. Included are appropriate plant lists and guidelines
for enhancing the image of the base and improving quality of life for residents and
installation personnel. Of some concern here, as in many Southwest installations,
is the overuse of irrigation in historic areas, and the need to replace ecologically
(and historically) inappropriate plants with more drought-tolerant species. Plan
implementation in these areas is expected to reduce both water usage and associated costs.
450
038
Consumer Preferences in Mixed Prairie Wildflower Plantings
G.L. Davis* and J. Schimelfenig; Horticulture Dept., Univ. of Nebraska, Lincoln,
NE 68583
A goal of this study is to establish temporal evaluations of the problems homeowners may encounter when establishing mixed prairie wildfl ower plantings.
These plantings are often attempted with the notion that the composition of the
planting will remain static over time with little or no maintenance. Six combinations of wildfl owers and prairie grasses were compared for consumer preference. A
survey was conducted at the long-term forbs research plots during the Festival of
Color, an open house event at the John Seaton Anderson Turfgrass and Ornamental
Research Area, Univ. of Nebraska Agricultural Research Development Center near
Mead, Neb. Of the 9000 participants in the festival, ≈850 visited the plots. Of those,
nearly 300 completed the survey instrument. Results from the fi rst year indicate
that the majority of respondents were homeowners who do their own yard work.
Most of them considered a low maintenance landscape to be an important way
in which to conserve resources such as water and fertilizer and reduce pesticide
use. Most had grown prairie wildfl owers and considered them to be low maintenance. The study showed that, depending on the planting composition, it would
require between 59 and 118 h of weeding to establish wildfl owers in the majority
of respondents’ home landscapes, which were between 1717 m 2 and 1525 m2.
The majority (56% ) of visitors preferred combinations that included annuals but
excluded prairie grasses. The majority (66% ) disliked the combinations of prairie
grasses without the inclusion of wildfl owers.
039
Wildflower Seed Source Affects Performance of Six Wildflower
Species
Jeffrey G. Norcini* 1, James H. Aldrich1, John G. Lilly2, and Lawrence A. Halsey2;
Univ. of Florida, North Florida Research & Education Ctr., Rt. 4 Box 4092,
Monticello, FL, 32344; 2Jefferson County Cooperative Extension Service, 275
N. Mulberry St., Monticello, FL 32344
Field plantings of six native wildfl ower species were established at fi ve sites
in 1997 from seeds derived from local native populations (local ecotype) and from
seeds purchased from commercial sources outside of Florida (nonlocal ecotype).
The species were Cassia fasciculata (partridge-pea), Coreopsis lanceolata (lanceleaf coreopsis), Gaillardia pulchella (blanketfl ower), Ipomopsis rubra (standing
cypress), Rudbeckia hirta (black-eyed susan), and Salvia lyrata (lyre-leaf sage;
cancer weed). They were evaluated once per month from June to Oct. 1997. Plantings were maintained as follows: no supplemental fertilization; irrigation as needed
up until early April to ensure germination; no pesticides except to control fi reants
and weeds on the perimeter of the plantings; plots were handweeded as necessary.
It was clearly evident from these evaluations that the local ecotypes generally were
better adapted to north Florida conditions than were the nonlocal ecotypes. The
most noteworthy differences were as follows: 1) the local ecotypes of Rudbeckia
and Gaillardia had longer fl owering periods than their nonlocal counterparts, 2)
the local ecotype of Coreopsis fl owered profusely while fl owering of the nonlocal
ecotype was sparse, and 3) the local ecotypes of Coreopsis and Salvia had less
disease incidence than their nonlocal counterparts.
1
040
Identifying Native Prairie Grass Seedlings
Virginia A. Gaynor* and Mary Hockenberry Meyer; Dept. of Horticultural Science,
Univ. of Minnesota, St. Paul, MN 55108
There is great interest in prairie gardens and prairie restorations in the central
United States. Small prairie gardens are often established with plugs, but most
restorationists and landscape contractors use seed for large plantings. If initial
establishment is poor, restorations are often interseeded the second or third
season. However, to evaluate early establishment and determine if interseeding
is necessary, contractors must be able to identify native grasses in the seedling
and juvenile stages. In this study we investigated vegetative characteristics of
native prairie grass seedlings. Seven species of native prairie grass were grown
in the greenhouse: Andropogon gerardii (big bluestem), Sorghastrum nutans
(Indian grass), Panicum virgatum (switch grass), Schizachyrium scoparium (little
bluestem), Bouteloua curtipendula (sideoats grama), Elymus canadensis (Canada
wildrye), and Bromus kalmii (Kalmís brome). Every 2 to 3 weeks after germination,
seedlings were photographed, pressed, and mounted. Additional photographs
were taken through the dissecting scope at key stages of development. Ligules
HORTSCIENCE, VOL. 33(3), JUNE 1998
and auricles were found to be useful in distinguishing species, and our close-up
photographs highlight these structures. Hairiness and color were variable within
a species and could not be used reliably in identifi cation. A seedling identifi cation
key will be presented for the species studied.
041
Improved Fiber Pots for Container Nursery Production
Eric J. Biddinger*, Robert D. Berghage, and David J. Beattie; Dept.of Horticulture,
The Pennsylvania State Univ., University Park, PA 16802-4200
There is an increasing interest in the use of fi ber pots to grow containerized
nursery plants. Of particular interest is the ability to incorporate chemicals to
modify plant growth, reduce microbial decomposition, and alter fi ber structure.
Four perennial plants Forsythia ‘Spring Glory’, Baptisia australis, Ilex x meserveae
‘Blue Girl’, and Coreopsis rosea were grown in 2.3-L fi ber containers. Containers
were treated with Cu(OH)2 (Spin Out® , Griffi n Corp.) at 1500 or 3000 ppm, TCMBT
(Busan® 30WB fungicide, Buckman Lab.) at 1700 or 3400 ppm, and combinations
of Cu(OH)2 and TCMBT. Untreated plastic and untreated fi ber pots were used as
controls. Plants were grown in a commercial nursery in central Pennsylvania for
5 months during the 1997 growing season. Plants were harvested in the fall. Data
included: root penetration of pot walls, plant growth, pot strength, medium root
distribution, and root zone temperatures. Results with TCMBT were inconclusive.
However, Cu(OH)2-treated pots had fewer penetrating roots and were stronger.
Root zone temperatures in fi ber pots were lower.
042
“Cold-Trapping” in Retractable Roof Structures To Avoid Spring
Frost Damage of Container-grown Nursery Crops
S.E. Svenson*, N. Bell , and A. Henderson; Dept. of Horticulture, North Willamette
Research and Extension Center, Oregon State Univ., 15210 NE Miley Road, Aurora,
OR 97002-9543
Compared to fi lm-covered quonset structures typically used for unheated cold
protection of nursery crops in Oregon, unheated retractable roof structures can
provide cooler day temperatures (lower average daily temperature, ADT) in late
winter and early spring. Late winter and spring growth and fl owering of six nursery
genera (12 replicate blocks), and air temperatures, were studied when crops were
cold-protected in a fi lm-covered quonset structure compared to a retractable roof
cold protection structure operated using predawn “cold-trapping.” Compared
the quonset structures, retractable roof structures had lower daily maximum
temperatures, lower ADT, and similar daily minimum temperatures. Shoot growth
of all crops was delayed by 2 to 4 weeks, and fl owering of Rhododendron ‘Hino
Crimson’ was delayed by 4 weeks, in the retractable roof structures. Erica ‘Irish
Bells’ had symptoms of cold-damage and did not fl ower when protected in the
quonset structure, compared to no damage and full-fl owering when protected in the
retractable roof structure. Arctostaphylos had more leaf spots, and less growth in
the quonset structures compared to the retractable roof structures. Our hypothesis
is that the lower ADT in the retractable roof structures delays de-acclimation to
cold temperatures (delaying vegetative and fl ower budbreak), providing extended
protection to frost damage. Higher relative humidity and higher daylight temperatures in the quonset structures may leave the earlier new growth and fl owering of
nursery crops more susceptible to frost damage and disease infestations compared
to the daily vented and cooler retractable roof cold-protection structures.
42
POSTER SESSION 1E (Abstr. 043–047)
Growth/Development/Productivity—Fruit
043
Regrowth Performance of Apple Nursery Plants in Relation to
Reserve and Current Uptake of Nitrogen
Lailiang Cheng* and Leslie H. Fuchigami ; Dept. of Horticulture, ALS 4017, Oregon
State Univ., Corvallis, OR 97331
Gala/M26 apple plants previously treated with foliar urea (0%, 2%, and 4% )
were fertigated with or without 15N-depleted ammonium nitrate by using a modifi ed
Hoagland solution after transplanting in the spring. Plants with high N reserves
had signifi cantly greater growth than plants with low N reserves. More nitrogen
was remobilized for new shoot and leaf growth in plants with high N reserves
HORTSCIENCE, VOL. 33(3), JUNE 1998
than plants with low N reserves. The amount of reserve N used for new shoot
and leaf growth was not affected by current supply of nitrogen. There was no
signifi cant difference in the amount of nitrogen from current uptake used for new
shoot and leaf growth between low and high N reserve plants up to 80 days after
spring budbreak. The amount of N from current uptake for new shoot and leaf
growth was negligible at 20 days after budbreak. Plants with low N reserves were
more dependent on current uptake for sustaining new shoot and leaf growth and
maintaining their nitrogen status than plants with high N reserves. After 80 days
of growth, plants with low N reserves did not catch up with the plants with high
N reserves.
044
Influence of Initial Seedling Size and Rate of Nitrogen Fertilizer
on the Growth of Containerized Pecan Trees
Nolan Farace* and C.E. Johnson; Dept. of Horticulture, Louisiana State Univ.,
Baton Rouge, LA 70803
Pecan seedlings were randomly selected and divided into two lots according
to size. Seven rates and three sources of nitrogen based fertilizers were applied
four times starting on 6 May, 20 June, 4 July, and 15 Aug. Leachates were taken
3 weeks after each application. The pH range after the fi rst application ranged from
6.0 to 7.0. After the fourth the pH had dropped to a range of 5.0 to 6.0. The TDS
ranged from 0 to 6.0 mS after the fi rst application to a 2.1 to 0.5 mS after the last
application. Growth rates varied slightly among treatments. The average growth
rate among seedlings was only slightly affected by nitrogen fertilize rates. Within
12 weeks the average growth was 1.3 mm. There were only slight differences in
growth between the low and high rates of NH4• NO3 fertilizer. The growth rate
decreased somewhat in response to increased rates of application of Ca• NO3.
045
Effect of Four Training Systems on Growth and Productivity of
‘Cortland’/M. 9 EMLA Apple Trees
J.R. Schupp* and S.I. Koller; Highmoor Farm, Univ. of Maine, P.O. Box 179,
Monmouth, ME 04259-0179
‘Cortland’/ M.9 EMLA trees were planted in 1991 at 1.8 X 4.2-m spacing. The
trees were trained to one of four systems: 1) Vertical Axis; 2) Y trellis; 3) Solen; or
4) Palmette trellis. Tree survival was 86% for Palmette trees and approached 100%
for the other three systems. Annual yield and cumulative yield per tree of Vertical
Axis and Y trellis was twice that of Solen or Palmette. Tree vigor was sub-optimal
relative to planting distance in this study. Trunk cross- sectional area of Vertical Axis
trees was larger than that of trees trained to Solen or Palmette, while trees trained
to Y trellis were intermediate in trunk growth. Canopy volumes of Vertical Axis and
Y trellis trees were similar, and greater than that of Solen or Palmette trees. Fruit
size on Solen and Palmette trees was larger than that of Y trellis trees in 1995 and
1996, while fruit size on Vertical Axis trees was intermediate. Cumulative yield per
cubic meter of canopy volume was the same for all four systems, suggesting that
differences in productivity among systems were attributable to the effects of tree
training practices on tree size, not to differences among systems in precocity or
effi ciency. The low heading cut needed to establish the lowest tier of branches on
the Palmette system reduced tree vigor and in some cases, resulted in mortality.
The horizontal training of the primary branches of the Solen severely reduced tree
vigor. In this study, where tree vigor was sub-optimal due to rootstock selection,
the additional restrictions in tree growth resulting from restrictive training methods
resulted in a signifi cant loss in productivity.
046
M anaging Vegetative Growth of Apples with Prohexadione
Calcium can Influence Mid-season Spray Coverage
J.R. Evans*, J.A. Balles, L.H. Bennett, B.A. Brinkman, A.H. Harrell , and J.H. Choate;
BASF Corporation, Research Triangle Park, NC, 27709
Prohexadione calcium (BAS 125W or Apogee™) is a plant growth regulator
being developed to control vegetative growth in apples. Prohexadione calcium
acts within a plant by blocking the biosynthesis of growth-active gibberellin.
The result is decreased cell elongation; thus, reduced shoot length. Applications
of prohexadione calcium beginning when the apple trees have 2 to 15 cm of
new shoot growth signifi cantly reduce seasonal vegetative growth. Mid-season
measurements of air blast spray coverage using water-sensitive cards show that
trees previously treated with prohexadione calcium have greater spray coverage
within the tree canopy than untreated trees. Hence, more effi cient crop protection
451
can be expected in apple trees treated with prohexadione calcium.
047
Harvest Field Sizing as a Technique to Remove Undersize
French Prunes
Richard Buchner* , Seeley Mudd, Bruce Carroll and Mark Gilles; Univ. of California Cooperative Extension, Tehama County, P.O. Box 370, 1754 Walnut St.,
Red Bluff, CA 96080
Overall profi tability is a major goal in successful prune production and a major
component in any prune management system. Large prune crops in 1996 and
1997 have stimulated considerable interest in undersize fruit. Undersize prunes
currently have marginal value and may represent a net loss because of costs to haul,
dry, and to market order payments on low value prunes. One technique to control
delivery size is to fi eld size at harvest. Field sizing involves installing size-sorting
devices on harvesters, which allow small prunes to fall out while valuable fruit is
collected. Field sizing is considered a “risky” strategy because of the potential to
remove prunes with economic value. During the 1997 harvest, 21 infi eld harvest
sizing evaluations were made in prune orchards throughout Tehama county. The
fi rst evaluation occurred on 12 Aug. 1997, at the start of prune harvest. The fi nal
evaluation was done on 5 Sept. 1997, at the tail end of harvest. The objective
was to sample throughout the harvest period to test fi eld sizing under various
sugar, size, and fruit pressure scenarios. The test machine was 1-inch bar sizer.
Of the 21 sample dates, undersize fruit was clearly not marketable in 20 of the 21
samples. Discarded fruit averaged 133 dry count per pound. Only one sample out
of 21 may have had market value at 86 dry count per pound. Although small in
size, these prunes had very high sugar content contributing to their dry weight.
In this evaluation, a 1-inch bar sizer did a good job of separating fruit with and
without market value under the 1997 price schedule. As harvest date becomes
later and soluble solids increase, the chances of sorting out marketable prunes
also increases.
42
POSTER SESSION 1F (Abstr. 048–061)
Crop Physiology/Temperature Stress—
Cross-commodity
048
The Presence of Heat-shock Proteins in Sun-exposed and
Heat-treated Apple Fruit
Mark Ritenour* 1, Larry Schrader1, and Maurice Ku2; 1Tree Fruit Research and
Extension Center, WSU, Wenatchee, WA 98801; 2Botany Dept., WSU, Pullman,
WA 99164
Sunburn of apples is frequently a signifi cant cause of cullage in Washington
State. Some cultivars are more susceptible to sunburn than others. Further, apples
that have acclimated to full sunlight exposure in the fi eld (“sun”) have been
reported to be less likely to sunburn when exposed to full sunlight than apples
growing within the canopy (“shade”). We hypothesize that heat-shock proteins
(HSPs) might be involved in these differences in sunburn susceptibility. Western
blots of total protein extracts from apple peel identifi ed the presence of protein
recognized by antibodies raised against small HSPs (smHSPs) from different
plant species. SmHSPs in apple were very low or non-detectable in “shade”
fruit, but were relatively high in “sun” or heat-treated (4 h at 40 °C) “shade” fruit.
SmHSP accumulation in ‘Fuji’ apples could be detected after the fi rst hour of a
4-h heat treatment at 40 °C, and continued to increase over the next 8 to 10 h. The
smHSPs did not begin to decline even after the apples had been held for 48 h at
room temperature. Initial studies indicate that cultivars differ in smHSP content.
Results from biweekly samplings of several cultivars will be reported.
049
Temperature Effects during Endodormancy Induction on Subsequent Anthesis and Growth of Peach Trees
Schuyler D. Seeley*, Raymundo Rojas-Martinez, and James Frisby; Dept. of Plants,
Soils, and Biometerology, Utah State Univ., Logan, UT 84322-4820
Mature peach trees in pots were treated with nighttime temperatures of –3, 6,
12, and 18 °C for 16 h and a daytime temperature of 20 °C for 8 h until the leaves
452
abscised in the colder treatments. The trees were then chilled at 6 °C for 40 to 70
days. Trees were removed from chilling at 40, 50, 60, and 70 days and placed in
a 20 °C greenhouse under increasing daylength, spring conditions. Anthesis was
faster and shoot length increased with longer chilling treatments. Trees exposed
to –3 °C pretreatment fl owered and grew best with 40 days of chilling. However,
they did not fl ower faster or grow better than the other treatments with longer
chilling times. There was no difference in fl owering or growth between the 6 and
12 °C pretreatments. The 18 °C pretreatment resulted in slower fl owering and
very little growth after 40 and 50 days of chilling, but growth was comparable to
other treatments after 70 days of chilling.
050
Effects of Decreasing Temperature and Photoperiod on
Carbohydrate Reserve Accumulation and 14 C-Photosynthate
Partitioning in Apple
Z. Wang* 1, K. Huang2, H. Mahmoud2, and B. Quebedeaux2; 1USDA-ARS, Remote
Sensing and Modeling Lab., Beltsville, MD 20705; 2Dept. of Natural Resource
Sciences and Landscape Arch., Univ. of Maryland, College Park, MD 20742
Carbohydrate reserves are major substrates for cold hardiness and respiration
during winter and for early growth during the following season for most woody
plants. In apple, carbohydrate reserve accumulation occurs mainly in late summer
and autumn as temperature and photoperiod decrease. However, information on
the response of reserve carbohydrate accumulation and photosynthate partitioning into sorbitol, sucrose, and starch in apple to decreasing temperature and
photoperiod is limited. One-year-old ‘Gala’ apple plants were grown in controlled
environments at 26 °C and 16-h photoperiod for 50 d and then either remained in
26 °C/16 h or were subjected to a lower temperature and shorter photoperiod for
28 d that resulted in four treatments of 26 °C/16h (HT/LD), 26 °C/8h (HT/SD), 13
°C/16h (LT/LD), 13 °C/8h (LT/SD). Newly fi xed 14C-photosynthates and reserve
carbohydrates were analyzed in leaves, stems, and roots. Leaf photosynthesis
and plant growth parameters were also examined. The LT treatments inhibited
plant shoot growth and leaf initiation rates while SD treatments had little additive
effect. Plants with LD treatments had greater specifi c leaf weight, but decreased
photosynthetic rates compared to SD regimes. A decrease in temperature altered
partitioning of newly fi xed 14C-photosynthates into sorbitol, sucrose, and starch
and carbohydrate accumulation in various plant organs. Low temperature effects
were modifi ed by photoperiod.
051
The Influence of Temperature and Low Light on Fruit Set and
Chemical Thinning of Apple Trees
R.E. Byers*; Virginia Polytechnic Inst. and State Univ., Alson H. Smith, Jr. Agricultural Research and Extension Center, 595 Laurel Grove Road, Winchester,
VA 22602
Fruit trees grown in the eastern U.S. environment are typically exposed to low
light conditions from cloudy/rainy periods that can reduce PAR to 10% to 15% of
full sun for 2 to 3 days. To magnify or concentrate the effect of temperature during
low light stress, fruit trees were moved from the fi eld into total darkness for 2 to 4
days at various temperatures and then returned to the fi eld. This provided low light
stress while eliminating the need for treatments involving various levels of light
and temperature during the day on photosynthesis. To reduce transplanting shock,
bearing apple trees used were grown in the fi eld in 25-cm-diameter root bags and
were on M.27 rootstock. After initial fruit set (at about 15 mm fruit diameter) trees
were dug and transplanted into 5-gal buckets and moved for short periods of time
(2 to 4 days) into various dark environments or sprayed with various thinning
chemicals and placed in growth chambers at 5, 10, 16, and 21 °C in the dark.
Immediately after dark treatments, trees were returned to the fi eld and placed in the
original holes. In 1995, we found that Elstar/M.27 apple trees placed in the dark
for 3 or 4 days and returned to natural sunlight conditions abscised all of their
fruit at 21 °C dark temperature but were retained at 5 °C. In 1996, we found that
Braeburn/M.27 apple trees placed in the dark for 2 days and returned to natural
sunlight conditions abscised all of their fruit at 16 and 21 °C dark temperature, but
were retained if the dark period was 5 °C. These data indicated that the dark period
temperature was very important for fruit retention. In addition, trees sprayed with
Carbaryl+Accel 3 h before placing in the growth chambers caused the development
of more pigmy fruit at all temperatures. Pigmy fruit also appeared to be related to
the combined effects of digging trees, treating with Carbaryl + Accel, and colder
temperatures. In 1997, we found that Stayman/M.27 apple trees placed in the dark
for 2 days and returned to natural sunlight conditions abscised most of their fruit
HORTSCIENCE, VOL. 33(3), JUNE 1998
at 21 °C dark temperature, but were retained if the dark period was 5 °C. Fruit
thinning occurred at 10 and 16 °C. Additional fruit thinning was signifi cantly
promoted by Carbaryl or NAA + Regulaid over the range of temperatures (5 to
21 °C), but thinning appeared to be most promoted at 21 °C dark temperature.
Unexpectedly, ethephon caused fruit thinning at all temperatures from 5 to 21 °C,
and thinning did not appear to be affected by temperature (ethephon defruited all
trees at all temperatures). We suspect that higher dark temperatures caused either
higher respiration rates or higher natural ethylene production, which promoted
fruit abscission whether treated with a thinner or not. In one fi eld experiment,
Carbaryl sprays were applied at 2-h intervals beginning at 6 a.m. until 8 p.m. to
Empire/Mark trees. Similar fruit thinning occurred when applied at temperatures
ranging from 18 to 36 °C. These data suggest that no differences in thinning were
related to daytime temperature.
052
Effects of Soil Temperature and Drought on Root–Soil Respiration in Apple under Field Conditions
Liqin Wang*, David M. Eissenstat, and Dora E. Flores-Alva; Dept.of Horticulture,
The Pennsylvania State Univ., 103 Tyson Bldg., University Park, PA 168024200
Root respiration is very important to root effi ciency, root lifespan, and carbon
cycling in plant ecosystems. Yet, the effects of soil temperature and moisture on
root respiration are poorly understood, especially under fi eld conditions. In this
study, we manipulated soil temperature and moisture by six bearing ‘Red Chief’
Delicious/ M26 trees near State College, Pa. Soil temperature was elevated 5 °C at
5-cm depth using circulating hot water and stainless steel grids. Soil temperature
was monitored using thermocouples and a data logger, and soil moisture was
monitored using TDR. Root–soil respiration was determined by static trapping at
the soil surface. Heating was conducted from 8 May to 28 Oct. Drought was initiated on 21 Aug. and lasted 2 months. Root–soil respiration was lowest in spring
and increased from June to late August. After September, respiration decreased
until the experiment ended in November. Root-soil respiration was not correlated
with root length density. Heating enhanced root–soil respiration about 15% to
20% in spring (May) and 10% in summer (June–August). After the drought
treatment began, heating increased root-soil respiration about 42% in wet soil,
but did not infl uence respiration in dry soil. Heating accentuated the effect of the
drought treatment on soil moisture. After 2 months of no irrigation and no rain,
soil moisture was reduced 5% in unheated soil and 10% in heated soil. Drought
slowed root–soil respiration 17% in unheated soil and 36% in heated soil, mainly
because heating increased respiration in wet soil, but compared to the unheated
treatment, had no effect in dry soil.
053
Freezing Tolerance in Rhododendron and Its Association with
Dehydrin Expression
Chon C. Lim* 1, Stephen L. Krebs2, and Rajeev Arora1; 1Division of Plant and Soil
Sciences, West Virginia Univ., Morgantown, WV 26506; 2David G. Leach Research
Station of the Holden Arboretum, Madison, OH 44057
This study examines whether dehydrin expression in leaves is associated
with varying levels of cold hardiness among evergreen rhododendrons. Initially,
differences in leaf freezing tolerance (LFT) were determined within three groups
of plants: 1) a cultivar group; ‘Chionoides’ (CND), ‘Grumpy Yellow’ (GY), and
‘Vulcan’s Flame’ (VF) 2) a segregating F2 population derived from a super coldhardy (R. catawbiense) x less-hardy (R. fortunei) cross, and 3) juvenile seedlings
and mature plants of wild-collected R. maximum. LFTs in fully acclimated cultivars
corresponded with their USDA hardiness zone ratings— CND (zone 4, –32 °C)
GY (zone 7, –16 °C), and VF (zone 6, –19 °C). F2 segregation was characterized
by a continuous, normal distribution of LFT values, with groups of progeny at the
“tails” differing in their mean LFT by 20 °C. Juvenile seedlings of R. maximum
exhibited LFTs that were 12 °C lower than LFTs from mature plants. Western blots
of leaf proteins revealed a common 50-kDa dehydrin that accumulated during
cold acclimation in all three cultivars and appeared to be quantitatively associated
with LFTs. Isoelectric focusing of the 50-kDa Rhododendron dehydrin revealed
two isoforms (pI 5.5 and 6.5). The more acidic isoform was detected only in the
hardiest (CND) cultivar. Experiments are underway to examine qualitative and
quantitative expression of dehydrins and its association with LFT in the segregating
F2 population and in the group of R. maximum plants differing in physiological
age.
HORTSCIENCE, VOL. 33(3), JUNE 1998
054
Changes in Membrane Fatty Acids in Cold-acclimated Turfgrass
Jenith Cyril* 1, R.R. Duncan2 , and W.V. Baird1; 1Dept. of Horticulture, Poole
Agricultural Center, Clemson Univ., Clemson, SC 29634-0375; 2Univ. of Georgia,
Griffi n, GA 30223
Three genotypes of seashore paspalum, ‘PI 299042’, ‘Adalayd’, and ‘PI
509018-1’ considered to be cold-sensitive, intermediately cold-tolerant and
cold-tolerant, respectively, were analyzed to investigate the biochemical basis of
cold tolerance. The cultivars were acclimated to 8/4 °C day/night temperatures
and rhizomes nodes and crowns were harvested at 7-day intervals over the 4week experiment. Total lipid was extracted from these tissues, and the fatty acids
present in the lipid fraction were identifi ed by gas chromatography. Palmitic acid,
stearic acid, linoleic acid and linolenic acid were the major fatty acids present. In
cold acclimated tissues, the level of palmitic acid and stearic acid did not change
signifi cantly during the treatment period. There was a decrease in the level of
linoleic acid by the second week of cold treatment. The amount of linolenic acid
increased signifi cantly during the second week of cold treatment corresponding to
the decrease in linoleic acid. The change in the amount was signifi cantly greater
in ‘PI 509018-1’ than in ‘Adalayd’ or ‘PI 299042’. These results are similar to
what was found for cultivars of bermudagrass that differ in their cold-tolerance
phenotypes. Desaturases are enzymes involved in introducing the double bonds
into the fatty acid chains. Research is underway to characterize and clone the genes
encoding the Ω3, Ω6, and Ω9 desaturases, which may have an important role
in affecting the cold tolerance by altering the degree of membrane lipid fatty acid
saturation.
055
Winter Survival Evaluation of 172 Groundcovers in Northern
Illinois
A.M. Shirazi*, E.A. HedBorn, S.A. Mehaffey, and A.S. Merritt; The Morton Arboretum, 4100 Illinois Route 53 Lisle, IL 60532-1293
The winter hardiness of many groundcover cultivars in northern Illinois is
not well-known. This study was designed to evaluate the survival of 172 plants
used in the groundcover path at The Morton Arboretum. Once a month, from
Sept.1997 to Jan. 1998, the plants chosen for this study were visually evaluated
and their vitality rated on a scale of 1 to 5 (1 = alive, 5 = dead). All nine cultivars
of Euonymus fortunei remained virtually unchanged throughout the study period.
Among six cultivars of Hedera helix, only ‘Gold Heart’ showed minor damage in
November. Nine Heuchera were evaluated and all exhibited excellent resistance to
cold temperatures. While all the Pulmonarias studied showed some cold damage
by November, ‘Bielefeld Pink’, ‘Little Blue’, ‘Roy Davidson’, Pulmonaria longifolia
var. cevennensis, and Pulmonaria offi cinalis ‘Sissinghurst White’ fared the best for
the longest period of time. Five cultivars of Pachysandra terminalis were included
in this study. None had signifi cant damage until November, and then only rated a
“2.” Of the eight Ajuga evaluated, Ajuga pyramidalis ‘Metallica Crispa’, and Ajuga
reptans ‘Braunherz’, ‘Catlin’s Giant’, and ‘Gaiety’, exhibited the best cold resistance.
Four Polygonums varied widely in their response to cold temperatures, but all
showed signs of severe damage in November. Polygonum ‘Border Jewel’ exhibited
the best tolerance, rating a “1” in October, but in November it was given a rating
of “4.” Their recovery in spring will be compared.
056
Timing and Duration of the Critical Period in Tomatoes for
Sensitivity of Fruit and Seed Production to Heat Stress
Suguru Sato*, Mary Peet, and Randy Gardner; Dept. of Horticultural Science,
North Carolina State Univ., Raleigh, NC 27695-7609
Peet et al. (HortScience, 1997) reported that the period of greatest sensitivity
to heat stress for fruit and seed production in tomatoes (Lycopersicon esculentum
Mill., line NC8288) was before pollen release. However the exact duration and
timing of the sensitive period was not established. For the present study, 2 weeks
before opening of the fi rst fl ower, tomato plants grown at 28/22 °C or 32/26 °C
were treated under the opposite temperature treatment for periods of 0, 5, 10, or
15 days. After this time they were returned to the initial temperature treatments
constituting an imposition (32/26 °C) or relief (28/22 °C) of heat stress for varying
periods before fl ower opening. All fl owers were vibrated at anthesis and pedicels
tagged to record date of pollination. Subsequently, tagged fl owers (or pedicels,
in the case of aborted fl owers) were examined to determine if a fruit had set, and
453
if so, whether it contained seeds. For plants initially grown at low temperature,
as the pre-anthesis period of exposure to heat stress increased, the amount of
seeded fruit produced decreased. For plants initially grown at high temperatures,
a pre-anthesis period of relief from heat stress of at least 10 days was required
for production of any seeded fruit. Further, for an individual fl ower, that 10- to
15-day period of low temperatures had to occur during the developmental period
starting at least 15 days before fl ower opening and ending no sooner than 5 days
before fl ower opening.
057
Cowpea Seedling Response to Chilling Levels
Lurline M arsh* ; Cooperative Research, Lincoln Univ., Jefferson City, M O
65101
Controlled environment was used to simulate three chilling levels to assess
differences in seedling growth of four cowpeas (Vigna unguiculata L.Walp),
IT82E-18, IT82E-16, Pinkeye Purple Hull and MN13. Genotypes chilled at 14/10
°C, 15/10 °C, and 16/10 °C, (day/night) for 7 days after planting (DAP) did not
differ in percent seedling emergence, which showed a maximum of 6% . At 14
DAP, genotypes differed in percent emergence at the 15/10 °C and 16/10 °C
temperatures, with ranges of 34% to 51% and 61% to 86% , respectively. By 21
DAP, cowpeas at these two chilling levels had ranges of 57% to 90% and 79%
to 94% emergence, respectively, and showed signifi cant differences. At the two
lower chilling regimes, the radicles failed to develop secondary roots and the
seed coats remained attached to some of the primary leaves. These were generally
chlorotic except for IT82E-16 at 15/10 °C. Genotypes at the highest chilling level
developed secondary roots and green primary leaves, which were twice the size
of those at 15/10 °C. When plants from the three chilling regimes were removed
to a warm greenhouse, the leaves became green and secondary roots developed
within a week. These results indicate that root development was more sensitive
to the chilling temperatures than seedling emergence.
058
A Study on the Recovery Following Freeze–Thaw Injury in Onion
and Chrysanthemum
Yiwei Jiang*, Chon C. Lim, and Rajeev Arora; Division of Plant and Soil Sciences,
West Virginia Univ., Morgantown, WV 26506
Onion (Allium cepa L. cv Sweet Sandwich) and Chrysanthemum (Dendranthema grandifl ora ‘Sunny Denise’) tissues were used to investigate protein
changes associated with recovery from freeze–thaw injury. Medium-sized onions
were slowly frozen to either –4 or –9 °C, subsequently thawed, and divided in
two halves. One half was used immediately for ion leakage (IL) measurements
and total and microsomal protein extraction, whereas the other half was allowed
to recover at 6 to 8 °C in the dark for 4 to 5 days. Chrysanthemum leaves were
frozen to –3.75 °C, and allowed to recover fi rst at 6 to 8 °C in the dark (1 d)
and then under 12-h photoperiod at 18 °C (3–4 d). Results indicate a 1.4- and
2.5-fold higher IL, compared to control, from onion tissues frozen to –4 or –9
°C, respectively. IL in –4 °C-treated tissues was the same as respective control
following recovery; however, it was further enhanced to 3.6-fold in –9 °C-treated
samples. Chrysanthemum leaf tissue exhibited a 1.6-fold increase in ion leakage following injury, but completely recovered to control levels after 4 to 5 d.
SDS-PAGE profi les revealed an absence of a 25-kDa microsomal protein in the
injured onion tissues but, its up regulation during recovery only in reversibly
injured tissues. Data also indicated an accumulation of 36-kDa soluble protein in
chrysanthemum leaf tissues during recovery. Experiments are underway to further
characterize these protein changes.
059
Changes in Non-structural Carbohydrates in Tulip Bulb Scales
during Cold Treatment and Greenhouse Forcing
Anil P. Ranwala* , Beth Hardin, and William B. Miller; Dept. of Horticulture,
Clemson Univ., Clemson, SC 29634
The energy and carbon needs for early shoot growth in tulips are mainly
provided by reserve carbohydrates in bulbs. The cold-treatment of bulbs before
greenhouse forcing enhances the breakdown and remobilization of reserve carbohydrates in bulb scales, and is necessary for proper shoot growth and fl owering
454
in tulips. Tulip bulbs are known to contain both starch and fructans as reserve
carbohydrates. We evaluated several extraction solvents, including ethanol and
distilled water, and several extraction temperatures to accurately determine the
amounts of different types of non-structural carbohydrates in tulip bulb scales.
Extraction with distilled water resulted in excessive solubilization of starch. For example, extraction at 70 °C solubilized more than 80% of starch to glucan polymers.
On the other hand, 80% ethanol at 70 °C extracted all soluble sugars including
fructans with no apparent solubilization of starch. The changes in non-structural
carbohydrates in the outermost bulb scale of tulip (Tulipa gesneriana L. ‘Frankfurt’)
during 12 weeks of cooling at 8.8 °C followed by 5 weeks of greenhouse forcing
were determined. Starch was the major carbohydrate in bulb scales consisting
of ≈70% of the dry weight at the beginning of cold treatment. Starch content
per scale decreased slightly during cold treatment, but rapidly after transferring
to greenhouse. Sucrose and soluble fructan content per scale increased during
cold treatment, then decreased after transferring to greenhouse. Glucose content
per scale remained fairly constant during cooling and greenhouse forcing, while
fructose content increased in the greenhouse.
060
Enhancement of Floral Initiation and Bud Development by Chilling of Root Cuttings in Primocane-fruiting Blackberries
Jose Lopez-Medina*, James N. Moore, and Kyung-S. Kim; Dept. of Horticulture
and Dept. of Plant Pathology, Univ. of Arkansas, Fayetteville, AR 72701
In previous studies we found that primocane-fruiting blackberries (PFB) form
fl ower buds soon after the plants start suckering from root cuttings collected in
winter or early spring. Research was carried out to test if the same phenomenon
holds true in summer-collected plant material. Root cuttings of A-1836, APF-13
and NC194 PFB were dug from the fi eld on 31 July 1997 and stored in plastic
bags at 2 °C for 32 days. On 1 Sept., freshly dug root cuttings along with the
cold-treated ones were stuck in 3.8-L plastic pots, which were kept in a lath house
for 4 weeks and then moved to a greenhouse under natural daylength. Signifi cant
differences occurred for plant emergence between chilled and non-chilled plants
(16 days vs. 31 days, respectively). Transition from vegetative to fl oral phase was
fi rst observed in cold-treated A-1836 and APF-13 at fi ve-node growth stage, with
fl oral structures clearly evident in both selections at seven nodes of growth 45
days after planting. Chilled APF-13 and A-1836 started to bloom on 26 Nov. and
5 Dec., respectively. The fi rst fruit of APF-13 were picked on 10 Jan. 1998. By
this date, cold-treated NC194 and all non-cold-treated plants remained stunted
with rosetted leaves, showing no signs of fl oral initiation. These fi ndings present
evidence that low-temperature exposure prior to shoot emergence greatly promotes
fl owering and fruiting in PFB. The results might have applicability in blackberry
culture under greenhouse conditions.
061
Microscopic Examination of Chilling Injury Symptoms in Ethanol-treated Cucumber Seedling Roots
Windy A. Boyd* and Paul H. Jennings; Dept. of Horticulture, Forestry and Recreation Resources, Kansas State Univ., Manhattan, KS 66506
Cucumber seedlings were germinated for 24 h at 25 °C and half were immersed
in a 500 mM ethanol solution for 2 h. After rinsing, seedlings were chilled for 96
h at 2 °C. Control and ethanol-treated samples were taken for light and electron
microscopy immediately before and after chilling, and after re-warming for 24
and 72 h. Preliminary experiments revealed visual chilling symptoms such as
pinching of the root in a region just above the root tip. This region was excised
under a microscope, fi xed, and mounted for microscopic observations. The cortical
cells of ethanol-treated seedlings before chilling appeared to be irregular in shape
with irregular edges, and some epidermal damage was evident. Chilling caused
much more epidermal damage in the control seedlings when compared to the
ethanol-treated seedlings. After chilling, cortical cells in the control seedlings were
observed to be irregularly shaped while those treated with ethanol had round cells.
Upon re-warming, control seedlings exhibited increasing epidermal damage with
broken cell walls, while ethanol-treated seedlings exhibited more differentiation
in the stele.
HORTSCIENCE, VOL. 33(3), JUNE 1998
42
POSTER SESSION 1G (Abstr. 062–064)
Water Use and Application—Vegetable
Crops
062
Plum Tomato Cultivar Evaluation Using Microirrigation
T.K. Howe* and A.A. Csizinszky; Gulf Coast Research & Education Ctr., IFAS,
Univ. of Florida, 5007 60th St. E., Bradenton, FL 34203 USA
Plum tomato (Lycopersicon esculentum Mill.) cultivars were evaluated in
a full-bed mulch, microirrigation management system. Yield and horticultural
characteristics were assessed for four entries, ‘Marina’, ‘Spectrum 882’, ‘Supra’,
and ‘Veronica’, during Spring and Fall 1997. Harvested marketable fruit were
separated by size into extra large, large, medium, and small categories. Spring:
Total marketable yields from three harvests combining all fruit sizes ranged from
46.6 t• ha–1 for ‘Supra’ to 57.1 t• ha–1 for ‘Veronica’. ‘Veronica’ produced signifi cantly higher total yield than the other three cultivars. There were no signifi cant
differences among the cultivars in yield of extra large (range: 2.3 to 2.9 t• ha–1) or
large (range: 11.4 to 13.0 t• ha–1) fruit. Only ‘Veronica’ (22.7 t• ha–1) and ‘Supra’
(18.9 t• ha–1) were signifi cantly different from each other in the yield of medium
fruit. Veronica’ produced signifi cantly more small fruit (19.2 t• ha–1) than any other
cultivar. Cull fruit yields ranged from 11.1 t• ha–1 for ‘Veronica’ to 16.9 t• ha–1 for
‘Supra’, which was signifi cantly greater than the other cultivars. Fall: Total marketable yields from six harvests were not signifi cantly different among the cultivars,
ranging from 22.0 t• ha–1 for ‘Spectrum 882’ to 31.4 t• ha–1 for ‘Marina’. Extra large
fruit yields ranged from 2.0 t• ha–1 for ‘Supra’ to 6.3 t• ha–1 for ‘Marina’, the only
cultivars signifi cantly different from each other. There were no signifi cant differences among the cultivars in yields of large (range: 7.9 to 13.8 t• ha–1), medium
(range: 8.7 to 13.8 t• ha–1) or small fruit (range: 2.7 to 3.4 t• ha–1). Cull fruit yields
ranged from 37.2 t• ha–1 for ‘Supra’ to 47.4 t• ha–1 for ‘Veronica’. Cuticle cracking
(rain check), black shoulder and nipple-tipped blossom ends were the primary
defects in the fall. ‘Marina’ and ‘Veronica’ produced signifi cantly more cull fruit
than either ‘Supra’ or ‘Spectrum 882’.
063
Study of the Regular and High Application of Water with Drip
Irrigation in Asparagus
Adán Fimbres Fontes*, Raúl Leonel Grijalva Contreras, and Manuel de Jesus
Valenzuela Ruiz; Apdo. Postal No. 125, Caborca, Sonora, Mexico 83600
Asparagus production in the past years has been increasing very rapidly
and now totals 5000 ha. The main problem in this zone is the depletion of the
aquifer (22 m in static level) and it is important to use of this resource rationally.
During 1997, a experiment of drip irrigation in asparagus (fi rst year planted)
was conducted. Three treatments were applied: 100% , 133% , and 166% of the
evaporation from a pan evaporation type A. The crop coeffi cient (Kc) applied was
60% . The results of the statistical analysis indicated that the best treatment was
166% (246.13 cm of total water applied) with a height of plant of 1.17 m, and the
lowest height of plant was for the 100% (0.87 m) with 121.97 cm of total water
applied.
064
WITHDRAWN
42
POSTER SESSION 1H (Abstr. 065–074)
Crop Physiology: Chemical/Developmental/Metabolic—Cross-commodity
065
Distribution of Seasonally Expressed Storage Proteins in Different-aged Shoots and Roots of ‘Loring’ Peach
M. Wisniewski * 1, R. Webb1, and L. Fuchigami 2; 1USDA-ARS, Kearneysville, WV
HORTSCIENCE, VOL. 33(3), JUNE 1998
25430, 2Dept. of Horticulture, Oregon State Univ., Corvallis, OR 97331
During autumnal leaf senescence, leaf nitrogen is translocated to other sites
for storage, especially bark tissues. By defi nition, proteins that accumulate in
large amounts in winter and are absent in summer are called storage proteins.
Previously, we have characterized three proteins in peach bark tissues that fall into
this category. Little is known, however, about the distribution of these proteins
in different-aged tissues or whether they have any function other than to act as
a nitrogen reserve. The present study characterizes the seasonal distribution of
a 60-, 19-, and 16-kDa protein in bark tissues of current-year, 1-year-old, scaffold, and trunk bark, and 4- to 5-year-old roots of ‘Loring’ peach. Verifi cation
of protein identity was based on molecular mass and reaction with antibodies
directed against each specifi c protein. Distribution of the proteins was variable.
The greatest amount of all three proteins was present in current-year and 1-year-old
shoots. These tissues also showed the greatest seasonal variation in the amount
of protein present. The 16-kDa protein was present only in the youngest shoots,
whereas the 19-kDa was present in all tissues examined. The 60-kDa protein was
absent in root tissue. The 60-kDa protein has been identifi ed as a dehydrin, and
the 16-kDa protein appears to be related to defensins. The identity of the 19-kDa
protein has not been confi rmed. The amino acid composition of the three proteins
will be presented and the implications of these results on management practices
will be discussed.
066
Endogenous Rhythm in Flowers of Stone Fruits
Zsuzsanna Orosz-Kovacs* , Miklos Faust, Attila Borhidi , Laszlo Gy. Szabo, and
Agnes Farkas; Janus Pannonius Univ., Pecs, H-7624 Hungary; U.S Dept. of
Agriculture, Belstville, MD 20705
It is known that the success of pollination of entomogam, autosterile stone
fruits depends on attractiveness of fl owers, pollen, and nectar production. In
addition to this a complete harmony is necessary between the pollen donor and
receiver in the volume of intrafl oral secretion, chemical composition, and timing
of appearance of attractants. Our investigation shows that the daily production
in stone fruits follows a set pattern. The 4 x 6-h rhythm (secretion four times,
6 h apart per day) usually indicates homogamy, whereas a 2 x 12 periodicity
indicates dichogamy. Successful pollination is unlikely when endogen rhythm
of two cultivars is asynchronized.
067
Floral Scent Production in Antirrhinum majus
Natalie Bennett* and Natalia Dudareva; Dept. of Horticulture and Landscape
Architecture. Purdue Univ., West Lafayette IN 47907
Despite the economic importance of fl oral scent for plant reproduction, little
is known about the molecular mechanisms of fl oral scent production. Floral scent
is often a complex mixture of low-molecular-weight compounds that are mainly
distributed within three groups: fatty acid derivatives, benzenoids, and isoprenoids.
Esters of such compounds are the most widespread type. Headspace analysis in
combination with gas chromatography and mass spectrometry of volatiles emitted from snapdragon fl owers revealed that methyl benzoate is one of the major
components of the ‘Maryland True Pink’ genotype. The activity of novel enzyme
S-adenosyl- L-methionine:benzoic acid carboxyl methyltransferase (BAMT), which
catalyzes the methyl esterifi cation of benzoic acid, was analyzed in different fl oral
tissues and at different stages of fl ower development. It has been found that
BAMT activity is highest in petals, both upper and lower lobes, and very low or
absent in other fl oral tissues and leaves. No detectable BAMT activity was found
in fl ower buds 1 day before fl ower opening. During the lifespan of the fl ower the
level of BAMT activity in petal tissue increases gradually and remains high in old
fl owers.
068
A Leaf Bud Development Scale for Rabbiteye Blueberry
D. Scott NeSmith * 1, Gerard Krewer 2, and Jeffrey G. Williamson 3; 1Dept. of
Horticulture, Georgia Station, Griffi n, GA 30223; 2Dept. of Horticulture, Rural
Development Center, Tifton, GA 31793; 3Horticultural Sciences Dept., Univ. of
Florida, Gainesville, FL 32611
Crop vegetative and reproductive development are frequently divided into
stages to describe progression of development. Such a description is useful in
denoting developmental differences between cultivars, for making crop management decisions based on growth stages, and for clear communication among
455
individuals concerned with research, management, and production of the crop.
We have developed such a scale for leaf bud development in rabbiteye blueberry
(Vaccinium ashei Reade). Our scale has six stages briefl y described as follows: 1)
dormant bud; 2) early green tip; 3) late green tip; 4) unfolding stage; 5) mouse-ear
stage; 6) fully opened bud. Categorizing buds in this manner has proven useful in
comparing rates of leaf development between cultivars and in response to winter
chilling. The stages appear to be relevant to highbush blueberries (V. corymbosum)
as well.
069
Clone and Growth Season Effects on Seven Carbohydrate-related Components and Their Correlation in Sweetpotato
Yu Xiang* 1 and Wanda W. Collins2; 1Dept. of Horticultural Science, Box 7609,
North Carolina State Univ., Raleigh, NC 27695; 2International Potato Center (CIP),
Apartado 1558, Lima, Peru
Approximately 50% of the world’s total sweetpotato output is used for producing starch or starch-derived products and for animal feeding. Knowledge of
cultivar and environmental effects on carbohydrate-related components and the
correlation among these components is essential for improving the raw products
utilization and providing an expanded market for sweetpotato. The objective of this
study was to investigate the variation of amylose content and ß-amylase activity as
well as their correlation with other starch-related components. Dry matter, starch,
total sugar, amylose and phosphate content, ß-amylase activity, and raw starch
digestibility were evaluated for 20 advanced selections in 2 years. Signifi cant
clone variation was detected for all seven components. Signifi cant growth season
effects were found for amylose and sugar content, ß-amylase activity, and starch
digestibility. ß-amylase activity has a negative correlation with starch (r = –0.57,
P ≤ 0.001) and dry matter (r = –0.39, P ≤ 0.05). Starch digestibility has a negative
correlation with amylose (r = –0.37, P ≤ 0.05) and phosphate content (r = –0.35,
P ≤ 0.05 ).
070
Jasmonic Acid and Environments Increase Steroidal Glycoalkaloid Biosynthesis in Solanum chacoense
Zhenbang Chen, N. Jean Flickinger, and A. Raymond Miller*; Dept. of Horticulture
and Crop Science, The Ohio State Univ. /OARDC Wooster, OH 44691 USA
Steroidal glycoalkaloids in Solanum chacoense have been found to deter
feeding by herbivores, especially to Colorado potato beetle. The steroidal glycoalkaloids of S. chacoense include solanine (chaconine), leptinines, and leptines,
which yield solanidine, leptinidine, and acetylleptinidine, respectively, upon acid
hydrolysis. To understand the regulation of their biosynthesis, tissue culture
plants were grown on MS media containing jasmonic acid, methyl jasmonate, or
arachidonic acid at different levels. After 1 month in culture, 100 µM jasmonic
acid stimulated solanidine, leptinidine, and acetylleptinidine accumulation 3- to
10-fold compared to control. Methyl jasmonate at 100 µM also induced solanidine
accumulation, but not leptinidine and acetylleptinidine. Arachidonic acid had
no effect on solanidine, leptinidine, and acetylletptinidine levels. Furthermore,
leptinidine and acetylleptinidine levels increased 5-fold and 100-fold, respectively,
after plants were transferred from culture in vitro to soil; meanwhile, solanidine
level decreased slightly. Solanidine, leptinidine and acetylleptinidine from plants
in vitro showed no changes during the same period. Our results indicated that
jasmonic acid and environmental factors play important roles in the biosynthesis
of steroidal glycoalkaloids in S. chacoense.
071
Effect of Antitranspirant and Fertilization on Flowering, Fruiting, and Biomass Production in ‘Early Girl’ Tomato Plants
Sanliang Gu* 1, Leslie H. Fuchigami 2, Lailiang Cheng2, Sung H. Guak2, and Charles
C.H. Shin3; 1Dept. of Fruit Science, Southwest Missouri State Univ., Research
Campus, Mountain Grove, MO 65711; 2Dept. of Horticulture, Oregon State Univ.,
ALS 4017, Corvallis, OR 97331; 3Great Lake Chemical Corp., P.O. Box 2200,
Highway 52, N.W., West Lafayette, IN 47906
Seedling plugs of ‘Early Girl’ tomato plants (Lycopersicon esculentum Mill.)
were potted in peatmoss and perlite (60:40% by volume) medium, fertilized
with 8, 16, 24, or 32 g NutriCote Total controlled-release fertilizer (type 100,
13N–5.67P–10.79K plus micronutrients) per pot (2.81 L), and treated with 0% ,
2.5% , 5% , or 7.5% antitranspirant GLK-8924 solution, at the four true-leaf stage.
Plants were tipped at the second infl orescence and laterals were removed upon
456
emergence. Flowering of both clusters were advanced by higher fertilization rates
and depressed by GLK-8924. Increasing rates of fertilization increased fl ower
and fruit number of the lower cluster and fruit set of upper cluster. GLK-8924
had no effect on fl ower number, fruit number, and fruit set. Fertilization increased
the biomass production of all plant parts while GLK-8924 reduced the biomass
production of leaves and fruit only. Root and stem biomass was not infl uenced
by GLK-8924. The effect of GLK-8924 on fruit dry weight was dependent on the
position of the cluster and GLK-8924 concentration. Fertilization did not interact
with GLK-8924 to infl uence fl owering, fruiting, and biomass production.
072
Regional Differences in Plant Development, Water Relations,
and Chloroplast DNA of Hard Maples
Rolston St. Hilaire* and William R. Graves; Dept. of Horticulture, Iowa State
Univ., Ames, IA 50011
Principal component analysis of foliar traits of hard maples (Acer saccharum
Marsh. and Acer nigrum Michx. f.) near 43°N latitude clustered data into two
populations composed of trees from different geographical regions. Seedlings
from these two regions, and a third, geographically intermediate region, were
grown in a greenhouse for 2 years with two irrigation frequencies to assess
regional differences in plant development and water relations. Leaves from the
most western region (west of 93°W longitude) had the highest specifi c mass (5.97
mg/cm2), trichome frequency (531/cm2), and stomate frequency (628/cm2). Across
regions, plants irrigated frequently had more stomates (596/cm 2) than plants irrigated sparsely (483/cm2). Traits similar across regions but higher with frequent
irrigation included surface area and mass of lamina, shoot-to-root ratio, the ratio
of lamina area to stem xylem diameter, and leaf water potential. Sparse irrigation
caused a comparatively large decrease in stomatal conductance of plants from
the most western region, and pressure-volume analysis showed no regional or
irrigation effects on leaf osmotic potential at full turgor. Identical banding patterns
resulted when Hinf I digested the PCR-amplifi ed trnL-trnF intergenic spacer region
of chloroplast DNA from each region; work with the rpL16 and ndhA introns is
proceeding. Trichome frequency on abaxial leaf surfaces, which differs regionally
both in nature and in controlled environments, is the most consistent character
we have measured for discerning populations.
073
Quantitative Seasonal Changes in Gross Turfgrass Morphometry
Steven C. Wiest*; Dept. HFRR. Kansas State Univ., Manhattan, KS 66506
Photographs of turfgrass canopies were taken throughout Spring, Summer,
and Fall 1997 at a height of 1.3 m using a 28-mm lens and fi lm sensitive to either
visible or infrared light. The species evaluated were warm-season Bermudagrass,
buffalograss, zoysiagrass, and cool-season tall fescue. Color spectra of digitized
photographs were obtained by fi rst separating the hue, saturation, and intensity
components of the color photo into separate 8-bit (256 gray levels) fi les. Calculations were then made on the basis of those color components. The infrared
photos were scanned as 8-bit fi les without conversion. Greenup was indicated by a
decrease in the frequency of hues between 0 and 50° (reds, browns, and yellows)
and an increase in the frequency of hues between 50 and 100° (green and yellowgreen). It is well-known that canopy refl ectance in the green wavelengths is primarily a function of chlorophyll density, whereas refl ectance of near-infrared radiation
is indicative more of cell structure. More near-infrared radiation is refl ected from
leaf surfaces than is green radiation, and less infrared is absorbed by internal leaf
structures than is visible radiation. Thus, it is possible to approximate canopy leaf
area ratios by using both visible and near-infrared photographic measurements.
Quantitative changes in visible and near-infrared canopy refl ectances, leaf area
ratios, and other morphometric parameters will be presented as a function of time
of the year and species. The results demonstrate the utility of using this relatively
inexpensive procedure to obtain quantitative measurements as a substitute for,
or in conjunction with, subjective visual ratings of turfgrass plots.
074
Dormancy-breaking Studies on Echinacea angustifolia
Ali O. Sari , Mario R. Morales*, and James E. Simon; New Crops and Plant Products
Lab., Dept. of Horticulture & LA, Purdue Univ., West Lafayette, IN 47907
Echinacea is a medicinal plant native to North America. It was used extensively
by native Americans in the treatment of their ailments. It is presently one of the
HORTSCIENCE, VOL. 33(3), JUNE 1998
most popular medicinal plants in the United States. Its popularity has created
a large market demand for the roots and foliage of the plant. The gathering of
echinacea from the wild is leading to the reduction of native populations and
the destruction of its genetic diversity. Cultivation of medicinal echinaceas is
hindered by a low seed germination. Dormancy breaking studies were done on
freshly harvested seeds of Echinacea angustifolia. Seed lots were placed under
light at a constant temperature of 25 °C and at alternate temperatures of 25/15 °C
for 14/10 h, respectively. Germination was more rapid and uniform and percent
germination higher at 25 °C than at 25/15 °C. Seed tap-water soaking, dry heating, and sharp heating alteration did not increase germination. The application of
1.0 mM ethephon (2-chloroethylphosphoric acid) increased seed germination to
94% at 25 °C and 86% at 25/15 °C. Untreated seeds gave 65% germination at
25 °C and 11% at 25/15 °C. The application of 2500 mg• L–1 and 3500 mg• L–1
of GA to dry seeds and 2500 mg• L–1 to seeds that have been soaked under tap
water and then dried increased germination to 82% , 83% , and 83% at 25 °C and
64% , 78% , and 64% at 25/15 °C, respectively.
42
POSTER SESSION 1I (Abstr. 075–078)
Postharvest Physiology—Tropical Fruits
075
Response of the Mamey Sapote (Pouteria sapota L. ) Fruit to
Storage
Juan C. Diaz-Perez*, S. Bautista, and R. Villanueva; Dept. of Biotechnology, Center
for the Development of Biotic Products, National Polytechnic Inst., Carretera
Yautepec-Jojutla Km 8, Yautepec, Morelos 62730, Mexico
The mamey sapote is a fruit highly appreciated by its sweet fl avor. Although
this crop has been cultivated in tropical America for several centuries, there is still
little horticultural information about it. The fruit is very perishable and postharvest
losses are usually large. The objective was to evaluate the postharvest changes
in fruit quality under storage conditions. Fruit grown in Morelos, Mexico, were
harvested when there was a color change from green to pink in the tissue just
below the fruit cortex. Fruit were stored at 10 °C or kept at 20 °C (65% RH) or
ambient temperature (Mean daily temperature = 27 °C) for 24 days or until fruit
deteriorated. After storage at 10 °C, fruit were kept at 20 °C to allow for fruit
ripening. Fruit kept at 27 °C ripened 3 days after harvest, while those at 20 °C
ripened 5 days after harvest. Fruit at 10 °C showed little physical or chemical
changes over the storage period. Ripening included fruit softening, a change in
pulp color from a yellow or pale pink to an intense pink color, and an increase in
SSC. No change in fruit cortex color was detected as ripening progressed. Ripe
fruit showed a 30% to 35% of SSC, and a fi rmness (resistance to penetration)
of 7 N. In overripe fruit, pulp color turned brown. Fruit stored at 10 °C and then
ripened at 20 °C showed an irregular ripening, with portions of the fruit with a
high fi rmness and others with a low fi rmness. This irregular ripening was more
severe on fruit stored at 10 °C for 14 days than those stored for 7 days. This
disorder was probably a result of chilling injury.
076
Fresh-cut Mango Fruit Slices
Arunya Limbanyen1*, Jeffrey K. Brecht1, Steven A. Sargent1, and Jerry A. Bartz2;
1
Horticultural Sciences and 2Plant Pathology Depts., Univ. of Florida, Gainesville,
FL 32611
Preparation and handling procedures for fresh-cut mango slices were developed using ‘Tommy Atkins’, ‘Haden’, and ‘Palmer’ mangoes. Fruit with yellow fl esh
color (no green color remaining) were optimum maturity for fresh-cut in terms of
maintenance of acceptable appearance, texture, and taste; riper fruit developed
fl esh breakdown and more browning. Postharvest life of fresh-cut mango at 5 °C
was 8 to 10 d with no evidence of chilling injury and was limited by fl esh browning
and loss of fi rmness. Respiration rates ranged from 32 to 40 mg CO2/kg per hr
and ethylene production was typically ≤0.1 µl • kg–1• hr–1. The SSC changed little
during storage, while pH varied from 3.5 to 4.8 and TA typically declined by 30%
to 40% . Peeling to a depth of at least 2 mm and trimming fl esh near the stem scar
was necessary to minimize browning. Imported fruit that had been heat-treated for
insect quarantine showed more severe browning than Florida fruit that had not
been heat-treated. Preparation in aseptic conditions and dipping fruit in a 100
HORTSCIENCE, VOL. 33(3), JUNE 1998
ppm NaOCl solution at pH 7 before and after peeling protected against decay during storage but dipping in chlorine after slicing without removal of excess liquid
resulted in fl esh translucency and breakdown. Dipping in 1% CaCl 2 solution had
no effect on fl esh fi rmness (Instron) or browning. Storage in an unvented plastic
clamshell container, which developed an atmosphere of 2.25% CO2 plus 19% O2,
did not improve shelf life, but a MA of 10% CO2 plus 10% O2 was subjectively
judged to slow browning and softening and resulted in no off fl avor compared to
air storage.
077
Quality of ‘Solo’ Papaya after Irradiation Treatment and Ripening
W.R. Miller* and R.E. McDonald; U.S. Dept. of Agriculture, ARS, U.S. Horticultural
Research Lab., 2120 Camden Rd., Orlando, FL 32803
Papaya (Carica papaya L.) imported into the United States must be certifi ed free of infestation by unwanted pests. Irradiation has been suggested as a
potential quarantine treatment for papaya. A study was conducted to characterize
fruit quality and condition at two stages of maturity and exposure to irradiation
treatment. ‘Solo’ papaya grown in Belize was transported in refrigerated sea van
containers to Florida. Fruit showing no yellow color or one-quarter yellow color
were irradiated at 0.6 kGy, held at 25 °C until ripe, and evaluated for quality and
condition attributes. Green peel papaya treated with irradiation developed peel
injury and had uneven ripening of pulp tissue following storage. Development of
peel or pulp color was not affected by irradiation. Fruit should show one-quarter
yellow peel color to avoid irradiation-induced peel damage. Irradiation may be a
viable quarantine treatment for papaya that can be applied to fruit at the source of
offshore production or on arrival at a facility in the United States.
078
Influence of Storage Period on the Postharvest Characteristics
of Five Mango (Mangifera indica L. ) Cultivars
Judith Zambrano*, Willian Materano, and Sagrario Briceño; Departamento de
Biología y Química, Núcleo Universitario Rafael Rangel, Universidad de Los
Andes, Trujillo, Venezuela
Five mangos cultivars (Mangifera indica L., ‘Palmer’, ‘Keitt’, ‘Spring Field’,
‘Kent’, and ‘Anderson’) were harvested at the preclimacteric stage. Fruits were
selected for study that were uniform and free of visual defects and stored for 18
days at 10 °C, 90% to 95 % RH. Fruits were evaluated every 3 days for pulp
and peel color, total soluble solids, titratable acidity, ascorbic acid content,and
total and reducing sugars. Pulp and peel color parameters (lightness, hue, and
chroma) were signifi cantly different among cultivars. The soluble solids content,
ascorbic acid, and starch content changed signifi cantly during storage and were
signifi cantly different among cultivars. Total and reducing sugars content did not
change signifi cantly after 10 days of storage. Results of this study indicated that
these fi ve mango cultivars have good storage potential.
42
POSTER SESSION 1J (Abstr. 079–087)
Postharvest Physiology & Food Science—
Vegetable Crops
079
‘Betasweet’, Carrot Designed for Flavor, Nutrition, and
Health
Leonard M. Pike*, Vegetable Improvement Center, 1500 Research Parkway, Suite
120, College Station, TX 77843-2119
‘BetaSweet’ is a new “designer” carrot that was conceived as a research
project with the objective to create a new high-quality vegetable with unique
characteristics. The gene responsible for purple or maroon color in carrots is a
natural one and has been around for many years. Carrot breeders have discarded
carrots that occasionally segregated to this color because orange has been the
preferred traditional color. In 1989, three carrots grown from Brazilian seed were
observed to have a blotchy maroon color mixed with the normal orange. Within
two generations of breeding effort, I had obtained a few carrot roots with nearcomplete maroon exterior color and orange interior. The contrast of orange and
457
maroon was very attractive in carrots cut as coins or sticks. The maroon and
orange color would serve as the perfect way to identify and promote this new
variety. Several additional generations were required using extensive laboratory
testing for low terpenoids (strong carrot fl avors), high sugars, high carotene, and
crispy texture. Thousands of carrot roots were analyzed and selected for those
qualities and for the dark maroon exterior and orange interior colors. The few best
for those characteristics were intercrossed, and re-selected for their adaptation
when grown under Texas climatic conditions.
080
Carotenoid, Tocopherol, and Ascorbate Variability in Cruciferous Vegetables
A.C. Kurilich* 1, G.J. Tsau2, L. Howard2, A. Brown1, B.P. Klein2, E.H. Jeffery2, M.
Kushad1, M.A. Wallig4, and J.A. Juvik1; Depts. of 1Natural Resources and Environmental Sciences, 2Food Science and Human Nutrition, and 3Vet. Pathobiology,
Univ. of Illinois, Urbana, IL 61801
Antioxidants have been associated with reduced risk of cardiovascular disease
and several types of cancer. Recent studies indicate that cruciferous vegetables
contain high levels of these antioxidants. We assayed the edible portions of 52
broccoli and 13 cabbage, kale, caulifl ower, and Brussels sprouts genotypes to
determine variability of α-carotene, β-carotene, α-tocopherol, γ-tocopherol, and
ascorbate within and between varieties of Brassica oleracea. Emphasis was placed
on broccoli due to its economic importance and consumer preference. Samples
of each genotype in replicated trials were harvested at fresh-market stage, frozen
immediately in liquid nitrogen, and placed in –80 °C. HPLC with an amine column
was used to measure ascorbate in fresh, frozen samples. Tissue for carotenoid
and tocopherol analysis was freeze-dried prior to extraction. Carotenoid and
tocopherol concentrations were simultaneously measured using a reverse-phase
HPLC system developed in our laboratory. Results indicate that there is substantial
variability both within and between varieties. Kale had the highest levels of these
compounds, followed by broccoli and Brussels Sprouts with intermediate levels,
then by cabbage and caulifl ower which were relatively poor sources. Based on dry
weight, broccoli heads ranged (in mg/g) from 0–2.9, 23–94, 24–222, and 2-–5
for α-carotene, β-carotene, α-tocopherol, and γ-tocopherol, respectively. The
range of ascorbate was 54–120 mg/100 g fresh weight. These results contradict
the general perception that all broccoli lines are equally benefi cial in potential
disease prevention. The information gained from this study can be used to help
consumers select foods that promote a healthy lifestyle and in breeding programs
to develop new germplasm that will enhance the antioxidant potential of our food
supply.
081
M ethyl Jasmonate Inhibits Postharvest Sprouting of Radishes
Chien Y. Wang*; Horticultural Crops Quality Lab., Plant Sciences Inst., USDA–
ARS, Beltsville, MD 20705-2350
Treatment of topped radishes (Raphanus sativus L., cv. Cherry Belle) with
methyl jasmonate was effective in inhibiting postharvest sprouting of new leaves
and the growth of roots. Radishes were trimmed to 10-mm tops and dipped in
various methyl jasmonate suspensions for 3 min. After storage at 15 °C for 7 days,
the growths of new leaves were 26, 22, 7, 3, and 1 mm in 0, 10–5, 10–4, 10–3, or
2 x 10–3 M methyl jasmonate-treated radishes, respectively. The lengths of root
growth were also reduced by methyl jasmonate particularly at higher concentrations. These treatments also substantially reduced weight loss possibly as a
secondary effect. Fumigation with methyl jasmonate vapor in enclosed containers
was also effective in inhibiting the sprouting of leaves and root growth, but to
a lesser extent than dipping treatments. Radishes stored at 0 °C did not show
any new growth of leaves or roots, and therefore were not affected by the methyl
jasmonate treatments.
082
Factors Affecting Seed Coat Yellowing of Pinto Beans
Muharrem Ergun*, E.T. Paparozzi, D. Nuland, D.P. Coyne, and D. Smith; Univ. of
Nebraska, Lincoln, NE 68583-0724
The pinto bean breeding line 94-4 (Phaseolus vulgaris L.) showed seed coat
yellowing in on-farm fi eld trials in Nebraska in 1996. After reviewing weather
data, sprinkler irrigation appeared to be one of the cultural factors involved with
increase in seed coat yellowing. Cultural conditions were again investigated in
458
1997 in on-farm trials. In one test half of the NE 94-4 plants were cut and combined
promptly while the other half of the cut plants were left on the ground, rained
upon, and combined later. Seed from the pods of former and latter treatments were
compared for degree of seed coat yellowing. Yellowing was recorded visually by
determining percentage of the yellow area on a bean seed. The seed from the pods
of the cut wetted plants showed more discoloration than seed from the plants that
were not rained on. In another experiment two or four samples (40 g each) were
taken from each of seven cultivars as well as NE 94-4 to determine degree of yellow discoloration of seed. The percent seed coat yellowing of the varieties/line
was as follows: ‘Apache’ 12.5% , ‘Bill Z’ 14.9% , ‘Buckskin’ 20.7% , ‘Chase’ 9.2% ,
‘NE-94-4’ 54.1% , ‘179’ 48% , ‘Vision’ 35.5% , ‘Winchester’ 10% . Results of pigment extraction and simulated irrigation experiments will be presented in order
to better explain the cause of pinto seed coat yellowing.
083
Changes in Sensory Quality of Minimally Processed Cantaloupe
Stored in Controlled Atmospheres
Silvina I. Portela and Marita I. Cantwell*; Dept. of Vegetable Crops, Univ. of
California, Davis, CA 95616
The effects of a range of controlled atmospheres (CA) on sensory quality and
acetaldehyde and ethanol concentrations in minimally processed cantaloupe melon
were studied. Cylinders (1.8 diam x 3.5–4.0 cm) were prepared from cantaloupe
melons cv. Durango harvested at commercial maturity. Pieces were stored in air
or six CA (1.5 and 3% O2, air + 7.5 or 15% CO2, and 3% O2 + 7.5 or 15% CO2)
for 15 days at 5 °C. After 9 days of storage, the pieces stored at 5 °C were fi rm,
had high chroma values and visual quality and aroma scores, and low decay and
off-odor scores. Elevated CO2 concentrations reduced microbial counts and the
combination of CO2 with 3% O2 provided additional control. All CA treatments
with CO2 maintained visual quality above the limits of salability at 15 days, while
quality of air-stored pieces was poor. The same CA also reduced loss of typical
cantaloupe aroma and development of off-odors. Acetaldehyde concentrations
increased after 9 days, but then declined. Ethanol levels increased linearly with
time in pieces stored in low O2 alone or with CO2. Pieces stored in CA had higher
soluble solids than those stored in air. Pieces prepared with a sharp borer maintained visual quality scores longer than those prepared with a blunt borer due to
the development of surface translucency and color changes. The sharpness of
the borers did not affect the development of decay nor the loss of characteristic
aroma.
084
Low Temperatures and High CO2 Atmospheres Best Maintain
the Quality of Fresh-cut Jicama (Pachyrhizus erosus)
M. Cantwell*, E.N. Aquino-Bolaños, E. Mercado-Silva, and G. Peiser; Dept. of
Vegetable Crops, Univ. of California, Davis, CA 95616 USA; Depto. Investigación
y Posgrado en Alimentos, Universidad Autónoma de Querétaro, Querétaro,
Mexico
The jicama is a chilling-sensitive specialty root vegetable used fresh for its
crisp sweet-starchy pulp. Our objective was to evaluate a range of storage temperatures and controlled atmospheres potentially useful to preserve the quality of
minimally processed jicama. Jicama root pulp was cut into 1.8 x 4-cm cylinders,
washed in chlorinated water, drained, and stored in glass containers at a range of
temperatures from 0 to 15 °C in air, or at 5 and 10 °C in controlled atmospheres
(0.3, 3, and 21% O2 with 0, 5% , 10% , or 20% CO2). Pieces were evaluated after
0, 4, 8, 12, or 16 days for visual quality, color, texture, and composition (soluble
solids, ethanol, acetaldehyde). Total aerobic plate counts were determined on
samples from some atmospheres. At temperatures >5 °C, browning was the most
signifi cant cause of quality loss. High CO2 atmospheres retarded the development
of brown discoloration at 10 °C. During storage at 0 or 5 °C in air, quality loss
was principally due to yeast and bacterial growth. The 10% CO2 atmospheres
helped maintain the white color and crisp texture of the pieces and retarded microbial growth. Atmospheres with 20% CO2 damaged jicama stored longer than
8 days. Atmospheres of 3% O2 or air with 10% CO2 resulted in acetaldehyde and
ethanol concentrations 4 and >10 times those of air-stored pieces after 8 days
at 5 °C. Although the jicama root is chilling-sensitive, our results demonstrate
that the quality of the minimally processed product is best maintained with low
temperatures in combination with high CO2 atmospheres.
HORTSCIENCE, VOL. 33(3), JUNE 1998
085
Changes in Lipid Peroxidation and Antioxidant Status in Ripening Muskmelon (Cucumis melo var. reticulatus) Fruit
Patrick J. Conner* and Timothy J Ng; Dept. of Natural Resource Sciences &
Landscape Architecture, Plant Science Bldg., Univ. of Maryland, College Park,
MD 20742
Muskmelons are perishable fl eshy fruits with a shelf life of less than 14 days.
This short timespan is a serious limitation to marketing of the fruits and reduces
the profi tability of the crop. Variation exists within and between melon types for
postharvest storage ability, indicating a breeding program aimed at introducing
longer storage times into muskmelon might be successful. However, there is a
fundamental lack of knowledge of the underlying physiological processes that
determine longer storage ability. Disruption of cellular membranes appears to be
a persistent feature of plant senescence. Melon fruit tissues show a progressive
decrease of membrane integrity, as measured by membrane permeability, as the
fruit matures. Loss of membrane integrity may hasten tissue breakdown due to a
loss of cellular compartmentalization and altered expression of membrane-bound
enzymes. This project examines melon fruit during their development and postharvest storage. Fruit were collected at 20, 30, and 40 days post-anthesis, and after
10 days of storage. Fruit tissue was examined for evidence of lipid peroxidation
which may contribute to the loss of membrane integrity. In addition status of the
key antioxidants glutathione (GSH), ascorbate, and vitamin E was assayed to
determine the possible breakdown sight of the cellular protection system. This
information may be directly useful in providing selection criteria for a breeding
program aimed at increasing muskmelon postharvest storage life.
086
Curing Influences Sugar M etabolizing Enzyme Activity in
Sweetpotato
Yuehe Huang*, David H. Picha, Charles E. Johnson, and Anthony W. Kilili ; Dept.
of Horticulture, 137 J.C. Miller Hall, Baton Rouge, LA 70803 USA
Sweetpotato roots (‘Beauregard’, ‘Hernandez’, and LSU breeding line 9496)
were cured (30 °C and 90% RH) for 10 days immediately after harvest to determine
the effect of curing on several sugar-metabolizing enzymes. Free sugars and activities of invertase, sucrose synthase (SS), and sucrose phosphate synthetase (SPS)
were assayed. Total sugars for the three genotypes ranged from 132.5 to 177.9
mg sugar/g DW at harvest, and from 162.3 to 204.3 mg sugar/g DW after curing.
Enzyme activity at harvest averaged over the three genotypes ranged from: 154
to 251 mol sucrose DW/h for invertase; 18.6 to 23.1 mol sucrose DW/h for SS,
and 7.4 to 15.7 mol sucrose DW/hr for SPS. Enzyme activity after curing averaged
over the three genotypes ranged from: 251 to 288 mol sucrose DW/h for invertase;
20.3 to 25.8 mol sucrose DW/h for SS, and 11.3 to 17.3 mol sucrose DW/h for
SPS. The increase in invertase activity during curing was highest in ‘Hernandez’
and lowest in the breeding line 9496. The increase in invertase activity correlated
to the increase in reducing sugar content for ‘Hernandez’ and ‘Beauregard’. Curing
also shifted the pH optima of invertase in ‘Hernandez’ from pH 5.2 to 7.6.
087
Water-absorbent Packet Beneficial to Fresh-cut Honeydews
Jin-He Bai * and Alley E. Watada; USDA/ARS, Bldg. 002, Beltsville, MD 207052350
Fluid accumulation and moisture condensation were of a concern on the
quality of fresh-cut honeydews in polymeric fi lm-wrapped containers; thus, the
effect of a water-absorbent packet in the container was evaluated. Honeydew cubes
were placed in plastic trays with and without water-absorbent packet and sealed
with polymeric fi lm, which was either left intact or perforated with a needle. The
samples were stored at 5 °C and visual quality score, color, texture (shear force)
soluble solids, pH, and microbial count were determined after 4, 8, and 14 days
of storage. Honeydew cubes in perforated fi lm packages without the absorbent
became unsalable on day 4, while those with a water-absorbent packet had salable
quality on day 8 and were unsalable by day 14. Main detriment in salability was
development of water-soaked lesions and deteriorated condition. There were less
water-soaked lesions in cubes held in sealed fi lm packages with or without an
absorbent packet than in perforated fi lm packages with an absorbent packet. Tissue
breakdown occurred earlier in sealed packages without an absorbent packet than in
packages with an absorbent packet. The absorbent packet retarded the decreasing
Hunter ‘L’ value, increasing hue angle (a/b), softening (shear force), and increasing
pH. Sealed fi lm retarded changes in color and in mesophilic bacteria, yeast, and
HORTSCIENCE, VOL. 33(3), JUNE 1998
mold population.. The oxygen in sealed packages decreased to 10% and carbon
dioxide increased to 6% by day 14, which was not harmful to the tissue. These
results indicate that the a water-absorbent packet was helpful in maintaining quality
of honeydew cubes held in containers with sealed or perforated fi lm.
42
POSTER SESSION 1K (Abstr. 088–094)
Crop Production—Small Fruit/Viticulture
088
Protected Culture Systems for Strawberry Production
Fumiomi Takeda*, Paul R. Adler, and D. Michael Glenn, USDA-ARS, Appalachian
Fruit Research Station, 45 Wiltshire Road, Kearneysville, WV 25430
Strawberry plants (cvs. Camarosa, Chandler, Sweet Charlie, Primetime,
Jewel, and Tribute) were grown in soilless culture systems in a greenhouse
from October to May. Fresh-dug and runner-tip Aplug® plants were transplanted
into two systems: vertically stacked pots (24 plants/m 2) containing perlite and
horizontal nutrient fi lm technique troughs (13 plants/m2). Plants were fertigated
continuously with recirculating nutrient solution. In a 7-month production cycle,
the plug plants bloomed earlier and produced more fruit during the fi rst month of
harvest (December) than the fresh-dug plants. Higher yields from plug plants were
a result of more fruit numbers and not larger fruit size. Fruit production averaged
6.0 and 3.5 kg/m2 in the trough and pot systems, respectively. The vertical growing system allows greater plant densities, but light intensity reaching the plants
in the lower sections of the tower can be less than 20% of levels measured at the
top. Establishment costs of protected culture systems are higher, but production
is earlier and labor costs are typically reduced. Greenhouse hydroponic culture
systems could extend the winter strawberry production to more northern locations.
089
Strawberry Waiting-bed Plants: A Valid Alternative to Increase
Early and Total Yields in Subtropical Regions
Daniel S. Kirschbaum* 1, Javier Honorato2, and Daniel J. Cantliffe1; 1Horticultural
Sciences Dept., Univ. of Florida, Gainesville, FL 32611-0690; 2INTA EEA Famailla,
CC 11. Famailla-4132, Tucuman, Argentina
Strawberry (Fragaria xananassa Duch.) production in subtropical areas is
characterized by a low late-fall and early winter fruit yield, a time when the value
of the crop is the highest of the season. Under this context, the objective of the
present study was to evaluate the feasibility of waiting-bed plants for late fall
and early winter production in order to increase early and total fruit yields in the
Argentine sub-tropic. Plants of the cultivar ‘Chandler’ produced in a waiting-bed
(WB), at high-latitude (HL), high-altitude (HA), or low-altitude (LA) were compared
at two locations in Tucuman, NW Argentina: Famailla (1995, experiment 1; 1996,
experiment 2) and Lules (1995, experiment 3). Total production from WB plants
was 41% higher than from HA plants in experiment 1. Total production from WB
plants was 83 % and 53 % greater than from HL plants and LA plants, respectively, in experiment 2. Early season fruit production was greater in WB (241% )
than HL plants in experiment 2. In experiment 3, early fruit production from WB
plants was greater than HL, HA, and LA, by 573, 177, and 158% , respectively. The
number of marketable fruit from WB plants was larger than in the other treatments
(139-231% ). WB percentages of marketable fruit were above 90% . The results
suggest that WB plants could be considered as an alternative to HL, HA, and LA
plants to improve strawberry production and yield distribution in South American
subtropical regions.
090
Weed Seed Banks in Established Strawberry Fields
Faye Propsom* and Emily Hoover, Dept. of Horticultural Science, Univ. of Minnesota, St. Paul, MN 55108
Weed control in strawberries, either in a new planting or one that is established,
is a major source of problems for growers in Minnesota. To control weeds, growers
need to know which weeds are a problem, which weeds are deleterious, and which
weeds have the potential to become a problem. Weeds present, soil type, and weed
seed bank information are needed in order to predict potential weed problems.
With different weed control practices applied between and within the rows, we
459
assumed weed seed bank populations would vary. In addition, we were interested
in seeing if the seed banks differed between soil types and individual farmer’s
cultural practices. Soil samples were collected from 13 commercial strawberry
fi elds located around the Twin Cities metro area. In 1996, samples were taken after
renovation and before mulch was applied. In 1997, they were taken after mulch
was removed and prior to renovation. The soil samples for each date, treatment,
and farm were dried, and organic matter was separated from inorganic. The weed
seeds were removed from the remaining organic matter, identifi ed and counted.
Soil types and cultural practices were used to compare the differences among the
farms.
091
Influence of Cover Crop on Soil Quality in Strawberry
Jillene Summers* 1, Gail Nonnecke1, Cynthia Cambardella2, Richard Schultz3, and
Thomas Isenhart3; 1Dept. of Horticulture, Iowa State Univ., 2USDA, National Soil
Tilth Laboratory; 3Dept. of Forestry, Iowa State Univ., Ames, IA 50011
Traditional cover crops, such as perennial ryegrass (Lolium perenne), and
sorghum-sudan grass (Sorghum sudanense), commonly are used in rotation
with strawberry in the midwestern United States to improve soil quality and
suppress weeds. The objective of the fi eld study was to investigate the effects of
various cover crops on soil quality and weed populations. The experiment was
established in 1996 at the Iowa State Univ. Horticulture Station, Ames, in plots that
previously were planted continuously in strawberry for 10 years. Nine treatments
were arranged in a randomized complete-block design with three replications.
Treatments included cover crops of Indian grass (Sorghastrum avenaceum),
switch grass (Panicum virgatum), big bluestem (Andropogon gerardii), black-eyed
susan (Rudbeckia hirta), marigold (Tagetes erecta ‘Crackerjack’), sorghum-sudan
grass, perennial ryegrass, strawberry (Fragaria xananassa ‘Honeoye’), and bare
soil (control). Of the prairie plants, Andropogon gerardii was the most diffi cult
to establish and thus had the highest percentage weed cover. Macroaggregate
mass of the soil at 0- to 15-cm depth was least in the bare-soil treatment and in
the other annual-plant treatment, Tagetes erecta ‘Crackerjack’.
092
Effect of Root-zone Temperature on Strawberry Growth and
Development
Melita Marion Biela* 1, Gail R. Nonnecke1, William R. Graves1, and Harry T. Horner2;
1
Dept. of Horticulture and 2Dept. of Botany, Iowa State Univ., Ames, IA 50011
Root-zone temperature (RZT) effects were studied to determine physiological
changes on whole-plant and microscopic levels of strawberry (Fragaria xananassa)
growth and development. A greenhouse experiment was conducted in 1997 with
‘Tristar’ day-neutral strawberry using a randomized complete-block design with
three RZT treatments (23, 29, and 35 °C) and four replications. The total number
of fl owers was less in plants subjected to 35 °C. Total weight of fruit yield was
highest at 29 °C and least at 23 °C, due possibly to later fruit development. Fresh
weight was highest in plants grown at 23 and 29 °C. Dry weight analysis showed
that root and leaf growth were inhibited at 35 °C. Throughout the duration of the
experiment, transpiration rates were lower in plants subjected to 35 °C. In general,
plants grown under RZT of 29 °C had more optimal vegetative and reproductive
growth than those grown under 23 and 35 °C.
093
Effect of Inoculum Level on Response of Strawberry Fruit to
Anthracnose Fruit Rot
Joel L. Shuman* and James R. Ballington; Dept. of Horticultural Science, Box
7609, North Carolina State Univ., Raleigh, NC 27695-7609
In North Carolina, anthracnose fruit rot of strawberry (Fragaria x ananassa
Duch.) is caused by the fungus Colletotrichum acutatum Simmonds. Little is
known about the mechanisms of fi eld resistance of fruits to anthracnose. It appears
that resistance of various plant parts including runners, crowns, and foliage is
not always correlated with resistance of fruit. Resistance of fruit may be simply
overwhelmed by excessive fungal conidia. Is there a threshold level of inoculum
and does this threshold vary for fruit of different cultivars? The objective of this
study was to determine the effect of inoculum level on the response of seven
strawberry cultivars/breeding lines to a single C. acutatum (CA-1) isolate. The
experimental design was a split-plot with fi ve levels of inoculum (0, 1 x 103, 1 x
104, 1 x 105, and 1x106 conidia/ml) as the whole plot and seven cultivars/breeding
lines (‘Apollo’, ‘Chandler’, ‘Camerosa’, ‘Pelican’, ‘Sweet Charley’, NCH 95-173, and
NCR 94-08) as the subplots with three replicates. The experiment was conducted
460
in a growth chamber at the Southeastern Plant Evironment Laboratory at North
Carolina State Univ. Mature, green fruit and fruit turning red were inoculated with
conidia. Lesion diameter, percent diseased tissue, and fruit weight were determined
daily. The seven cultivars/breeding lines had differing levels of fruit rot resistance
and fruit fi rmness/skin toughness.
094
Strawberry Cultivar Performance and Susceptibility to Tarnished Plant Bug Injury
D.T. Handley*, M.A. Schupp, and J.F. Dill; Univ. of Maine Cooperative Extension,
Monmouth, ME 04259
Twelve strawberry cultivars established in matted row plots in 1993 were
treated with insecticides for tarnished plant bug or left untreated for the 1994,
1995, and 1996 seasons. ‘Honeoye’, ‘Cavendish’, and ‘Oka’ had the highest yields
of marketable fruit. ‘Jewel’, ‘Chambly’, and ‘Kent’ had lower, but acceptable, yields.
‘Lateglow’, ‘Blomidon’, ‘Seneca, NY1424’, ‘Settler’, and ‘Governor Simcoe’ had
lower yields than other varieties. Tarnished plant bug populations were very low
during the 1994 and 1996 seasons, and thus feeding pressure may have been
too low for any differences in susceptibility between varieties to be expressed. In
1995, when tarnished plant bug feeding pressure was greatest, ‘Oka’, ‘Cavendish’,
and ‘Honeoye’ had the lowest injury levels. ‘Kent’ and ‘Lateglow’ had the highest
levels of injury. Insecticide sprays signifi cantly reduced the percent of injured fruit
for most cultivars, but did not signifi cantly increase the weight of marketable fruit
harvested. This is due to injury being most prevalent on lower order, and thus
smaller, fruit. Cultivars that produced high yields, had low injury levels, and had
the least difference between sprayed and unsprayed treatments are most likely to
have resistance to tarnished plant bug injury. ‘Oka’, ‘Cavendish’, and ‘Honeoye’
were the most promising cultivars in this regard.
42
POSTER SESSION 1L (Abstr. 095–108)
Breeding & Genetics—Genetics/Cell and
Tissue Culture
095
In Vitro Shoot Regeneration from Callus Derived from Marubakaido Apple Rootstock under Different Aluminium Concentrations
Marisa F. de Oliveira1, Gerson R. de L. Fortes* 2, and João B. da Silva3; 1Faculty
of Agriculture, FAEM/UFPEL, P.O. Box 343; 96001-970 Pelotas, RS, Brazil; 2EMBRAPA/CPACT P.O.Box 403 96001-970 Pelotas, RS, Brazil; 3Faculty of Agriculture,
Inst. of Physic and Mathmatic 96001-970 Pelotas, RS, Brazil
The aim of this work was to evaluate the organogenesis of Marubakaido
apple rootstock under different aluminium concentratons. The explants were calli
derived from apple internodes treated with either 2,4-dichlorophenoxyacetic acid
or pichloram at 0.5 and 1.0 µM and under fi ve different aluminium concentrations
(0 , 5 , 10 , 15 , 20 mg/L). These calli were then treated with aluminium at 0, 5
, 10, 15, and 20 mg/L. It was observed shoot regeneration only for those calli
previously treated with pichloram. There were no signifi cant difference among the
aluminium concentrations.
096
In Ovule Culture in Peach: Embryo Perforation, Duration of
Culture, and M edia Effects on Seed Growth and Seedling
Survival
David H. Byrne* 1, Marissa Rizzo2, Katrina Porter1, David Ramming3, Natalie Anderson1, and Jonathan Sinclair1; 1Dept. of Horticultural Sciences, Texas A& M Univ.,
College Station, TX 77843-2133 USA; 2Centro Ricerche Produzioni Vegetali, Via
Vicinale Monticino 1969, 47020 Diegaro di Cesena (FO), Italy; 3Horticulture Crops
Research Lab., USDA/ARS, 2021 South Peach Ave., Fresno, CA 93727 USA
In the breeding of early maturing peach and nectarine cultivars, the use of
embryo rescue techniques is invaluable since the embryos of these materials
are not mature by the time the fruit is mature. Thus the seed does not germinate
under normal stratifi cation/germination procedures. Peach embryos between 3
and 6 mm in length were cultured in ovule on WPM under treatments that varied
HORTSCIENCE, VOL. 33(3), JUNE 1998
in sucrose levels (4% and 6% ),the use of vitamins (casein hydrosylate, ascorbic
acid, and panthotenic acid) and hormones (BAP and GA3), and the duration
of the treatment (7, 14, 21, and 28 days). A fi ve-seed sample was measured
for length, fresh weight, and dry weight before and after treatment. The treated
embryos were then cultured in a embryo rescue media (WPM, 3% sucrose) at 5
°C for 45 days in the dark and then brought out to room temperature under lights
(12-h day). After 2 to 4 weeks the embryos were rated for germination, size, and
root number. Embryo perforation treatment resulted in larger embryos but not in
better germination than the smaller unperforated embryos. Among the embryos
cultured without perforation, the addition of vitamins and hormones caused the
production of plants with more roots and shoots but not necessarily with better
survival. Both levels of sucrose worked reasonable well. As the time of in ovule
treatment increased, embryo growth and plant survival was enhanced.
097
Shoot Regeneration and Reduction of Contamination of Date
Palm (Phoenix dactylifera L. )
1
2 1
Essam A. Mawlood* and Karim H. Al-Juboory ; P.O.Box 540, Bahla 612, Oman;
Univ. of Illinois, Dept. of Natural Resources and Environmental Sciences, 1201
West Gregory Drive, Urbana IL 61801 USA
This experiment was conducted at the Zaffarania Experimental Station in Baghdad, Iraq. The seeds of date palm cultivars ‘Zahdy’ and ‘Khastawy’ were cultured
on Murashige and Skoog (MS) medium containing 0.5 mg/L NAA and 2.0 mg/L
BA. Seeds were treated with 10, 20, 30, and 40 pulses of excimer laser radiation.
The results indicate that these seeds exhibited signifi cantly less contamination
than control. The highest percentage germination for both cultivars was obtained
with explants trerated with 40 pulses excimer laser radiation. Compared to other
treatments, the shoot regeneration was greater with seeds from the ‘Khastawy’
cultivar. Scanning electron microscope showed regeneration occurred about 5
months after.
2
098
Genetic Modification of ‘Royal Gala’ Apple by Agrobacteriummediated Transformation and Colchicine-induced Mutation
Qingzhong Liu1, Freddi Hammerschlag* 1, and Rengong Meng2; 1USDA/ARS Fruit
Laboratory, Beltsville, MD 20705; 2USDA/ARS HCRL, Corvallis, OR 97300
As part of a program to develop transgenic Malus x domestica Borkh. cv.
Royal Gala with improved disease resistance, transgenic diploid and tetraploid
plants with cecropin MB39 gene were regenerated. Transgenic diploid plants were
obtained from etiolated internodal explants by Agrobacterium tumefaciens-mediated transformation using the plasmid binary vector pGV containing a chimeric
gene consisting of a secretory sequence from barley-amylase joined to a modifi ed
cecropin MB39 coding sequence and placed under control of wound-inducible
osmotin promoter from tobacco. The integration of the cecropin gene into apple
genome was confi rmed by Southern blot analysis. The transformation effi ciency
was 1.5% . Both non- and transgenic tetraploid plants were produced by cocultivating leaf explants from wild type and transgenic diploid shoots with colchicine
at 25 mg/L in apple regeneration medium containing 10 µM TDZ. Twenty-two
tetraploid lines were obtained from 90 explants. Flow cytometry was used for
ploidy determination. The tetraploid plants were distinguishable from the diploid
on morphological as well as cytogenetic grounds. Both the transgenic diploid
and tetraploid plants are now being evaluated for resistance to fi reblight.
099
Transformation of ‘Bosc’ Pear (Pyrus communis L. ) with the
rolC Gene from Agrobacterium rhizogenes and Characterization
of Transgenic Plants
Ralph Scorza* , Richard L. Bell, Chinnathambi Srinivasan, and Kevin Webb;
USDA-ARS Appalachian Fruit Research Station, 45 Wiltshire Rd., Kearneysville,
WV 25430
Pear production in the United States relies on a few major cultivars, including
‘Bosc’. While there is a need for new cultivars, genetic improvement of the existing
major cultivars through genetic transformation could have a major impact on the
industry. We have developed a system for regeneration and transformation of pear.
While the major objective of the transformation project is to improve resistance
to fi re blight (Erwinia amylovora) in major pear cultivars, tree size control is also
one of the objectives in the genetic improvement of pear that may be approached
through transformation. Traditionally, manipulation of tree size and vigor in estab-
HORTSCIENCE, VOL. 33(3), JUNE 1998
lished cultivars has been achieved through the use of size-controlling rootstocks.
There are no completely satisfactory size-controlling rootstocks for pear. Genetic
transformation provides an approach to developing new size-controlling rootstocks
and also to directly affect the growth of the transgenic scion cultivar using genes
that affect plant growth such as the rolC gene isolated from the bacterium A.
rhizogenes, the causal agent of “hairy root” disease. This gene has been shown
to alter growth and development in a number of plant species. To investigate the
potential utility of the rolC gene in altering the growth of pear trees, ‘Bosc’ pear
was transformed with A. tumefaciens EHA101 carrying a pGA482-based plasmid
containing the NPTII and GUS genes, and the rolC gene under the control of its
native promoter. Four clones were isolated that were kanamycin-resistant and
GUS-positive. PCR assays and DNA blots indicated the presence of the rolC gene
in these clones. Each transgenic clone has been multiplied in vitro and planted
in the greenhouse where transgene expression and plant growth are being evaluated.
100
Development of an Agrobacterium-mediated Transformation
System for ‘Beurre Bosc’ Pear
Richard L. Bell*, Ralph Scorza, and Chinnathambi Srinivasan; USDA, ARS, Appalachian Fruit Research Station, 45 Wiltshire Road, Kearneysville, WV 25430
An effi cient regeneration/transformation system was developed for ‘Beurre
Bosc’ pear. Young leaves were harvested from in vitro shoots proliferated on a
medium containing MS basal salts and 5 BAP, 0.5 µM IBA, and 0.6M3. Shoot
regeneration was optimized using a modifi cation of the medium of Chevreau and
Leblay (1993). Explants were cultured on shoot induction medium contained 10
µM TDZ and 1 µM IBA for 4 weeks in the dark, and then transfered to a similar,
but auxinless, regeneration medium until shoots developed, usually after an additional 4 to 8 weeks. Leaf tissues were transformed by co-cultivation for 3 days
with Agrobacterium tumefaciens EHA101 carrying a pGA482 plasmid containing
NPTII, GUS, and rolC genes, followed by cultivation on SIM containing 300 mg/L
timentin. Putative transgenic plants were selected on shoot induction medium
containing 80mg/L kanamycin, and multiplied on shoot proliferation medium.
Four clones were confi rmed as transgenic using the GUS histochemical assay
and Southern blots for the NPTII and rolC genes. Plants of each clone have been
rooted and successfully transfered to the greenhouse for further analysis of gene
expression.
101
In Vitro Propagation of Garlic (Allium sativum L. )
H. El-Badry, G.I. Shalaby, N.M. Kandeel, and M.H. Aboul-Nasr*; Horticulture
Dept., Assiut Univ., Egypt
This study was carried out in the Tissue Culture Laboratory and the Experiment
Field of the Dept. of Horticulture, Assiut Univ. Two garlic cultivars i.e., El-Balady
(local cultivar) and the Chinese were used. Two media, MS and B5, were supplemented with 4% , 8% , 12% and 16% sucrose. The 8% sucrose gave best number
of roots, root length and leaf length as compared to the other sucrose concentrations used in this study. Four percent or 16% sucrose gave the lowest values
of these characters. The MS gave higher values in most of the studied characters
than that of the B5. In another experiment three growth regulators i.e. IBA, BA and
GA3 or used at 0, 5, 10, 20 ppm in two media, MS and B5 supplemented with 3%
sucrose. All the studied growth regulators gave higher values than the control in
respect of the all studied characters. The IBA was better than BA and GA3 in root
formation, while GA3 was better than BA and IBA in leaf formation. It is found that
5 ppm of IBA formed the highest number of roots, root length and percentage of
root formation. On the other hand, the 20 ppm of GA3 gave the highest number of
leaves and leaf length. The garlic plantlets were successfully acclimatized in the
laboratory giving 67.8% survival for the Balady cv. and about 62.6% for Chinese
cv. The survival rate of these plantlets were 74.5% for the Balady cv. and 78.5%
for the Chinese cv. on transfer to the open-fi eld. No chromosomal aberrations
was noticed.
102
Influences of Growth Regulators and Cultivars on Callus and
Shoot Production of Alfalfa
Guochen Yang* and Marihelen Kamp-Glass; Dept. of Natural Resources & Environmental Design, North Carolina A& T State Univ., Greensboro, NC 27411
Alfalfa seeds of Cimarron VR, CW1446, CW2440, C94-118, C94-785, and
461
WL311 were used as explants. BA, zeatin, and TDZ were evaluated on callus initiation, development, and shoot production. Callus initiation and development toward
shoot organogenesis were enhanced when BA was added in the culture medium.
Calli produced from BA treatments were compact, solid, and dark green. Similar
results were obtained when zeatin was added in the culture medium. However,
no shoots were produced from such calli. Multiple shoots were produced directly
from each individual explant when TDZ was added to culture medium. However,
when higher concentration of TDZ was used, number of shoots per explant was
decreased, and dwarf shoots were produced. No apparent difference on shoot
production was observed among the cultivars tested so far. Data on number of
shoots per explant from two of these cultivars need to be statistically analyzed.
103
Use of Microsatellites for the Identification of Potato Somatic
Hybrids
Alexander A.T. Johnson* and Richard E. Veilleux; Dept. of Horticulture, Virginia
Polytechnic Inst. and State Univ., Blacksburg, VA 24061-0327
Somatic hybrid plants were obtained through protoplast fusion of monoploid
potato. Of three separate fusions, two were interspecifi c between Solanum phureja
and S. chacoense, whereas one was intraspecifi c between two S. phureja clones.
Microsatellites, or SSRs, were employed to distinguish true somatic hybrids
from somaclones of unfused protoplasts. Primers fl anking eight different SSR
loci obtained from GenBank accessions for potato were developed for PCR
amplifi cation. Microsatellites consisted of di-, tri-, and tetra-nucleotide repeat
units that varied from 4 to 20 repeats per locus. The majority of microsatellites
were highly polymorphic between the S. phureja and S. chacoense clones and the
presence of both parental alleles in fusion regenerants indicated their interspecifi c
hybrid nature. One interspecifc somatic hybrid could be identifi ed at three of the
four examined loci (two tri- and one di-nucleotide repeat loci). The parents were
monomorphic at the remaining di-nucleotide repeat, thereby rendering it unsuitable
for hybrid identifi cation. A similar result was obtained for another interspecifi c
hybrid, with four of fi ve loci appearing polymorphic between the parents and in
the somatic hybrid. Less polymorphism was observed between the parents of an
intraspecifi c S. phureja somatic hybrid, with only one locus (a tetra-nucleotide
repeat) of fi ve examined showing polymorphism. Results indicate that SSRs are
a consistent and reliable means for somatic hybrid identifi cation in potato. In
order to reduce the cost and time of maintaining numerous calluses through a
lengthy tissue culture regeneration phase, a technique was developed to screen
calluses prior to regeneration. Using SSRs and a rapid DNA extraction method,
hybrid and nonhybrid calluses could be distinguished rapidly without adversely
affecting subsequent regeneration of shoots from the callus.
104
Derivation and Comparison of Androgenic and Gynogenic
Monoploid Potato Families
Rebecca J. Cutright* and Richard E. Veilleux; Dept. of Horticulture, Virginia
Polytechnic Inst. and State Univ., Blacksburg, VA 24061
Monoploid potato (2n = 1x = 12) can be derived either paternally through
anther/microspore culture or maternally through crossing with a haploid-inducing
pollinator. Evidence from other genera suggests that androgenic and gynogenic
haploid populations derived from the same parent may differ due to gametic
selection and/or epigenetic factors. Our objectives were to derive androgenic
and gynogenic monoploid populations from each of two diploid (2n = 2x =
24) Solanum phureja clones and compare their phenotypic characteristics in a
greenhouse study. A haploid-inducing pollinator, S. phureja IVP101, was crossed
to two selections of S. phureja (PP5 and BARD1-3). A total of 185 fruit was obtained from PP5 and 398 from BARD1-3, resulting from 85% and 65% fruit set,
respectively. Seed lacking the dominant embryo spot marker carried by IVP101
were selected and germinated in vitro. From 29,300 PP5 x IVP101 seeds, 278
were spotless, resulting in 27 monoploids. Approximately 35 monoploids were
obtained from the 99,500 BARD1-3 x IVP101 seeds, of which 500 were spotless.
In anther culture, PP5 and BARD1-3 yielded 0.16 and 1.67 embryos per anther,
respectively, of which 51% and 44% of the regenerants were monoploid. A total
of 32 anther-derived monoploids has been obtained from PP5 and 130 from
BARD1-3. Rooted cuttings of 21 androgenic and 21 gynogenic PP5 monoploids
were established in a greenhouse in each of three randomized complete blocks.
Data were collected on height, vigor, and stem number. Although the gynogenic
monoploids appeared slightly more vigorous, there were no signifi cant differences
between the androgenic and gynogenic populations for vigor and stem number
462
(P > 0.05). Mean height of the gynogenic monoploid population (13 cm) was
signifi cantly greater at 4 weeks than the androgenic monoploid population (9
cm); P < 0.05.
105
Direct Regeneration of Pennisetum setaceum ‘Rubrum’
Claude Meliza* and Houchang Khatamian; Dept. of Horticulture, Forestry and
Recreation Resources, Kansas State Univ., Manhattan, KS 66506
Pennisetum setaceum ‘Rubrum’ (Crimson Fountain Grass) is an attractive ornamental grass. It is adaptable to a wide range of soil types and is drought-tolerant.
Nodal explants were taken from containerized plants either grown in greenhouse
or outside. The explants were surface-sterilized in 95% ethyl alcohol for 10 min
followed by 10 min in 10% Clorox bleach and rinsed three times each for 5 min
with sterile double-distilled water. The explants were then cultured in glass tubes
of 25 x 150-mm fi lled with half- and full-strength MS medium supplemented with
1 or 3 mg/L BA and 0.5 mg/L NAA. Shoot regeneration occurred within 1 to 2
weeks. The best medium for shoot regeneration was 1/2MS supplemented with 1
mg/L BA plus 0.5 mg/L NAA. Microshoots were transferred into rooting medium
consisting of 1/2MS supplemented with 0.25 NAA. Rooting took place within 5
to 6 weeks. Plantlets were then planted in soilless medium, placed under mist for
1 week, and transferred into the greenhouse for further growth.
106
Exogenous Polyamine Application Improves Shoot Elongation
In Hazelnut (Corylus avellana L. ) Micropropagation
Mehmet Nuri Nas* and Paul E. Read; Univ. of Nebraska–Lincoln, Dept. of Horticulture, Lincoln, NE 68586-0724
Buds from newly developed shoots obtained from forced outgrowth of
mature, unpruned fi eld-grown trees of Corylus avellana L. were cultured in vitro
on Murashige and Skoog (1962) medium and a Modifi ed Driver and Kuniyuki
(1984) medium containing different levels of N-6 Benzyladenine (BA) (1.5, 2.5,
or 3.5 mg/L) supplemented with or without a combination of Putrescine (0.2 mM)
+ Spermidine (0.2 mM) + Spermine (0.05 mM). Shoot elongation varied among
genotypes, media and treatment with/or without polyamines. The best shoot elongation occurred on modifi ed DKW medium containing BA plus polyamines.
107
Induction of Callus from Seedling Explants of Citrus macrophylla W. Rootstock
S. Guzman*, J. Jimènez, J. FarÌas, C. Salazar, M. Hernández, and A. Michel;
Universidad de Colima, Facultad de Ciencias Biologicas y Agropecuarias, Tecoman, Colima 28100, Mexico
Citrus macrophylla is an important citrus rootstock for Mexican lemon (Citrus
aurantifolia S.). This study was conducted to select explant type and to optimize
cultural requirements for induction callus of C. macrophylla in vitro. The explants
tested were leaf, epicotyl, cotyledon, and root segments excised under sterile
conditions from 4-week-old nucellar seedlings. The various medium comprising
either basal of Murashige and Skoog (MS) or Murashige and Tucker (MT) salts
suplemented with various concentrations of plant growth regulators, including
naphthaleneacetic acid (NAA), 2,4-dichlorophenoxyacetic acid (2,4-D) and 6furfurylaminopurine (kinetin) were used for the establishment of the explants. All
cultured explants initiated callus from the cut ends after 2 weeks, when cultured
on a modifi ed MT medium suplemented with 6 mg NAA and 0.2 mg kinetin;
cotyledon segments were the best explant for callus induction and development
(43 mm2). Root segments were the lowest explants for callus induction.
108
Induction and Culture of Apex of Axillary Shoots of Papaya in
Vitro from Mature Field-grown Trees
S. Guzman*, J. Jiménez, J. FarÌas, and G. Löpez. Universidad de Colima, Facultad
de Ciencias Biologicas y Agropecuarias, Tecoman, Colima 28100, Mexico
The papaya (Carica papaya L.) is a tropical fruit tree grown in many coastal
region of Colima. The experiments were conducted to optimize cultural requirements for induction and culture of shoot of C. papaya cv. Red Lady in vitro. The
crown, fruits, and leaves were removed from 1-year-old trees in the fi eld for stimulate growth of lateral shoots with application of 289 µM gibberellic acid solution
along steam surface. Apex (2 x 2 mm) of the shoots induced were established in
Drew and Smith (DS) medium containing 1 µM 6-benzylaminopurine (BAP) and
HORTSCIENCE, VOL. 33(3), JUNE 1998
1 µM naphthaleneacetic acid (NAA). After 90 days of establishment, the explants
were transferred to a multiplication medium consisting of DS medium containing
different concentrations of BAP and NAA (0:0, 2:0.1, 2:0.5, 2.5:0.5 and 3:0.5 µM,
respectively). Individual shoots were excised from the proliferating cultures and
subcultured onto fresh medium at 30- to 40-day intervals. The shoot number
induced of trees in the fi eld was of 47.5 per plant. After three subculture of shoot
the best multiplication factor per subculture (6.9) was when 2 or 2.5 uM of BAP
and 0.5 µM of NAA were added to DS medium.
42
POSTER SESSION 1M (Abstr. 109–114)
Crop Production—Fruit Cultivar Evaluation
109
Performance of 25 Carica papaya Lines in Middle Georgia
Anand K. Yadav* and Xin Y. Li ; Agricultural Experiment Station, College of
Agriculture, Home Economics and Allied Programs, Fort Valley State Univ., Fort
Valley, GA 31030-3298
The purpose of this study was to evaluate plant survival, growth, fruiting, and
stresses of papaya in middle Georgia and select fi ve to eight superior genotypes
for further evaluation and enhancing cold hardiness through biotechnological
approaches. Greenhouse-raised seedlings of 25 lines of papaya acquired from
National Repository at Hilo, Hawaii, and India, were established in the fi eld during
Spring 1995. Replanting of some lines was necessitated by plant losses, extended
through Summer 1996 and included some papaya lines from the Univ. of Florida,
Homestead. In the initial planting, the plant spacing was 5' x 5' in a RBD with four
replications containing four plants of each line. During the winter times, plants were
protected by covering the entire area with 6-mil clear polyethylene and providing
four electric heaters and six high-speed fans. Observations were made on survival,
plant height, fruiting height, fruit data (number, weight, and yield), and tolerance
to biotic and abiotic stresses. No female plants of several papaya lines survived.
Plant height in May 1997 ranged from 27 to 98 inches, while fruiting heights were
19 to 55 inches. There were 16 fruits per plant with an average weight of 657 g
per fruit. Total fruit yield was the highest for FVSU-45 followed by Criolla, and
then PI-491601. We did not observe any serious plant stresses other than crown
rot and damping-off. Based on above performance, eight lines (HCAR 010, 036,
192, 217, PI-491593, PI-491596, Carifl ora, and the FVSU-45) were selected for
cold hardiness study in vitro.
110
Performance of Early Ripening Clingstone Peach Selections
in South Carolina
Gregory L. Reighard and David R. Ouellette* ; Dept. of Horticulture, Clemson
Univ., Clemson, SC 29634
The processing peach industry in South Carolina is largely based on ‘Babygold’
varieties, which are late-season clingstone peaches. New varieties of high-quality peaches and nectarines with non-melting fl esh that ripen earlier would allow
more fl exibility in seasonal processing schedules and avoid overlap with pome
fruits. Twenty-four numbered selections from the Univ. of Arkansas and Rutgers
Univ. breeding programs that ripen before ‘Babygold 5’ were planted in 1995
near Clemson, S.C. Trees were budded on both Lovell and Guardian rootstocks.
Bloom dates, fruit maturity dates, fruit yield, weight, soluble solids, fi rmness, fl esh
color, and tree growth were taken in 1997. No differences were observed among
rootstocks for variety bloom and harvest dates, fruit yields, fruit quality or tree
growth. Differences were found among varieties in all traits measured or scored.
‘NJC126’, ‘A378’, ‘A485’, and ‘A82-8’ ripened the earliest. ‘A429’, ‘A473’, and
‘A219’ ripened the latest, about a week before ‘Babygold 5’. ‘A378’ and ‘NJC126’
had small fruit (<90 g); whereas ‘A473’, ‘A43-143’, ‘A9’, ‘NJC130’, and ‘NJC142’
had large fruit (>170 g). ‘A429’, ‘A473’, ‘A43-143’, and ‘NJC142’ had the highest
yields (31–39 kg/tree). An interaction between variety and rootstock was evident
for fruit yield in some scion/rootstock combinations.
111
Evaluation of Industrial Peach Cultivars
Raúl Leonel Grijalva Contreras*, Manuel de Jesus Valenzuela Ruiz. Adan Fimbres
Fontes, Arturo Lopez Carbajal , and Rogelio A. Juarez Gonzalez; Apdo. Postal No.
HORTSCIENCE, VOL. 33(3), JUNE 1998
125, Caborca, Sonora, Mexico 83600
Sixteen industrial peach cultivars from Brazil and ‘Flordagold’ on ‘Nemaguard’
rootstock were planted at a 5 x 5-m spacing in 1986. The best cultivars were ‘Cap
de Bosc’, ‘Petisco’, ‘Diamante’, and ‘Magno’, with yields of 32.8, 28.1, 27.6, and
27.2 t/ha, respectively. ‘Flordagold’ yielded 16.1 t/ha. That maturation period was
from 21 June to 19 Aug. The average fruit weight was 80 to 176 g, and soluble
solids were 13.1 to 16.1 °Brix. ‘Diamante’ is the recommended cultivar because
of its dual utility (table and industrial). ‘Diamante’ is characterized by its yellow
fruit with stick seed and an average fruit weight of 176 g. It matures in mid-June.
One negative characteristic is that the fruit is prone to oxidation, manifesting in a
stain. One advantage in growing this cultivar as an industrial product is a reduced
need for labor. These results were validated on a 35-ha farm during 1997.
112
Performance of Peach and Nectarine Cultivars in the Gulf Coast
Area of Alabama
R.C. Ebel * 1, W.A. Dozier, Jr.1, A.A. Powell 1, A.W. Caylor1, M.L. Nesbitt2, N.R.
McDaniel 2, and W.R. Okie3; 1Dept. of Horticulture, 101 Funchess Hall, Auburn
Univ., Auburn, AL 36849; 2Gulf Coast Substation, 8300 State Highway 104,
Fairhope, AL 36532; 3USDA–ARS, S.E. Fruit and Tree Nut Research Lab., 21
Dunbar Road, Byron, GA 31008
There are a limited number of peach and nectarine cultivars available with
chilling requirements that perform well in the Gulf Coast area of Alabama. A test
planting of 40 peach and 13 nectarine cultivars was established in 1985 at the
Gulf Coast Substation at Fairhope, Ala. The plot was prepared and trees grown
according to commercial procedures. Blocks of four trees of each cultivar were
planted on a 6 x 6-m spacing. Chill hours were calculated each year based on
number of hours at or below 7.3 °C starting from and including the fi rst 10 consecutive days a total of 50 h were accumulated to 15 Feb. Data collected included
date of full bloom, fi rst harvest date, and total yield. Fruit were measured or rated
for skin color, attractiveness, fi rmness, stone freeness, pubescence, fl esh color,
dessert quality, shape, weight, percent with split pits, and occurrence of malformed
sutures and extended tips. All cultivars were evaluated for 9 years (1987–1995).
The peach varieties that performed best in order of harvest date were ‘Flordaking’, ‘Texstar’, ‘Suzi Q’, ‘Starlite’, ‘Sunbrite’, ‘Junegold’, ‘Bicentennial’, ‘Brighton’,
‘Magnolia’, ‘Sunland’, ‘La Feliciana’, ‘Sam Houston’, ‘Flavorcrest’, ‘La Festival’, ‘La
Pecher’, ‘Idlewild’, and ‘Rio Grande’. The nectarine varieties that performed best
were ‘Armking’, ‘Sunlite’, ‘Karla Rose’, ‘Carolina Red’, and ‘Rose-princess’.
113
Three New Peaches and a Nectarine for the Southeastern
United States
W.R. Okie*, USDA-ARS, S.E. Fruit & Tree Nut Research Lab., 21 Dunbar Rd.,
Byron, GA 31008
Four new varieties have been released from the USDA–ARS Stone Fruit Breeding program located in central Georgia. All are adapted to the humid Southeastern
U.S. climate. ‘Rubyprince’ is an early yellow-fl eshed peach with excellent size,
fi rmness, and color. The slow-softening fruit ripens in early June at Byron, about
with ‘Dixired’, but is slightly lower chilling (about 800 h below 45 °F). ‘Blazeprince’
is a very fi rm yellow-fl eshed peach with a solid red blush that ripens in late midseason between ‘Harvester’ and ‘Redglobe’. It is susceptible to bacterial spot
disease similar to ‘O’Henry’. It requires about 850 chill hours. ‘Southern Pearl’ is
a large white-fl eshed, mid-season peach with very good acid fl avor and medium
fi rmness. It ripens about with ‘Harvester’ or ‘Redhaven’. Chilling requirement is
only about 650 h, similar to ‘Springcrest’. ‘Juneprincess’ nectarine ripens in about
the same season as ‘Southern Pearl’ and produces large, attractive, fi rm fruit that is
less prone to rain cracking than many nectarines. Skin color is bright red, typical
of California nectarines, with yellow fl esh. Chilling requirement is about 850 h.
114
Cumulative Yield, Tree Growth, and Yield Efficiency of 18 Asian
Pear Cultivars
Fenton E Larsen* and Stewart S. Higgins; Dept. of Horticulture and Landscape
Architecture, Washington State Univ., Pullman, WA 99164-6414
Eighteen Asian pear cultivars on Pyrus betulaefolia rootstocks were planted
in 1990 at Washington State University’s Royal Slope Research Unit in central
Washington State. Annual trunk diameters have been measured since planting,
and annual harvest records have been kept since 1995. The six cultivars with
463
the largest trees, ranked in decreasing order of trunk cross-sectional area, were
‘Daisui Li’ (144 cm2), ‘Ishiiwase’, ‘Huhoot Li’, ‘Shin Li’, ‘Shinsui’, and ‘Yoinashi’
(123 cm2). The six cultivars with the smallest trees were ‘Twentieth Century’ (91
cm2), ‘Chojuro’, ‘Shinseiki’, ‘Shinko’, ‘Yakumo’, and ‘Tarusa Crimson’ (38 cm2).
‘Tarusa Crimson’ was signifi cantly smaller than all other cultivars. The six highestyielding cultivars, ranked in decreasing order of cumulative yield, were ‘Daisui Li’
(183 kg/tree), ‘Shinseiki’, ‘Shin Li’, ‘Shinko’, ‘Chojuro,’ and ‘Olympic’ (107 kg/tree).
‘Daisui Li’ had signifi cantly higher cumulative yield than all other cultivars. The six
lowest-yielding cultivars were ‘Yoinashi’ (71 kg/tree), ‘Huhoot Li’, ‘Tarusa Crimson’,
‘Yakumo’, ‘Shinsui’, and ‘Nangon Li’ (19 kg/tree). The six highest-ranking cultivars
for cumulative yield effi ciency were ‘Shinseiki’ (1.6 kg• cm–2), ‘Shinko’, ‘Chojuro’,
‘Daisui Li’, ‘Tarusa Crimson’, and ‘Olympic’ (1.2 kg• cm–2). The six least-effi cient
cultivars were ‘Ishiiwase’ (0.7 kg• cm–2), ‘Yakumo’, ‘Yoinashi’, ‘Huhoot Li’, ‘Shinsui’, and ‘Nangon Li’ (0.2 kg• cm–2). ‘Daisui Li’ and ‘Tarusa Crimson’ had similar,
relatively high, cumulative yield effi ciencies, but for different reasons. ‘Daisui Li’
produced high yields on large trees while ‘Tarusa Crimson’ produced low yields
on small trees. In contrast, the relatively high effi ciencies of ‘Shinseiki’, ‘Shinko’
and ‘Chojuro’ resulted from high yields produced on small trees.
83
POSTER SESSION 2A (Abstr. 115–118)
Floral/Seed/Crop Physiology—Fruits/Nuts
115
Wax Morphology and Gas Exchange of Peach and Apple Leaves
as Influenced by Soybean Oil Emulsions and Rain
117
Morphological, Anatomical, and Chemical Characterization of
Guanabana Seeds, Annona muricata L.
Hector Villamil * and German Corchuelo; Facultad de Agronomia, Universidad
Nacional de Colombia, A.A. 14490, Bogota, Colombia, S.A.
This study was carried out to determine the physiological factors affecting
seed germination of a tropical fruit guanabana, Annona muricata L. The ontogeny
of the seed was studied looking for the identifi cation and determination of the
seed coat, ruminated endosperm, and endosperm tissues. Four development
stages of the seed were considered: very tender, tender, juvenile, and mature.
Cross, longitudinal, longitudinal-medium, cross-basal, and longitudinal-basal
sections were done using the cryostat microtome. Portions were done of about 5
µm thick. Portions of cross-sections of the seed coat showed the transversal and
oblique fi bers of this tissue, which constitutes an impermeable layer in the seed.
Medium-longitudinal-sections showed the distribution of the ruminated tissue
and it was observed the micropylar stopper and the hilum cavity rounded by the
collarette. This cavity is the only structure that permits the water diffusion through
the seed. It was found that the hilum cavity is communicated to the endorperm
through little crevices that are formed by the non-vascular ruminated tissue. The
miniature embryo, which is embedded by the endosperm, is surrounded by the
ruminated tissue. The qualitative chemical composition of the mature endosperm
showed the distribution of proteins, starch, lipids, and sugar content. A high
content of lipids was detected in these seeds (33% ) using the soxlhet extraction
method.
118
Main Physiological Factors Affecting the Germination of Annona muricata L. Seeds
B. R. Bondada*, C.E. Sams, D.E. Deyton, and J.C. Cummins; The Univ. of Tennessee, Dept. of Plant & Soil Sciences, P. O. Box 1071, Knoxville,TN 37901
A study was conducted to investigate the infl uence of rain on retention of
soybean oil emulsions and their infl uence on wax morphology and gas exchange
of apple and peach leaves. Peach and apple trees were grown in 19-liter pots in a
greenhouse (25 °C). Two different soybean oil emulsions were sprayed on trees
in a randomized block design with fi ve replications. Twenty-four hours after the
oil sprays, the trees were subjected to three rainfall regimes, 0.25, 1.25, and 2.54
cm. The surface wax and the oil residue on leaves were determined gravimetrically
after chloroform extraction. A negative relationship existed between rainfall and oil
retention. Peach leaves receiving 0.25, 1.25, and 2.54 cm rainfall lost 19%, 62%,
and 82% of the applied oil, respectively. There were no differences in oil retention
between top, middle, and bottom layers of the canopy, indicating that leaf age did
not infl uence oil retention. Oil residue loss from apple leaves was similar to that
from peach. Scanning electron microscopy revealed that the leaf wax morphology
was not affected by the soybean oil emulsions and occurred as striations on both
leaf surfaces. However, one of the emulsions partially washed off the waxes from
apple leaf surfaces whereas the other emulsion did not exhibit this phenomenon.
Furthermore, both of the soybean oil emulsions induced partial or full stomatal
closure, which infl uenced stomatal conductance and transpiration.
German Corchuelo* and Hector Villamil ; Facultad de AgronomÌa, Universidad
Nacional de Colombia. A.A. 14490, Bogota, Colombia, S.A.
Dormancy and latency factors such as moisture content, temperature, growth
regulators, and seed-coat affecting germination of the Annona muricata L., a
tropical fruit, were studied. Three types of fruits were used with presence of stylar
residues (medium and big size) and absent of stylar residues. The fruits were taken
from 4-year-old trees, which were naturally pollinated. A complete randomized
design was used for the study, with 50 seeds per experimental unit and four
replications per treatment. The variables measured were days and percent of germination, and average germination velocity. The seed germination was affected by
the moisture and oxygen content, because the structure of the seed and their high
content of the lipid in there. The length of the germination period was determinated
by the concentration of the exogen hormones applied, the temperature range, the
kind of scarifi cation used, the substrate utilized and the moisture content present
during the assays. Highly signifi cant differences were found among treatments.
The optimal conditions for germination (97.5% ) were: 30 °C of temperature, no
scarifi cation, sand as substrate, and 750 ppm of gibberellic acid. The average of
days to germination was 24.5 days. No signifi cant differences were found for the
different kind of fruits used in this assay. The results showed that this species
presented characteristics of recalcitrant seeds.
116
Influence of Stratification and Seed Age on Germination of
Penstemon Seeds
83
Dale T. Lindgren* and Daniel M. Schaaf; Univ. of Nebraska West Central Center,
Route 4, Box 46A, North Platte, NE 69101
Seeds of eight Penstemon selections, stratifi ed for 10, 8, 6, 4, 2, or 0 weeks
in 1989 and 1990, displayed signifi cant germination differences between species, between weeks of stratifi cation, and between years. Germination varied
from zero with P. digitalis in both 1989 and 1990 with no stratifi cation, to 68.0%
and 72.8% with P. angustifolius in 1989 and 1990, respectively, for 10 weeks of
stratifi cation. In 1991 through 1997, seeds of four of the selections were stratifi ed
for 0 or 8 weeks. Seeds that were 3 to 4 years old germinated as well as or better
than seeds 1 to 2 years old. All seeds that were 9 years old had no germination,
except for Penstemon ‘Prairie Splendor’, which averaged 7% germination with
no stratifi cation. Stratifi cation signifi cantly increased germination of seeds up to
4 years old. Germination of Penstemon seed varied with stratifi cation, seed age,
and species/line.
464
POSTER SESSION 2B (Abstr. 119–133)
Root Zone: Irrigation & Nutrition—Floriculture/Foliage/Greenhouse Crops
119
Use of De-inked Paper Sludge in Potting Mixes for Geranium
and Zinnia Production
Robert R. Tripepi * and Charlyn A. Koehn; Plant Science Division, Univ. of Idaho,
Moscow, ID 83844-2339
De-inked paper sludge from newsprint recycling was evaluated as an alternative
amendment in bedding plant production. ‘Sweet Dreams’ geranium (Pelargonium
x hortorum) and ‘Crystal White’ zinnia (Zinnia angustifolia) were grown in square
10-cm pots in one of fi ve media. Media contained 0% , 20% , 40% , 60% , or
80% de-inked paper sludge by volume. All mixes contained 10% perlite, and
peatmoss was used to bring the volume to 100% . Initial chemical and physical
HORTSCIENCE, VOL. 33(3), JUNE 1998
characteristics of the media were determined. Plants were grown in a greenhouse
for 8 weeks, and then plant height, shoot dry weight, and average plant width were
determined. Media containing 20% or less paper sludge had an average pH of
4.4, whereas those containing more sludge had an average pH of 7.0. Cation
exchange capacity of the media decreased signifi cantly as the volume of sludge
increased. Media containing 60% or more paper sludge were better aerated, but
held less water than those made with 40% or less de-inked sludge. Geraniums
grown in 20% or less paper sludge were at least 18% taller than those grown in
medium containing 40% or more de-inked sludge, but average dry weights and
plant widths of these plants were unaffected by the media. Zinnia plants grown in
20% or less paper sludge produced four times more shoot dry weight and were at
least 34% taller and 20% wider than those grown in 40% or more sludge. Overall,
zinnias grown in 40% or more sludge were unacceptable for commercial sale. A
volume of 20% de-inked paper sludge could safely be included in potting media
used for production of ‘Sweet Dreams’ geranium and ‘Crystal White’ zinnia.
(v/v) rooting media containing 0% , 25% , or 50% by volume of coal bottom ash
(CBA) that had been sieved through 6-mm mesh. Individual fl ower longevity
was recorded from the fi rst day of fl ower opening until senescence. There was
no signifi cant effect among levels of CBA on fl ower longevity. However, fl ower
life varied signifi cantly among cultivars from 9.5–9.9 days in ‘Aglia’ to 15.1–15.8
days in ‘Dark Delias’. Per-plant bloom numbers increased linearly with increase
in percent CBA for all cultivars. Plant diameters were reduced by CBA in ‘Aglia’,
but not affected by CBA in the other three cultivars. Plant heights of ‘Dark Delias’
were increased at 50% CBA over that of plants in 0% CBA. Visual quality indices
were signifi cantly greater for plants in CBA media compared to that for plants in
0% CBA. Top fresh and dry weights within each cultivar were equal among CBA
levels. Within cultivars, there were no signifi cant differences among plants at
different CBA levels in plant transpiration rate, stomatal conductance, and net
photosynthesis when measured with an LCA3 Leaf Chamber Analyser. However,
there were signifi cant differences in these processes among cultivars.
120
Co-blended Composts for Production of Potted Chrysanthemum
123
Dry Weight Partitioning among Roots, Shoot Bottoms and Tops,
and Leaves of Hydrangea macrophylla Cuttings Rooted in Coal
Bottom Ash or Peat : Perlite Media Containing Four Levels of
Dolomitic Limestone
Catherine S.M. Ku* and John C. Bouwkamp; Dept. of Natural Resource Sciences
and Landscape Architecture, Univ. of Maryland, College Park, MD 20742-5611
Blending polymer dewatered biosolids (PDB), poultry litter (PL), and yard
wastes (YW) composts improved the usefulness of these composts as potting
substrate. This study was to evaluate the optimum blending ratio of these three
composts for potted chrysanthemum production. ‘Boaldi’, ‘Yellow Boaldi’, and ‘Red
Akron’ were planted in six compost blends at compost levels of 75% and 100%
and two commercial substrates. The PDB, PL, and YW composts were blended
on a 2:1, 1:1, and 1:2 ratios (v/v); Sunshine mix 1 and Pro Gro 300S were the
control. All treatments were replicated fi ve times. Plants were fertilized with 150
or 300 mg• L–1 N from 21N–2.2P–16.6K once weekly. Plants grown in blends at
the 75% compost level and 300 mg• L–1 N treatment produced greater number
of branches, fl ower buds, plant height, plant width, and plant grade than those at
100% compost level and 150 mg• L–1 N treatment. The PDB + YW blends at the
75% compost level and high-fertility treatment produced premium-quality plants
that were better than any of the control plants.
121
Producing Blue and Pink Flowers on Hydrangea Using Coal
Bottom Ash as a Media Component
Bradford C. Bearce* and Dharmalingam S. Pitchay; West Virginia Univ., Morgantown, WV 26505
Rooted terminal tip cuttings of hydrangea (Hydrangea macrophylla Thunb.
‘Blaumeise Lace Cap’) were transplanted into 10-cm azalea pots containing 1
peat : 1 vermiculite (by volume) into which CBA (sieved through 6-mm screen)
had been mixed at 0% , 25% , or 50% on 18 Aug. 1996. They were then grown
until bud maturation on 21Nov., precooled, and brought into the greenhouse for
forcing on 9 Jan. 1997. The substrate pH levels were adjusted to 6.0–6.5 for
pink fl owers with dolomitic lime and with Al 2(SO4)3 to a pH range of 5.0–5.5.
Measurements were performed at anthesis on 19 Apr. There were no signifi cant
differences in fresh and dry weight and root quality index from 0% through 75%
CBA media, but these parameters were reduced in 100% CBA for both blue- and
pink-fl owered plants. Plant heights and diameters were equal in 0% through 75%
CBA and ranged from 16.33 to17.56 cm and 17.33 to 18.06 cm, respectively, but
were signifi cantly reduced in 100% CBA for blue-fl owered plants. Plant heights
and diameters were equal in 0% through 100% CBA for pink-fl owered plants and
ranged from 21.0 to 24.0 and 19.3 to 23.5 cm, respectively. Diameters of blue
infl orescences ranged from 95.9 to 104.9 cm, and these were equal on plants in
0% through 100% CBA. However, diameters of pink infl orescences ranged from
114.2–155.6 cm and were signifi cantly reduced on plants in 25% , 50% , and
100% CBA.
122
New Guinea Impatiens Flower Life and Growth Response to
Coal Bottom Ash Level in the Root Substrate
Dharmalingam S. Pitchay, M arlene Cross, Bradford C. Bearce* , and Edwin
Townsend; West Virginia Univ., Morgantown, WV 26505
On 26 Mar. 1997, New Guinea impatiens (Impatiens x New Guinea) cultivars
‘Aglia’, ‘Anaea’, ‘Bora-bora’, and ‘Dark Delias’, were planted in 1 peat : 1 vermiculite
HORTSCIENCE, VOL. 33(3), JUNE 1998
Dharmalingam S. Pitchay, Susan Myers, and Bradford C. Bearce*; West Virginia
Univ., Morgantown, WV 26505
Terminal tip cuttings of hydrangea (Hydrangea macrophylla Thunb. ‘Blaumeise
Lace Cap’) were rooted in 100% coal bottom ash (CBA) sieved through 2-mm
mesh or 1 peat : 1 perlite (v/v) containing 0, 3, 6, or 18 g• L–1 of dolomitic lime
on 13 July 1997. Rooting performance of the terminal cuttings was monitored
weekly for 5 weeks. The pH values were 7.0–7.8 (100% CBA media), 6.3–6.9
(peat:perlite, 18 g• L–1 lime), 6.0–6.5 (peat:perlite, 6 g• L–1 lime), 4.2–5.2 (peat:
perlite, 3 g• L–1 lime), and 3.6–5.2 (peat:perlite, 0 g• L–1 lime). Leaf tissue Ca was
higher in 100% CBA than that in peat:perlite media after the 2nd week, implying
that uptake from the media may have occurred. Total fresh weight of the rooted
cuttings increased signifi cantly over 5 weeks and, at week 5, the highest cutting
fresh weights were in peat:perlite media with 3, 6, or18 g• L–1 of lime. No signifi cant
differences in shoot tip fresh and dry weights were observed among peat:perlite
media, but these were reduced in 100% CBA. Root dry weight and root quality
indices were greater in peat:perlite media with 3, 6, and 18 g• L–1. The poorer
rooting of hydrangea cuttings in CBA was attributed to the supraoptimal pH range
and the substantially lower air capacity (5.25% by volume) compared to that of
peat:perlite (15.1% ). The superior rooting in peat:perlite media with lime may
have been due to the favorable pH range.
124
Evaluation of Zeolite-based Soilless Root Media for Potted
Chrysanthemum Production
Janet L. Carlino1, Kimberly A. Williams* 2, and Earl R. Allen3; 1Dept. of Natural
Resources and Environmental Sciences, Univ. of Illinois, Urbana, IL 61801; 2Dept.
of Horticulture, Forestry, and Recreation Resources, Kansas State Univ., Manhattan,
KS 66506; 3Zeoponic Gardens, Mason City, IL 62664
Chrysanthemum growth and nutrient leaching of three clinoptilolite-based root
media, which were formulated and provided by Boulder Innovative Technologies,
Inc. and ZeoponiX, Inc., were compared to the performance of control plants grown
in Sunshine Mix #2 (3 peat: 1 perlite, v/v). The control received 210 mg• L–1
N from an 18N–4P–15K soluble fertilizer at each irrigation. The experimental
zeolite-based medium NZ, which contained untreated zeolite and received the
same soluble fertilizer as the control, leached lower concentrations of NH4-N, K,
and PO4-P for most of the production cycle compared to the control. Medium
EZ1 was formulated to provide N, P, and K as fertilizer nutrients and produced
plants similar to the control based on ratings, height, width, and dry mass, but
not fresh mass, at harvest when the fertilizer rate was half of that applied to the
control, 105 mg• L–1 N. Medium EZ2, which did not receive P or K from soluble
fertilizer, produced plants similar to the control based on rating, height, and dry
mass, but not width or fresh mass, with soluble fertilizer input reduced to only
N. Tissue N, P, and K concentrations of plants grown in media EZ1 and EZ2 were
lower than those of control plants. With further refi nements, these zeolite-based
products show promise for decreasing nutrient leaching during crop production
and allowing for application of lower rates of soluble fertilizers.
465
125
Growth and Nutrient Response of Petunia and M arigold in
Tire-containing Media
Ame A. Moore*, John M. Swiader, and Kimberly A. Williams; Dept. of Natural
Resources & Environmental Sciences, Univ. of Illinois, Urbana, IL 61801
This study was conducted to determine the feasibility of using rock phosphate
and acid pretreatment to reduce Zn availability in root media containing waste tire
material for petunia and marigold production. Petunia x hybrida ‘Ultra Crimson
Star’ and Tagetes patula ‘Orange Boy’ were grown in the greenhouse in media
consisting of 4 perlite : 6 peat (v/v), 4 tire : 6 peat (v/v), or 4 tire (acid washed
with 0.5 N HNO3) : 6 peat (v/v); and containing various amounts of fi nely crushed
rock phosphate ranging from 0 to 40 g. Bulk density was higher, while container
capacity was lower in tire-containing media; air-fi lled porosity was comparable in
both tire- and perlite-containing mixes. Total plant dry weight was highest in both
crops grown in 4 perlite : 6 peat. Tissue concentrations of Zn were 2- to 3-fold
higher in plants grown in media containing tire material. Tissue P was lower in
petunia grown in tire media, but not in marigold. Compared to untreated tires,
acid washing of tire components reduced tissue Zn levels in both crops, but had
little effect on growth response. Visual analysis indicated that crop quality in tire
media was unsatisfactory for petunia, but acceptable in marigold. Rock phosphate
reduced leachate Zn levels in marigold, but not in petunia, and had no signifi cant
effect on growth and nutrition response in either crop. The data suggest that in
addition to Zn, some other factor(s) may have limited growth of both species in
tire-containing media.
126
Enhanced Growth of Amaryllis (Hippeastrum hybridum) Seedlings in Horse Manure Medium
Norma R. Palispis*; Camp 7, Baguio City, Philippines
An experiment was conducted to compare the growth of amaryllis seedlings
in the following media: pure horse manure, 1:1 garden soil–horse manure (v/v),
and 1:1 garden soil–wood shavings (v/v). Final values for fresh weight increment,
dry weight, leaf area, leaf area index, leaf length increment, bulb width increment,
leaf area ratio, and crop growth rate were signifi cantly highest and lowest in horse
manure and 1:1 garden soil –wood shavings, respectively. Net assimilation rate,
relative growth rate, and moisture content were similar for all treatments.
127
The Response of Marigold (Tagets patula) Roots in Coppertreated Plug Containers
Gisele Martins*, Robert Geneve, and Sharon Kester; Dept. of Horticulture and
Landscape Archtecture, Univ. of Kentucky, Lexington, KY 40506
A study was conducted with marigold ‘Little Devil Flame’ to evaluate the effects
of copper-treated containers on root system development in marigold (Tagets
patula). The internal walls of plugs were painted or without SpinOut (Griffen
Corp., Valdosta, Ga.), a form of cupric hydroxide in latex paint. Two marigold
seeds were sown directly into the plugs fi lled with MetroMix 360 (Scott’s) and
thinned after 5 days. Plants were grown under standard greenhouse conditions.
After 14 days, half of the plants were transplanted into 6-packs and in the other
half medium was washed from and the root system were digitally analyzed using
MacRhizo (Regent, Inc.). Shoot and root dry weight also were collected. Five days
later, the same data were collected from the transplanted plants. Copper hydroxide
reduced root and shoot growth prior to transplanting. Average root length of
untreated plants was 41% larger than copper treated plants before transplanting
and 25% larger after transplanting. There were no carryover effects of the copper
on subsequent root growth. Copper-treated plants grew an average of 59.3 mm,
while untreated plants grew 53.1 mm after transplanting. Root tips were killed
when they contacted the copper-treated container surface. These roots had shorter
internal and external link lengths and a greater average root diameter. It appears
that the initial effect of copper on marigold roots system is to kill the root tip and
inhibit further elongation. Overall branching pattern in the root system was not
altered until after transplanting.
128
Effect of Fertilizer Concentration on Growth of Variegated and
Non-variegated Double Impatiens
Brian E. Whipker1, Shravan K. Dasoju2*, Michael S. Dosmann2, and Jeffery K. Iles2;
Dept. of Horticultural Science, Box 7609, North Carolina State Univ., Raleigh, NC
27695-7609; 2Dept. of Horticulture, Iowa State Univ., Ames, IA 50011-1100
1
466
Double impatiens (Impatiens wallerana) ‘Blackberry Ice’ (variegated-leaf type)
and ‘Purple Magic’ were grown on fl ood benches and irrigated with 50, 100, 200,
or 300 mg• L–1 N to study the effect of fertility on growth and development. Leaf,
stem, bud, and total shoot dry mass exhibited a quadratic concentration effect with
maximum growth for both cultivars occurring at 100 mg• L–1 N. Tissue concentrations of N, P, and K exhibited a quadratic concentration effect and increased with
fertilization concentration, however, levels were higher for ‘Blackberry Ice’ than
‘Purple Magic’ over all fertilization concentrations. Tissue Mg levels also increased
with fertilization concentration, but levels were higher for ‘Purple Magic’. Tissue Ca
concentrations were similar for both cultivars and levels decreased as the fertilizer
concentration increased. For maximum shoot growth and fl ower bud production,
growers should apply 100 mg• L–1 N when growing double impatiens on fl ood
benches.
129
Effect of Slow-release Fertilizer Concentration and Placement
on Petunia Growth in Two Irrigation Systems
Kimberly A. Klock* and Timothy K. Broschat; Univ. of Florida, Fort Lauderdale
Research and Education Center, 3205 College Ave. Fort Lauderdale, FL 33314
Our objective was to compare growth and fl owering of petunia ‘Ultra Red’ in
top-watered and subirrigation systems at four slow-release fertilizer concentrations and at four different fertilizer placements in the pot. Petunia plugs were
transplanted into 400-ml pots fi lled with 60% peat: 25% vermiculite: 15%
perlite (by volume). Prior to planting, Osmocote 14N–6.2P–11.6K was either
top-dressed (TD), placed in the middle of the pot (M), placed at the bottom of the
pot (B), or incorporated into the medium at rates of 0.5, 1.0, 2.0, or 3.0 g/pot.
Petunia shoot dry mass linearly increased as fertilizer concentration increased.
Top-watered petunias had signifi cantly greater shoot dry mass than subirrigated
petunias. Best petunia growth in both irrigation systems was in media with fertilizer
at I, TD, or M compared to growth in media with fertilizer at B. Leachate soluble
salt concentrations from top-watered benches were consistently 2x greater than
concentrations from subirrigated benches. However, leachate NO3-N concentrations were not different throughout the experiment for subirrigated benches but
decreased over time for top-watered benches. Midpoint and fi nal media soluble salt
and NO3-N concentrations were not different between the two irrigation systems.
As fertilizer concentration increased, midpoint and fi nal media soluble salt and
NO3-N concentrations linearly increased.
130
Interaction Between Powdery Mildew and N and K Fertility in
Begonia
Monica A. David*, John M. Swiader, Darin M. Eastburn, and Kimberly A. Williams; Dept. of Natural Resources & Environmental Sciences, Univ. of Illinois,
Urbana, IL 61801
Nine fertility treatments, consisting of a 3 x 3 factorial arrangement of three
N rates (30, 120, 240 µg• ml –1) and three K rates (30, 120, 240 µg• ml –1), were
applied by constant liquid feed to cuttings of Hiemalis begonia ‘Hilda’ grown in
15-cm plastic pots containing 7.5 peat : 2.5 perlite medium. Prior to transplanting, one-half of the plants were naturally inoculated with Erysiphe cichoracearum
to induce powdery mildew infection; while the remaining plants received weekly
application of Bayleton (Triadimefon). Shoot growth in fungicide-treated plants
increased with increasing rates of both N and K, with highest dry matter production
(≈8.0 g/plant) with either 120N–240K or 240N–120K. Disease development in
plants treated with fungicide was slight, averaging < 7% of the total leaf surface
area infected with mildew, irrespective of N and K rates. Shoot dry weights in
inoculated plants were markedly repressed, averaging 3.1 g/plant, as disease
occurrence was extensive in all treatments. Signifi cant interactions between N and
K fertility affected mildew development in inoculated plants. At the high rate of N,
K nutrition had little effect on mildew rating, whereas at 30N and 120N, mildew
counts decreased with increasing K rate up to 120 K.
131
The Effect of Field Irrigation Practices on Disease Suppression
in Zinnia elegans
Linda Gombert* 1, Susan Hamilton1, and Mark Windham2; 1Dept. of Ornamental
Horticulture and Landscape Design, 2Dept. of Entomology and Plant Pathology,
Univ. of Tennessee, Knoxville, TN 37996
The objective of this study was to determine if fi eld irrigation practices affect
HORTSCIENCE, VOL. 33(3), JUNE 1998
the development and suppression of three diseases, alternaria blight (Alternaria
zinniae), powdery mildew (Erisyphe cichoracearum) and bacterial leaf and fl ower
spot (Xanthomonas campestris pv. zinniae), on Zinnia elegans. Many commercial
growers will no longer produce this popular bedding plant and cut fl ower crop
due to high incidence of these three diseases. Plants of 17 different varieties of
Z. elegans were started from seed and transplanted into cell-packs to be grown
on as bedding plants. They were later transplanted into the fi eld and subjected to
one of three watering regimes: natural rainfall plus overhead irrigation, natural
rainfall plus sub-irrigation, and natural rainfall only. Weekly evaluations were
performed to rate each variety on its susceptibility to disease based upon severity of infection as well as portion of plant affected. Results will be presented on
irrigation method and its infl uence on disease susceptibility and resistance on
the 17 varieties evaluated.
132
Evaluation of Disease Resistance among 57 Varieties of Zinnia elegans
Linda Gombert* 1, Susan Hamilton1, and Mark Windham2; 1Dept. of Ornamental
Horticulture and Landscape Design, 2Dept. of Entomology and Plant Pathology,
Univ. of Tennessee, Knoxville, TN 37996
Fifty-seven of the most widely grown, commercially popular varieties of Zinnia
elegans were evaluated for disease susceptibility under uniform fi eld conditions.
Plants were started from seed and transplanted into cell-packs to be grown on
as bedding plants. They were later transplanted into the fi eld and observed for
development and progression of the diseases alternaria blight (Alternaria zinniae),
powdery mildew (Erisyphe cichoracearum), and bacterial leaf and fl ower spot
(Xanthomonas campestris pv. zinniae). Evaluations were performed throughout
the growing season in order to rate each variety on its susceptibility to disease
based upon severity of infection as well as portion of plant affected. Results will be
presented on disease susceptibility and resistance of the 57 varieties evaluated.
133
Use of Digital Analysis of Radicle Extension of Marigold Seedlings as an Early Indicator of Seed Vigor
Kay Oakley*, Robert Geneve, Gunching Siriwitayawan, and Sharon Kester; Dept.
of Horticulture and Landscape Architecture, Univ. of Kentucky, Lexington, KY
40546
Several seed vigor tests were conducted on Marigold ‘Little Devil Flame’ and
correlated with digital analysis of radicle extension. Seed from a single lot was
deteriorated by the accelerated aging (AA) method at 41 °C for 24 and 72 h. Seed
moisture content of unaged seed was 15.23%, mildly aged seed (24-h AA) was
40.77%, and moderately aged seed (72-h AA) was 52.85%. After AA treatment, all
seeds were dried to near 15% moisture. Vigor level was assessed 7 days after AA
treatment by standard germination and soilless-mix plug emergence tests according
to the Association of Offi cial Seed Analysts Rules for Testing Seed. The standard
germination test revealed an 84.5% germination for unaged seed, 49.5% germination for mildly aged seed, and 28.5% germination for moderately aged seed. The
plug emergence test showed an 88.9% normal emergence for unaged seed, 65.28%
germination for mildly aged seed, and 9.72% germination for moderately aged
seed. Additionally, the radicle of seedlings established under standard germination
conditions was digitally analyzed after 4 days. According to digital analysis, average
radicle length for unaged seed was 2.10 cm, 1.91 cm, for mildly aged seed, and
1.27 cm for moderately aged seed. Radicle length after 4 days showed an R2 of 0.81
when regressed against standard germination and an R2 of 0.99 with seedling
emergence tests. These results suggest that digital analysis of radicle extension
could provide a sensitive, reproducible test for seed vigor.
83
POSTER SESSION 2C (Abstr. 134–141)
Crop Production—Small Fruits & Viticulture
134
Viticultural Performance of Thirteen Rootstocks Grafted to
‘Chardonnay’ in the Russian River Valley, Sonoma County,
California
HORTSCIENCE, VOL. 33(3), JUNE 1998
Rhonda J. Smith* 1 and James A. Wolpert2; 1Univ. of California Cooperative Extension, Sonoma County, Santa Rosa, CA 95403; 2Dept. of Viticulture and Enology,
Univ. of California, Davis, CA 95616
Thirteen grapevine rootstocks grafted to Vitis vinifera L. ‘Chardonnay’ clone
4 were compared over 5 years of fruiting in a replicated trial. The scion and all
rootstocks were certifi ed as virus tested and true-to-type. Green-growing bench
grafted vines were planted in 1989 and vine growth and yield component data
collected in 1993–1997. Planting density was 2.44 x 3.66 m vine by row (1122
vines/ha). All vines were harvested on one date each year. Analyses conducted
on the5-year averages of most parameters indicated the year by treatment (rootstock) interaction was signifi cant (P < 0.05). Within years, rootstock response
was signifi cantly different for most parameters. In the last 3 years (1995 to 1997),
AXR#1 and 5C were among the highest-yielding stocks, ranging from 15.2 to 26.8
kg/vine and 13.8 to 26.1 kg/vine, respectively. Among the lower-yielding stocks
during the same period was 101-14, which ranged from 11.6 to 22.9 kg/vine.
Other low-yielding rootstocks included 110R and 779P. Vine yield was not highly
correlated with either cluster number or cluster weight in any year; however, AXR#1
consistently produced among the highest number of clusters per vine. 5C had the
greatest pruning weights in 1994 and 1995 (3.2 and 3.1 kg/vine, respectively)
and 1045P had the highest in 1996 (2.4 kg/vine). 1045P also had the greatest
shoot weights in each of the last 3 years for which pruning weights are available
(1994–96). In 1994 and 1995, 101-14 had among the lowest shoot weights and
shoot numbers per vine.
135
Selection of Cold-hardy Rootstocks
Mary Peterson* and Emily Hoover; Dept. of Horticultural Science, Univ. of Minnesota, St. Paul, MN 55108
Cold-hardy candidates from the Univ. of Minnesota Vitis collection were evaluated for potential use as commercial rootstocks for the production of cold-tender
grapes in conditions typical of the eastern and midwestern United States. The 53
genotypes studied were selected from the collection based on past fi eld performance and cold-hardy parentage. These were compared with standard commercial
rootstocks for these regions— C3309 and SO4— for characteristics typically
evaluated in rootstock production: rooting ability, vigor, phylloxera resistance,
disease resistance, fi rst season root development, suitability of rootstock wood,
ease of grafting and callusing, and growth of scion bud. In addition, indications
of onset of dormancy were monitored to identify those genotypes with potential
to infl uence scion dormancy regime for the purpose of increasing scion coldhardiness.
136
Assessing Organic Nitrogen Acquisition of Ericoid Mycorrhizae
in Highbush Blueberry (Vaccinium corymbosum L. ) Plants by
Using an 15 N Tracer
Wei Qiang Yang*, Barbara L. Goulart, and K. Demchak; Horticulture Dept., The
Pennsylvania State University, University Park, PA 16802
The ability of mycorrhizal highbush blueberry plants to acquire soil organic
nitrogen under different organic amendment regimes was investigated in a fi eld
experiment by using an 15N tracer. Plants inoculated with an ericoid mycorrhizal
isolate from the genus Oidiodendron had lower leaf 15N enrichment than uninoculated plants, indicating mycorrhizal (M) plants absorbed more unlabeled soil
nitrogen than nonmycorrhizal (NM) plants. The unlabeled nitrogen was presumably from soil organic N sources which might be less available to NM plants. M
plants produced more plant dry weight and larger canopy volume, presumably
as a result of improved N acquisition ability. In the study, the effect of pre-plant
organic amendments on the growth of highbush blueberry plants was clearly
demonstrated. The forest litter amendment produced higher dry mass than either
the rotted sawdust amendment or no amendment. The rotted sawdust amendment
produced the smallest plants. These results suggested that organic amendments
with different C:N ratios might have affected soil N availability by affecting the
N mineralization process. The implication of these fi ndings in the production of
highbush blueberry in mineral soils will be discussed.
137
Nitrogen Acquisition Efficiency of Ericoid Mycorrhizae in Highbush Blueberry (Vaccinium corymbosum L. ) Plants
Wei Qiang Yang*, Barbara L. Goulart, and K. Demchak; Horticulture Dept., The
467
Pennsylvania State Univ., University Park, PA 16802
In laboratory and growth room experiments, protease activity among a diverse
group of ericoid mycorrhizal fungi (isolated from two native and two commercial
blueberry sites) was screened via a sensitive fl uorescent assay and the effi ciencies
of mycorrhizal symbionts to use organic (a protein) and inorganic N were determined. There were differences in extracellular protease activity among mycorrhizal
isolates within the same genera. Two isolates from a native blueberry site showed
the highest extracellular protease activity. Plants inoculated with these two isolates
produced more dry weight as compared to the control or plants inoculated with
other isolates with lower protease activity when protein was used as the sole
nitrogen source. These results suggested that some of the mycorrhizal isolates
from native blueberry sites might be more effi cient in acquiring soil organic N
than those isolated from commercial blueberry sites. This possibility was further
examined by using 15N and the results from 15N labeling will be discussed. Our
study indicated that it was possible to isolate and identify ericoid mycorrhizal
fungal strains which might be useful to increase the host’s ability to utilize soil
organic N sources.
138
Spot Treatment of Granular Hexazinone in Wild Blueberries
David E.Yarborough* and Tim M. Hess; Univ. of Maine, 5722 Deering Hall,
Orono, ME 04469
Preemergence application rates of hexazinone have been reduced because of
the concerns of it leaching into the groundwater. Spot treatments of a 10% granular
fomulation of hexazinone, Pronone MG, would allow for selective post-emergence
control of weeds not controlled by the reduced preemergence rate. For each weed
species, St. Johnswort, bunchberry, bracken fern, dogbane, and witchgrass/fall
panicum, 10, 1-m2 plots were established and treated with either 0, 1 or 2 hg/ha
a.i. Pronone. Treatment dates were: 27 June 1996 for St. Johnswort, bunchberry,
and bracken fern and 12 July 1996 for dogbane and witch grass/fall panicum.
Cover was evaluated on 25 July and 17 Sept. 96. Weed and blueberry cover were
assessed on 25 June 1997. Dogbane and bracken fern were initialy controlled
the fi rst year with the 2 kg/ha rate of Pronone being most effective. In the year
after treatment, the dogbane at both rates and the bracken fern treated with the low
rate recovered. St. Johnswort, witchgrass/fall panicum, and bunchberry was not
signifi cantly reduced by the postemergence treatment of Pronone. Heavy rainfall
after treatment dates, including more than 3 inches of rainfall on 13 July 1996,
may have infl uenced the hexazinone movement and reduced its effectiveness. The
uncertainty of the timing and amount of precipitation make the success of this
method doubtful.
139
Impact of an Open Trellis on Canopy Growth, Light Interception,
Yield, and Leaf Physiology of Red Raspberry (Rubus idaeus)
Stephen F. Klauer*, J. Scott Cameron, and Chuhe Chen; Washington State Univ.
Research and Extension Unit, Vancouver, WA 98665
After promising results were obtained with an open-style split trellis (two
top wires) in its initial year, two new trials were established in 1997 in northwest
(Lynden) and southwest (Woodland) Washington. For the split trellis, actual yields
were 33% (machine-picked 1/2 season) and 17% (hand-picked) greater, respectively, for the two locations compared to the conventional trellis (one top wire). In
Woodland, canes from the split trellis had 33% more berries, 55% more laterals,
69% more leaves, and 25% greater leaf area compared with the conventional
trellis. Greatest enhancement of these components was in the upper third of the
canopy. Laterals were also shorter in this area of the split canopy, but there was
no difference in average total length of lateral/cane between trellis types. Total dry
weight/cane was 22% greater in the split trellis, but component partitioning/cane
was consistent between the two systems with fruit + laterals (43% ) having the
greatest above-ground biomass, followed by the stem (30% to 33% ) and the
leaves (21% to 22% ). Measurement of canopy width, circumference, and light
interception showed that the split-trellis canopy fi lled in more quickly, and was
larger from preanthesis through postharvest. Light interception near the top of the
split canopy was 30% greater 1 month before harvest with 98% interception near
the top and middle of that canopy. There was no difference between the trellis types
in leaf CO2 assimilation, spectra, or fl uorescence through the fruiting season, or
in total nitrogen of postharvest primocane leaves.
140
Toxicity of Minor and Micronutrients in Cranberry
Teryl R. Roper* and Armand R. Krueger; Dept. of Horticulture, Univ. of Wisconsin,
Madison, WI 53706
Cranberry showed signifi cant yield response to applied fertilizer. Some growers
apply large quantities of some minor and micronutrients in an effort to increase
yields. Tissue levels for nutrient suffi ciency and excess have been determined
in cranberry, but toxicity levels have not been determined. We exposed rooted
cuttings of ‘Stevens’ cranberry (Vaccinium macrocarpon Ait.) to high concentrations of individual nutrients in solution culture and then aeroponics. Shoot boron
concentration rose rapidly, but not root concentration. At 300 ppm boron, leaf
necrosis appeared and dry weight accumulation slowed. Copper and zinc accumulated in roots, but not in tops and thus will be diffi cult to diagnose. Shoot
growth slowed with elevated root copper. Sulfur accumulated quickly in shoots
and reduced growth when it exceeded 0.65% . These tissue levels are far higher
than historical results from grower samples.
141
Horticultural Perspective: History of White Pine Blister Rust
Kim E. Hummer*; USDA-ARS NCGR, 33447 Peoria Road, Corvallis, OR 97333
White pine blister rust, Cronartium ribicola J. C. Fischer, requires a pine (Pinus
L.) and a Ribes L. as obligate alternate hosts. The center of diversity for this rust
is east of the Ural Mountains, where the organism evolved with P. cembra L and
R. nigrum var. sibericum L over several million years. Susceptible Pinus strobus
L from North America was imported into England in 1710 and was transplanted
throughout eastern Europe. In 1865, rust was fi rst reported on these introduced
pines in Eastonia. In the late 1800s, the white pine nursery industry continued
to develop in Europe, but was declining in the United States. American foresters
began importing white pines from Europe. Rust was found on cultivated currants
in New York in 1906 and U.S. inspectors began examining for the disease. In
1910, infected white pines were imported from France into Vancouver, British
Columbia; in 1911, infected pines were found in New Hampshire, Vermont,
Massachusetts, Connecticut, Pennsylvania, Indiana, Ohio, Ontario, and Quebec.
Additional rust-infected imported pines were found in nurseries in Wisconsin in
1913, and Minnesota in 1914. Rust spread to native pines in New York by 1915
and to Idaho by 1927. A summary of the blister rust control program, the recent
spread of the disease, and the present state regulations will be presented.
83
POSTER SESSION 2D (Abstr. 142–149)
Postharvest Physiology—Temperate Fruit
Crops
142
A Contrast in Ethylene Production and Respiration between
Melting- and Nonmelting-flesh Peaches
Ernesto A. Brovelli* 1, Jeffrey K. Brecht2, Wayne B. Sherman2, and Charles A. Sims3;
1
Nutrilite, Lakeview, CA 92567-8403, 2Horticultural Sciences Dept., IFAS, Univ. of
Florida, Gainesville, FL 32611-0690, 3Food Science and Human Nutrition Dept.,
IFAS, Univ. of Florida, Gainesville, FL 32611-0370
A connection between ethylene production and the melting trait in peaches
has been reported by other authors. In our study, we refute the notion that ethylene
production levels in nonmelting-fl esh (NMF) peach (Prunus persica L.) fruit are
normally lower than those in melting-fl esh (MF) fruit. While in fact during ripening NMF fruit (‘Oro A’ and FL 86-28C) reached lower fi rmness levels than MF
(FL 90-20 and ‘TropicBeauty’) fruit did, NMF fruit produced consistently higher
levels of ethylene than MF counterparts. In both MF and NMF genotypes, fruit
from later harvests were in a more advanced phase of their ethylene production
and respiratory drift than those from earlier harvests. Fruit size did not necessarily
infl uence levels of respiration or ethylene production. However, when fruit from
different sizes had different initial ethylene production rates, those differences
were maintained later in other phases of the ethylene production pattern.
143
Oxygen Consumption and Carbon Dioxide Production Rates
468
HORTSCIENCE, VOL. 33(3), JUNE 1998
of ‘Red Gold’ Nectarines as Affected by Gas Composition and
Storage Temperature
Maria Botero-Omary* 1, Robert F. Testin2, James W. Rushing3, and Nihal C.
Rajapakse4; 1Concentrate Development, Nutrilite, Lakeview, CA, 92567; 2Dept.
of Packaging Science, and 4Dept. of Horticulture, Clemson Univ., Clemson, SC
29634; 3Clemson Univ., Coastal Research and Education Center, 2865 Savannah
Highway, Charleston, SC 29414
The effects of gas composition and temperature on both the O2 consumption
(RRO2) and CO2 production (RRCO2) rates of ‘Red Gold’ nectarines were investigated. Three temperatures (0, 10, and 20 °C) and six gas combinations of initial
O2 (1% , 5% , and 20% ) and CO2 (0 and 15% ) with the balance N2 were used.
Triplicate glass jars containing two fruits each were fl ushed with the respective
certifi ed gas mixtures and stored in environmental chambers maintained at 0, 10,
and 20 °C. Head space O2 and CO2 concentrations were monitored until O2 levels
dropped to 1% or less. Both RRO2 and RRCO2 showed signifi cant increases (P <
0.05) as temperature increased from 0 to 20 °C at the gas concentrations tested.
The RRO2 increased slightly (P < 0.05) as initial O2 concentration increased while
showing no changes at the range of initial CO2 concentrations used in the study.
For RRCO2, no signifi cant changes (P < 0.05) were observed as gas concentrations varied at constant temperatures. This information is useful in establishing
empirical models for modifi ed atmosphere packaging predictions.
144
Fruit Volatiles to Control Postharvest Rot of Stone Fruits and
Pears
L.J. Skog1* , D.P. Murr2, and B.E. Digweed1; 1Horticultural Research Inst. of
Ontario, Univ. of Guelph, 4890 Victoria Ave. N, P.O.Box 4000, Vineland Station,
ON, L0R 2E0; 2Horticulture Dept., Univ. of Guelph, Guelph, ON, N1G 2W1
Volatile compounds are ubiquitous in plants, giving fruits their characteristic aroma and fl avor. There is increasing evidence that these compounds can
protect plants from pathogenic organisms. In this trial ≈25 volatile compounds
were tested for effi cacy against Monilinia fructicola and Penicillium expansum.
Both in vitro tests on agar plugs of actively growing pathogens and in situ tests
on inoculated stone fruits and pears were conducted. The volatile compounds
were grouped into three categories based upon fungicidal activity in vitro: highly
effective (fungicidal concentration ≤100 M), moderately effective (fungicidal
concentration between 100–200 M) and ineffective (fungicidal concentration
>200 M ). Highly effective compounds included: acetaldehyde, citral, 2-ethyl-1hexanol, 2,exadienal, E-2-hexenal, 4-hexen-3-one, linalool, (E,E)2,4-nonadienal,
E-2-nonenal, E-3-none-2-one, salicylaldehyde, and valeraldehyde. Moderately
effective compounds included: (E,Z) 2,6-nonadienal, propionaldehyde, terpinene,
butyl acetate, E-cinnamaldehde, hexanal, E-2-hexen-1-ol, Z-3-hexen-1-ol and
isoamyl acetate. Ineffective compounds included: butyrolactone, ethanol, ethyl
acetate, and methyl acetate. Effectiveness of the compounds varied with both
strain and type of microorganism tested. Concentraions required for effective
control were much higher when the compounds were tested on inoculated fruit.
Phytotoxicity was a problem with some compounds.
145
Changes in Fruit Phenolic Composition and Antioxidant Capacity during Storage
W. Kalt* , C.F. Forney, and J. McDonald; Agriculture and Agri-Food Canada,
Atlantic Food and Horticulture Research Centre, 32 Main St., Kentville, NS, B4N
1J5, Canada
Ripe fruit of strawberry, raspberry, and highbush and lowbush blueberries
were stored at 0, 10, 20, or 30 °C for up to 8 days. Total phenolic and anthocyanin
content was measured at regular intervals during the storage period as well as the
total antioxidant capacity, using the method of Cao et al. (Clin. Chem. 1995, 41/12
17391744). There were signifi cant differences in all parameters among the species, and after storage. Across all species and storage treatments, the antioxidant
capacity was correlated with the content of phenolics (R = 0.77) and anthocyanins
(R = 0.85). Both species of blueberry had more than twice the antioxidant capacity
of either raspberry or strawberry; antioxidant capacity of the highbush and lowbush blueberries did not change during storage. During storage at temperatures
greater than 0 °C, anthocyanin content of raspberries and strawberries increased
substantially, and this increase was accompanied by an increase in total antioxidant
capacity. Since dietary antioxidants such as anthocyanin fl avonoids have been
suggested to have positive health benefi ts, postharvest anthocyanin formation
HORTSCIENCE, VOL. 33(3), JUNE 1998
may have a desirable effect on the health quality of certain fruit.
146
Ethylene Inhibitor, 1-M ethylcyclopropene, Delays Apple
Softening
Sylvia M. Blankenship* and C.R. Unrath; Dept. of Horticultural Science, North
Carolina State Univ., Raleigh, NC 27695-7609
Three apple cultivars, Jonagold, Ginger Gold, and Gala, were treated at harvest
with “EthylBloc,” a commercial formulation of 1-methylcyclopropene (MCP). The
apples were sealed in a container and the compound entered the fruit as a gas.
Apples were treated for 16 h at 22 °C. Fruit were then stored at 22 or 0 °C. In
some cases fruit were retreated after 20 days. Overall MCP treated fruit showed
less softening than untreated fruit. Soluble solids and starch iodine ratings were
similar in all fruit. ‘Ginger Gold’ fi rmness was 85 N at harvest, and after 20 days at
22 °C it was 75 N in MCP-treated fruit and 53 N in the control. In addition, there
were large numbers of rotten fruit in the control, but not in the MCP treated fruit.
Fruit fi rmness in ‘Gala’ was ≈64 N in the control and 95 N in the MCP-treated
fruit after 30 days at 22 °C. Treated and untreated fruits stored at 0 °C showed
less difference in fi rmness than fruit stored at 22 °C. However, in ‘Jonagold’ fruit
there was a 13 N difference in fi rmness between treated and untreated fruit after
2 and 4 months 0 °C storage.
147
‘Ginger Gold’: A Summer Apple with Storage Potential in CA
Cynthia L. Barden*; Dept. of Horticulture, Pennsylvania State Univ., P.O. Box 309,
Biglerville, PA 17307-0309
‘Ginger Gold’ is a high-quality summer apple with potential for processing and
fresh markets. Although summer cultivars typically exhibit poor storage quality,
data from three seasons indicate that storage potential is high for ‘Ginger Gold’
in low-O2 controlled atmosphere storage. In 1995, fruit harvested 25 Aug. (85N)
were stored in air (0 °C), 3% O2/<2% CO2 (0 °C) or 0.7% O2/1% CO2 (0 °C) for
4 or 7 months. After 4 months, fi rmness of fruit stored in air, 3% O2 and 0.7%
O2 were 53N, 67N, and 80N, respectively. After 7 months, apples stored in air
were soft (45N) and had excessive decay (55% ), cracking (48% ), and breakdown
(61% ). However, fruit stored in 0.7% O2 were of good quality (76N, 4% decay,
4% cracking, and no breakdown). No low-oxygen injury occurred. Apples were
harvested on 14, 21 and 28 Aug. 1996 (85N, 80N, and 76N, respectively) and
stored in air (0(C), 1.5% O2/1% CO2 (0(C), 1% O2/1% CO2 (0 °C) or 0.7% O2/1%
CO2 (0 °C). Soluble solids were ( 9.5 at harvest, with starch scores of 3.5–4.5.
After 2 months in air the fi rmness began to decrease rapidly and after 4 months
ranged from 49–62N. Apples stored for 4 months in CA (≤1% O2) maintained
fi rmness >70N. In 1997, fruit were harvested 14, 21, 28 Aug. and 4 Sept. (102,
96, 89, and 82N, respectively and 12–13.3 °Brix). After 4 months in CA, fruit
were still of high quality (>83N, > 13.2 °Brix).
148
Ethylene Influences α-Farnesene Biosynthesis of Apples
H.P.V. Rupasinghe* 1, G.Paliyath2, and D.P. Murr1; Depts. of 1Horticultural Science
and 2Food Science, Univ. of Guelph, Guelph, Canada N1G 2W1
Ethylene (C2H4) production or ripeness of fruit at harvest have been shown to
infl uence α-farnesene accumulation and superfi cial scald development of apples.
Effects of a 15-hr treatment with 500 ppm C2H4 and 7.5 ppm 1-methylcyclopropene (1-MCP), or 10-min dip in 200 ppm aminoethoxy vinyl glycine (AVG) on
C2H4 production rate (EPR), hexane-extractable α-farnesene content in the skin,
head-space α-farnesene evolution using solid phase micro extraction (SPME),
and in vivo α-farnesene synthase activity of ‘Delicious’ apples stored for 2 months
at 0 °C were investigated. Compared to untreated fruits, AVG and 1-MCP treatments reduced EPR by 95% and α-farnesene content in the skin by 75% at day
6. C2H4-treated fruits evolved over 50% higher α-farnesene, but had reduced
α-farnesene content in the skin and head-space. However, enzyme activity was
marginally increased in C2H4-treated fruits.
149
Assessment of Relationships between Fruit Peel Nutrient Concentrations and Storage Decay Incidence in ‘d’Anjou’ Pear
F.J.A. Niederholzer * and R.A. Spotts; Oregon State Univ. Mid-Columbia Ag
Research and Extension Center, Hood River, OR 97031
Fruit were sampled from 12 mature ‘d’Anjou’ pear trees at commercial
469
harvest in each of two orchards in the Hood River Valley in 1996 and 1997. In
1997, separate fruit samples were obtained from the upper and lower canopy of
each tree. Fruit fi rmness and starch index were determined for each sample in
1997. Fruit peel samples were obtained from fi ve (1996) and 10 (1997) fruit per
sample, and peel N, P, K, Mg, Ca, Mn, Zn, Fe, Cu, and B concentrations (% dry
weight) determined. The remaining fruit were drenched with a dilute solution of
blue mold (Penicillium expansum) and placed in cold storage. Decay incidence
was evaluated after 3 and 5 months. In 1996, with the exception of Ca, fruit peel
nutrient concentrations were not correlated with incidence of storage decay. A
strong negative correlation between fruit peel Ca concentration and blue mold
incidence was present in the samples from one orchard in 1996. Fruit peel Ca
concentrations varied with year, tree, and canopy location. Results from the 1996
and 1997 seasons will be presented.
83
POSTER SESSION 2E (Abstr. 150–158)
Crop Production—Vegetable Crops
150
Trellised Field Production of Seedless Cucumbers
Charles A. McClurg*, Dept. of Natural Resource Sciences and Landscape Architecture, Univ. of Maryland, College Park, MD 20742
Production of seedless cucumbers (Cucumis sativus L.) may offer small-scale
vegetable producers an opportunity for a specialty product for a niche market.
Field production studies for four years using commercially available cultivars
and a trellis system utilizing readily available fencing materials indicate acceptable yields can be achieved if strict attention is given to pest control. Since the
cultivars do not have genetic resistance to diseases, fungal and bacterial diseases
can result in severe yield reductions. Management of insects, especially those
vectoring bacterial diseases, will also be crucial in some regions. Although the
cultivars tested were developed for greenhouse production, some can produce
good yields of attractive fruit when grown in fi eld culture.
151
Yield and Quality Evaluation of Zucchini and Yellow Squash
Varieties
M.L. Infante*, S.A. Garrison, S.A. Mangano, and P.R. Probasco; Rutgers Cooperative Extension of Gloucester County, 1200 North Delsea Drive, Clayton, NJ
08312
In Summer 1997, zucchini (ZC) and yellow squash (YS) varieties were evaluated for yield and aesthetic qualities at the Rutgers Agricultural Research and
Extension Center in Bridgeton, N.J. Only green ZC varieties and straightneck YS
varieties were tested These types are commercially acceptable to fresh markets in
New Jersey. Trials included 15 ZC and 11 YS varieties from seven participating
seed companies. Experimental design included two sites arranged in a randomized
complete-block design with three replications. Site 1 included the ZC varieties and
Site 2 included YS varieties. Squash plants were grown on raised beds with black
plastic mulch and drip irrigation. Squash was hand seeded on 30 May and harvests
began on 7 July. Pesticides and fertilizers were applied according to the 1997
Rutgers Commercial Vegetable Recommendations Gluide. Plots were harvested,
graded, weighed, and yield data recorded three times weekly; 12 harvests (over
4 weeks) for ZC and 15 harvests (over 15 weeks) for YS. Of the 15 ZC varieties,
fi ve expressed exceptional quality and highest yields: ‘Spineless Beauty’, ‘Zucchini
Elite’, ‘Select’, ‘XPHT-1776’, ‘XPHT-1777’. Statistics showed that yields for these
fi ve varieties and two other ZC varieties were signifi cantly higher than other ZC
varieties trialed. There were no statistically signifi cant yield differences among
the 11 YS varieties evaluated. Fruit color from ZC and YS was subjectively rated
to classify fruit into three categories: Dark Green, Medium Green, Light Green for
ZC and Golden, Pale Yellow, and Yellow-Green for YS.
152
Yield and Fruiting Span of Tropical Vegetable Crop Parwal in
a Temperate Climate
Wayne F. Whitehead* and Bharat P. Singh, Agricultural Research Station, Fort
Valley State Univ., Fort Valley, GA 31030-3298
Parwal, Trichosanthus dioica (Roxb.), is extensively cultivated in several
areas of India, with the state of Bihar leading in total acreage and yield. This
470
perennial cucurbit is a dioecious tropical vine producing small fl eshy fruits used
as a vegetable. The purpose of this study was to determine the total yield, duration of fruiting, and period of maximum yield of parwal for the middle Georgia
climate. A ratio of one male to four female plants were established in 1995 on
wire trellises (24.4 m long). Fruits from 16 female 4.65-m2 trellis sections were
harvested weekly during Summer 1996. Data on fruit number (FNO), fruit fresh
yield (FFY), and fruit dry yield (FDY) were recorded. Plants produced fruits over
a 15-week period starting at the beginning of July and ending at the middle of
October. The last 2 weeks of August were the peak time of production for FNO (25
fruits/plant), FFY (687.1 g/plant), and FDY (72.2 g/plant). Mean seasonal fruit
number was 190 fruits/plant, while seasonal fresh fruit yield and fruit dry yield
were 5.0 and 0.5 kg/plant, respectively. Results of this study indicate that parwal
is able to produce fruits over 3 months in middle Georgia’s temperate climate and
that maximum fruit production occurs during the second half of August.
153
Eggplant Variety Evaluation in West Central Florida
T.K. Howe* and W.E. Waters; Gulf Coast Res. & Ed. Ctr., IFAS, Univ. of Florida,
5007 60th St. E., Bradenton, FL 34203 USA
Eggplant (Solanum melongena) varieties and advanced breeding lines were
evaluated in a full-bed polyethylene mulch system during Spring and Fall 1997.
Yield and horticultural characteristics were assessed for eight entries in the spring
and 13 in the fall. Spring: Highest U.S. Fancy yield from the two earliest harvests
was 9.6 t• ha–1 from ‘Kiko’ with a mean fruit weight of 0.64 kg and 1% of the total
harvested fruit as cull quality. Highest U.S. Fancy yield from all fi ve harvests
was 31.2 t• ha–1 from PX 984 with a mean fruit weight of 0.50 kg and 16% cull
fruit. Seasonal yields combining U.S. Fancy, U.S. No. 1, and U.S. No. 2 grades
ranged from 11.4 t• ha–1 for ‘Special Hibush’ to 47.3 t• ha–1 for ‘Neon’, with four
entries not signifi cantly different than ‘Neon’. Fall: U.S. Fancy yields from the
two earliest harvests ranged from 0.5 t• ha–1 for ‘Oria’ to ‘Agora’ (2.7 t• ha–1). Five
other entries were not signifi cantly different than ‘Agora’ in early U.S. Fancy yield;
‘Orient Express’, ‘No. 226’, ‘Neon’, ‘Ghostbuster’, and ‘Vernal’. Greatest U.S. Fancy
yield for all six harvests was produced by ‘Santana’ with 25.7 t• ha–1, with a mean
fruit weight of 0.45 kg and 14% cull fruit. Seasonal yields combining all grades
ranged from 17.1 t• ha–1 for ‘Machiaw’ to 41.2 t• ha–1 for ‘Santana’, with six entries
not signifi cantly different than ‘Santana’.
154
Changes in External and Internal Quality Characteristics of Three
Tomato Cultivars Grown at Seven Different Sowing Seasons
Md. Shahidul Islam*, S. Khan, and S.M.M. Hossain; Division of Olericulture,
Horticulture Research Center, Bangladesh Agricultural Research Inst., Gazipur
1701, Bangladesh
Seasonal fl uctuations of the physical and biochemical characteristics of three
tomatoes, including two large-fruited and one cherry-fruited cultivars, were studied
in seven different sowing time at an interval of 45 days. Seasonal variation were
noted in the external and internal quality characteristics. The seasonal pattern of
ripening exhibited a rapid fi rst ripening during summer, followed by a progressive
decline until the winter season. Fruits picked during early winter to spring had higher
constituents compared to summer season. The fruits matured during the summer
season showed higher accumulation of organic and ascorbic acid; but the crop
duration was found to be shortened. On the other hand, the fruits matured during
winter to spring season had higher fi rmness, soluble sugars and longer growing
period. The lycopene synthesis was enhanced during spring to winter seasons. Of
the climatic factors recorded, temperature is predominantly implicated in affecting
tomato fruit quality. The results indicated that, fi rmness, total soluble solids and
turning point of hue (arctan a*/b*) act as the indicators of fruit maturity, and breaker
stage is more appropriate stage of harvesting in all the seasons studied. But regarding
nutritional value and appearance, and for fresh consumption, pink stage of ripening is the best for harvesting. In the present study, although cropping season and
growing temperature differed widely, but the cumulative temperature (°C day; from
fl owering to maturation) difference among growing seasons was small, and most
suitable harvest period was found to be around 1000 °C day. Thus, for consumption,
marketing and transportation, the fruits availing around 1000 °C days cumulative
temperature are congenial to be harvested.
155
Evaluation of Carrot Cultivars Over Multiple Locations for Suitability of Quality and Harvest Characteristics
HORTSCIENCE, VOL. 33(3), JUNE 1998
William Terry Kelley* 1,2, James Reid2, Randy Franks2, Rick Reed2, Anthony Bateman1, and Sharad Phatak1; 1Dept. of Horticulture and 2Cooperative Extension
Service, Univ. of Georgia, P.O. Box 1209, Tifton, GA 31793
Fresh-market carrots (Daucus carota L. sativus) have only been produced
on any signifi cant scale in Georgia since the early 1990s. Because most of the
southeast U.S. carrot production is on muck-type soils, production practices
had to be established for carrot production on mineral soils. Included in the
establishment of these practices was the evaluation of varieties to fi nd those of
suitable yield. Additionally, these varieties had to possess low bolting, suffi cient
quality, and produce a suffi cient top to be harvested mechanically. Many of the
varieties produced in western states were not suitable for production in Georgia.
After several years of testing under experiment station conditions, plots were
established on farms at three separate locations. Plantings were established 1
Oct. and 24 Nov. 1997 in Jeff Davis County and on 4 Nov. 1997 in Wayne County.
Plots consisted of three twin rows on a 1.-m bed with 35 cm between twin rows.
Plots were a minimum of 6 m in length. Normal fertility and cultural practices were
used. Evaluations of external color, length, overall marketability, smoothness, and
top suffi ciency were made on 27 Mar., 8 May, and 30 May, respectively. A total of
36 varieties were examined in replicated plots. Although there were some differences in smoothness and color, there were greater differences among varieties for
marketability, and particularly length and top suffi ciency. Several varieties were
identifi ed that would be suitable for production in Georgia.
156
Artichoke: A New Crop for Northwestern Mexico
Gerardo Araiza-Celaya, Raul L. Grijalva-Contreras*, Francisco Lopez-Vilches, and
Victor Salvador Rivas; Growers Clubs SOCOADA of Caborca, SOCOADA-FIRA
and INIFAP. Apdo. Postal 125, Caborca, Sonora, México
Vegetable production in the Caborca area is about 6500 ha ,and the main crops
are asparagus, muskmelon, watermelon, and pea. However, our objetive was to
evaluate the artichoke as a new crop for this area. We planted one 5-ha plot with
‘Esmerald’. The planting date was 18 Oct. 1996, and the distance between rows and
plants were 1.0 m and 1.6 m (6250 plants/ha). During the fi rst year of production,
the fi rst harvest was on 24 Mar. 1997, and the last harvest 10 May. There was a
total of seven harvests, with a yields of 400 boxes/ha for table production and
23,000 heads/ha for industrial use. The was 497 dollars/ ha, which is very low
compared with other vegetables crops.
157
Root Development of Bean (Phaseolus vulgaris L. ) is Affected
by Trifluralin Herbicide
Jim E. Wyatt*, Dept. of Plant and Soil Sciences, Univ. of Tennessee, West Tennessee Experiment Station, 605 Airways Blvd., Jackson, TN 38301
The objectives of this study were to investigate the effects of trifl uralin (TRI)
herbicide on plant vigor and lateral root growth of snap beans. Lexington silt
loam soil, which had not been treated with herbicides for at least 3 years, was
used in this study. TRI herbicide was mixed with appropriate amounts of soil in
a cement mixer to provide a constant rate of 560 g ai/ha TRI. To simulate TRI
herbicide incorporation, bands of treated and untreated soil were layered into
30 x 30 x 15 cm (vol 13,500 cm3) bottomless wood boxes. Treatments were 1)
control, 2) 2.5-cm treated band placed 2.5 cm below soil surface (BSS), 3) 2.5
cm treated band placed 5.1 cm BSS, 4) top 5.1 cm with treated soil, or 5) top 7.6
cm with treated soil. ‘Benton’ snap beans were planted in each box and grown in
the greenhouse for 25 days. Plant measurements made included plant height, leaf
area, and fresh and dry weight. The root system of each plant was washed and
roots arising from the hypocotyl, transition zone, and primary roots were counted.
All roots from each box were combined, dried overnight at 100C and weighed.
Plant top weight and leaf area were not affected by TRI treatments. Plants were
shorter in all TRI treatments except where placement was banded at 5.1 cm BSS.
More adventitious roots were produced on hypocotyls when TRI was applied in
a 2.5-cm band at 2.5-cm BSS or in the top 5.1 cm of soil. Total root weight was
lower and fewer lateral roots developed in all soil bands treated with TRI.
158
Tomatoes Remember being Brushed
Thomas Björkman* and L.C. Garner; Dept. of Horticultural Sciences, Cornell
Univ., Geneva, NY 14456
Tomato seedlings grown in close proximity elongate rapidly in a shade-avoid-
HORTSCIENCE, VOL. 33(3), JUNE 1998
ance response. A daily touch stimulus can eliminate the extra growth associated
with shade avoidance. Experiments to determine how the touch stimulus is
integrated were performed on tomato seedlings grown in plug trays 22 mm apart,
starting when two fully expanded leaves overlapped between plants to induce the
shade-avoidance response. The standard touch stimulus was applied by brushing the surface of the canopy 10 times each morning with a piece of Styrofoam
sheet. This treatment reduced the daily growth rate from 7.7 to 5.8 mm/day, but
quadrupling the dose further reduced growth only slightly (J. Amer. Soc. Hort.
Sci. 121:894). The ability of the plants to sum individual stimuli was tested by
varying the interval between the individual strokes. Intervals of 0.01, 0.1, 1 and
10 min all produced the same growth response. Thus, the individual strokes were
perceived as a single stimulus. Had they been perceived as separate stimuli, long
intervals would have increased the response. There was no refractory period of
insensitivity following the stimulus; that would have reduced the response at longer
intervals. The height reduction was directly proportional to the number of days
that the treatment was applied, indicating that each day of treatment reduced the
growth rate for only 1 day (from 5.9 mm/day to 2.7 mm/day). Thus, brief stimuli
are integrated during the day and expressed as a reduction of growth the next
diurnal cycle.
83
POSTER SESSION 2F (Abstr. 159–171)
Breeding & Genetics—Cross-commodity
159
Survey Of Carotenoid and Tocopherol Variability in Corn
A. C. Kurilich* and J.A. Juvik; Dept. of Natural Resources and Environmental
Sciences, Univ. of Illinois, Urbana, IL 61801
Recent investigations into carotenoid and tocopherol activity indicate that
these antioxidants are associated with the prevention of cancer and cardiovascular
disease. Both carotenoids and tocopherols can be found in corn. A replicated
survey of 21 sweet and dent corn inbreds was conducted to determine qualitative and quantitative variability of carotenoid and tocopherol content and form
in corn germplasm. Ears were harvested at 20 days after pollination (DAP) and
frozen in liquid nitrogen to remove kernels. Lyophilized samples were extracted,
then analyzed using a reverse-phase HPLC method developed in this laboratory
to simultaneously identify and quantify the carotenoids: lutein, zeaxanthin, βcryptoxanthin, α-carotene, and β-carotene, as well as the α-, δ- and γ- forms of
tocopherol. The primary carotenoids in immature corn were found to be lutein,
and zeaxanthin, with the γ form of tocopherol dominating. Mean values among
the genotypes were observed to range from 0.6 to 20 and 9 to 30 mg/g dry weight
for lutein and γ-tocopherol, respectively, suggesting variability among inbreds
in genes regulating the metabolism of these compounds. From this data, parents
have been chosen for the creation of two segregating F2:3 populations, which will
be used to study genetic associations of these compounds. This survey also found
signifi cant variability in antioxidant compounds between IL731a and W6786 for
which a saturated linkage map containing 94 probes has already been constructed.
Genetic investigations of this population will be conducted in the near future. The
observed genetic variability suggests the possibility of developing germplasm
with enhanced levels of these chemoprotectant compounds.
160
Flavor Analysis of rin/+ and Other Tomato hybrids and Inbreds
Using Sensory and Chemical Methods
J.W. Scott* 1 and E.A. Baldwin2; 1Univ. of Florida, IFAS, Gulf Coast Research and
Education Center, 5007 60th Street East, Bradenton, FL 34203; 2USDA/ARS Citrus
and Subtropical Products Lab., P.O. Box 1909, Winter Haven, FL 33880
Consumer dissatisfaction with commercial tomato (Lycopersicon esculentum
Mill.) eating quality is well-known. An array of tomato cultivars were tested for
overall fl avor by experienced or trained taste panels over several seasons. Fruit
were also analyzed for aromatic volatiles, soluble solids (SS), and titratable acidity
(TA). ‘Solar Set’ was the most consistent cultivar for overall fl avor, always ranking in the most preferred statistical group. Cultivars that were bred for increased
fi rmness, either by crossing fi rm lines (ultrafi rms) or that were heterozygous for
the ripening inhibitor (rin) gene, tended to rank low in overall fl avor and sweetness. Comparisons made included ultrafi rm lines, rin/+ hybrids with one to three
backcrosses to the high-fl avored parent of ‘Solar Set’ (Fla. 7060), Fla. 7060, and
471
‘Solar Set’ with two rin backcrosses. Experienced panel ratings were highest for
Fla 7060 followed by the rin/+ hybrids (in descending order of backcrosses to
Fla. 7060), followed by the ultrafi rm lines. SS and TA were highest in one ultrafi rm
(SS = 9.1, TA = 0.68) and lowest in one of the rin/+ hybrids (SS = 6.3, TA = 0.37)
while the rest of the samples showed intermediate values. Analysis of fl avor
volatiles showed Fla. 7060 to be generally higher in most volatiles compared to
the ultrafi ms and two of the rin/+ hybrids. Signifi cant differences were found for
methanol, ethanol, 1-penten-3-one, hexanal, trans-2-hexanal, trans-2-heptenal,
cis-3-hexenol, 2+3-methylbutanol, 6-methyl-5-hepten-2-one, 2-isobutylthiazole,
and geranylacetone.
161
Variability for Starch Digestibility in Dry Bean (Phaseolus
vulgaris L. )
G.L. Hosfi eld*, M.R. Bennink, C.W. Beninger, R.M. Engleright, and M.T. Ospina;
USDA Agricultural Research Service, Michigan State Univ., East Lansing, MI
48824 USA
Undigested starch is a major contributor to gastrointestinal discomfort experienced from eating cooked dry beans (Phaseolus vulgaris L.). Plant breeders are
interested in identifying genetic stocks of beans with highly digestible starch to
use in food quality improvement programs. Before a selection program for starch
digestibility can be initiated, genetic variability must be ascertained. Breeding
lines and cultivars from several dry bean market classes were evaluated for their
starch digestibility using a laboratory procedure involving the determination of
total dietary fi ber with 3-enzymes. Grinding raw and cooked beans using a mill
with the same-size screen (either 40 or 60 mesh) resulted in larger particles in
the raw than in the cooked bean sample and infl ated the amount of indigestible
starch in the raw bean samples. In an experiment in which cooked and raw beans
were ground with different size sieves, we found that in order to obtain cooked and
raw beans with comparable particle sizes (thus providing accuracy and reliability
to indigestible starch determinations), the cooked beans should be ground and
sieved through a 40-mesh screen, and raw beans through a 60-mesh screen.
Navy bean was the market class with the most digestible starch (≈10% ). Black
beans and kidney bean had the least digestible— starch >15% . Manteca, a Latin
American market class with a pale yellow seed coat, was similar in digestibility
to navy beans. Although the evidence is anecdotal, Manteca beans are favored
for their qualities of taste, texture, and good digestibility. The current research
on indigestible starch appears to confi rm the high digestibility, low-fl atulence
attributes of Manteca bean.
162
Estimation of Correlation Coefficients between 17 Quantitative
Traits in Hazelnut
Qiang Yao* and Shawn A. Mehlenbacher; Dept. of Horticulture, Oregon State
Univ., Corvallis, OR 97331
Thirty-fi ve hazelnut (Corylus avellana L.) progenies and 41 parent genotypes
were used to estimate phenotypic and genetic correlation coeffi cients among 17
nut, kernel, and phenological traits from 1994 to 1996. Correlation coeffi cients
were large and positive for nut size traits (nut length, width, depth, nut weight
and kernel weight). Phenological traits (days of opening of female fl owers, time
of catkin elongation and leafi ng out) were also highly correlated. But most other
traits were uncorrelated with each other. Plots of progeny means and individual
seedling values were inspected to verify which data points to have bigger effect
on coeffi cients. These results and their application in the OSU hazelnut breeding
program will be discussed.
163
Marker-assisted Selection for Improved Emergence and Eating
Quality in Sweet Corn
Gad G. Yousef* and John A. Juvik; Dept. of Natural Resources and Environmental
Science, Univ. of Illinois, Urbana, IL 61801
Marker-assisted selection is proposed to be more effective than phenotypic
selection in improving complex traits with low heritability. This study was designed
to test empirically the effi ciency of marker-assisted selection (MAS) vs. phenotypic
selection (PS) in enhancing economically important characters in sweet corn using
composite populations consisting of selected F2:3 families from two populations. In
previous studies in our laboratory, these segregating populations were developed
and assayed for genes infl uencing sweet corn emergence and eating quality. The
214 F2:3 families in the fi rst population (W678su1 X IL731ase1) were classifi ed
472
into three sub-populations according to segregation for the se1gene. Marker-assisted selection and phenotypic selection were applied on the two homozygous
sugary1 and sugary enhancer1 sub-populations separately. The second population consisted of 117 F2:3 families from the cross of Ia453sh2 X IL451bsh2. The
genotypic selection was based on the polymorphism of fi ve RFLP markers linked
to QTL associated with signifi cant effects on emergence and eating quality in the
F2:3 generation. Twenty percent of the families in each population with the highest
and lowest genotypic scores and phenotypic performance values were selected to
constitute the MAS and PS composites, respectively. Emergence was evaluated
in four different environments in Illinois and Wisconsin, while eating quality
traits were evaluated in Illinois only. Results for emergence, with relatively high
h2, in two out of three populations indicated that marker-assisted selection was
superior to phenotypic selection. The effectiveness of MAS on enhancing stand
establishment and eating quality will be discussed.
164
Molecular Markers Linked to Heat Tolerance of Broccoli
Yau-Wen Yang*; Inst. of Botany, Academia Sinica, Taipei, Taiwan 11529
A heat-tolerant broccoli cultivar was derived from the cross between two inbred
lines. One inbred line of S7 is selected from a local cultivars in southern Taiwan
, and the other of S6 is from the progenies of hybrids between broccoli and white
fl owering kale. The heat tolerance of this cultivar is believed to be inherited from the
white fl owering kale, which has been grown in southern Taiwan for a long period
of time and has the characteristic of heat tolerance. Several molecular markers that
may be linked to the heat tolerance were indentifi ed and may be able to be used in
the future breeding program of broccoli and its related varieties.
165
Molecular Tagging of Gummy Stem Blight Resistance in Watermelon
Young-Seok Kwon1, Young Hyun Om1, Leigh Hawkins2, and Fenny Dane* 2; 1National Alpine Agricultural Experiment Station, Pyongchang, South Korea; 2Dept.
of Horticulture, Auburn University, AL 36849
The fungus Didymella bryoniae causes gummy stem blight (foliar phase) and
black rot (fruit phase) in cucurbits. As resistance to other diseases have been
incorporated into cucurbits, losses due to gummy stem blight have increased.
Populations derived from crosses between a cultivated watermelon (SS-4),
susceptible to the fungus Didymella bryoniae and resistant plant introduction
accessions (PI 189225 and PI 272778) are used to detect molecular markers
linked to gummy stem blight disease resistance. Genomic DNA was purifi ed
from primary leaves of watermelon seedlings before seedlings were inoculated
with a spore suspension of the fungus. Disease severity was rated 4 days after
inoculation. DNA bulked from resistant or susceptible BC seedlings was amplifi ed
to detect AFLP markers. Linkages between gummy stem blight resistance and
AFLP markers were identifi ed and should facilitate evaluation and selection of
watermelon populations segregating for gummy stem blight resistance.
166
‘Duplin’ and ‘Sampson’ Southern Highbush Blueberries
James R. Ballington and Susan D. Rooks*, Dept. of Horticultural Science, North
Carolina State Univ., Raleigh, NC 27695
‘Duplin’ (NC 1852) and ‘Sampson’ (NC 2675) are southern highbush blueberry
genotypes that bloom with ‘Croatan’, the predominant highbush cultivar in eastern
North Carolina, and ripen with or slightly later than ‘Croatan’. ‘Duplin’ appears to
have fl ower bud hardiness similar to standard highbush cultivars when grown at
intermediate elevations in the mountains of western North Carolina. ‘Sampson’
appears to be bud hardy primarily in the piedmont and coastal plain of North
Carolina. Yield overall has been equal to or better than ‘Croatan’ and ‘O’Neal’.
Fruit size, color, picking scar, fi rmness and fl avor are superior to ‘Croatan’. Both
‘Duplin’ and ‘Sampson’ were found to be tolerant to stem blight caused by Botryosphaeria dothidea in greenhouse screening in North Carolina. ‘Sampson’ also
appears resistant to Botrytis blossom blight in Oregon. ‘Duplin’ and ‘Sampson’ are
recommended for trial as potential replacements for ‘Croatan’ in the commercial
blueberry region of eastern North Carolina.
167
Development and Release of the Novel Near-oblate Butternuttype Squash Variety ‘Butterbowl’
HORTSCIENCE, VOL. 33(3), JUNE 1998
D.P.Coyne* 1, J.M.Reiser1, D.Smith1, L.Sutton1, D.Lindgren1, and A.M.Ibrahim2;
1
Univ. of Nebraska, Lincoln, NE 68583; 2U.S. Agricultural Research Station, 1636
East Alisal St., Salinas, CA 93905
‘Butterbowl’ (NE-RBN-4) is a novel, small-sized (0.8 to 1.36 kg), fl avorful
(sweet), early maturing (90–95 days), near-oblate butternut type winter squash
variety (Cucurbita moschata Duch. Ex Poir). No Butternut squash variety is similar
in shape to ‘Butterbowl’. ‘Butterbowl’ (S6) was derived from selfi ng a near-oblate
open-pollinated S4 line derived from a cross of two true breeding crookneck lines
(allelic test) NE-BNCR-67-1-7 (mutant out of ‘Butternut 23’) X golden Cushaw
(Agway Co.). Total fruit yield and fruit weight of ‘Butterbowl’ were nearly similar to
Butternut ‘Ponca’. The total fruit weight of ’Waltham’ was greater than ‘Butterbowl’
in two out of four trials. The vining habit of ‘Butterbowl’ (1.7 to 2.0 m) is more
compact than ‘Waltham’ or ‘Ponca’. ‘Butterbowl’ is suitable for small gardens with
limited space due to its compact plant habit. No crookneck fruit developed in
‘Butterbowl’ in all tests. ‘Butterbowl’ is resistant to bacterial spot, black fruit rot,
and vine borer while it is moderately susceptible to powdery mildew. ‘Butterbowl’
fruit should be used for consumption up to 45 to 55 days after harvest because
slight fruit shriveling occurs at that time due to moisture loss. The fruit cooks
uniformally in a microwave oven due to its more uniform fl esh thickness.
168
Early Nodulin Genes are Not Markers of the Capacity of Woody
Legumes to Nodulate
Carol M. Foster1,3,4*, Faye M. Rosin2,3, James A. Schrader1,3, and William R.
Graves1,3; 1Interdepartmental Plant Physiology Program; 2Molecular, Cellular,
Developmental Biology Program; Depts. of 3Horticulture and 4Botany; Iowa State
Univ., Ames, IA 50011
Knowing whether trees can develop nodules in which nitrogen is fi xed is important for managing inputs during culture. Early nodulin genes, such as ENOD2
and ENOD12, could function as molecular markers for the capacity to nodulate
if they are conserved only in species that nodulate. Several nodulating species
are known to possess these genes; but, their occurrence has not been studied
among non-nodulating taxa, including Cercis canadensis L. (redbud), Gleditsia
triacanthos L. var. inermis Willd. (honey locust), and Gymnocladus dioica (L.)
C. Koch (Kentucky coffee tree). Our objective was to determine the relationship
between the capacity to nodulate and the occurrence of putative ENOD2 or ENOD12
genes by probing the genomes of these non-nodulating species and the genomes
of two legumes that nodulate, Albizia julibrissin Durazz. (silk tree) and Laburnum
alpinum (Mill.) Bercht. & J. Presl (Scotch laburnum). ENOD2 and ENOD12
cDNA clones from Glycine max (L.) Merill (soybean) and Pisum sativum L. (pea),
respectively, and cloned ENOD2 PCR fragments from Maackia amurensis Rupr.
& Maxim. (Amur maackia) and Styphnolobium japonicum (L.) Schott (Japanese
pagodatree) were used as probes for Southern hybridizations. Sequences from
genomes of silk tree, Scotch laburnum, honey locust, and Kentucky coffee tree
hybridized to ENOD2 probes on Southern blots. Putative ENOD12 sequences
were detected in the genomes of Scotch laburnum, redbud, and honey locust.
Thus, we conclude that ENOD2 and ENOD12 can not be used as markers for the
capacity to nodulate.
169
Heritability of Postharvest Longevity of Antirrhinum majus L.
Cut Flowers
Kenneth R. Schroeder* and Dennis P. Stimart; Dept. of Horticulture, Univ. of
Wisconsin, 1575 Linden Dr., Madison, WI 53706
Breeding for postharvest longevity of cut fl owers has not been done to any
great extent in spite of the potential benefi ts from reduced chemical preservative
usage and increased popularity of cuts due to longer vaselife. Some studies
have reported broad-sense heritabilities for postharvest longevity of 36% to
46% and narrow-sense heritabilities of 0% to 38% . Postharvest longevity of cut
fl owers of Antirrhinum majus L. (snapdragon) inbreds range from 2 to 16 d with
the F1 hybrids intermediate at 8.1 d when evaluated in deionized water. It would
appear postharvest longevity of snapdragon cut fl owers should be a selectable
trait. In an effort to determine narrow-sense heritability for postharvest longevity
of snapdragon cut fl owers, a generation means analysis was established using
single-seed descent S4 generation inbreds with postharvest longevities of 2 and
15 d. Plants were grown in greenhouses at the Univ. of Wisconsin, Madison,
in August and harvested in Nov. 1997 for postharvest evaluation. Experimental
design was a randomized complete block with 2 environments and 3 replications.
Nonsegregating generations (P1, P2, and F1) consisted of 10 plants per replication,
HORTSCIENCE, VOL. 33(3), JUNE 1998
backcrosses 30 plants per replication, and the F2 with 60 plants per replication.
Data will be presented on narrow-sense heritability of postharvest longevity of
snapdragon cut fl owers.
170
Segregation for Double Spine Trait in Hybrids of Microcitrus
inodora
Kim D. Bowman*; U.S. Horticultural Research Lab., ARS, USDA, 2120 Camden
Road, Orlando, FL 32803
Several Microcitrus species are valuable as parents in breeding citrus rootstocks and scions because of useful characteristics, such as monoembryony,
very short juvenility, short fruit maturation time, and resistance to Phytophthora
and nematodes. The large-leaf Australian wild lime, Microcitrus inodora (F. M.
Bail.) Swing., also possesses a trait that is generally undesireable in new hybrids,
double axillary spines. Most F1 hybrids between M. inodora and single-spine
Microcitrus and Citrus species were observed to possess the double spine trait.
In crosses of M. australasica (F. Muell.) Swing. x M. inodora, M. papuana H.
F. Winters x M. inodora, and M. warburgiana (F. M. Bail.) Tan. x M. inodora,
double spines were present in 80% , 81% , and 87% of the progeny, respectively.
In hybrids of Citrus species with M. inodora, percentage of double spines varied
from 43% in progeny from M. inodora x Citrus aurantium L., to 100% in progeny
from M. inodora x Citrus ichangensis Swing. When double-spined hybrids of M.
inodora were used as parents in crosses with other single-spined Citrus species
or hybrids, progenies varied from 0 to 86% with double spines. The patterns
of inheritance suggest that the double spine trait is controlled by an allele of a
nuclear gene that is dominant and homozygous in M. inodora, but that one or
more other independently segregating alleles are necessary for expression of the
double spine trait in advanced generation hybrids.
171
Identification of a RAPD Marker Closely Linked to Fruit Color
in Muscadine Grapes (Vitis rotundifolia )
Zhongbo Ren, Jiang Lu*, and Olusola Lamikanra; Center for Viticultural Sciences,
Florida A& M Univ., Tallahassee, FL 32307
The major fruit color phenotypes in grapes are either white (including green,
yellow, bronze etc.) or red (including pink, reddish) and black (including purple).
Like other fruits, anthocyanin (Acy) pigments in the berry skin contribute to
the colors of grapes. These water-soluble pigments are phenolic compounds
as secondary metabolite and accumulated essentially in the epidermal cells
of fruits. Seedling screening can be performed if a genetic marker for the fruit
color is available. A F1 population of 82 progenies derived from a cross of two
muscadine grape (Vitis rotundifolia) cultivars, ‘Summit’ x ‘Noble’, was used for
tagging the gene determining the fruit color. ‘Noble’ is a red grape while ‘Summit’ is white. Segregation of berry color in the F1 population indicated that the
red color is controlled by a single dominant gene. RAPD (Random Amplifi ed
Polymorphic DNA) technique and Bulk Segregant Analysis (BSA) was used for
tagging the fruit color trait. A total of 350 oligonucleotide 10-mers were screened
for polymorphisms between the red- and white-colored DNA pools (each pool
was consisted of seven individual DNA samples). Two RAPD fragments linked to
the target gene were identifi ed and one of them, a 650-bp fragment completely
co-segregated with the 56 progenies of red berries, while the white fruit progenies
were absent of the RAPD fragment. The cosegregation data clearly indicated that
the 650-bp RAPD fragment is tightly linked to the red fruit trait. The marker DNA
was isolated from the agarose gel, cloned, and sequenced. A pair of 18-mers and
20-mers fl anking the RAPD fragment were designed based on the sequencing
information. The RAPD marker was reamplifi ed in red-fruited muscadine grapes
with this pair of universal primers .
83
POSTER SESSION 2G (Abstr. 172–174)
Irrigation—Woody Ornamentals/Landscape/Turf
172
Interaction of Irrigation Frequency and Container Drain Hole
473
Design on Growth of Three Nursery Crops
Sven E. Svenson*, Dept. of Horticulture, North Willamette Research and Extension
Center, Oregon State Univ., 15210 NE Miley Road, Aurora, OR 97002-9543.
Three replicate blocks were installed for high-, medium-, and low-frequency
irrigation, providing the equivalent of 25 mm, 8.75 mm, or 5.5 mm of daily rainfall,
respectively. For three ornamental plants potted in 2.5-L pots, three container
designs were tested: traditional drainholes located at the base of the sidewall (0%
water storage), drainholes raised on the sidewall to provide 20% water storage
(based on a water-fi lled pot), or drainholes raised on the sidewall to provide 40%
water storage. The experiment was a 3 irrigation frequency x 3 container design
factorial treatment arrangement within a randomized complete-block design using
10 representative plants of each species within each of three replicate blocks.
The largest Ilex ‘Hetzii’, Rhododendron ‘Hino Crimson’, and Geranium ‘Claridge
Druce’ were grown using high-frequency irrigation with 0% water storage or
using medium-frequency irrigation with 20% water storage. Geranium shoot
weight was signifi cantly less only when grown using low-frequency irrigation in
containers with 0% water storage, or when grown using high-frequency irrigation
in containers with 40% water storage. Of the three species tested, only Ilex ‘Hetzii’
grew roots below the level of the raised drainholes, with these roots exhibiting
thickened, enlarged diameters.
173
Production of Bareroot Roses Using Underground Drip Irrigation
U.K. Schuch* 1, J. Karlik2, and J.O. Becker3; 1Dept. of Horticulture, Iowa State Univ.,
Ames, IA 50011; 2Univ. of California, Coop. Extension, Kern County, Bakersfi eld,
CA 93307; 3Dept. of Nematology, Univ. of California, Riverside, CA 92521
The majority of rose producers in Kern County, Calif., use furrow irrigation
to produce ≈50% of the rose plants in the United States. Two experiments were
conducted to test the feasibility of producing bareroot roses using underground
drip irrigation. Three rose (Rosa hybrida) cultivars, ‘Dr. Huey’, ‘Manetti’, and ‘Pink
Simplicity’, were used in both experiments. In the fi rst experiment, drip tape was
placed at a depth of 10, 20, 30, or 40 cm. After one growing season, plants irrigated with drip tape at 10-cm depth produced less shoot and total dry weight
than plants irrigated with tape placed between 20 and 40 cm. ‘Manetti’ was the
most vigorous cultivar and produced ≈70% more shoot and total dry weight than
the other two cultivars. In the second experiment, the plants of the three cultivars
were spaced 15, 20, or 25 cm apart within the row and irrigated with drip tape
placed at 20-cm depth. Total dry weight increased linearly with increased spacing
of plants within the row. ‘Manetti’ and ‘Pink Simplicity’ produced higher shoot and
total dry weight than ‘Dr. Huey’ plants.
174
Frequent Irrigation Increases Growth of Pot-in-Pot Sugar and
Red Maple
Robert K. Witmer*, Roger Harris, and Alex X. Niemiera; Dept. of Horticulture,
Virginia Polytechnic Inst. and State Univ., Blacksburg, VA 24061-0327
In Virginia, pot-in-pot production of shade trees is normally accomplished
by growing bareroot whips in 56-L containers for two complete growing seasons
(production cycles). This study monitored the growth of Acer saccharum L. ‘Green
Mountain’ (sugar maple), a species with moderate growth rate, and Acer rubrum
L. ‘Franksred’ (red maple), a species with a fast growth rate, under standard
once-a-day irrigation regime (1X) and a cyclic three-times-a-day regime (3X).
Equal daily volumes of water were applied under each regime. Height growth rate
increased for sugar maples but decreased for red maples in production cycle two
compared to production cycle one. Stem diameter growth rates remained steady
for red maple, but increased slightly for sugar maple. A 3X irrigation regime
increased stem diameter of red maples, but had no other effect on either species
in year one. Height and stem diameter growth of both species were increased
by the 3X treatment during production cycle two. This study indicates that the
standard production period results in decreased growth in the second production
cycle for red maple, but not for sugar maple. Growth rates can be enhanced with
a 3X irrigation regime for both species in production cycle two. The 3X irrigation
regime only increases the stem diameter growth of red maple in the fi rst production
cycle.
474
83
POSTER SESSION 2H (Abstr. 175–187)
Crop Protection/Rowcovers/Mulches—
Vegetable Crops
175
Evaluation of Herbicides for Control of Annual Weeds in Asparagus (Asparagus officinalis)
Gerardo Martinez Diaz, Arturo Lopez Carvajal *, and Leonel Grijalva Contreras R.;
Apdo. Postal 125 Caborca, Sonora, Mexico 63600
This research was conducted under fi eld conditions in 1993 with a cooperative
farmer with the aim of evaluating the effects of herbicides for the control of annual
weeds (pre-emergence). The herbicides and rates (a.i./ha) applied were: Diuron
2.4 and 1.2 L, Linuron 1.5 and 0.7 L, Metribuzin 1.4 and 0.7 L, Simazina 1.5 L,
Trifl uralin 1 L and Naptalam+ Bensulide 4+3 L and 2+2 L. Two check plots were
also included, one free of weeds and the other with weeds. A randomized block
design was used with four replicates. The experimental units were 4.5 x 10-m
plots. Trifl uralin showed 56% of control and Naptalam+ Bensulide exhibited 24%
at both rates, while Diuron (97% to 100% ), Linuron (87% to 96% ), Metribuzin
(96% to 100% ), and Simazina (96% ) showed the best controls with either doses;
of these, Linuron at 0.7 L/ha registered the lowest control (87% ). None of the
herbicides evaluated showed any plant toxicity.
176
Plastic Mulch Color Effects on Light Micro-environment and
Watermelon Plant Growth
N.K. Damayanthi Ranwala* and Dennis R. Decoteau; Dept. of Horticulture, Clemson
Univ., Clemson, SC 29634-0375
This study was conducted to evaluate the spectral properties of various colored
plastic color mulches and to determine the effects of upwardly refl ected light from
the mulch surfaces on watermelon plant growth when differences in root zone
temperatures are minimized. Two-week-old watermelon plants were grown with
black mulch, red-painted mulch, SRM-Red mulch (Sonoco, Inc., Harstville, S.C.),
and white mulch. Total light refl ection (58 µmol • m–2• s–1 in 400–700 nm) and red:
far-red (R:FR = 0.44) of refl ected light were lower in black mulch and highest in
white mulch (634 and 0.92, respectively). Both black mulch and white mulch had
same blue:red (B:R = 0.6) while white mulch had higher B:FR (0.58) in refl ected
light compared to black mulch (0.26). Refl ective properties of red mulches were
somewhat similar, and R:FR, B:R, and B:FR were 0.8, 0.2, and 0.18, respectively.
However, SRM-Red mulch had highest total light (355 µmol • m–2• s–1 in 400–700
nm) transmission through the mulch, and R:FR, B:R, and B:FR were 0.84, 0.28,
and 0.23, respectively. Light transmission through the other mulches was nonsignifi cant. Watermelon plants grown with black mulch and red mulches had
higher internode lengths compared to white mulch after 20 days. Further, plants
grown under black had signifi cant higher petiole elongation accompanied with
higher dry mass partitioning to petioles, and lower partitioning to roots, stems,
and leaves. There was no effects of surface mulch color on total plant dry mass
or photosynthesis although plants with black had higher transpiration rate. This
suggests the differential regulation of dry mass partitioning among plant parts due
to mulch color. The similar plant responses with black mulch and white mulch to
plants treated with FR or R light at the end of photoperiod implies the involvement
of phytochrome regulation of growth due to mulch surface color.
177
Agronomic Evaluation of Different Watermelon Varieties
(Citrullus vulgaris Sch. ) with Fertigation and Plastic Mulch
F. Radillo-Juárez* and J. Farias-Larios; Facultad de Ciencias Biológicas y
Agropecuarias, Universidad de Colima, Apartado postal 36, 28100 Tecomán,
Colima, México
The cultivation of watermelon is profi table for producers because of its high
price and demand in the export market to United States and Canada. The crop
profi tability depends on the suitable management and agronomic practices and the
selection of variety of the plant based on its productive capability. This characteristc
is a cornerstone for the success in the establishment and yield of the crop. The
present study was conducted to determine the vegetative growth and production
of variety improvement of watermelon under irrigation conditions and plastic
HORTSCIENCE, VOL. 33(3), JUNE 1998
mulch. The experiment was established in a muddy-sandy soil with 7.6 pH. The
varieties evaluated were: Charleston Gray, Peacock Improved, Peacock WR-60,
Tatum, Sunshade, Jubilee, and Chilen Black. Results show that all varieties in
relation to yield and quality of fresh fruit presented similar yield, Sunshade and
Jubilee registred heightest production with 39.9 and 37.3 ton/ha, respectively,
of fresh fruit with characteristics for export and for national consumption of 19.5
and 15.1 ton/ha. They have higher economic value. In relation to agronomic
characteristics, the results show that ‘Tatum’ was earlier to fl owering at 36 days
and begin the ninth node fl ower. The greater longitude of the main sprout was in
‘Peacock Improved’, with 4.8 m; in size of fruit in ‘Charleston Gray’, and ‘Tatum’
had the greater longitude and diameter of fruit, with 45.6 and 21.4 cm, respectively. The varieties presented a similar yield of fresh fruit; although there exists
an economically signifi cant difference for quality of fruit, presenting the greater
profi tability. ‘Sunshade’ and ‘Jubilee’ are the most promising varieties to improve
the economy of the producers.
178
Effect of Planting Method, Mulch, and Rowcover Combinations
on Yield and Fruit Quality of ‘Earliqueen’ Muskmelon
David T. Handley*, Sheri I. Koller, and James F. Dill; Univ. of Maine Cooperative
Extension, Monmouth, ME 04259
Three techniques to enhance the development and yield of ‘Earliqueen’ muskmelon, including transplanting, plastic mulch, and rowcovers, were applied in all
combinations to determine which practice or practices offered the most benefi cial
effects on early maturity, and total marketable yield. Using transplants (two true
leaf stage) as opposed to direct seeding had the greatest effect on increasing early
yield. Black plastic mulch also signifi cantly increased early yield. Rowcovers did
not provide an overall increase in early yield, although the highest early yield was
achieved from the transplant/mulch/rowcover combination. Black plastic mulch
had the greatest effect on total marketable yield. Transplanting also signifi cantly
increased total yield. A slight increase observed for rowcover treatments was not
signifi cant. The combination of transplanting/plastic mulch/rowcover produced
the highest marketable yield of any treatment. Direct seeding combined with no
mulch produced the lowest yields and the lowest percent of marketable fruit.
Under the conditions of a prolonged, cool, cloudy spring, followed by a hot,
dry summer, the use of transplants and black plastic mulch provided signifi cant
increases in marketable yield of ‘Earliqueen’ muskmelons. Rowcovers did not
provide signifi cant yield effects, probably due to low light levels during the early
growth period.
179
Muskmelon (Cucumis melo L. ) Responses to Floating Rowcover
Hassan Elattir*, Mohamed Derouich, and Abdelhaq Hanafi ; Institut Agronomique
et Vétérinaire Hassan II, Complexe Horticole d’Agadir, Rabat, Morocco
Two groups of Cucumis melo L. cv. Galia F1 were seeded on 10 Jan. 1994. The
fi rst group was direct-seeded in a loam sandy soil and covered at the same time
with perforated polyethylene fl oating rowcover. The other group was seeded in a
nursery and the muskmelon seedlings were transplanted and covered by perforated
polyethylene in 7 Feb. 1994. The experiment was conducted in the Complexe Horticole experiment station located 17 km southeast of Agadir in a randomized block
design with four treatments and four replications. Floating rowcover increased
minimal and maximal air temperatures by 0.92 to 2.43 °C and 3,71 to 6.99 °C,
respectively. Ten centimeters deep, soil temperatures of covered treatments were
higher by 0.35 to 0.57 °C and 0.71 to 1 °C at 7 AM and 4.30 PM respectively.
Plant early yield recorded in the four treatments: transplanted muskmelon with
fl oating rowcover, direct seeded muskmelon with fl oating rowcover, transplanted
muskmelon without cover and direct seeding without cover was 2003.9 g, 1219.2
g, 500.9 g, and 60.6 g respectively.
180
Effect of Mulch Type and Color on Honeydew Melon (Cucumis
melo L. ) Production in Western Mexico
J. Farias-Larios*, C. Sandoval, F. Radillo, J.G. Lopez, and S. Guzman; Facultad
de Ciencias Biologicas y Agropecuarias, Universidad de Colima. Apartado postal
36, 28100 Tecomán, Colima, Mèxico
Recently, honeydew melons cultivation has spread greatly in the western
Mexico for its high price and demand for export market to the United States,
Canada, and Japan. Information on production systems of this melon type is lack-
HORTSCIENCE, VOL. 33(3), JUNE 1998
ing. The present study was conducted to determine the effect of various mulches
on yield of honeydew melon grown in tropical region. Treatments evaluated
were: clear, white, brown, black, silver/black, and black/silver as plastic mulches
colors and rice and corn straw used as organic mulches and bare soil as control.
All polyethylene were of 125 thickness. These were arranged in a randomized
complete-block design with four replications. ‘Honey brew’ (Sakata) hybrid melon
plants were transplanted each 0.50 cm as single on the center row on 27 Mar.
Results show that the all polyethylene mulches, irrespective of color, were superior
to rice, corn straw and bare soil in improving the number and weight of fruits and
yield of honeydew melons. Among the mulch colors, clear plastic increased the
number and weight of fruits in 34 and 0.727 g with respect to control. Yield was
also enhanced by clear mulch with 226.05 kg, compared with organic mulches
and the control with only 113. 30, 111.50, 100.20 kg/plot of 10 m2 respectively.
Clear and black plastic completely suppressed the weed growth. Total soluble
solids were also affected by the mulch type at the fi rst harvest, the best content
(more of 10.0% ) was obtained with white and brown plastic mulches, and organic
mulches, while that bare soil showed 8.05% . Organic mulches were found as a
low-input alternative agricultural system for honeydew melons production.
181
Threshold Monitoring, Trap Cropping, and Aluminum Mulch Repulsion for Management of Cucumber Beetles on Cucurbits
John S. Caldwell*, Sam Johnson, Michael LaChance, and Stephanie Stockton;
Dept. of Horticulture, Virginia Polytechnic Inst. & State Univ., Blacksburg,
VA 24061-0327
Three approaches to cucumber beetle [striped, Acalymma vittata (Fabricius)];
spotted, Diabrotica undecimpunctata howardi Barber] management on cucurbits
were tested on 11 farms in Virginia. Visual counts of striped cucumber beetles/fi ve
squash plants were similar in 1996 (2.6 ± 3.1, max 16) and 1997 (3.1 ± 3.8, max
18), but counts on adjacent yellow sticky traps were higher in 1996 (11.5 ± 14.5,
max 66) than in 1997 (4.9 ± 4.1, max 16). Correlation between visual and card
counts was stronger in 1996 (r = 0.66) than 1997 (r = 0.38). Regression indicated
that a threshold of fi ve beetles/fi ve plants was equivalent to 16 beetles/trap in
1996, but only six beetles/trap in 1997. On two peak count dates in Aug. 1996,
trap crop squash cultivar NK530 had 10 beetles/sticky card, signifi cantly higher
than the three to seven beetles/sticky card on ‘Seneca’ and ‘Scallop’. Similar
trends were seen in visual counts in these plots. In 1997, ‘NK530’ also showed
preferential beetle attraction over pumpkin cultivar Howden. On early squash in
1997, cucumber beetle counts on two June peak dates were higher on black plastic
(40 and 23 beetles/trap) than on solid aluminum (eight and fi ve beetles/trap) or
black with aluminum strips (15 and 10 beetles/trap). Black plastic required 1.8
insecticidal applications compared to none for solid aluminum. There were no
signifi cant differences in cumulative yield, although yield at fi rst picking was 38%
less on aluminum. Premiums for lower pesticide use (25% ) compare favorably
with the $102/acre added expense for aluminum plastic.
182
Banded Cucumber Beetle (Diabrotica balteata LeC. ) Injury
during Sweetpotato Development
Lewis W. Jett* 1, Rick N. Story2, and Abner M. Hammond2, 1Louisiana State Univ.
Sweet Potato Research Station, Chase, LA 71324-0120; 2Dept. of Entomology,
Louisiana State Univ., Baton Rouge, LA 70894
Banded cucumber beetle (Diabrotica balteata LeC.) larvae can cause signifi cant
injury to the sweetpotato [Ipomoea batatas (L.) Lam.] by boring small holes in the
storage root. Often, these holes expand with development to produce crater-like
scars. The objective of this research was to characterize the effects of Diabrotica
injury to storage roots by simulating the injury through development. Deep (i.e.,
penetrating the vascular cambium) and shallow (i.e., not penetrating the vascular
cambium) injuries were infl icted at 10-day intervals on ‘Beauregard’ sweetpotato
commencing 35 days after transplanting (DAT) through 85 DAT in 1996 and 1997.
Visual evaluation indicated signifi cant healing of deep injury through 55 DAT, with
the diagnostic cratered appearance more prevalent on storage roots injured at 35
and 45 DAT. Moreover, deep injury in early development (35, 45 DAT) signifi cantly
expanded in diameter and depth, reducing marketable yield. Signifi cant healing
of shallow injury was observed through 75 DAT. The results of this research can
be used by growers and researchers to assess the stage of development in which
Diabrotica injury occurred.
475
183
Use of Cover Crop Mulches in a Processing Tomato Production
System
E.V. Herrero*, J.P. Mitchell , E. Campiglia, W.T. Lanini , S. Temple, and G. Miyao;
Univ. of California, Davis, CA 95616
Conventional processing tomato production in California relies on inputs of
synthetic fertilizers, water, and tillage to achieve high yields. Recently, there has
been interest in reducing off-farm inputs and increasing soil quality by reducing
tillage and increasing organic matter. Thus, this experiment examined the use of
cover crops and no-till tomato production. Experiments were conducted in 1996
and 1997 at two sites, Five Points and Davis, Calif. Winter-grown cover crops
included barrel medics, subterranean clover, pea, vetch, triticale, ryegrass, oat,
and fallow controls. Cover crop plots were divided into three parts and nitrogen
fertilizer added at 0, 112 or 225 kg/ha. Cover crops were mowed, and 3 weeks
later, tomatoes were no-till transplanted into each plot. Weed cover at all sampling
dates was less than 5% on all plots at the Five Points site, with no signifi cant
differences among treatments. At Davis, weed cover was much higher, but was
also not signifi cant among treatments. Tomato yields were highest (93 ton/ha)
on the fallow plots and lowest (58 ton/ha) on the barrel medic plots at the Five
Points site. At Davis, tomato yields were generally very low due to competition
from weeds. The barrel medic cover crops plots had the highest tomato yields
at this site (34 tons/ha), with plots without cover crops having the lowest yields
(12 tons/ha). Tomato yields were 18% and 29% higher when 112 kg/ha or 225
kg/ha of nitrogen was added, compared to no nitrogen.
184
Mulch Type Influences Yield of Fall Tomato
S.B. Sterrett* , H.E. Hohlt, and C.P. Savage, Jr.; Virginia Tech, Eastern Shore
Agricultural Research and Extension Center, Painter, VA 23420
Because of environmental concerns relating to the potential for surface runoff
from plastic culture, the potential of six cover crops [pearl millet (Pennisetum
glaucum ), sorgham (Sorghum bicolor), cowpea (Vigna sinensis), buckwheat
(Fagopyrum esculentum), soybean (Glycine max), and millet/cowpea combination
was compared to a plastic mulch for fall tomato production in 1996. All cover
crops were chemically desiccated prior to tomato transplanting. The use of plastic
mulch signifi cantly increased early marketable yield; soybean or millet/cowpea
mulch signifi cantly reduced the production of large fruit. Total marketable yield
of cover crop mulches except millet/cowpea was similar to that of plastic mulch.
In 1997, full (0.9-m) and narrow (0.45-m) plastic mulched beds were compared
to desiccated millet or sorghum mulches or straw mulch applied at planting.
Early marketable yield was greatest for straw mulch. Total marketable yield of
straw and both plastic mulch treatments was signifi cantly higher than that for
desiccated mulches. Width of the plastic mulched bed did not signifi cantly affect
total marketable yield.
185
Enhancing Earliness in Peppers using Rowcovers and Waterfilled Tubes
Anusuya Rangarajan* and Betsy Ingall ; Dept. of Fruit and Vegetable Science,
Cornell Univ., Ithaca, NY 14853
Vegetable growers around New York State are using rowcovers and earlier
planting dates to produce early peppers, due to the higher prices received compared to the main season. However, high temperatures often achieved under the
tunnels can contribute to blossom abscission of peppers. Water-fi lled polyethylene
tubes, which are placed underneath rowcovers, have been shown to moderate
temperatures under low and high tunnels. These tubes of water, placed between
or as near to plant rows as possible, under the tunnel, absorb heat during the
day and radiate heat during the night. Two tubes, clear and black, were compared
for impact on earliness of two varieties of bell pepper. Both tubes were 12" fl at
diameter and fi lled with water to an 8" fl at diameter. Each bed had two rows of
peppers, with the water tubes placed down the center. White, perforated plastic
was placed over hoops to create row tunnels. Air temperature measurements in
the tunnels indicated that both the clear and black tubes decreased the daytime
temperatures compared to the tubeless tunnels. The black tubes absorbed more
heat during the day. At night, both tubes were equally effective at providing a
slight warming of tunnel canopy temperatures. However, clear tubes kept soil
temperatures warmer at night and reduced overall soil temperature fl uctuations. The
black tubes showed no advantage for regulating soil temperature. No signifi cant
differences were detected for total yield among different water tubes or cultivars.
476
However, clear tubes contributed to a 30% increase in early yields, compared to
control or black tubes. Economics of water tube use in early pepper production
will be presented.
186
Effects of Cover Crops and Tillage on Sweet Corn Production
Gary R. Cline* and Anthony F. Silvernail ; Community Research Service, Kentucky
State Univ., Frankfort, KY 40601
A split-plot factorial experiment examined effects of tillage and winter cover
crops on sweet corn in 1997. Main plots received tillage or no tillage. Cover crops
consisted of hairy vetch, winter rye, or a mix, and N treatments consisted of plus
or minus N fertilization. Following watermelon not receiving inorganic N, vetch,
and mix cover cropsproduced total N yields of ≈90 kg/ha that were more than four
times greater than those obtained with rye. However, vetch dry weight yields (2.7
mg/ha) were only about 60% of those obtained in previous years due to winter kill.
Following rye winter cover crops, addition of ammonium nitrate to corn greatly
increased (P < 0.05) corn yields and foliar N concentrations compared to treatments not receiving N. Following vetch, corn yields obtained in tilled treatments
without N fertilization equaled those obtained with N fertilization. However, yields
obtained from unfertilized no-till treatments were signifi cantly (P < 0.05) lower
than yields of N-fertilized treatments. Available soil N was signifi cantly (P < 0.05)
greater following vetch compared to rye after corn planting. No signifi cant effects
of tillage on sweet corn plant densities or yields were detected. It was concluded
that no-tillage sweet corn was successful, and N fi xed by vetch was able to sustain
sweet corn production in tilled treatments but not in no-till treatments.In previous
years normal, higher-yielding vetch cover crops were able to sustain sweet corn
in both tilled and no-till treatments.
187
Inhibition of Fungal Growth by Macerated Plant Tissues in a
Closed Environment
Craig S. Charron*, Catherine O. Chardonnet , and Carl E. Sams; Dept. of Plant
and Soil Sciences, The Univ. of Tennessee, Knoxville, TN 37901
The U.S. Clean Air Act bans the use of methyl bromide after 2001. Consequently, the development of alternative methods for control of soilborne pathogens
is imperative. One alternative is to exploit the pesticidal properties of macerated
tissues of Brassica spp. This study tested the potential of several Brassica spp.
for control of fungal pathogens. Pythium ultimum Trow or Rhizoctonia solani
Kühn plugs on potato-dextrose agar on petri dishes were sealed in 500-ml glass
jars (at 22 °C) containing macerated leaves (10 g) from one of six Brassica spp.
Radial growth was measured 24, 48, and 72 h after inoculation. Indian mustard
(B. juncea) was the most suppressive, followed by ‘Florida Broadleaf’ mustard
(B. juncea). Volatile compounds in the jars were sampled with a solid-phase
microextraction device (SPME) and identifi ed by gas chromatography-mass
spectrometry (GC-MS). Allyl isothiocyanate (AITC) comprised over 90% of the
total volatiles measured from Indian mustard and ‘Florida Broadleaf’ mustard.
Isothiocyanates were detected in jars with all plants except broccoli. (Z)-3-hexenyl
acetate was emitted by all plants and was the predominant volatile of ‘Premium
Crop’ broccoli (B. oleracea L. var. italica), ‘Michihili Jade Pagoda’ Chinese
cabbage (B. pekinensis), ‘Charmant’ cabbage (B. oleracea L. var. capitata), and
‘Blue Scotch Curled’ kale (B. oleracea L. var. viridis). To assess the infl uence of
AITC on radial growth of P. ultimum and R. solani , AITC was added to jars to
give headspace concentrations of 0.10, 0.20, and 0.30 mg• L–1 (mass of AITC per
volume of headspace). Growth of both fungi was inhibited by 0.10 mg• L–1 AITC.
0.20 mg• L–1 AITC was fungicidal to P. ultimum although the highest AITC level
tested (0.30 mg• L–1) did not terminate R. solani growth. These results indicate
that residues from some Brassica spp. may be a viable part of a soilborne pest
control strategy.
83
POSTER SESSION 2I (Abstr. 188–192)
Education
188
“The Greenhouse of the Future”: Using a Sponsored Competition in a Capstone Course
HORTSCIENCE, VOL. 33(3), JUNE 1998
Ricky M. Bates* and David A. Baumbauer; Dept. of Plant, Soil and Environmental
Sciences, Montana State Univ., Bozeman, MT 59717-3120
Horticulture students often lack practical experience integrating information
from diverse sources to solve complex real-life problems. Capstone courses
seek to remedy this by giving students an opportunity to demonstrate a range of
workplace skills such as teamwork, effective communication, and critical thinking.
Sponsored competitions provide educators with an active-learning framework
into which the goals of a capstone course can be developed. In 1996 the U.S.
Dept. of Energy and the Epcot Center announced the “Greenhouse of the Future”
competition. The competition sprang from an interest by sponsoring agencies
to promote the development of new environmentally sound technologies for
greenhouse food production and was open to all U.S. undergraduate students.
The competition encouraged the formation of interdisciplinary student teams under
the direction of a faculty advisor and offered the winning entry a $10,000 research
grant and the opportunity to display the new technology at the Epcot Center in
Florida. The M.S.U. entry focused on the development of season-extending
energy retention systems designed for small greenhouses, production testing of
cool-season, stress-tolerant crops such as Mesclun salad greens, and the use
of an environmentally neutral growing system. Sponsored competitions present
an important tool for achieving certain educational objectives and may be one
way to help students think on a higher level. Encouragement and development of
similar competitions within the green industry is needed. Competition guidelines,
components of the M.S.U. winning entry, and integration of the competition into
the capstone course “Greenhouse Management” will be discussed.
Gregory E. Welbaum* and Scott Hudson; Dept. of Horticulture, Saunders Hall,
Virginia Tech, Blacksburg, VA 24061-0327
A teaching homepage was created on the World Wide Web at: http://www.hort.
vt.edu/faculty/welbaum/hort4764 to teach an introductory college level course
on vegetable crops. The homepage was designed to be viewed using Netscape
software. Reading assignments and class outlines are formatted as .pdf fi les and
can be viewed using Adobe Acrobat Reader. This software can be downloaded
from the homepage. The homepage is linked to additional pages entitled: “Course
description,” “Instructor,” “Text and other printed reference material,” “Class
schedule and assignments,” “Class related pictures,” “Sample test questions,”
“Chat room,” “Class project,” “Other web sites of interest,” and “Grading.” Twohundred pages of text and outlines describing production of vegetables using
plasticulture, vegetable seed technology, vegetable production under protective
cover, and other topics as well as descriptions of 28 individual vegetables are
available through the homepage. There are more 500 pictures and descriptions of
vegetables and vegetable crop production linked to this website. Students can be
examined using a computer testing system call Whizquiz that grades and corrects
each exam. A Chat Room allows discussion among students and the instructor.
Discussion sessions can be conducted between students and guests at distant
locations. Student term projects on a range of subjects relating to vegetable crops
are linked to the homepage. Links are provided to over 25 other World Wide Web
sites with additional information on vegetable crops. This teaching homepage
has been used for two semesters and students’ evaluation of the system will be
provided.
189
A Web Site as an Aid in Teaching the Identification Of Landscape Plants
192
The Use of a Multidisciplinary, Culturally Rich Web Site by
Youth and Formal and Informal Educators to Increase Appreciation and Awareness of Plants and Other Cultures
Patrick J. Breen * ; Dept. of Horticulture, Oregon State Univ., Corvallis, OR
97331
Web sites were developed as an aid in teaching landscape plant materials at
Oregon State Univ. A three-quarter course sequence emphasizes identifi cation of
woody landscape plants by their scientifi c names and, when appropriate, variety or
cultivar names. Different groups of plants are introduced in each quarter: deciduous
(fall), conifers and broadleaf evergreens (winter), and fl owering plants (spring).
Approximately 160 plant specimens are introduced each term, fi rst by photographic
slides and then by tours through the campus and surrounding areas. Each course
is supported by a separate Web site that contains an informational summary and
several images of each plant introduced. There are about 600 plant images per
site. Plants on the Web sites are listed alphabetically by scientifi c name with
links to specifi c images of that specimen (e.g., plant habit, leaves, fl owers, etc.).
Particular morphological characteristics used in plant identifi cation are sometimes
labeled in the images and some links provide side-by-side comparisons to aid
in distinguishing similar plants. Students are not encouraged to use the Web
sites as the major device to improve their plant identifi cation skills, but rather
to rely on frequent examination of live specimens in landscape situations. The
Web sites are viewed as supplementary supports, especially to assist students in
comparing similar plants, to provide a convenient source of plant images specifi c
to each course, to permit visual study during inclement weather and at night, and
in reviewing course material.
190
Undergraduate Program Growth and Enhancement: The Results
of Curriculum Assessment in Landscape Contracting
Martin R. McGann, Dan T. Stearns*, and Larry J. Kuhns; Dept. of Horticulture,
Pennsylvania State Univ., University Park, PA 16802
Following a recent curriculum assessment effort involving faculty, students,
and industry representatives, the Dept. of Horticulture at Penn State developed a
strategic action plan for future growth and evolution of its landscape contracting
program. Highlights of the plan include: establishment of a landscape management
option with emphasis on weed, pest, and disease management, plant establishment and plant maintenance; refi nement of an internship program; continuation
of collaborative and experiential learning opportunities; and development of a
course that addresses current issues in the landscape profession. Additional actions resulting from the assessment process range from the addition of a Spanish
course to support for the establishment of a campus arboretum.
191
A World Wide Web Site for Teaching Vegetable Crops
HORTSCIENCE, VOL. 33(3), JUNE 1998
Bindu R. Bhakta* and Daniel J. Tennessen; Cornell Univ., Dept. of Floriculture
and Ornamental Horticulture, Ithaca, NY 14853
Throughout history, people have forged an intricate relationship with plants.
As a result, ethnobotany, the study of this association between people and plants,
has begun to receive great attention. Like ethnobotany, horticulture is a fi eld of
study that humans depend on to enhance and beautify their living and working
environments. In order to promote the fi elds of horticulture and ethnobotany,
a multidisciplinary, “plant-centered” web site about Asian Indian ethnobotany
was assembled. Novel or unique plants were used to promote exploration of
multicultural experiences that refl ected the increasing diversity in today’s formal
and non-formal classrooms. The web site contained pictures, video and audio
clips, experimental activities, links to other web sites, places to visit these plant
specimens, and supplemental materials for individuals interested in conducting further scientifi c investigations. Seven ethnobotany units were developed:
Vegetable Diversity, Healing Plants, Indian Staples, Sacred Plants, the Easel of
Indian Textiles, Tastes of India, and Ceremonial Plants. Outreach programs were
conducted in Ithaca-area schools and 4-H clubs to evaluate youth interest in the
topics presented in the web site. This educational program allowed middle school
students the unique opportunity to conduct a self-guided exploration of important
Indian ethnobotanical plants, while gaining important and valuable horticultural
experience in plant classifi cation, structure, growth substances, propagation, and
diseases. This program also provided important exposure for both youth interested
in pursuing ethnobotany or horticulture as a future career and for those with no
previous horticultural or ethnobotanical experience. In conclusion, this web site
used a novel multicultural approach to allow youth to develop an awareness for
plants in other cultures while cultivating appreciation of plants important in their
own cultures.'
83
POSTER SESSION 2J (Abstr. 193–201)
Propagation—Woody Ornamentals/Landscape/Turf
193
Micropropagation of Adult Red Maple and Sugar Maple
David A. Connolly, John E. Preece* , and J.W. Van Sambeek; Dept. of Plant,
477
Soil and General Agriculture, Southern Illinois Univ. and USDA Forest Service,
Carbondale, IL 62901
Micropropagation studies were conducted to determine the best methods
to achieve axillary shoot proliferation for adult Acer rubrum (red maple) and
A. saccharium (sugar maple). The fi rst experiment was conducted to compare
the effects of 0.001, 0.01, 0.1 µM, 1 µM, and 10 µM thidiazuron (TDZ) using
Driver-Kuniyuki-Walnut medium (DKW). The second experiment was conducted
to examine the effects of DKW, Woody Plant Medium (WPM) and Long and
Preece (LP) media in factorial combination with 0.01 and 0.1 µM TDZ. The third
experiment was conducted to study the transfer timing (14 or 28 days) and the
media solidifi cation (agar-solidifi ed or stationary liquid) on sugar maple. Both
red maple and sugar maple explants on DKW with 0.1 µM TDZ produced the
most and longest axillary shoots; however, sugar maple produced fewer axillary
shoots than red maple. Red maple explants produced the most callus on DKW
with 10 µM TDZ and the least on DKW with 0.001 µM TDZ. Sugar maple explants
produced more shoots when explants were placed horizontally and transferred
every 14 days than when placed vertically or transferred less frequently.
194
Shoot Regeneration from Rhododendron Leaf Explants and
Callus
Sarah S. Crist* and John E. Preece; Dept. of Plant, Soil and General Agriculture,
Southern Illinois Univ., Carbondale, IL 62901-4415
Shoots were regenerated adventitiously from leaf explants and from callus to
determine if there is any effect on somaclonal variation and tissue proliferation of
the three rhododendron cultivars, Arctic Pearl, P.J.M. Elite, and Purple Gem. The
focus of this paper is regeneration. Leaves from shoot cultures were placed on a
pre-conditioning medium for 2 weeks containing 10 µM indolebutyric acid (IBA)
and 50 µM isopentenyladenine (2iP) and then transferred to treatment media.
The six media tested were 0.1, 1.0, or 10.0 µM thidiazuron (TDZ) or 25.0, 50.0,
or 75.0 µM 2iP. All treatment media contained 10 µM IBA. Data were collected
on shoot regeneration after 24 weeks. Shoot number increased with increasing
levels of TDZ for ‘P.J.M. Elite’, but decreased with increasing concentrations of
TDZ for ‘Arctic Pearl’. Shoot number for ‘Purple Gem’ leaf explants was greatest
when there was 1.0 µM TDZ in the medium. In another experiment, leaf explants
were placed on the same preconditioning medium for 2 weeks as above and then
transferred to three treatment media containing 0.1, 1.0, or 10.0 µM TDZ and 100
µM IBA. Callus was produced on leaf explants after 4 weeks, regardless of cultivar
or level of TDZ. After 11 weeks, adventitious shoots regenerated from ‘Purple Gem’
callus regardless of level of TDZ and from ‘Arctic Pearl’ callus when the medium
contained 0.1 or 10.0 µM TDZ. After 11 weeks, there were no visible shoots on
‘P.J.M. Elite’ callus.
195
Epicormic Shoot Forcing of Adult Red Maple, Sugar Maple,
and Eastern Black Walnut
David A. Connolly, Amy B. Bailey, John E. Preece*, and J.W. Van Sambeek; Dept.
of Plant, Soil and General Agriculture, Southern Illinois Univ. and USDA Forest
Service, Carbondale, IL 62901
Dormant stem sections from three individuals each of Acer rubrum (red maple)
and A. saccharium (sugar maple), and three clones of Juglans nigra (eastern black
walnut) were collected from lower lateral branches of trees at least 30 years old.
The stem sections were cut into 50-cm-long segments and placed horizontally
in soilless media in a greenhouse. Two experiments were conducted to determine
which treatments were most effi cient for the production and elongation of epicormic
shoots from latent buds below the bark. The fi rst experiment consisted of a factorial
arrangement of two levels of shading (not shaded or covered with 48% Saran shade
cloth) and two levels of fl ooding (not fl ooded or fl ooded to a depth of 1/3 to 1/2
the diameter of the stem sections). Flooded treatments contained 0.025% NaClO
to control microbial growth. The second experiment consisted of three media
treatments: perlite, vermiculite, or a 1 perlite: 1 vermiculite (by volume) medium.
No stem segments of any species in fl ooded treatments produced softwood shoots.
Neither shading nor media treatments affected shoot number or length for any of
the species. Additional sugar maple segments collected after budbreak produced
more and longer shoots than those collected while dormant.
196
Axillary Shoot Proliferation of Adult Eastern Black Walnut
478
Amy B. Bailey, John E. Preece*, and J.W. Van Sambeek; Dept. of Plant, Soil and
General Agriculture, Southern Illinois Univ. and USDA Forest Service, Carbondale,
IL 62901
Softwood shoots of adult Juglans nigra (eastern black walnut) were forced from
latent (epicormic) buds below the bark of large stem sections in a greenhouse.
Once suffi ciently long, the shoots were excised, surface-disinfested, and cut into
1-cm-long nodal or apical segments for establishment in culture vessels. Two
experiments were conducted, each using explants of three different clones. The fi rst
experiment compared the effect of cytokinins: 0.3, 1.0, or 3.0 µM benzyladenine
(BA) and 0.1, 0.3, or 1.0 µM thidiazuron (TDZ) arranged factorially. The basal
medium was agar-solidifi ed Long and Preece (LP) with 0.05 µM indole-3-butyric
acid (IBA) and 30 g/L sucrose. The second experiment compared the agar-solidifi ed
basal media: Driver-Kuniyuki-Walnut (DKW), Woody Plant Medium (WPM) and
LP, all with 1.0 µM BA, 0.3 µM TDZ, 0.05 µM IBA, and 30 g/L sucrose. Regardless
of the BA concentration, explants on media containing 0.1 µM TDZ produced few,
if any, axillary shoots while explants on media containing 1.0 µM TDZ excessive
amounts of callus. Explants in media containing 0.3 µM TDZ, at all levels of BA,
produced the greatest number of shoots and minimal callus. Male catkins were
produced by 17 explants on various media. Fifteen of the catkin-producing explants
were from one walnut clone. Axillary shoot number and callus production were
not signifi cantly affected by basal medium for any of the three clones.
197
Tumor Incidence and Shoot Morphology Differences in Rooted
Cuttings from Rhododendron With and Without “Tissue Proliferation”
Mark H. Brand* 1 and Richard Kiyomoto2; 1Dept. of Plant Science, Univ. of Connecticut, Storrs, CT 06269; 2Dept. of Forestry & Horticulture, Connecticut Agr.
Expt. Station, New Haven, CT 06504.
Tissue proliferation (TP) occurs in Rhododendron and is characterized by
basal tumors that often develop numerous dwarf shoots. Growers need to know
if the TP condition will persist in plants grown from normal-appearing cuttings
collected from plants with TP tumors. Cuttings of seven cultivars were collected
from plants with TP [TP(+)] and without TP [TP(-)] and rooted. Plants were grown
in containers outdoors for a minimum of 2 years. For all cultivars, plants grown
from TP(+) cuttings had more leaves per growth fl ush than plants grown from
TP(-) cuttings. Shoots of TP(+) plants were either similar in length to shoots of
TP(-) plants, or were shorter, as was the case for ‘Boule de Neige’, ‘Catawbiense
Album’, and ‘Montego’. ‘Montego’ and ‘Scintillation’ TP(+) leaves were shorter,
narrower, had smaller leaf areas and larger length to width rations than leaves
from TP(-) shoots. No difference in leaf size and shape were detected for other
cultivars. TP tumors were not observed on any plants. Another study examined
the effect of stock plant age from tissue culture on development of TP symptoms in
rooted cuttings. ‘Montego’ plants grown from cuttings collected from microplants,
3-year-old TP(+) plants, 6-year-old TP(+) plants and TP(-) plants were compared.
Plants grown from 6-year-old TP(+) and TP(-) cuttings did not develop tumors.
83% of plants from microplant cuttings and 74% of plants from 3-year-old
TP(+) cuttings formed tumors. Plants from microplant cuttings were more likely
to develop large tumors that surround half or more of the stem than plants from
3-year-old TP(+) cuttings.
198
Utilization of Different Seedling Explants for in Vitro Propagation of Hibiscus syriacus
M.M. Jenderek* 1 and A.J. Olney2; 1Dept. of Biology, 2Dept. of Plant Science,
California State Univ., Fresno, CA 93740
Hibiscus syriacus is a diffi cult species in micropropagation due to its
endogenous contamination and recalcitrant shoot formation; therefore, studies
on using explants other than shoot tip or axillary buds of growing shrubs were
initiated . Three different seedling fragments (root, hypocotyl, and leaf petiole)
from aseptically germinated seedlings of hibiscus (var. Aphrodite) were evaluated
for adventitious bud formation, shoot and leaf development. The explants were
cultured on McCown’s woody plant basal salt medium supplemented with KNO3
(800 mg/L), adenine sulfate (80 mg/L) and MS vitamins containing BA or 2iP
or TDZ at 0.5, 1.0, 2.2, 4.4 and 10 mM. Adventitious buds were present on all
of the three different explants grown on medium containing TDZ; however, the
most abundant bud formation, with many small leaves originating from callus
was observed on hypocotyl explants cultured on medium with 1 mM of TDZ.
HORTSCIENCE, VOL. 33(3), JUNE 1998
Petiole explants were the most frequent to develop short shoots (≈15 mm) and
one to nine leaves without callus formation, where 70% of hypocotyl and the root
explants formed leaves originating from callus. Callus was induced on all explant
types regardless of the level or type of cytokinin used. However, the number of
shoots produced by any explant type was low, petioles cultured on 0.5 and 1mM
of TDZ were the most suitable material for non-callus shoot development in H.
syriacus. Hypocotyl explants proved to be an excellent source for adventitious
bud formation but their ability to develop shoots needs to be investigated.
199
Somatic Embryogenesis and Plant Regeneration of Wiregrass
(Aristida stricta) and Creeping Bluestem (Schizachyrium scoparium var. stoloniferum)
Wusi Chen1, Jeffrey G. Norcini* 1, Robert S. Kalmbacher2, and James H. Aldrich1;
Univ. of Florida, North Florida Res. & Edu. Ctr., Rt. 4 Box 4092, Monticello, FL
32344; 2Univ. of Florida, Range Cattle Res. & Edu. Ctr., 3401 Experiment Station,
Ona, FL 33865
Initiation of callus and induction of embryogenesis were achieved from both
wiregrass and creeping bluestem. MS basal medium containing coconut milk, sucrose, and 2,4-D were used to initiate callus from young infl orescence of wiregrass
and creeping bluestem. The presence of 2,4-D was found to be essential for the
induction and early development of embryoids, possibly up to the globular stage.
In the case of bluestem, initiation of embryogenic callus required the presence of
a low concentration of BA; using only 2,4-D resulted in more non-embryogenic
callus. More globular embryos were formed when embryogenic cultures grew
rapidly without subculturing, or after being transferred to a hormone-free or a
reduced 2,4-D medium. Plant regeneration was carried on a hormone-free MS
medium. Initiation of cell suspension and induction of embryoid formation of
wiregrass were achieved. However, maintaining cell suspensions seems to have
some problems. A majority of the cells were thick-walled, elongated, and nondividing. No embryos were formed in suspension cultures planted onto solid
media. Reinitiation of cell suspension culture of wiregrass is in progress. Initiation of creeping bluestem cell suspension culture was carried out in MS basal
medium containing coconut milk, sucrose, and 2,4-D. The maintenance of the
cell suspension cultures and induction of embryoid formation were tested under
different combinations and concentrations of growth regulators. Suspension
cultures were selected and planted onto semi-solid MS basal medium with or
without growth regulators. Somatic embryoids formed from suspension culture
3 to 4 weeks after being planted on semi-solid medium. Germination and plant
regeneration of somatic embryoid of creeping bluestem are in progress.
1
200
Propagation of Alnus maritima [Marsh. ] Nutt. (Seaside Alder)
James A. Schrader* and William R. Graves; Interdepartmental Plant Physiology
Program, Dept. of Horticulture, Iowa State Univ., Ames, IA 50011
We are interested in the potential of seaside alder as a shrub or small tree for
managed landscapes. This species has received little attention from horticulturists and occurs naturally only in small, disjunct populations in Maryland and
southern Delaware (Delmarva Peninsula), northwestern Georgia, and south-central
Oklahoma. Our objective is to optimize asexual (softwood cuttings and tissue
culture) and sexual propagation of seaside alder while testing for differences in
propagation success among populations. Terminal softwood cuttings collected
11 June 1997 (Delmarva) and 25 Aug. 1997 (Oklahoma) were treated with IBA
at various concentrations and provided intermittent mist in a greenhouse for 10
weeks. Up to 44% rooting was achieved by using 1 g IBA/kg on cuttings from
Delmarva; replication over time will be used to determine whether poorer rooting of cuttings from Oklahoma (maximum of 17% with 8 g IBA/kg) was due to
genotypic effects or the time of collection. Strobili were collected during late 1997
from multiple plants in the three populations. Unstratifi ed seed from Oklahoma
showed from 40% to 76% germination after 21 days depending on the tree of
origin. The only previous data of germination of unstratifi ed seeds was a report
of 5% to 20% for seeds from Delmarva, so provenance as well as stratifi cation
effects on germination are being evaluated.
201
Mitotic Activity Dynamics in Recalcitrant Seeds Acer sachharinum during Maturation and Germination
L. Kozeko*, V. Troyan, and L. Musatenko; Dept. of Phytohormonology, N.G.
HORTSCIENCE, VOL. 33(3), JUNE 1998
Kholodny Inst. of Botany, Kiev, Ukraine
In orthodox seeds the cell division within the embryo meristems arrests during
maturation at embryo moisture content (MC) 65% to 47% , and the maturation
completion and transition of seeds to quiescent state occurs at MC about 10%. The
arrest of cycling happens asynchronously in different meristematic tissues during
desiccation: fi rst in shoot and then in root. The aim of this work was to defi ne a
mitotic activity dynamics in recalcitrant seeds with the high MC at maturation end
and the absence of quiescent state characteristic of it. The object was seeds of
Acer saccharinum, using widely for planting of greenery in Kiev city. The mitotic
activity was determined in 0.5 mm of the embryo root pole (RP) and 0.5 mm of the
shoot pole with embryo leaves (SP). The A. sachharinum seeds completed them
maturation at MC 53% (FW basis). During maturation the mitotic index (MI) in
RP decreased from 3.2% in immature seeds (at embryos MC 80% ) to 0 in mature
seeds and in SP–from 5.4% to 3.3% , respectively. Cell division in SP arrested
by dehydration of mature embryos to MC 46% by PEG 6000 (30% ). The seeds
lost viability by desiccation to MC 34% . The mature seeds were able to germinate
immediately after abscission. During seed germination the cell division reactived
in RP and increased in SP already before root protrusion. In plantlets 10–15 mm
long the MI increased to 8% in RP and 12% in SP. Thus, the strategy of immediate germination of recalcitrant A. sachharinum seeds includes a preservation of
cell division in SP of mature embryos, in contrast with orthodox seeds, and high
mitotic activity levels in meristems of germinating embryos before and after root
protrusion.
83
POSTER SESSION 2K (Abstr. 202–208)
Crop Physiology/Environmental—Crosscommodity
202
Growth of Ornamental Plants in Compacted Soils in Relation
to Root Growth under Low Oxygen and High Atmospheric Pressure
Michael Knee* and Ruth Brake; Dept. of Horticulture and Crop Science, The Ohio
State Univ., Columbus, OH 43210
In urban situations, particularly after construction, herbaceous ornamentals may
be planted into soils that are compacted or have poor structure so that plant roots
may encounter poor aeration or physical resistance. Low oxygen concentrations
may be the most important aspect of poor aeration and are readily reproduced in
the laboratory. High atmospheric pressure might be used to screen for the ability
to grow against physical resistance. We tested the suggestion that “native” plants
would grow better in compacted soils than typical bedding plants and for differences in tolerance to low oxygen or high pressure. Plants were grown from seed
in the greenhouse at four levels of compaction in peat-based medium and in fi eld
soil. Shoot dry weights of the native plants Asclepias tuberosa, Echinacea purpurea,
and Schizachyrium scoparius, were less affected by growth in compacted soil or
peat medium than those of the bedding plants, Antirrhinum majus, Gypsophila
elegans, Impatiens balsamina, Tagetes patula and Zinnia elegans. The oxygen
content of media declined with compaction to a minimum of 10 kPa. Half maximal
root elongation was observed at 1 to 3 kPa oxygen for most species without any
separation between the groups. A presure of 1100 kPa reduced root elongation of
the bedding plants by 50 to 70% but only 5 to 20% for the native plants.
203
Establishment of Prairie Forbs and Grasses after Production
in Compacted Media
Nicole Cavender*, Laura Thomas and Michael Knee; Dept. of Horticulture and
Crop Science, The Ohio State Univ., Columbus, OH 43210
Native prairie plants are believed to grow better in compacted soils than
traditional bedding plants. We used 10 species of forbs and grasses to test the
hypothesis that establishment in the fi eld would be improved by greenhouse
production of seedlings in compacted media and in topsoil as opposed to a
peat-based medium. Media were compacted by applying 50 g• cm –2 while fi lling
cells in a tray. Uncompacted controls were simply loose-fi lled. The seedlings were
transplanted into plots that were untilled or tilled. Plants were photographed with
a digital camera at different stages and the images were analyzed by computer
479
to estimate growth non-destructively. At the time of transplanting estimated area
per seedling was 15 to 140% higher for plants grown in compacted media than
in uncompacted for 10 out of 13 species. Preliminary observations indicated that
differences between plants from compacted and uncompacted media persisted in
the fi eld and that plants grew better in the tilled plots than in untilled. Seedling
area was similar after production in topsoil or peat medium and there was no
overall difference in the fi eld. Plants from seedlings produced in topsoil were
larger than those from peat-based medium in untilled plots but the converse was
true for plants in tilled plots.
204
Effects of Sucrose and Oxygen on Nitrate Reductase Activity
and Growth of Kentucky Bluegrass
Zhongchun Jiang* and Richard J. Hull; Plant Sciences Dept., Univ. of Rhode
Island, Kingston, RI 02881-0804
Nitrate reductase activity (NRA) in turfgrass roots should play an important
role in the N metabolism of the whole plant because a major part of the shoots is
removed by mowing. However, preliminary experiments demonstrated a lack of in
vivo NRA in roots of Kentucky bluegrass grown in Hoagland’s nutrient solutions,
which were constantly aerated. We hypothesized that O2 inhibited NRA by oxidizing
carbohydrate available for NO3– reduction in roots. To test this hypothesis, Kentucky bluegrass (Poa pratensis L.), cultivar Merit, was grown in nutrient solutions
containing 0.1 mM NO3– . Grass cultures were treated with +O2 (solution aerated),
–O2 (not aerated), +Suc (sucrose added to solution, fi nal concentration = 25 mM)
or –Suc (not added) for 12 days. Plants were harvested at 5:00 pm, separated into
shoots and roots, and analyzed for in vivo NRA. The results partly supported the
above hypothesis because the –Suc–O2 roots showed signifi cantly higher NRA
than –Suc+O2 roots. However, +Suc roots did not exhibit greater NRA than –Suc
roots, possibly because of a decreased pH in the solutions. Oxygen increased
root growth and hence the growth of the whole plant, while sucrose decreased
leaf N content and leaf NRA but did not improve growth.
205
First-year Growth Response of Ornamental Trees to Municipal
Wastewater Application
Brenda L. Jessen*, Geno Picchioni, and John G. Mexal; Dept. of Agronomy and
Horticulture, New Mexico State Univ., Las Cruces, NM 88003
The U.S.–Mexico border region has experienced rapid population growth in the
past 30 years, resulting in natural resource degradation and declining public
health. Many U.S.–Mexico border municipalities have inadequate systems for
dealing with their waste. A major concern is the threat posed by water pollution,
particularly that caused by minimally treated and improperly disposed human
wastes. Border wastewater systems need to reduce contaminants, as well as safely
recycle nutrients. Existing technology supports the land application of wastewater
to tree production for low-cost, low-technology wastewater purifi cation. Chemical
analyses of the wastewater has shown that the water possesses an EC of 2.7 to 3.0
dS/m and an SAR of 6 to 7 indicating both high total salinity and sodicity that are
potentially damaging to most woody horticultural crops. This project, located in
Ojinaga, Mexico, assesses fi rst-year growth characteristics and survival of three
fast-growing trees useful for pulpwood production, Eucalyptus camaldulensis
(three clones), hybrid Populus spp. (three clones), and Robinia pseudocacia
(seedling propagated) following application with saline wastewater. Signifi cant
variation in trunk cross-sectional area was exhibited among clones. Eucalyptus
clones showing the greatest increase in trunk area growth also exhibited ≈80%
dieback during the winter months. Preliminary data indicated that one of the
Populus clones may be the best option for effective wastewater treatment and
economic sustainability through the sale of pulpwood for Ojinaga and other
U.S.–Mexico border communities.
206
Growth, Morphology, and Physiology of Intsia bijuga Trees
Under Varied Light Conditions
Robin A. DeMeo and Thomas E. Marler*; College of Agriculture and Life Sciences,
Univ. of Guam, Mangilao, GU 96923
Six studies were conducted with Intsia bijuga seedlings to determine the
methods and extent of shade tolerance for this species. Growth differences were
minimal among plants receiving varied light exposure, although treatments ranged
from 19% to 100% sunlight exposure. Light saturated photosynthesis of leaves
on plants receiving 24% sunlight was achieved at a photosynthetic photon fl ux
480
(PPF) of about one-fourth of that for the leaves on plants receiving 100% sunlight
exposure. However, photosynthesis under conditions of extremely low PPF was
higher for shade-grown plants than for full-sun plants. Shaded plants exhibited
lower dark respiration, light compensation point, and light-saturated photosynthesis than full sun plants. Leafl et thickness, palisade layer number, and stomatal
density of leaves of shaded plants were reduced compared with full sun plants.
At seedling emergence and for several months thereafter, the plants responded
to shade primarily with obligate sun plant characteristics. After the plants were
established, however, responses to the varied light conditions indicated facultative
structural and physiological characteristics.
207
Fatty Acid Concentration in Portulaca oleraceae L. is Altered
by Photosynthetic Photon Flux
U.R. Palaniswamy*, R.J. McAvoy, and B.B. Bible; Dept. of Plant Science, Univ.
of Connecticut, Storrs, CT 06269-4067
Purslane (Portulaca oleraceae L.) seedlings were grown under an instantaneous
photosynthetic photon fl ux (PPF) of 299 or 455 µmol • m–2• s–1 for a daily duration of either 8, 12, 16, or 20 h. Thus plants were exposed to a daily PPF of 8.6,
12.9, 17.2, and 21.5 mol • m–2• d–1 in the low PPF treatment (299 µmol • m–2• s–1)
and 13.1, 19.7, 26.2, and 32.8 mol • m –2• d–1 in the high PPF treatment (455
µmol • m–2• s–1). All treatments received a 20-h photoperiod using a PPF of ≈5
µmol • m–2• s–1. At low PPF, purslane grown under 16-h PPF duration produced the
highest concentration of total fatty acid (TFA), linoleic acid (LA), and linolenic acid
(LNA) per unit leaf dry mass (DM) and leaf area; but at high PPF, the concentration
of these compounds was highest under 8- and 12-h PPF duration. Trend analysis
indicated that maximum TFA, LA, and LNA concentrations occurred with a PPF
of 14.1, 16.9 and 17.2 mol • m–2• d–1 respectively; and protein, chlorophyll, and
LNA concentrations in thylakoid membranes were maximized at PPF of 21.8,
19.9, and 16.1 mol • m–2• d–1, respectively. LNA as percent of TFA was unaffected
by treatment. DM increased with PPF up to the highest PPF exposure of 32.8
mol • m–2• d–1.
208
Sensitivity of Selected Vegetable and Weed Seedlings to
Ultraviolet-B Radiation
Nancy H. Furness1, Mahesh K. Upadhyaya* 1, and Douglas P. Ormrod2; 1Dept.
of Plant Science, Univ. of British Columbia, Vancouver, BC V6T 1Z4, Canada;
2
Biology Dept., Univ. of Victoria, Victoria, BC Canada
Relative sensitivity of selected vegetable and weed seedlings to ultraviolet-B
(UV-B) radiation (280–320 nm) was investigated. Seedlings were grown for 4
weeks in a greenhouse, in chambers equipped with UV-B-emitting fl uorescent
tubes and Mylar (control) and cellulose acetate (UV-B) fi lters. UV-B radiation
reduced seedling height, leaf area, and leaf fresh weight in tomato (Lycopersicon
esculentum ‘Cour Di Bue’), broccoli (Brassica oleracea var. Italica ‘Purple Sprouting’), cabbage (Brassica oleracea var. Capitata ‘Red Drumhead’), and cucumber
(Cucumis sativus ‘Straight Eight’), leaf area and leaf fresh weight in beet (Beta
vulgaris ‘Cylindra’ and ‘Early Wonder’), seedling height and leaf area in spinach
(Spinacia oleracea ‘Long Standing Bloomsdale’), lettuce (Lactuca sativa ‘‘Red
Salad Bowl Everest’) and ‘Savoy’ cabbage, and seedling height in ‘Chinese Tip
Top’ cabbage and lettuce (‘Saladin’). ‘Winterton’ cabbage was not affected. UV-B
radiation decreased leaf area and leaf fresh weight in common chickweed (Stellaria media) and corn spurry (Spergula arvensis) and seedling height in green
foxtail (Setaria viridis) and redroot pigweed (Amaranthus retrofl exus). Tillering
was stimulated in response to UV-B in green foxtail. There was no effect of UV-B
on lady’s-thumb (Polygonum persicaria) growth. Leaf number was not affected
by exposure to UV-B in any species. The differential morphological sensitivity of
vegetable and weed seedlings may result in altered competitive relationships under
enhanced UV-B levels expected with the depletion of the earth’s ozone layer.
83
POSTER SESSION 2L (Abstr. 209–219)
Crop Production—Herbs/Medicinals
209
Hydroponic Greenhouse Production of Fresh-market Basil in
HORTSCIENCE, VOL. 33(3), JUNE 1998
Colorado
C. Elizabeth Succop* and Steven E. Newman; Dept. of Horticulture and Landscape
Architecture, Colorado State Univ., Fort Collins, CO 80523-1173
Fresh-market basil has become a viable greenhouse commodity in Colorado.
Marketing pressures and profi t advantages also encourage the production of
certifi ed organic produce. The research objectives were to determine the length of
time basil plants were productive in the greenhouse and to compare the production of fresh-market basil grown with three root zone systems and two fertilizer
treatments. The three systems were hydroponic rockwool slab culture, hydroponic
perlite raised bed culture, and hydroponic peat/perlite/compost bag culture. The
two types of hydroponic fertilizer treatments were a salt-based formulated nutrient solution and an organic solution consisting of fermented poultry compost,
hydrolized fi sh emulsion, and soluble kelp. The plants were harvested once per
week for fresh weight determination. The results from the two runs show greater
productivity for the plants in the perlite system as well as the bag mix system
when fertilized with the organic fertilizer compared to salt-based fertilizer. However,
productivity of the plants in the rockwool system was greater with the salt-based
treatment compared to the organic treatment.
210
Nitrogen Fertilization of Basil
M. Rangappa* and H.L. Bhardwaj ; Agricultural Research Station, Virginia State
Univ., Petersburg, VA 23806
Sweet basil (Ocimum basilicum) is an important culinary herb in Virginia and
other areas. The objective of this study, conducted during 1997, was to determine
optimal N rate for fresh and dry matter yield. Seed of Broad Leaf sweet basil were
direct-seeded on 18 June in rows 0.75m apart in a RCBD design with 8 replications. Four N rates (0, 25, 50, and 75 kg N/ha) were used. Calcium nitrate (15.5%
N) was used as the fertilizer source. All plants from 1-m row length from middle
row of each plot were harvested by hand on 23 Sept. and fresh weights were
recorded. The plant material was dried at 70°C for 48 h to record dry weights.
The moisture content at harvest was calculated from fresh and dry weights. The
fresh yields following 0, 25, 50, and 75 kg N/ha were 3.7, 5.4, 6.4, and 6.8 kg/m2,
respectively. The yield difference between two highest N rates was not signifi cant,
however, both these rates had signifi cantly higher yield than the two lowest rates.
Similar results were also obtained for dry matter yields. The highest N rate of 75
kg N/ha resulted in signifi cantly higher dry matter yield (1.3 kg/m2) as compared
to the other three rates. The lowest dry matter yield was obtained after the control
treatment (0.6 kg/m 2). An opposite relationship between N rate and moisture
content was observed when the highest moisture content resulted from control
and 50 kg N/ha treatments. These results indicate that optimum N rate for sweet
basil in Virginia is 50 to 75 kg/ha.
211
Ethephon for American Ginseng (Panax quiquefolium L. ) Inflorescence Removal
A.E. Fiebig* 1, J.T.A. Proctor1, D. Murr1, and R. Releeder2; 1Dept. of Horticultural
Science, Univ. of Guelph, Guelph, ON, N1G 2W1, Canada; 2Agriculture and AgriFood Canada, Pest Management Center, Delhi, ON, N4B 2W9, Canada
Varying concentrations (500-4000 mg• L–1) of ethephon, an ethylene-releasing
compound, were applied to 3-year-old ginseng (Panax quinquefolium L.) plants
in fi elds of southern Ontario. The effects of this chemical on fruit removal, plant
damage, infructescence morphology, and root mass were studied and compared to
the normal practice of manual infl orescence removal. The highest concentrations
had the highest rates of removal but also caused the greatest amount of damage
to the whole plants when compared to the mid-range concentrations. The lowest
concentrations showed less foliar damage but did not provide suffi cient fruit
removal to mimic hand removal. When individual infl orescences of the ethephon
treatments were studied, the seed heads had fewer ripe berries and more unpollinated fl orets than the untreated controls. When root masses were compared,
high and low concentrations showed lower masses than those of the standard
production practice of hand removal. However, mid range concentrations showed
similar root mass increase to manual removal. When all parameters were considered, the concentration range giving the best results was 1000-1500 mg• L–1.
Multiple applications of ethephon, at weekly intervals, had an additive effect on
fl ower removal and plant damage. Treatments having an additive concentration
of over 2000 mg• L–1 had detrimental effects on all parameters. Those within the
1000–1500 mg• L–1 range showed the highest similarity to the hand removal
benefi ts.
HORTSCIENCE, VOL. 33(3), JUNE 1998
212
Inflorescence Removal Effects on Root Yield of American
Ginseng (Panax quiquefolium L. )
J.T.A. Proctor*, D.C. Percival , and D. Louttit: Dept. of Horticultural Science, Univ.
of Guelph, Guelph, ON, N1G 2W1 Canada
American ginseng is a perennial herbaceous plant grown for its fl eshy root and
seeds. Little is known about fruit set and development in ginseng. In commercial
practice a small proportion of 2-year-old plants may bear fl owers and seed but
these seeds usually are not harvested. Seeds from 3-year-old plants are harvested
and used for establishing plantings, but seed from 4-year-old plants, if available,
are preferred. Some growers remove fl owers manually from plants in June at an
estimated cost of $2500 per ha and claim higher root yields. The objective of
this work was to determine the effect of infl orescence removal in 1 or 2 years
on root yield. Manual removal of infl orescences from mature (3-and 4-year old)
American ginseng plants at commercial timing (early July, ≈25% fl owers open)
increased root yield at harvest compared to plants where the infl orescences were
retained. Consecutive infl orescence removal for 2 years (3rd and 4th) increased
yields 55.6% compared to 34.4% for removal in one year only (4th). Root size
distribution analysis showed that most roots (≈40%) were in the medium category
(10–20g): infl orescence removal did not infl uence root size distribution. Root yield
for 3-year-old plants increased quadratically with plant density with plants lacking
infl orescences having an estimated yield increase of 25% . Maximum yields of 2.4
kg• m–2 for defl owered plants were suggested at a plant density of 170 plants/m2.
To maximize ginseng root yield all plants should have infl orescences removed
except those needed to provide seed for future plantings.
213
Growth, Opium Gum Yield, and Photoperiod Response in Five
Opium Poppy (Papaver somniferum L. ) Cultivars
Z. Wang*, M.C. Acock, and B. Acock; USDA–ARS, Remote Sensing and Modeling
Laboratory, Beltsville, MD 20705
To develop models for estimating growth, fl owering time and gum yield of
opium poppy, we compared variability among fi ve cultivars (T, L, B1, B2, B3) from
different latitudes in three Southeast Asian countries. Variability in the relationships between gum yield, capsule volume, and dry weight was also examined.
Plants were grown in six growth chambers at a 11-, 12-, 13-, 14-, 15-, or 16-h
photoperiod (PP) with a 12-h 25/20 °C thermoperiod. The main capsule was lanced
for opium gum at 10, 13, and 16 d after fl owering (DAF). Plants were harvested
at 21 DAF and separated into leaves, stems, and capsules. Flowering time for B2
was affected least by PP and B1 the most. Flowering times for B3, L, and T were
similar across the range of PPs. All cultivars showed a signifi cant increase in
fl owering time from 14 to 13 h PP. Cultivars that fl owered late (such as B1) had
greater biomass than those that fl owered earlier. However, cultivars that fl owered
earlier (such as L) had more dry matter partitioned into capsule than late-fl owering
ones. B2, B3, and L had the highest gum yields while B1 had the lowest. Positive
correlations were found between gum dry weight and capsule volume (or dry
weight) for T and L, but no correlations were observed between these variables
for B1, B2, and B3. Our results indicated that plant dry weight varied as much as
77% and fl owering time varied up to 40% even though the critical photoperiod
was the same for all cultivars. The ratio of gum yield to capsule dry weight were
signifi cantly different between B1 and T.
214
Toxic Metals in Different Varieties of Seabuckthorn (Hippophae
rhamnoides)
I. Lobacheva1 and W. Letchamo* 2; 1Biotek Inc., Altai, Russia. 2Flora Labs. Inc., &
Trout Lake Farm, 42 Warner Road, WA 98650 USA
Seabuckthorn (Hippophae rhamnoides, L) (Oblepiha, Siberian pineapple,
Sandorn, Sha-ji), from the Eleagnaceae family, is one of the most important and
leading sources of pharmaceutical, nutritional, and cosmetic products in Tibet,
Russia, and China. Hippophae oil is an important component of the cream for
protection from cosmic radiation, tan-enhancing, cell tissue regeneration, wound
healing, and antiaging properties. It is a good source of natural antioxidants, and
is used to boost the body immune system, adaptation to extreme conditions, and
increased performance body performance. The fruits, seeds, leaves, and cork
contain a large amount of chemical elements, essential oils, vitamins A, B, C, E,
carotenoids, fl avonoids, palmitic and palmitoleic acids, unsaturated fatty acids,
α-sitosterol, proteins, minerals, and many other bioactive compounds. As part
481
of the selection and genetic improvement program to develop superior varieties
of higher fruit yield, quality and resistance, varietal difference in the uptake or
accumulation of heavy (toxic) metals in the berries was investigated. The variation in the content or accumulation of Zn, Cu, Pb, Cd, and Fe in the berries of
three varieties of Hippophae (Chuiskaja, Zivko,, and Chechek) with differing
morphological, and fruit quality was studied. The plants were grown under similar conditions, at Lisavenko Inst. for fruit trees research in Russia. There was a
signifi cant difference in the concentration of the metals among the three varieties.
Variety ‘Tchuiiskaja’ was found to have signifi cantly higher concentration (P < 0.05)
of Cu, Pb, and Fe. The lowest concentration of the metals was recorded for the
variety ‘Chechek’. The obtained results enable us to suggest, that the Hippophae
varieties may signifi cantly vary in the accumulation toxic elements in their berries.
This fact should be well considered during selection and improvement program
for Hippophae.
215
On the Standardization of Seabuckthorn (Hippophae rhamnoides L) Oil
I. Lobacheva1 and W. Letchamo* 2; 1Biotek Inc., Altai, Russia; 2Flora Labs. Inc., &
Trout Lake Farm, 42 Warner Road, WA 98650 USA
Seabuckthorn (Hippophae rhamnoides, L) (Oblepiha, Siberian pineapple,
Sandorn, Sha-ji), a perennial from the Eleagnaceae family, has attracted the interest of North American natural products industry because of its effective multiple
applications in cosmetic, nutriceutical, and veterinary industries. The oil obtained
from the berries, bark, and leaves, and is known to contain carotenoids, vitamins,
and essential fatty acids. The objective of this investigation was to elaborate and
establish reliable, but inexpensive, methods in the process of standardization of the
quality of oblepiha oil. Data of the phytochemical analysis of oblepiha oil obtained
from various research reports and industrial and experimental sources, located in
different parts of Russia (ex-USSR), were extensively investigated and statistically
evaluated. An indirect method of standardization of oblepiha oil, based on the
content of carotenoids and unsaponifi able fraction of the oil, has been proposed.
The correlation between total carotenoids and unsaponifi able lipids in extracted
oil of oblepiha (r = 0.76; P ≤ 0.05) has been shown. The strong relationship between carotenoids, unsaponifi able lipids, and sterin fractions in the raw material
and industrial oil indicates the possibility of using the level of total carotenoid
concentration as a reliable and direct approach to indirectly determine the effi cacy
of oblepiha oil for nutritional, pharmacological, and cosmetic applications.
216
A Comparative Study of Rhodiola rosae under Cultivation and
Natural Growing Conditions
W. Letchamo1, T. Kireeva* 2, and A. Shmakov3; 1Flora Labs. Inc., & Trout Lake Farm,
42 Warner Road, WA 98650 USA; 2Dept. of Biology and Physiology, Edmurtia
State Univ., Ezchevsk, Russia; 3Altai State Univ., Barnaul, Russia
Rhodiola rosae L., from the Crassulacea family, is a perennial widely known
in Russian folk and offi cial medicine for its adaptogenic properties. The extracts
from the roots of Rhodiola rosae is known to be a better alternative to ginseng
because of its better effects, safety for people having high blood pressure, cardiac
and kidney problems, pregnancy, and minors. Rhodiola is collected mostly from
the wild, and this practice has resulted in the decimation of the wild population
in Altai mountains and in southern Siberia. The objective of this investigation was
to fi nd the best method of production and guarantee the availability of the raw
material without compromising the quality. Plants were studied under naturally
growing conditions and brought into cultivation. We used seeds to propagate.
Morphological traits, fl owering, leaf area, shoot and root yield, and content of
salidroside (biologically active component in the root) were measured in 50
plants. The measurements were taken during the 1st, 2nd, and 3rd years of the
cultivated plants, while parallel measurements were taken from the same place
of naturally growing plants. Plants under natural conditions did not receive any
agronomic treatment, while normal agronomic practices were given for plots
under cultivation. We found signifi cant difference an all measured parameters.
Though higher root yield was obtained from cultivated plants, the concentration
of salidroside was found to be higher naturally grown plants. With the increasing
age of the cultivated plants, however, the concentration of salidroside signifi cantly
increased. The total yield of salidroside, g/m2 was found to increase consistently
each year for cultivated variants compared to plots under natural growth.
482
217
Development of Thymus vulgaris Varieties for North American
Commercial Organic Cultivation
W. Letchamo* and T. Kireeva; Flora Laboratories Inc., & Trout Lake Farm, 42
Warner Road, WA 98650 USA
Five different cultivars of Thymus vulgaris originating from various geographical sources (Canada, F.R. Germany, former GDR, and Spain) were fi rst propagated
by cuttings from each cultivar in the greenhouse and then cultivated organically
in the fi elds during the periods of 1993–1995 (Quebec, Canada) and 1996–1997
(Washington State). The fi eld-grown plants were harvested in mid-September. The
oils obtained through steam distillation of the dried leaves from each cultivar were
analyzed by means of TLC followed by GC. The oil content varied from 1.38%
to 2.04% in Quebec, and 1.41% to 2.25% , depending on the cultivar used. The
highest oil content was obtained from ‘Madrid’, followed by ‘RH-1’ and ‘Laval-1’.
More than 95% of the oil, with a total of 24 components, were identifi ed in the
samples. ‘Laval-1’, recently developed in Quebec, ‘Madrid’ from Spain, and ‘RH-1’
from Germany were established to belong to thymol-chemotypes, while ‘RH-2’
from Germany was found to be carvacrol-chemotype. ‘QDLB’, from the former
GDR, was characterized by its ≈39% thymol, 17% carvacrol, and 3.52% linalool
content in the oil. The content of thymol and its ratio was found to change slightly
with shifting cultivation of the cultivars from Europe to North America. Other
important constituents in the essential oils were also p-cymene (10.87–22.89% ),
g-terpinene (2.21–8.85% ), α-pinene (0.87–2.23% ), sabinene (0.00–1.77% ),
borneol (0.00–3.69%), geraniol (0.59–3.48%), and terpinen-4-ol (0.21–3.08%).
As ‘Laval-1’ and ‘RH-1’ showed better overwintering ability and produced relatively
higher leaf yields. These two cultivars were found to be prospective cultivars for
commercial organic cultivation for North America. Results obtained from various
growing areas are presented.
218
The Selection and Development of High-quality Echinacea for
Industrial Processing
W. Letchamo*; Flora Laboratories Inc. & Trout Lake Farm Co. 42 Warner Road,
WA 98650 USA
Echinacea is one of the oldest medicinal plants that had been used by the native Indians of North America for bacterial and viral ailments. With the increasing
scientifi c fi ndings about the usefulness of Echinacea in natural immune stimulation of humans, the demand for high-quality echinacea product in natural food
markets in the United States and Europe has been growing. However, most of the
commercial supply of echinacea originates either from heterogeneous material
or wild collections. Trout Lake Farm in Washington State is the leader in production and processing of echinacea. The objective of this investigation was to fi nd
and develop high-quality echinacea lines or cultivar for commercial biological
production and processing. The variation in morphological traits, ripening period,
the root and shoot yields, resistance to diseases and insects, and the content of
active substances (cichoric acid, echinacoside, isobutylamides, and essential
oil) in E. purpurea was carried out during the 1996 growing season. We found
dramatic variations in plant height, color and size of the leaves, fl owers and period
of fl ower induction, yield, and the accumulation of the active substances.
219
Two Methods for the Rapid Assessment of Leaf Yields of Erythroxylum coca ‘Coca’
Mary C. Acock*; USDA/ARS Remote Sensing and Modeling Lab., Beltsville, MD
20705, USA
To determine the extent of world coca (Erythroxylum) production, methods for
rapid estimation of yield (leaf mass) are required. The objective of this research
was to compare two methods for rapidly acquiring data to estimate yield. The plant
canopy analyzer (PCA) method was based on measuring canopy light interception
with the LI-COR PCA, calculating leaf area index (L), and converting L to leaf dry
weight using specifi c leaf area (SLA) values. The canopy subsample method was
based on calculating leaf dry weight of a subsample from leaf and branch number, leaf size, and SLA, then multiplying by the ratio of the canopy volume to the
subsample volume. PCA measurements underestimated leaf yields when values
of L were ≥1.0. PCA estimates could be corrected by adjusting for the observed
difference between leaf yields and PCA estimates. The corrected PCA and canopy
subsample methods had errors of similar magnitude, both slightly underestimating
yield. Both methods performed well when tested against data from a subsequent
harvest. The canopy subsample method uses simple equipment and can be ap-
HORTSCIENCE, VOL. 33(3), JUNE 1998
plied in almost any environmental condition, but requires more time in the fi eld
than the PCA method. The corrected PCA method has slightly less random error
than the canopy subsample method but requires expensive equipment, uniform
light conditions in the fi eld of view, and cannot be applied when raining.
83
POSTER SESSION 2M (Abstr. 220–227)
Breeding & Genetics—Reproductive
Biology
220
Characterization of the Reproductive M ode in Guayule In
Vitro
Roy N. Keys1, Dennis T. Ray* 1, and David A. Dierig2; 1Dept. of Plant Sciences,
The Univ. of Arizona, Tucson, AZ 85721; 2USDA-ARS, US Water Conservation
Laboratory, Phoenix, AZ 85040
Guayule (Parthenium argentatum Gray, Asteraceae) is a latex-producing perennial desert shrub that is potentially of economic importance as an industrial crop
for the desert Southwest. It is known to possess complex reproductive modes.
Diploids are predominantly sexual and self-incompatible, while polyploids show
a range of apomictic potential and self-compatibility. This paper describes the
development of a relatively rapid and simple technique for characterizing reproductive modes of breeding lines of P. argentatum. Initial fi eld experiments were
based on an auxin test used successfully to characterize reproductive mode in
the Poaceae. The application of 2,4-dichlorophenoxyacetic acid inhibited embryo
formation in P. argentatum, but this was not the case with other auxins tested.
Results of fi eld experiments were ambiguous because: 1) the fl oral structure of
P. argentatum is such that auxins might not have penetrated to the ovules, and
2) there was potential self-fertilization by pollen released within isolation bags.
Therefore, in vitro culture of fl ower heads was tested because it provided much
better control of environmental conditions, growth regulator application, and pollen
release. Auxin alone, or in combination with gibberellic acid or kinetin, inhibited
parthenogenesis in vitro. Embryo production did not vary using two substantially
different nutrient media. In vitro fl ower head culture using a (Nitsch and Nitsch)
liquid nutrient medium without growth regulators, enabled characterization of the
reproductive mode of seven breeding lines, ranging from predominantly sexual to
predominantly apomictic. The results of this technique were substantiated using
RAPD analyzes of progeny arrays from controlled crosses.
221
Interspecific Crossability of Nine Diploid Fragaria Species
Bob Bors* and J. Alan Sullivan; Dept. of Horticultural Science, Univ. of Guelph,
Guelph, ON, N1G 2W1 Canada
As part of a wild species introgression program, Fragaria vesca, F. viridis, F.
nubicola, F. nipponica, F. nilgerrensis, F. pentaphylla, F. gracilis, F. daltoniana, and
F. iinumae were crossed in most combinations possible, the exceptions being F.
daltoniana and F. iinumae, which produced only a few fl owers each. Crosses with
F. vesca as a female and either F. gracilis, F. nipponica, or F. iinumae as males
produced good seed set, but seedlings died in the cotyledon stage in every case.
No seed set occurred when F. iinumae was crossed with F. viridis or F. nubicola. F.
pentaphylla, F. gracilis, and F. iinumae were observed to be self-incompatible while
F. daltoniana was self-compatible. Three overlapping groups based on crossing
data have emerged. Within the following groups, hybrid plants were obtained in
all species combinations, although not necessarily for reciprocal combinations:
Group A: F. vesca, F. viridis, F. nubicola, and F. pentaphylla. Group B: F. vesca,
F. nilgerrensis, F. daltoniana, and F. pentaphylla. Group C: F. pentaphylla, F.
gracilis, and F. nipponica. Fertile or semifertile diploid hybrids were obtained
for all species combinations within group A indicating genomic similarity or that
breeding at the diploid level could occur with these species. Fertility has not been
determined for hybrids in groups B and C. It is interesting to note the presence
of F. pentaphylla in all three groups, perhaps this species plays an important role
in Fragaria evolution.
222
Reproductive Efficiency in Muscadine Grapes
HORTSCIENCE, VOL. 33(3), JUNE 1998
C.L. Gupton*, USDA, ARS, Small Fruit Research Station, P. O. Box 287, Poplarville, MS 39470
To determine the berry production effi ciency of selected muscadine grape
cultivars, pollen production, size, and viability; time of pistil receptivity; mode of
pollination; number of fl ower per cluster; and percentage fruit set were studied.
Each of 17 hermaphroditic cultivars except ‘Noble’ produced a high percentage
of viable pollen grains. Pollen size averaged 32 and 51 µm in 2 years. Even at
this small pollen size, our observations suggest insects rather than wind as the
primary means of pollen transfer to pistillate fl owers. Pistils were not receptive
until the calyptra dehisced, thereby ensuring that pollen can reach the pistil when
it is receptive. ‘Carlos’ produced 68.5 and ‘Black Beauty’, ‘Doreen’, ‘Fry’, ‘Sweet
Jenny’, and ‘Supreme’ produced from 38 to 46 fl owers per cluster. Percentage fruit
set ranged from a high of 22 to 34 for ‘Fry’, ‘Sweet Jenny’, ‘Doreen’, and ‘Supreme’,
and a low of 12 to 14 for ‘Carlos’ and ‘Black Beauty’. These results suggest that
pollination may not be a problem in present muscadine cultivars. Variation in
yield among cultivars apparently relates to genetic differences in cluster number
and berry weight.
223
M eiotic Behavior in an Amphidiploid Rose and Its Hybrid
Progeny
Yan Ma* and David H. Byrne; Dept. of Horticultural Sciences, Texas A& M Univ.,
College Station, TX 77843, USA
The amphidiploid rose 86-7 (Rosa wichuraiana x R. rugosa rubra) and its
hybrids with the tetraploid breeding selection 82-1134 were analyzed for meiotic
confi guration frequencies and meiotic abnormalities. Genomic relationships in
these hybrids were interpreted with the aid of a model of meiotic chromosome
association in tetraploids. The optimized solutions to this model indicated a pattern intermediate between the “211” pattern, with one pair of closest genomes,
and the “ring4” pattern, in which one of three possible pairing arrangements is
strongly suppressed. The same confi guration frequencies could also refl ect a “4:0”
pattern of equally similar genomes with more than two independent pairing and
chiasma-forming domains per chromosome. The observed meiotic abnormalities
included chromosome stickiness and asynchronous chromosome contraction
within cells. Pollen stainability varied independently of meiotic irregularity or
multivalent frequency.
224
Screening for Ploidy Variation in Collections of Malus (Apple)
Species by Flow Cytometry
Laura L. Benson* 1, Nancy Wheeler2, and James R. McFerson3; 1USDA–ARS Plant
Genetic Resources Unit, Cornell Univ., Geneva, NY 14456; 2 William Smith College,
337 Pultney, Geneva, NY 14456; 3 Washington Tree Fruit Research Commission,
1719 Springwater Ave., Wenatchee, WA 98801
Flow cytometry was used to determine the ploidy levels in three subsets of the
apple germplasm collection held by the USDA–ARS Plant Genetic Resources Unit.
C-values ranging from diploid to pentaploid DNA content have been reported in
the genus Malus, but cytogenetic information is often not available for specifi c
trees. Diploid, triploid, and tetraploid clones were found in the core collection,
a diverse group of Malus species and hybrids. Ploidy level may vary within and
between Malus species in the wild. The progeny of 38 M. sieversii trees sampled
from a natural population near Targabatai, Kazakstan were screened with fl ow
cytometry. All the tested progeny had diploid C-values. Gigas characters such as
larger leaves and fruit are sometimes associated with elevated ploidy levels. Ten
elite scions of large-fruited M.sieversii were evaluated. All 10 had C-values in
the diploid range. While fl ow cytometry of nuclei liberated from leaf tissue gave
the expected DNA content for cultivars with previously known ploidy levels, this
technique could not distinguish a known 2-2-4-4 periclinal chimera from diploid
individuals.
225
Pollination Mechanisms of Ebenus cretica
M.E. Lydaki and J.C. Vlahos*; Technological Educational Institute (TEI) of Heraklion, Stavromenos 71500 Heraklion Crete, Greece
Ebenus cretica L., is an endemic plant of Crete with potential as a cut fl ower
or fl owering potted plant. It is a herbaceous perennial evergreen subshrub that
fl owers from April to June. It forms numerous thick racemes with an average of 50
pink or purple fl owers 10 to 12 mm long. A great variability in major morphological
characteristics exists among the populations of E. cretica on the island; however,
483
color variants are very rare. Selection and breeding is a necessary prerequisite
before the plant is marketable; therefore, research conducted at the TEI of Heraklion
since 1994 has focused on artifi cial self- and cross-pollination of pink-fl owered
ebenus plants. It has been concluded that the zygomorphic fl owers of E. cretica
are pollinated by insects (bumblebees); the tripping mechanism occurs and seeds
are formed by either cross- or self-pollination. For self-pollination, unripe fl ower
racemes were enveloped in paper bags and shaken by hand or wind to release
pollen; however, this method gave poor results. Best results were obtained by
tripping the fl owers while avoiding the introduction of foreign pollen. Self-incopatibility was not observed.Cross-pollination was achieved by emasculating
fl owers on the female parent, 2 to 4 days prior to the dehiscence of the anthers.
The corolla is half-white and half-pink at this stage, turning to a uniform pink
when the pollen is ripe. The stigma appears to be fully receptive at least 2 days
before the dehiscence of the anthers. Each fertilized ovule gives one mature seed
≈3 weeks after pollination. This research indicates that breeding techniques can
be applied without diffi culty to E. cretica in order to develop uniform plant material
and new varieties/hybrids with desirable characteristic.
226
Stigmatic Pollen Grain Deposition by Honey Bees and Bumble
Bees after Single Bee Visits to Pistillate Watermelon Flowers
M.S. Stanghellini * 1, J.T. Ambrose1, and J.R. Schultheis2; Dept. of Entomology,
Dept. of Horticultural Sciences, North Carolina State Univ., Raleigh, NC 27695
As a means to assess pollinator effi ciency, the number of pollen grains deposited by honey bees (Apis mellifera L.) and bumble bees (Bombus impatiens
Cresson) after single visits to pistillate watermelon [ Citrullus lanatus (Thunb.)
Matsum. & Nakai] fl owers was compared. Pistillate fl owers were enclosed in nylon
bags prior to anthesis, and were then exposed to single visits by each bee species (RCBD: 10 fl owers per bee species per replicate; 4 replicates). Pollen grains
were removed from stigmata immdiately after bee visitation by use of a glycerin
jelly-gelatin mixture that was mounted onto microscope slides. Light microscopy
was used to count the number of pollen grains per slide. Bumble bees deposited
signifi cantly more pollen grains than did honey bees (P < 0.05). After single bee
visits to fl owers, bumble bees deposited an average of 481 pollen grains, while
honey bees deposited an average of 119 pollen grains. Although multiple bee
visits are usually required to set watermelon fruit, this work demonstrates that
bumble bees are more-effi cient pollinators of watermelon at the single visit level
than are honey bees.
227
Use of a Backcross Population to Target Genes Controlling
Androgenesis in Potato
Tatiana Boluarte* and R.E.Veilleux; Dept. of Horticulture, Virginia Polytechnic Inst.
and State Univ., 206 Saunders Hall, Blacksburg, VA 24061
Genes for anther culture response (ACR) need to be mapped to enable effi cient
transfer of the trait to unresponsive but agronomically desirable clones. The
objective of this study was to fi nd extremes for ACR in a segregating population
to target genes controlling this trait using bulk segregant analysis. Populations
resulting from backcrosses (BC) of a diploid interspecifi c clone [CP2: Solanum
chacoense (chc: low ACR) and S. phureja (phu: high ACR)] to both parents were
used to characterize two phases of androgenesis in a preliminary study: microspore
embryogenesis and embryo regeneration. Among 24 plants from each BC, consistently high- and low-responding genotypes with regard to embryo production
were identifi ed. Low ACR clones in each BC produced from 0.0–0.1 embryos per
anther (EPA), whereas high ACR clones in the chc and phu BC produced from
1.4–2.9 and 2.8–7.5 EPA, respectively. The frequency of embryos regenerating
into plants ranged from 3% to 20% for the chc high EPA clones and 12% to 64%
for the phu high EPA clones. Ploidy of regenerated plants was determined by fl ow
cytometry. The frequency of monoploid regenerants among the high EPA clones
ranged from 3.6% to 68% . Since these populations showed suffi cient genetic
variation for ACR, a series of statistically designed experiments were conducted to
develop high and low ACR bulks. From four groups of phenotypically characterized
PBC plants, a high ACR bulk (–x = 4.9 EPA; n = 14) and a low ACR bulk (– x =
0.12 EPA; n =9 ) were constructed.
484
128 POSTER SESSION 3A (Abstr. 228–234)
Pest Management—Woody Ornamentals/
Landscape/Turf
228
Effect of Preemergent Herbicides on Growth of Dwarf Nandina,
Eleagnus, Asiatic Jasmine, Bradford Pear, and Arizona Ash
H. Brent Pemberton * , William E. Roberson , and Garry V. M cDonald ; Texas
A& M Univ. Agricultural Research and Extension Center, P.O. Box E, Overton,
TX 75684
The list of species that are known to tolerate the use of Factor® (prodiamine),
a preemergent herbicide, in a containerized production system is limited. Plants of
swarf nandina (Nandina domestica ‘Firepower’), eleagnus (Eleagnus x eggingei ),
and Asiatic jasmine (Trachelospermum asiaticum) growing in 3.8-L containers
were obtained from a local nursery and treated with herbicide treatments to
determine effects on growth. Plants were treated with one or two applications of
Factor® 65WG at either 0, 1.4, 2.8, or 5.5 kg• ha–1 (0.9, 1.8, or 3.6 kg• ha–1 active
ingredient, respectively). The fi rst application was made on 10 Aug. 1995 and the
second application was made on 19 Oct. 1995. Plants were grown under 30%
Saran shade and watered and fertilized as needed. Plants of Arizona ash (Fraxinus
sp.) and Bradford Pear (Pyrus calleryana ‘Bradford’) ptted in 19-L containers were
treated with herbicide treatments on 25 Oct. 1995 for fall weed control at a local
nursery. Treatments included a single application of Factor® 65WG at either 0,
1.4, 1.8, or 2.8 kg• ha–1 (0.9, 1.2, or 1.8 kg• ha–1 active ingredient, respectively)
with or without Gallery® (isoxaben) at 1.2 kg• ha–1 (0.9 kg• ha–1 active ingredient).
There was no effect of the herbicide treatments on growth of eleagnus. Herbicide
treatments did not affect shoot dry weight and did not have a deleterious effect on
shoot length and root dry weight of Asiatic jasmine or affect trunk caliper growth
of the two tree species. Factor® did affect the growth of dwarf nandina. Plant
height and shoot and root dry weight were not affected. However, plant width was
decreased by all Factor® treatments when compared to untreated plants.
229
Preemergent Weed Control in Container-grown Herbaceous
Perennials
Scott Dunn, James E. Klett*, and David Staats; Dept. of Horticulture, Colorado
State Univ., Fort Collins, CO 80523
During the 1997 season, preemergent herbicides were applied to containergrown herbaceous perennials and evaluated on the basis of weed control, phytotoxicity, and effect on plant growth. The herbicides and rates were: Napropamide
(Devrinol 10G), 0.72 and 1.44 kg a.i./ha; Oryzalin (Surfl an 40AS), 0.36 and 0.72
kg a.i./ha; Oxadiazon (Ronstar 2G), 0.72 and 1.44 kg a.i./ha; Oxyfl uorfen + Oryzalin
(Rout 3G), 0.54 and 2.16 kg a.i./ha; Oxyfl uorfen + Pendimethalin (Scott’s OH II),
0.54 and 1.09 kg a.i./ha; and Trifl uralin (Trefl an 5G), 0.72 and 1.44 kg a.i./ha.
Herbicides were applied to Phalaris arundinacea ‘Picta’, Scabiosa caucasica,
Sedum spectabile ‘Autumn Joy’, Pennisetum setaceum ‘Rubrum’, and Salvia
argentea. Phytotoxicity symptoms (visual defects and lower dry weights) were
apparent with Napropamide on Phalaris (at both rates). All herbicides provided
good weed control.
230
Toxicity, Uptake, and Distribution of Simazine in Canna hybrida
‘King Humbert’: Implications for Phytoremediation
Patrick C. Wilson* 1, Ted Whitwell 2, and Steven J. Klaine1; 1Dept. of Environmental
Toxicology, Clemson Univ., Pendleton, SC 29670; 2Dept. of Horticulture, Clemson
Univ., Clemson, SC 29634
This research focuses on the potential use of Canna hybrida ‘King Humbert’‚
for removing simazine from contaminated water generated at golf courses and
ornamental nurseries. Because of simazine’s herbicidal activity, it is important
for levels in solution not to exceed plant tolerance levels. Tolerance levels for C.
hybrida were determined by dosing plants for 7 d with 0, 0.01, 0.03, 0.1, 0.3, 1.0,
or 3.0 mg simazine/L nutrient media. Measurements of 7-d fresh mass production
and photosynthetic effi ciency (Fv/Fm) were taken. Simazine uptake and distribution
within the plant was determined by dosing plants with 2.03 mCi 14C-simazine
(0.243 mg/L) for 1, 3, 5, or 7 d. Plant tissues were analyzed by combustion and
HORTSCIENCE, VOL. 33(3), JUNE 1998
liquid scintillation counting. Fresh mass production was reduced 66% and 78%
for plants exposed to 1.0 and 3.0 mg/L, respectively. Likewise, photosynthetic
effi ciency was reduced to 66% and 40% of the controls at the same respective
concentrations. Plant uptake of simazine accounted for 13%, 34%, 48%, and 65%
of the original simazine in the dosing solution after 1-, 3-, 5-, and 7-d exposure,
respectively. This simazine was distributed primarily between roots and leaves.
231
Suppression of Liverwort Growth in Containers Using Irrigation,
Mulches, Fertilizers, and Herbicides
Sven E. Svenson*; Dept. of Horticulture, North Willamette Research and Extension
Center, Oregon State Univ., 15210 NE Miley Road, Aurora, OR 97002-9543
Liverwort (Marchantia sp.) is often a serious weed in many nursery and
greenhouse operations. Combinations of irrigation frequencies, surface mulches,
surface fertilizers and herbicides were applied to the surface of the growing medium
in 10-cm square pots planted with Rhododendron or Picea. Liverwort infestations
were evaluated as the percentage of media surface covered. Mulches were placed
at least 1/2-inch thick on the surface of the growing media. Five blocks of two
pots per treatment were used in a completely randomized design. Oyster shell,
hazelnut shell, and copper-treated geotextile mulches provided good suppression
(less than 10% surface coverage) of liverwort for up to 6 weeks, while rockwool,
peatmoss, coarse sand, perlite and pumice mulches required low-frequency irrigation to provide fair suppression (less than 40% surface coverage). Surface
applications of oxadiazon (Ronstar), oryzalin (Surfl an), iron oxide, copper sulfate,
and manganese sulfate provided good suppression of liverwort for up to 4 weeks
using low-frequency irrigation, but suppression was nearly eliminated if highfrequency irrigation was applied. Some combination applications of mulches and
herbicides or fertilizers provided good suppression for 8 weeks (high-frequency
irrigation) or 12 weeks (low-frequency irrigation). Liverwort suppression was fair
when untreated geotextile mulches were used, but suppression was good (even
under high-frequency irrigation) when copper-treated geotextile mulches were
used.
232
Evaluation of Nurse Crops for Weed Control and Plant Establishment in Prairie Restoration
Lisa M. Barry and Michael N. Dana*; Dept. of Horticulture and Landscape Architecture, Purdue Univ., West Lafayette, IN 47907-1165
Nurse crops are often recommended in prairie restoration planting. This work
investigated several alternative nurse crops to determine their utility in prairie
planting. Nurse crops were composed of increasing densities (900, 1800, or 2700
seeds/m2) of partridge pea, spring oats, spring barley, Canada wild rye, or equal
mixtures of partridge pea and one of the grasses. The experimental design was
a randomized complete-block set in two sites with three blocks per site and 48
treatments per block. Each 3 x 3-m plot contained 1 m2 planted in Dec. 1995 or
Mar. 1996 with an equal mix of seven prairie species. The nurse crops were sown
over each nine square meter area in April 1996. Plots lacking nurse crops served
as controls. Evaluated data consisted of weed pressure rankings and weed and
prairie plant dry weight. Nurse crop treatments had a signifi cant effect on weed
pressure in both sites. Barley (1800 and 2700 seeds/m2) as well as partridge pea
+ barley (2700 seeds/m2) were most effective at reducing weed pressure. When
weed and prairie plant biomass values were compared, a signifi cant difference
was observed for site quality and planting season. Prairie plant establishment was
signifi cantly greater in the poorly drained, less-fertile site and spring-sown plots
in both sites had signifi cantly higher prairie biomass values. Overall, after two
seasons, there was no advantage in using nurse crops over the control. Among
nurse crop treatments, oats were most effective in reducing weed competition and
enhancing prairie plant growth.
233
Evaluation of Three Soil-applied Insecticides for Root Weevil
Control in Container-grown Nursery Crops
R.L. Rosetta, S.E. Svenson*, and N.C. Bell; Dept. of Horticulture, North Willamette
Research and Extension Center, Oregon State Univ., 15210 NE Miley Rd, Aurora,
OR 97002-9543
To determine effi cacy of insecticides for adult root weevil control in containergrown plants, adult stages of black vine root weevil, Otiorhynchis sulcatus, were
established in two container-grown plant species, arborvitae (Thuja occidentalis
‘Emerald’) and rhododendron (Rhododendron ‘Vulcan’) in May 1997. Seven root
HORTSCIENCE, VOL. 33(3), JUNE 1998
weevil adults were placed onto the soil surface of each 1-gal plant and covered
with a damp paper towel. Insecticides were applied during daylight hours on 20
May 1997. Foliar treatments were applied using a manually pressurized backpack
sprayer. Baits and granular treatments were applied by hand to the soil surface.
On rhododendrons, treatments consisted of: 1) an untreated control; 2) Topcide
(lamda-cyhalothrin, 1.2 oz/100 gal); 3) Topcide (lamda-cyhalothrin, 4.8 oz/100
gal); 4) Pinpoint 15G (acephate, 16.5 lb/a); 5) Pinpoint 15G (acephate, 33.0 lb/a);
6) Cryolite (Sodium aluminofl uoride-based bait, 30 lb/a); and 7) Gowan 1885
(30 lb/a). There were fi ve blocks per treatment, each containing fi ve plants. At 1
and 7 days after treatment, root weevils were collected from each container and
evaluated for moribundity and mortality. Treatments 1, 3, 5, and 6 were applied to
arborvitae and evaluated 1, 3, and 8 days after treatment. Cryolite, Gowan 1885,
and Pinpoint 15G (high rate) had the highest mortality (70% to 79% ) compared
to untreated (11% to 17% ) or Topcide-treated plants. Pinpoint 15G and both
sodium aluminofl uoride bait treatments may provide an effective, viable option
for adult root weevil control when pesticides cannot be applied in the evening
or when reduction of risks from foliar cover sprays to non-target organisms is
desirable.
234
Soybean Oil Used as an Alternative Pesticide on Nursery
Stock
A.L. Lancaster* 1, D.E. Deyton1, C.E. Sams1, C.D. Pless2, D.C. Fare3, R.E. Moran1,
and J.C. Cummins1, 1Dept. of Plant and Soil Science, 2Dept. of Entomology and
Plant Pathology, 3Dept. of Ornamental Horticulture and Landscape Design, The
Univ. of Tennessee, Knoxville, TN 37901
Research was conducted to determine if soybean oil sprays may substitute for
petroleum oil for control of insects on nursery crops. Dormant fi eld-grown ‘Globe’
arborvitae shrubs infested with Fletcher scale were sprayed on 9 Mar. 1997 with
0% , 2% , 3% , or 4% soybean oil. One hundred scales per plant were evaluated on
4 Apr. 1997. Spraying 2% to 4% soybean oil on dormant arborvitae caused ≥97%
mortality of Fletcher scale compared to only 7% mortality on untreated plants. of
white pine, viburnum,, ‘Anthony Waterer’ spirea, ‘Green Beauty’ boxwood, western
red cedar, ‘Blue Star’ juniper, ‘Blue Pacifi c’ juniper, ‘Japanese Garden’ juniper, and
arborvitae plants in trade gallon pots and ‘Densiformus’ yew and dwarf ‘Alberta’
spruce in trade quart pots were sprayed with 0% (water control), 1% , or 2%
soybean oil (emulsifi ed with Latron B-1956) or 2% SunSpray Ultra-Fine Spray
oil on 26 Aug. 1997 for phytotoxicity evaluation. No phytotoxicity occurred on
western cedar, spirea, boxwood, yew, arborvitae, or viburnum. Spraying Sunspray
or soybean oil caused initial loss of blue color on blue junipers and white pine.
Spraying 1 or 2% soybean oil or 2% SunSpray caused phytotoxicity to ‘Blue Star’
juniper. The ‘Blue Pacifi c’ juniper, ‘Japanese Garden’ juniper, and Alberta spruce
were slightly damaged by 2% but not by 1% soybean oil.
128 POSTER SESSION 3B (Abstr. 235–242)
Postharvest Physiology—Floriculture
235
Cytokinin and Auxin Sprays Affect the Incidence of Poinsettia
Bract Necrosis
R.J. McAvoy and B.B. Bible*; Dept. of Plant Science, Univ. of Connecticut, Storrs,
CT 06269-4067
In 1996, ‘Supjibi red’ poinsettias were sprayed at initial anthesis with the
cytokinin benzyladenine (BA) (10 or 100 ppm), or with the cytokinin analogs
CPPU or thidiazuron (1 or 10 ppm), or with Accel (10 or 100 ppm BA)— a 10:1
mixture of BA and gibberellin. A spray of thidiazuron at 1 or 10 ppm, Accel at 10
or 100 ppm, or BA at 100 ppm suppressed the incidence of necrosis relative to
untreated plants. However, cytokinin treatments tended to induce the expansion
of young bracts and fading of bract color. In a separate 1996 study, plants were
sprayed with 100 ppm BA at 2-week intervals between visible bud and initial anthesis; and in 1997, 20 ppm of the auxin indole-3-butyric acid (IBA) was applied
at similar intervals. The later in bract development that BA was applied, the lower
the incidence of necrosis observed at 6 weeks after anthesis. In contrast to BA
treatment effects, necrosis was highest with late IBA applications (when observed
3 weeks after anthesis). Late sprays of IBA induced bract epinasty. A 1:1 mixture
485
of BA plus IBA applied at initial anthesis at 25 or 50 ppm BA, suppressed bract
necrosis without causing adverse side effects.
236
Early Onset of Poinsettia Bract Necrosis is Associated with
Condensed Tannin Accumulation
R.J. McAvoy* 1, B.B. Bible1, and M.R. Evans2; 1Dept. of Plant Science, Univ. of
Connecticut, Storrs, CT 06269-4067; 2Dept. of Horticulture, Iowa State Univ.,
Ames, IA 50011
The early onset of bract necrosis in poinsettia (Euphorbia pulcherrima Willd.
ex. Klotzch) is characterized by small dark-stained spots that precede the development of enlarged necrotic lesions. Electron micrographs of adaxial epidermal and
subepidermal tissues with early symptoms of necrosis revealed large, electron
dense deposits in cell vacuoles. These spherical bodies resembled condensed
tannins observed in the epidermal tissues of peach and apple fruit. Chemical
analysis of bract tissues showed higher condensed tannin concentrations in
bract samples with 2 mm diameter lesions than in samples with lesions less than
0.5 mm (equivalent to catechin concentrations of 59 and 13 mg• g–1 fresh mass,
respectively). Tannin bodies were not observed in micrographs from parallel
samples of healthy appearing bracts, and chemical analysis revealed only trace
concentrations of condensed tannins in these tissues (0.2 mg• g–1 fresh mass).
The evidence suggests that condensed tannins accumulate in affected cells at the
earliest observable stages of bract necrosis.
237
Mechanisms of the Prevention of Cold Storage-induced Postharvest Leaf Chlorosis by Supplemental Light and Gibberellins
in ‘Stargazer’ Hybrid Lilies
Anil P. Ranwala* and William B. Miller; Dept. of Horticulture, Clemson Univ.,
Clemson SC 29634
Leaf chlorosis induced by short-term, postproduction cold storage is a common postharvest disorder in potted lilies. In ‘Stargazer’ hybrid lilies, 2 weeks of
storage at 4 °C results in chlorosis in more than 30% of leaves by 6 days after
transferring to 22 °C. Because we observed that foliar sprays of GA4+7 or supplemental light during cold-storage could prevent this leaf chlorosis in Lilium sp.
‘Stargazer’ hybrid lilies, this study was conducted to investigate the mechanisms
underlying these preventive effects. Hybrid lilies at “puffy bud” stage were stored
for 2 weeks at 4 °C either in darkness (control), provided with 40 µmol • m–2• s–1
light by cool-white fl uorescent lamps, or sprayed with 100 mg• L–1 GA4+7 prior to
storage. Leaves from lower half of the plant were sampled during cold storage and
upto 6 days after transferring to 22 °C. Leaf chlorophyll, total nitrogen, and soluble
protein concentrations decreased slightly during cold-storage in all treatments, but
decreased rapidly after transferring to 22 °C only in control plants. Total soluble
sugar concentration (TSS) in leaves decreased in control and GA4+7-treated plants
during cold storage, whereas TSS increased in plants provided with light. After
transferring to 22 °C, TSS decreased in all treatments, but the decrease was more
rapid in control plants. SDS-PAGE protein profi les revealed that degradation of
larger polypeptides that occurred in control plants did not occur in GA4+7-treated
plants or plants provided with light. Catalase and superoxide dismutase activities
in leaves decreased in control plants after transferring to 22 °C, whereas these
activities were maintained in other treatments.
238
Effect of Flower Age on Ethylene Synthesis in Big Bend
Bluebonnet, Lupinus havardii
Katherine L. Vasquez* 1, Wayne A. Mackay2, Marisa M. Wall 1, and Tim D. Davis2;
1
New Mexico State Univ., Dept. of Agronomy & Horticulture, P.O. Box 30003,
Dept. 3Q, Las Cruces, NM 88003; 2Texas A& M Univ. Research and Extension
Center, 17360 Coit Road, Dallas, TX 75252
Endogenous ethylene production of an advance breeding line and an unimproved population of L. havardii was measured to determine at what age open
fl owers begin to synthesize ethylene. Twenty to 30 immature fl ower racemes from
greenhouse-grown plants were randomly selected and tagged in each plant population. Every 24 h, the uppermost open fl ower was tagged on the selected racemes.
On the 10th day, tagged racemes were harvested from each population group.
Flowers were removed from the raceme, placed into 10-ml vials (six fl owers/vial),
and incubated at room temperature (25 ± 2 °C). Ethylene was analyzed using a gas
chromatograph. Detectable ethylene levels were most prevalent in 3- to 4-day old
486
fl owers. Mean ethylene rates were 1.7 nl/g per h and 1.1 nl/g per h for 4-day-old
fl owers of the advance breeding line and unimproved population, respectively.
Senescing fl owers (10 days old) of the advanced breeding line and unimproved
population had ethylene rates of 7.9 and 6.7 nl/g per h, respectively.
239
Relationship Between Postharvest Longevity of Cut Flowering
Stems and Intact Flowers of Greenhouse-grown Antirrhinum
majus L.
Kenneth R. Schroeder* and Dennis P. Stimart; Dept. of Horticulture, Univ. of
Wisconsin, 1575 Linden Dr., Madison, WI 53706
Considerable variation exists in Antirrhinum majus L. (snapdragon) for
postharvest longevity of cut fl owering stems. We have seen a range of 2 to 16 d
postharvest life of snapdragon inbreds used in our experiments when evaluated in
deionized water. A correlation between longevity of intact fl owers and cut fl owers
has been reported for roses and tulips. In an effort to test this relationship on
snapdragons, plants from a short-lived (5 days) and long-lived (16 days) inbred
were grown in a greenhouse at the Univ. of Wisconsin, Madison, in Spring 1997.
Plants began fl owering in Apr.1997. The fi rst three fl orets on each plant were
tagged when fully open and the date of senescence recorded for each individual
fl oret. Results showed a signifi cant difference in longevity of intact fl orets. Mean
fl oret longevity of the short- and long-lived lines was 13 and 25 days, respectively
(LSD0.05 = 1.03 days). This is an indication that selection for postharvest longevity
of snapdragons may be done based on intact fl ower longevity.
240
Vase Life of Cut Rose Flowers Harvested at Different Months
and Treated with Poly(2-Hydroxypropyldimethylammonium
Chloride)
Hidemi Izumi* and Atsuo Fujii; Faculty of Biology-Oriented Science and Technology, Kinki Univ., Naga, Wakayama 649-6493, Japan
Flowering rose (cv. Rote Rose) stems, harvested at different months of
the year, were placed in 250 ppm poly(2-hydroxypropyl- dimethylammonium
chloride)(PHPAC) solution or in water as the control at 4 °C for 24 h. They were
then transferred to water and held at 20 °C for 6 or 7 days. Bent-neck of control
roses was the greatest with those harvested in July, least with December or May
harvest, and intermediate with October harvest, and occurred after day 2, 4, 4, and
3 at 20 °C, respectively. PHPAC reduced the occurrence and degree of bent-neck of
all roses and had the greatest inhibitory effect on roses harvested in July. PHPAC
accelerated fl ower opening of roses harvested in July and December. Rates of
water uptake and transpiration decreased during the holding period, and PHPAC
retarded the decrease after day 3-4 of all roses. Hydraulic conductance in the basal
3 cm segment of all rose stems decreased during holding and PHPAC retarded the
decrease. Electrolyte leakage from the basal 3 cm of the stem was greater with the
PHPAC-treated stems than that of the control of all roses. These results indicate
that PHPAC suppressed bent-neck probably by reducing the rate of decrease in
water uptake and transpiration, which related to the hydraulic conductance and
electrolyte leakage in the basal 3 cm of the stems.
241
Vaselife Evaluations of Autumn Sedum, Lobelia, Hardy Amaryllis, Oregano, and Blue Spirea
Karen L.B. Gast*; Dept. of Horticulture, Forestry and Recreation Resources Kansas
State Univ., Manhattan, KS 66502-5506 USA
Specialty cut fl owers have come of age. In 1996, the value of domestic fresh
cut roses, carnations and mums were $195 million while the value of “other”
fl owers was $251 million. As consumers acquire a taste for more new and different
fl owers, postharvest information is needed to determine what growers, vendors
and consumers can expect for vaselife from these fl owers and how the vaselife
can be best extended. The vaselife of autumn sedum, lobelia, hardy amaryllis,
oregano, and blue spirea was evaluated with and without pretreatments of STS
and holding solutions of fl oral preservatives or water. Results were varied among
the different species for the best handling procedures. Lobelia, blue spirea and
autumn sedum fl owers benefi tted from the use of STS. The longest vaselife for
oregano was 8.5 days, for blue spirea was 11.3 days, for lobelia was 14 days, for
hardy amaryllis was 7 days and for autumn sedum was 32.5 days.
HORTSCIENCE, VOL. 33(3), JUNE 1998
242
Effects of Ethylene Scrubber and Light on Yellowing of Geranium Transplants
Guiwen W. Cheng*, Steven A. Sargent, and Donald J. Huber; Horticultural Sciences
Dept., PO BOX 110690, Univ. of Florida, Gainesville, FL 32611-0690
The yellowing of geranium transplants under simulated non-refrigerated
transit conditions was investigated with ± KMnO4-based ethylene scrubber or
supplemental light. The transplants were stored in the dark at 20 °C in glass jars or
cartons, some of which were treated with ± ethylene scrubber (8 g) and/or ± light.
Transplants (8) were removed daily for measurement of leaf yellowing intensity (=
percentage of the sum of the products of yellowing rate and leaf number within the
rate over the potential maximal sum, where rate 0 equals no yellowing; 1, discrete
margin yellowing; 3, yellowing along margin; 4, uniform yellowing). Yellowing
was evident after 1 day storage (3 days postharvest). The yellowing of ‘Pinto Red’
geranium transplants stored in cartons progressed similarly ± ethylene scrubber
(≈99% yellowing intensity on day 5). In jars, the scrubber delayed the yellowing
of ‘Pinto Red’ from 83% to 75% by the end of the 5-day test period. In a separate
test of ‘Pinto Salmon’ in jars, yellowing was delayed from 68% without scrubber to
30% with scrubber. Weak incandescent light plus scrubber substantially reduced
yellowing in ‘Pinto Pink’(43% ) compared with dark, – scrubber (96% ) after 6 day
storage. Under fl uorescent light, yellowing in ‘Pinto Pink’ was ≈20% . The results
showed that the absence of light was the key stress factor causing yellowing in
geranium transplants. Yellowing retardation by ethylene scrubber was observed
only in a closed system and the effect was variety dependent.
128 POSTER SESSION 3C (Abstr. 243–248)
Crop Physiology: Genetics/Cultivars/Selection—Cross-commodity
243
Genotypic Influences on Fatty Acid Profiles and Germinability
of Pecan Pollen
William R. Nail * 1, J. Benton Storey2, and L.J. Grauke2; 1Dept. of Horticulture,
Plant and Soil Sciences Bldg., Michigan State Univ., East Lansing, MI 488241325; 2Dept. of Horticultural Sciences, Texas A& M Univ., College Station, TX
77843-2133
Pollen of pecan [ Carya illinoinensis (Wangenh.) K. Koch] from fi ve protandrous and fi ve protogynous genotypes was analyzed for germinability and fatty
acid profi le. Fatty acid profi les as a function of genotype were distinctive in all
selections, but only three of the genotypes had fatty acid profi les that were easily
distinguishable from others by canonical discriminant analysis. Specifi c fatty
acid percentages infl uenced germination in some genotypes. Total saturated and
unsaturated fatty acids infl uenced pollen germination to a greater degree than
individual fatty acids. The effects of fatty acids on pollen germination of protandrous genotypes were opposite those on ‘Stuart’, the only protogynous genotype
to be infl uenced by fatty acid percentages.
244
Evaluation of Prunus cerasus Germplasm for Cold Resistance
Hannah M. Mathers* 1 and A.F. Iezzoni 2; 1Oregon State Univ., 15210 NE Miley
Rd., Aurora, OR 97002; 2Dept. of Horticulture, Michigan State Univ., East Lansing,
MI 48824
Knowledge of the level of cold stress resistance and how this resistance is
inherited in sour cherry is essential to cultivar development and future germplasm
collection. Twig and fl ower bud samples of two sweet cherries (Prunus avium L.),
12 sour cherries (Prunus cerasus L.), and one ground (Prunus fruticosa Pall.)
were collected once a month from Aug. 1990 to Mar. 1991, preconditioned, and
subjected to freeze tests and differential thermal analysis. LTEs were detected in
all stems of P. cerasus investigated and were strongly correlated to xylem ITs
in December to March. LTEs were strongly correlated to phloem-cambium ITs
in November. Xylem ITs were the selected method for evaluating sour cherry
cold resistance in December to March. Phloem-cambium ITs were the selected
method for November. The degree of hardiness of the phloem-cambium in late
fall and early spring is a factor determining P. cerasus germplasm geographic
HORTSCIENCE, VOL. 33(3), JUNE 1998
distribution and commercial production. The principal component (PC) analyses,
of the phloem-cambium and cortical tissues, depict gradations between minimum
survival temperatures of the two presumed progenitor species of sour cherry,
sweet cherry and ground cherry suggesting that cold is a major selective force,
contributing to sour cherry population variation.
245
Induction of Chlorophyll-deficient Phenotypes in Tillandsia
fasciculata Swartz Var. fasciculata by Physical and Chemical
Mutagens
Yong Cheong Koh* and Fred T. Davies, Jr.; Dept. of Horticultural Sciences, Texas
A& M Univ., College Station, TX 77843-2133
Seeds of Tillandsia fasciculata var. fasciculata were treated with gamma radiation, gamma and thermal neutron radiations, or ethyl methanesulfonate (EMS)
and grown in vitro. Observed chlorophyll defi cient phenotypes included yellowish-green, yellow, variegated and albino. The highest combined percentages of
chlorophyll defi cient phenotypes was 8.7% for the gamma radiation treatment (2.7
krad), 4.6% for the gamma and thermal neutron radiations treatments (combined
dose of 2.7 krad at a gamma to thermal neutron ratio of 7.4:1.0), and 10.8% for
the EMS treatment (0.4% EMS x 5 h). Some yellowish-green and yellow seedlings
multiplied in half strength MS medium with 0.3 or 0.5 µM BA and IBA and the
newly formed shoots retained their respective mutant phenotypes. However, the
variegated seedlings were sectoral or mericlinal chimeras and when they multiplied, the newly formed shoots were not variegated. The chlorophyll a/chlorophyll
b ratio of the wild type seedling was 1.1 whereas that of the yellowish-green and
the yellow seedlings was 2.0. Electron micrographs showed that compared to
the wild type chloroplasts, the chloroplasts of the yellowish-green and yellow
seedlings had fewer grana and fewer thylakoids within each granum.
246
Changes of Lipid Components During Dormancy in Blackberry
Cultivars
Amir B. Izadyar and Shiow Y. Wang* ; Fruit Lab., Plant Sciences Inst., USDA-ARS,
Beltsville, MD 20705-2350
Changes in phospholipids, galactolipids, and fatty acid were determined
in two cultivars of blackberries, ‘Triple Crown’ and ‘Hull Thornless’, during
dormancy and budbreak. Under fi eld conditions, ‘Triple Crown’ required lower
chilling units (CUs) than ‘Hull Thornless’ to overcome dormancy. ‘Triple Crown’
and ‘Hull Thornless’ achieved full budbreak after receiving 600 and 1000 CUs,
respectively. Under cold-temperature treatments, ‘Triple Crown’ needed 400 CUs,
while ‘Hull Thornless’ needed 600 CUs at 4 °C to obtain 100% budbreak. The
shoots kept at intermittent 6/24 °C (6 °C for 16 h, and 24 °C for 8 h) did not reach
full budbreak even after receiving 1000 CUs. An increase in phospholipids and
glycolipids was observed during the termination of dormancy. The increase in
phospholipids occurred earlier than the increase in glycolipids. The percentage
of 18:2 fatty acid decreased while 18:3 increased and there was approximately
a fi ve-fold increase in the 18:3/18:2 ratio observed at the time of budbreak. The
increase in the 18:3/18:2 ratio could serve as an indicator of dormancy termination
and growth resumption in blackberry.
247
Biomass Partitioning and Yield of Three Asparagus Hybrids
W. Alan Erb*, Linda Parsons, and Mark Pyeatt; KSU–Horticulture Research Center,
1901 E. 95th South, Wichita, KS 67233
This study was conducted to learn when an asparagus plant partitions its
biomass into leaves, stems, buds, and rhizomes, and roots and to determine
when after harvest the crown of the plant is rejuvenated to the point that harvest
can begin again. The plants used in this study were generated by sowing seed on
Jan. 1995, transplanting seedlings into 1.8-L containers (5 sand : 4 soil : 1 peat)
in Mar. 1995 and on Mar. 1996, placing the crowns into 9.5-L containers. During
Fall 1996, the number of shoots per plant were recorded and this data was used
to group plants into six classes. The study was started on 8 Apr. 1997 by fi rst
removing six plants/cultivar (one from each class) and biomass partitioning each
crown into buds and rhizomes, and roots. The remaining plants were harvested
eight times and after the fi nal harvest on 20 Apr. another set of plants (six/cultivar)
were partitioned. Starting on 3 June, a set of plants were partitioned every 2 weeks
until 21 Oct., when growth stopped in the fall. Atlas and UC157 F1 produced the
most spears and had the highest yield and they also had the highest total dry
487
weight, leaf dry weight, and stem dry weight. There were no cultivar differences
in rhizome and root dry weight. However, ‘Jersey Giant’ and ‘Atlas’ had the highest
rhizome and root weight ratio. The highest bud dry weights occurred on 20 May,
23 Sept., 26 Aug., and 21 Oct. and the highest rhizome and root dry weights were
on 21 Oct., 12 Aug., 26 Aug., and 23 Sept. The bud dry weight recorded on 12
Aug. was equal to the bud dry weight recorded on 8 Apr. Also on 12 Aug., leaf
dry weight and rhizome and root dry weight were higher than almost all the other
dates. In addition, above-ground shoot counts and bud dry weights were higher
on 26 Aug. than on 12 Aug. All this data indicates that in this study sometime after
12 Aug. and before 26 Aug., the asparagus crown was completely rejuvenated
and ready for another cycle of harvesting.
248
Identification of cDNAs from Cornus sericea that Encode a
Family of Dehydrin-like Proteins
Eric Sarnighausen*, Dale Karlson, Yan Zeng, and Edward Ashworth; Dept. of Horticulture and Landscape Architecture, Purdue Univ., West Lafayette, IN 47906
Three cDNAs, which apparently encode a family of dehydrin-like proteins, were
isolated from cold-acclimating wood tissues of Cornus sericea. The nucleic acid
sequences of these cDNAs are similar to each other (minimum 58% identical).
Two of the cDNAs are predicted to encode proteins of 44 and 48.6 kDa. The third
cDNA did not contain the complete open reading frame, but apparently encodes
a much larger protein. The predicted amino acid sequences from all three cDNAs
share homology with members of the dehydrin family of proteins. This family of
proteins is characterized by the presence of a highly conserved lysine-rich consensus sequence (EKKGIMDKIKEKLPG) known as the K-segment, a tract of serine
residues, and in most instances, an N-terminal consensus sequence (DEYGNP)
designated as the Y-segment. The cDNAs isolated from C. sericea encode putative
proteins with these common motifs. Each has a tract of serine residues, and either
one or two lysine-rich segments. However, a unique feature of the cDNAs from
C. sericea is that they encode putative proteins having 21, 24, and 27 repeated
sequences similar to the Y-segment, whereas previously identifi ed members of
the dehydrin family exhibit only one to three such repeats. The signifi cance of
this difference is not known. Dehydrins have been implicated in desiccation tolerance, and typically accumulate in response to dehydrating conditions, such as
occur during drought, salt-stress, low temperatures, and during the late stages of
embryogenesis. In C. sericea, expression of these transcipts changed seasonally.
Northern blot analysis detected high levels of transcript in October and January,
and no detectable message in June.
128 POSTER SESSION 3D (Abstr. 249–252)
Hydroponics & Seed Establishment—
Vegetable Crops
249
Improving Productivity of Hydroponically Grown Cowpea using
Intracanopy Lighting
Jonathan M. Frantz*, Robert J. Joly, and Cary A. Mitchell ; Dept. of Horticulture
and Landscape Architecture, Purdue Univ., West Lafayette, IN 47907-1165
High planting densities of planophile- or horizontal-leafed crops creates a
problem called mutual shading, whereby leaves in the upper portions of plant
canopies shade lower leaves. This can reduce overall crop productivity. In an effort
to negate this problem in growth chambers, light intensity typically is increased
from large overhead lamp banks. This is both expensive and ineffi cient. We have
investigated the use of small, low-wattage lamps arranged in three-dimensional
space allowing cowpea (Vigna unguiculata L. Walp ‘IT87D-941-1’) to grow up and
around the lamps in a technique called “intracanopy lighting.” This illuminates the
interior portions of plant stands and keeps the majority of the canopy productive.
Results obtained from this novel alternative to high intensity light from overhead
lamps showed productivity rates as good as traditional production methods while
using less than 25% of the light energy. We have continued to investigate variables
associated with improved productivity in high density plantings including: lamp
orientation, total light energy, photoperiod, and CO2 concentration. Intracanopy
lighting has the potential to signifi cantly reduce the amount of energy required
to produce a crop in a controlled environment.
488
250
Performance of Three Species of Salad-type Plants Grown
under Narrow-spectrum Light-emitting Diodes (LEDs) in a
Controlled Environment
G.D. Goins* 1, N.C. Yorio1, H.R. Kagie1, and R.M. Wheeler2; 1Dynamac Corporation
and 2NASA Biomedical Operations Offi ce, Kennedy Space Center, FL 32899
Light-emitting diodes (LEDs) are a promising light source for growing crop plants
in spacefl ight systems because of their superior safety, durability, small mass and
volume, wavelength specifi city, and long life. To address the usefulness of LEDs
as a plant lighting source, radish (Raphanus sativus L. cv. Cherriette), lettuce
(Lactuca sativa L. cv. Waldmann’s Green), and spinach (Spinacea oleracea L. cv.
Nordic IV) were grown using nutrient fi lm technique hydroponics under cool-white
fl uorescent (CWF) lamps, red LEDs (peak emission 660 nm), and red LEDs + 30
µmol • m–2• s–1 supplemental blue fl uorescent (BF) light (400–500 nm). Each lighting treatment was maintained in a separate controlled-environment chamber with
total photosynthetic photon fl ux (PPF) maintained near 300 µmol • m–2• s–1 and
a photoperiod of 18-h light/06-h dark. Results showed signifi cant reductions in
total dry mass (TDM) accumulation for radish plants grown under red LEDs + 30
µmol • m–2• s–1 BF or red LEDs only as compared to CWF-grown plants. Although
TDM tended to decrease with decreasing BF for lettuce, treatment differences were
not signifi cant. TDM for spinach plants was signifi cantly less under red LEDs
compared to CWF or red LEDs + 30 µmol • m–2• s–1 BF. Interestingly, single-leaf
photosynthesis and leaf conductance were not signifi cantly different for any treatment, regardless of species. The data suggest a species-specifi c response for the
amount of blue necessary for normal plant growth.
251
Moisture Soil Level Determination in Husk Tomato (Physalis
ixocarpa Brot. ) Crop in Western Mexico
F. Radillo-Juárez* and J. Farias-Larios; Facultad de Ciencias Biológicas y
Agropecuarias, Universidad de Colima, Apartado postal 36, 28100 Tecomán,
Colima, México.
When moisture conditions in soil are suitable, the husk tomato has good
vegetative growth and high yield. The objective of this work was determine the
minimum available moisture level to obtain the highest yield, and establish an
irrigation calendar. Treatments evaluated were: 15% , 30% , 45% , and 60% of
moisture reduction in soil, according to the gravimetric method, in a randomized
complete-block design with four replications. The variance analysis and Duncan
test were carried out at a 0.05 level of probability for following variables studied:
Fresh fruit yield (kg/ha), plant height, root length, and fruit diameter. The results
show that a 30% reduction moisture level was remarkable with a 28,610.67-kg/ha
yield of fresh fruit. In relation to agronomics characteristics, the results show that,
for plant height, root length, and fruit diameter were remarkable with the 15%
and 60% reduction moisture, respectively. This was due to the greater interval
of irrigation and tendency of root system to search for moisture. The greater
vegetative growth and yield is with a moisture level of 65% to 80% present in
soil, indicating that the husk tomato tolerates this 30% of reduction moisture,
with higher values producing more stress in plants and modifying the vegetative
growth and production.
252
Yard Trimmings–Biosolids Co-compost can Substitute for
Sphagnum Peatmoss in Tomato (Lycopersicon esculentum
Mill. ) Transplant Media
Monica P. Ozores-Hampton*, Charles Vavrina, and Thomas A. Obreza; Univ. of
Florida, Southwest Florida Research and Education Center, 2686 State Road 29
North Immokalee, FL 34142-9515
Large volumes of a compost made by mixing and co-composting yard trimmings (YT) and biosolids (BS) feedstocks have recently become available to the
Florida vegetable industry. Compost used as vegetable transplant medium may
be less expensive than traditional Sphagnum peatmoss, which is a non-renewable
resource. ‘Agriset 761’ tomato seed were planted in fi ve combinations of compost,
peat, and vermiculite media: 0:70:30 (control), 18:52:30, 35:35:30, 52:18:30, and
70:0:30 by weight, respectively. The presence of compost in the media increased
leaf area, shoot dry weight, and number of leaves 21 days after treatment (DAT),
and leaf area, shoot dry weight, root dry weight 28 DAT compared with the control.
There were no differences in root dry weight 21 DAT and number of leaves 28 DAT
between treatments containing compost and the control. Plants in the compost
treatments had greater fi nal leaf area, shoot dry weight, root dry weight, and stem
HORTSCIENCE, VOL. 33(3), JUNE 1998
diameter but less chlorophyll content compared with the control. There was no
effect of compost rate on any of the response variables measured. Neither fi nal
leaf number nor stem length were affected by media composition. The results
suggest that YT/BS co-compost can be used as an alternative to peat media for
tomato transplant production, and that the rate of use is not critical.
128 POSTER SESSION 3E (Abstr. 253–259)
Postharvest Physiology—Solanaceous Crops
253
Characterization of Glutamate-1-Semialdehyde Aminotransferase and Its Activity Throughout Tomato Fruit Development
and Ripening
Richard E. Finger, David J. Hannapel , and Richard J. Gladon*; Dept. of Horticulture,
Iowa State Univ., Ames, IA 50011-1100 USA
Glutamate-1-semialdehyde aminotransferase (GSAT) is a key enzyme in the
regulation of chlorophyll biosynthesis and a plausible site to regulate chlorophyll
loss during fruit development via a decrease in its activity. The primary objective
of this research was to characterize GSAT from tomato fruit by varying substrate
concentration and pH and to measure GSAT in various organs of the tomato plant.
A secondary objective was to measure GSAT activity and chlorophyll concentration
at 5-day intervals from 10 d to 60 d postanthesis during tomato fruit development
and ripening. An optimum pH of 7.0 was found, and a maximum velocity (Vmax)
of 2.3 nmol • g–1 of tissue and a Km of 119 mmol • L–1 were calculated for GSAT.
Activity among organs was greatest at 3.84 nmol • g–1 tissue in leaves of 4-week-old
seedlings, 1.67 nmol • g–1 tissue in fruits 15 days postanthesis, and below 0.70
nmol • g–1 tissue in roots, stems, and overripe fruits (65 d postanthesis). During
fruit development, GSAT activity was greatest at 10 d postanthesis and declined
to day 25. Activity increased from day 25 to a peak at day 40 and then decreased
again during ripening to 60 d postanthesis. Total chlorophyll and chlorophyll a
concentrations in tomato fruit declined throughout development and ripening with
the greatest decrease between 10 d and 25 d postanthesis. Thus, GSAT activity
may contribute to the control of chlorophyll concentration in tomato fruit from 10
to 25 d postanthesis when chlorophyll loss mirrors the decline in GSAT activity.
254
Effect of Potassium Permanganate-based Scrubber on Microenvironment Ethylene Levels and Tomato Ripening
Guiwen W. Cheng*, Steven A. Sargent, and Donald J. Huber ; Horticultural Sciences Dept., PO BOX 110690, Univ. of Florida, Gainesville, FL 32611-0690
The effectiveness of a potassium permanganate-based ethylene scrubber on
removing simulated package atmospheric ethylene and its effect on ripening of
tomato fruit were investigated. In a closed system (glass jars ) (fresh wt./container
vol. ratio = 0.29) at 12 °C, ethylene released by tomatoes at the turning stage
accumulated to 26 ml/L within 2 days [(CO2) = 9% ] and 33 ml/L within 6 days
[(CO2) = 14% ]. Ethylene, however, was undetectable in head space of jars containing 8-g scrubber materials. In the presence of ethylene scrubber, respiration
rates were reduced as indicated by the delay in CO2 accumulation. After holding
at 20 °C for 6 days following a 16-day, 12 °C storage, deformation under 9.8 N
was less in fruit with scrubber (2.9 mm) than fruit without scrubber (3.6 mm).
Under a fl ow-through system, however, fruit surface color and deformation were
similar with and without scrubber. The results indicate that an ethylene scrubber
can slightly retard ripening of unripened tomato fruit stored in closed environment
conditions.
255
Electronic Nose: A Non-destructive Technology to Screen Tomato Fruit with Internal Bruising
Celso L. Moretti * 1, Steven A. Sargent1, and Rolf Puschmann2; 1Horticultural
Sciences Dept., Univ. of Florida, Gainesvillle FL, 32611; 2Plant Biology Dept.,
Federal University of Vicosa, Vicosa, 36571-000, Brazil
Tomato (Lycopersicon esculentum Mill) fruit, cv. Solar Set, were harvested
at the mature-green stage and gassed with 100 mg• kg–1 of ethylene at 20 °C. At
the breaker stage, fruit were held by vacuum to avoid fruit rotation and dropped
HORTSCIENCE, VOL. 33(3), JUNE 1998
from a 40 cm height on a metallic, solid, smooth surface. Following impact, fruit
were stored at 20 °C and 85% to 95% relative humidity until table-ripe stage.
Bruised and unbruised fruit were then placed individually inside the electronic
nose-sampling vessel and the 12 conducting polymer sensors were lowered into
the vessel and exposed to the volatile given off by the fruit. Data were analyzed
employing multivariate discriminant analysis (MVDA), which maximizes the
variance between treatments. The degree of dissimilarity was defi ned using the
Mahalanobis distance and posterior probabilities were calculated to accurate
re-classifi cation of cases. The differences found between bruised and unbruised
fruit were highly signifi cant (P < 0.0041). The Mahalanobis distance between
groupings (28.19 units) was a dramatic indicative of the differences between the
two treatments. The re-classifi cation of bruised and unbruised fruit using a single
linear discriminant function was highly accurate, being 1.0 for both bruised and
unbruised fruit. The electronic nose proved to be a useful tool to nondestructively
identify and classify tomato fruit exposed to harmful postharvest practices such as
mechanical injuries. However, there are still some factors that must be investigated,
including system stability and the development of specifi c sensors for specifi c
commodities.
256
Influence of the β-subunit Protein on Pericarp Softening, Cell
Wall Hydrolysis, and Ultrastructural Changes in Ripening
Tomato Fruit
Jong-Pil Chun and Donald J. Huber*; Horticultural Sciences Dept., PO BOX
110690, Univ. of Florida, Gainesville, FL 32611-0690
The function of the β-subunit protein in the cell wall metabolism of ripening
tomato fruit is unknown. We examined pericarp softening, and polygalacturonase
isozyme 2-mediated cell wall and pericarp tissue hydrolysis using tomato fruit
(‘Ailsa Craig’) expessing an antisense gene for the cell wall-subunit protein.
Softening of pericarp tissue was accelerated in the β-subunit-defi cient compared
with wild-type fruits, decreasing from an average of 22 N at the mature-green stage
(both lines) to 9 N (12.7, wild) at the turning-pink stage to 2.5 N (5.1, wild) at the
ripe stage. Pectin solubilization was enhanced signifi cantly in the antisense line
compared with the wild type, but differences in depolymerization patterns were
minimal. Scanning electron microscopy of pericarp tissue revealed no differences
in the tomato lines at the mature-green stage. During ripening, the pericarp tissue
of the antisense fruit exhibited a more extensive loss in cell wall rigidity evident
from the collapsed appearance of cell walls. Application of purifi ed PG2 to the cut
surface of mature-green pericarp tissue induced ultrastructural changes paralleling
those observed during ripening of the two fruit lines. Refracture of PG2-treated,
mature-green pericarp tissue showed that enzyme activity was confi ned to the
tissue surface in wild type fruit, but penetrated at least several cell layers in
the antisense line. Although some workers have suggested that the role of the
β-subunit is not related to PG1(PG2+subunit) formation, we conclude that the
protein infl uences pericarp tissue softening and cell wall hydrolysis by limiting
the mobility and catalytic capacity of PG2.
257
Chilling Injury Determination in Tomato Fruit using Electrolyte
Leakage and Chlorophyll Fluorescence Techniques
M.A. Moura*, G.A. Mendonça, and F.L. Finger; Plant Science Dept., Federal Univ.
of Viçosa, Viçosa, Brazil
The present work was carried out to evaluate chilling injury in tomato fruit,
cv. Santa Clara and EF-50, employing chlorophyll fl uorescence and electrolyte
leakage techniques. Fruit were harvested at the mature-green stage and stored at
5 and 10 °C for 14 days. Chlorophyll fl uorescence was analyzed every 2 days,
whereas electrolyte leakage was measured every 7 days. It was observed that cv.
Santa Clara stored at 10 °C had no statistical alteration in Fv/Fm ratio and did
not show a signifi cant increase in electrolyte leakage. These results indicate that
tomato fruit, cv. Santa Clara, were not injured during the analyzed period. On the
other hand, fruit stored at 5 °C showed a signifi cant decrease in Fv/Fm ratio after
6 days whereas electrolyte leakage was signifi cantly higher at the 14th day of
storage. For cv. EF-50, it was observed that fruit stored at 10 °C had a signifi cant
decrease in the Fv/Fm ratio after 10 days, although there was no statistical difference for electrolyte leakage. For fruit stored at 5 °C, it was verifi ed that Fv/Fm
ratio signifi cantly decreased after 2 days and electrolyte leakage was signifi cantly
higher after 7 days of storage. Based on the results presented, it is suggested
that tomato fruit, cv. Santa Clara, is potentially more resistant to chilling injury
than cv. EF-50 and chlorophyll fl uorescence proved to be a useful tool to study
489
physiological stresses such as chilling injury.
258
Effect of Harvest Maturity and Ethylene Gassing on Tomato
Flavor Volatile Concentrations
E.A. Baldwin1, J.W. Scott* 2, and F. Maul ; 1USDA/ARS Citrus and Subtropical
Products Lab., Winter Haven, FL 33883; 2Univ. of Florida Gulf Coast Res. Ctr.,
Bradenton, FL 34203; Univ. of Florida, Gainesville, FL 32611
Tomato fruit (Lycopersicon esculentum Mill.) cvs. Solar Set and Olympic
were harvested at three maturity stages: green (stage 1, USDA color classifi cation) gassed with 100 ppm ethylene, green not gassed, turning (stage 4), and
red-ripe (stage 6). After ripening at 21 °C, the fruit were homogenized with CaCl 2
and analyzed for important fl avor volatile compounds. For ‘Solar Set’, acetone,
ethanol, 1-penten-3-one, hexanal, and trans-2-heptenal were signifi cantly higher
in red-harvested fruit, while 2+3-methylbutanol, and trans-2-hexenal were higher
in green-harvested fruit. trans-2-Hexenal was at higher levels in green-harvested
fruit not gassed compared to those that were gassed for ‘Solar Set’. ‘Olympic’ fruit
followed similar trends for harvest maturity and gassing, but there were fewer
signifi cant differences in volatile levels. Using a multivariate discriminant pattern
recognition procedure, red fruit were separated from turning and green-harvested
fruit, while green-gassed separated from non-gassed based on the aroma volatile
profi le within each cultivar.
259
Characterization of Ethylene and CO2 Production, Ethylene
Binding Sites, and 1-Aminocyclopropane-1-carboxylic Acid in
Different Types of Peppers
Lucia E. Villavicencio* and Sylvia M. Blankenship; Dept. of Horticultural Science,
North Carolina State Univ., Raleigh, NC 27695
Peppers are very popular as a vegetable, ornamental, and spice. They have
been classifi ed as non-climacteric fruits, but some types of hot peppers have
been reported as climacteric. Comparisons of ethylene and CO2 production,
binding sites and 1-aminocyclopropane-1-carboxylic acid (ACC) content between
pepper types were made. Experiments in both fi eld and greenhouse conditions
were conducted. Fruits were harvested at different stages of maturity. They were
placed in jars at 27 °C and ethylene and respiration rate were determined by gas
chromatography. All the variables studied showed differences among pepper types.
These variations were more evident in wild types than in cultivated types. Variability in the results was also higher in wild types. When the same type of pepper
grown in the greenhouse and in the fi eld were compared, signifi cant differences
were evident. Differences in maturity patterns were observed among types. These
results suggest that ripening patterns, ethylene production, respiration rates and
ethylene binding sites are highly dependent on the type of pepper. Differences are
also dependent upon the stage of maturity and should be taken in account when
harvesting and storing pepper fruits.
128 POSTER SESSION 3F (Abstr. 260–267)
Crop Physiology: Water Status/Stress—
Cross-commodity
260
The Relationship Among Storage Condition and Seed Moisture
Content Revisited
Jian Fang* 1,2 , Frank Moore III1, Eric E. Roos2 , and Christina Walters2; 1Dept. of
Horticulture and Landscape Architecture, Colorado State Univ., Fort Collins, CO
80523; 2USDA–ARS National Seed Storage Lab., 1111 South Mason Street, Fort
Collins, CO 80521-4500
Seed moisture content (MC) changes depending upon relative humidity (RH)
and temperature (T). This relationship was revealed by studying the interaction of
RH and T at equilibrium. Maize, cucumber, onion, lettuce, watermelon, and pea
seeds were equilibrated over various saturated salt solutions (1% to 93% RH) at
temperatures from 5 to 50 °C. Five-hundred-eleven subset models were selected
from a complete third-order model MC = 0 + 1*RH + 2*T + 3*RH2 + 4*T2 + 5*RH*T
+ 6*RH3 + 7*T3 + 8*RH*T2 + 9*RH2*T using Mallows’ minimum Cp as the selection criterion. All six best subset models were found to have the same functional
490
form, MC = 0 + 1*RH + 2*T + 3*RH2 + 5*RH*T + 6*RH3 + 9*RH2*T. Coeffi cients
had essentially the same respective values among species, except for the onion
and pea models (P ≤ 0.05). All models indicated that seed MC increased as RH
increased and decreased as temperature increased. A previous paper (Vertucci
and Roos, 1990) indicated that optimum RH for orthodox seed storage is between
19% and 27% . Using these models, the range for the optimum moisture content
for storage of most orthodox seeds can be quickly calculated for any given storage
temperature.
261
M easurement and Calculation of Total Plant Water Use of
Citrus
T. Mills, K. Morgan, L. Parsons*, and A. Wheaton; Univ. of Florida Citrus Research
and Education Center, 700 Experiment Station Rd., Lake Alfred, FL 33850-2299
This preliminary study serves to parameterize a modifi ed Penman–Monteith
equation for young citrus trees. Two-year-old citrus trees (‘Hamlin’ grafted on Carrizo citrange) were planted individually into 1500-L (1.5-m-diameter) plastic pots
in late Oct. 1997. Pots were placed upon industrial scales with a maximum weight
capacity of 2270 ± 0.05 kg. Continuous weight measurements were made every
minute and average half-hourly values recorded. An automated weather station was
located within 10 m of the pots and half hourly values of temperature, humidity,
wind speed, rainfall, and net radiation were recorded. Meteorological data, coupled
with diurnal measurements of stomatal conductance taken periodically throughout
the experimental period and leaf area for each tree allow calcuatiion of total plant
water use using a modifi ed Penman–Monteith equation. These calculation may be
cross-checked using weight change measurements. Such model parameterization
for citrus will aid irrigation management of citrus in the fi eld as it provides a link
between the physiological and meteorological aspects which drive plant water
use.
262
Drought Behavior of Nonbearing Clingstone Peaches on GF 677
Rootstock Cultivated under Field Conditions
Jorge A. Zegbe*; Intituto Nacional de Investigaciones Forestales, Agrícolas y
Pecuarias. Campo Experimental Calera. Apartado Postal No. 18 Calera de V.R.,
Zac., 98500 México, and International Foundation for Science. Grev Turegatan
19, SE-114. 38. Stockholm, Sweden
Water relations, chlorophyll and proline content, and vegetative growth were
obtained from three clingstone peach genotypes (S135‚) grafted on peach x
almond hybrid (GF 677‚) rootstock (S135/GF 677) and seedling trees from S135
(SPTS135). The experiment was carried out under fi eld conditions during the dry
season (April–June) to evaluate the infl uence of the GF 677 rootstock on scion in
1997. Leaf water and osmotic potentials tended to be lower in S135/GF 677 than
SPTS135 trees and irrigated seedlings peach trees (control). Although S135/GF
677 trees developed the lowest osmotic potential, the turgency was similar to
SPTS135 trees. Relative water content and transpiration rate were the lowest in
S135/GF 677 trees; SPTS135 trees were intermediate between S135/GF 677 and
control trees. Chlorophyll and proline levels were increased in S135/GF 677 and
SPTS135 trees compared with the control. Shoot growth was signifi cantly delayed
in S135/GF 677 trees compared with SPTS135 and control trees. Even though
some scion physiological variables were modifi ed by the GF 677‚ rootstock, the
effect was not big enough to confer signifi cant drought resistance to the scion.
263
Depletion Evaluation of the Available Moisture in ‘Mission’
Olives
Adán Fimbres Fontes*, Raúl Leonel Grijalva Contreras, Manuel de Jesús Valenzuela Ruíz; Apdo. Postal No. 125 Caborca, Sonora, Mexico 83600
The area of olives in the region of Caborca has been increasing in the past
years to 4500 ha. Olives in other regions do not need the application of water, but
here at Caborca evaporation is greater than rainfall. Because of this, an experiment
was conducted in 1997 to determine the optimum water requirements for olives
(table olives) in a sandy loam soil. The results indicated that the greatest yield
(22.68 kg/tree) was with 40% depletion of the available moisture (AM) in the
soil, and the lowest yield (7.46 kg/tree) was with 100% depletion of the available
moisture in the soil. The total water applied with the 40% depletion of the AM
was of 239.81 cm (2.4 m).
HORTSCIENCE, VOL. 33(3), JUNE 1998
264
WITHDRAWN
265
Determining the Performance of Five Ornamental Grasses
under Reduced Moisture Conditions
James T. Cole* and Janet C. Cole, Dept. of Horticulture and Landscape Architecture, 360 Agriculture Hall, Oklahoma State Univ., Stillwater, OK 74078-0511
An experiment was conducted to evaluate the performance of fi ve ornamental
grass species under reduced moisture. This experiment was conducted in the
greenhouse with three water treatments for each species: 1) Well-watered plants
were irrigated daily throughout the experiment, 2) acclimated-plants were exposed
to four drought cycles prior to a fi nal drought period in which measurements were
taken, and 3) non-acclimated plants received daily irrigation until undergoing a
drought cycle in which measurements were taken. A drought cycle was defi ned as
the time from irrigation until Time Domain Refl ectometry (TDR) measured 0 (zero).
Preliminary observations determined the plants to be under severe stress, but
capable of recovering at TDR measurements of 0. All plants were established from
tillers of a single parent for each species. Two plants of each species for the three
treatments were established in fi ve blocks. Leaf water potential, osmotic potential,
transpiration, stomatal resistance, and relative water content were measured during
the drought cycle. At the end of the experiment the leaf area and root and shoot dry
weights were determined, root to shoot ratio and leaf area ratio were calculated,
and the plants were analyzed for macronutrient and micronutrient contents.
266
Water State and Release from Dormancy in Blueberry Flower
Buds
Cécile M. Parmentier* 1, Lisa J. Rowland1, and Michael J. Line2; 1Fruit Lab. and
2
Environmental Chemistry Lab., USDA–ARS, Beltsville Agricultural Research
Center, Beltsville, MD 20705
Three blueberry (Vacciunium section Cyanococcus) genotypes, that have different chilling requirements and levels of cold hardiness, were studied. Dormancy
was evaluated and water status determined, using Nuclear Magnetic Resonance,
throughout the accumulation of chilling that leads to release from dormancy.
Among the two highbush cultivars studied, ‘Bluecrop’ (Vaccinium corymbosum)
was the most dormant and ‘Gulfcoast’ (Vaccinium corymbosum x Vaccinium
darrowi ) was the least dormant. The rabbiteye cultivar Tifblue (Vaccinium ashei )
had an intermediate dormancy. From estimates of chilling requirements (CRs),
it appeared that the cultivar with the deepest dormancy had the highest CR. The
NMR results showed that ‘Bluecrop’ buds had the lowest relaxation times (T2),
indicating that water was relatively more bound in ‘Bluecrop’ buds than in the
buds of the two other cultivars. Whatever the cultivar, no signifi cant variation
of T2s and water content of the buds was noted throughout the accumulation of
chilling, even after CRs were satisfi ed. On the other hand, a transition from bound
to freer water occured if the plants were placed under forcing conditions (24 °C,
long day) after they had received enough chilling to satisfy their CRs. The results
suggested that the level of bound water was more associated with the level of cold
hardiness rather than with the level of dormancy.
267
Soil–Root Interface Water Potential in Sweet Corn Affected by
Organic Fertilizations and Effective Microbe Applications
H.L. Xu*, H. Umemura, and T. Higa; International Nature Farming Research Center,
Hata, Nagano 390-14, Japan
We examined effects of organic fertilizations and effective microbes (EM,
mainly Lactobacillus, Rhodopseudomonas, Streptomyces, and Aspergillus)
applications on soil-root interface water potential Ψs-r of ‘Honey-Bantam’ sweet
corn. The contributions to Ψs-r from root amount and root activity were analyzed
using the Ohm’s law. Plants were grown in 1/5000 a Wagner’s pots fi lled with
Andosol and six treatments were made as follows: 1) organic materials fermented
anaerobically with EM added; 2) anaerobic organic materials; 3) organic materials
fermented aerobically with EM added; 4) aerobic organic materials; 5) chemical
fertilizers with EM applied, and 6) chemical fertilizers. One month after sowing,
as soil water decreased, Ψs-r was maintained higher in organic fertilized plants
than chemical fertilized ones and also higher in plants with EM applications than
those without EM. The relatively high Ψs-r was contributed by both their large root
HORTSCIENCE, VOL. 33(3), JUNE 1998
amount and high root activity. As a consequence, photosynthesis under soil water
defi cit conditions were also maintained relatively high in these plants. Maintenance
of a high Ψs-r favored plants to resist against water defi cits. Moreover, the Ψs-r
analysis is a practicable additional means to examine the soil-plant water status
under undisturbed conditions.
128 POSTER SESSION 3G (Abstr. 268–273)
Crop Production—Cross-commodity
268
Protective Border Plantings for Ag/Urban Interfaces
Wayne L. Schrader*, Karen L. Robb, and Valerie J. Mellano, Univ. of California
Cooperative Extension, San Diego, CA 92123-1219
Protective border barriers were established at three sites in commercial
fl oriculture, and strawberry fi elds in San Diego County, Calif. These border
plantings were used to provide a physical barrier between agricultural fi elds and
adjacent urban development, and to evaluate the effects of border plantings on
insect populations, spray drift, and crop/barrier interactions. Border plantings
consisted of native plants with overlapping fl owering periods to provide nectar
and pollen to benefi cial insects throughout the year. Yellow sticky traps were used
to monitor insect populations, and water sensitive paper was used to evaluate the
reduction of spray drift by the border plantings. Results indicate that protective
border plantings: 1) can be used to form attractive physical barriers that reduce
visual pollution and spray drift; 2) provide habitat for pests as well as benefi cial
insects; 3) support benefi cial insects that may help reduce the population peaks
of pest insects during spring and summer months; and 4) have little effect on
adjacent crop fi elds.
269
Foliar Application of Ethephon Decreases Apical Dominance
in ‘Orchid’ Petunia (Petunia x hybrida Vilm. -Andr. )
Darren L. Haver* 1 and Ursula K. Schuch2; 1Dept. of Botany and Plant Sciences,
Univ. of California, Riverside, CA 92521; 2Dept. of Horticulture, Iowa State Univ.,
Ames, IA 50011
Ethephon was applied as a foliar spray to 36-day-old petunia seedlings to
determine its effectiveness at reducing apical dominance by increasing lateral
shoot development. Ethephon application at rates of 125, 250 and 500 mg• L–1 to
whole shoots of Petunia x hybrida ‘Orchid’ decreased apical dominance compared
to the control. The average length of a lateral shoot increased 56% as ethephon
application rates increased from 0 to 500 mg• L–1. In Expt. I, ethephon-treated
plants had a greater number of laterals than control plants. The number of nodes
produced before the fi rst fl ower bud was initiated increased from 15 to 21 as
rates of ethephon increased from 0 to 500 mg• L–1. Ethephon delayed anthesis
up to 10 days when applied at 500 mg• L–1 and up to 8 days when applied at 250
mg• L–1. The number of visible fl ower buds increased in all ethephon-treated plants
compared to the control. Ethephon at 250 mg• L–1, increased shoot and root dry
mass 37.9% and 20.4% , respectively, compared to untreated controls. Roots
appeared healthy in both experiments, but phytotoxicity (mild chlorosis) occurred
in Expt. II on plants treated with 500 mg• L–1. The experiment was repeated twice
with similar results.
270
Effects of Trichoderma harzianum Strain T-22 Sprays on Incidence of Sooty Blotch and Fly Speck of Apple and Botrytis
Fruit Rot of Raspberry
Richard K. Kiyomoto* ; Forestry & Horticulture Dept., Connecticut Agr. Expt.
Station, New Haven, CT 06504
Tests were made to determine the effectiveness of Trichoderma harzianum T-22
sprays in controlling sooty blotch (Zygophiala jamaicensis) and fl y speck (Gloeodes pomigena) in fi ve experimental scab-resistant apple varieties and botrytis
fruit rot in fi ve fall-bearing red raspberry cultivars. T-22 and S-12 surfactant used
in these studies were supplied by BioWorks, Inc., Geneva, N.Y. Treatments applied
to runoff on foliage and fruit were: unsprayed; T22 (1.2 g• L–1), T22 + S-12 (1.2
g• L–1 + 0.5 g• L–1), Captan 50W +T22 (1.2 g• L–1 + 1.2 g• L–1), and Captan 50W
491
(1.1 g• L–1). Raspberry treatments substituted Rovral for Captaon 50W. Cultivars in
the apple and raspberry trials were planted in a randomized complete block design
with three blocks in the apple and four blocks in the raspberry planting. All spray
treatments were applied to each cultivar in a block. Apples were treated on 5 Aug.,
19 Aug, 2 Sept., and 16 Sept. and fruit were evaluated as cultivars ripened from
29 Sept. to 17 Oct. Raspberries were treated on 30 July (34% to 86% bloom),
14 Aug., 28, Aug., and 9 Sept. Evaluation for Botrytis was made throughout this
period and data are presented for 12 Sept. Incidence of sooty blotch and fl yspeck
were ≈50% lower in T22 treatments than in unsprayed controls, but the difference
was not signifi cant. Captan treatments had signifi cantly lower incidence of sooty
blotch. Captan and T22 treatments had less fl yspeck than the unsprayed controls,
but the differences were not signifi cant. Signifi cant cultivar x treatment interactions
may have resulted from the prolonged evaluation period and obscured differences
in treatment effects In the fall raspberries 10% of untreated, 5% of T22 and T22 +
S-12-treated, and 2% of Rovral and Rovral + T22 fruit were infected with Botrytis.
These differences were highly signifi cant.
271
Bioremediation of Greenhouse Effluent using Constructed
Wetlands
Michelle S. Meche* 1, Harvey J. Lang1, and Ann L. Kenimer2; 1Dept. of Horticultural Sciences and 2Dept. of Agricultural Engineering, Texas A& M Univ., College
Station, TX 77843
Due to problems of water shortages and increased legal constraints concerning
effl uent content, nursery and greenhouse operations are in need of new methods
of cleaning and reusing irrigation water. Using constructed wetlands to improve
water quality is a low-cost and rapidly emerging ecotechnology, and is currently
used for treating wastewater from cattle operations, catfi sh ponds, and residential
subdivisions. To examine the effectiveness of constructed wetlands, a greenhouse
was equipped with fi ve free-standing wetland cells planted with Equisetum hyemale
(Horsetail). Cells consisted of 0.9 x 2.4-m metal tanks fi lled with pea gravel (about
0.7 m deep) with inlet and outlet sampling ports. Each cell collected runoff from
individual greenhouse benches stocked with impatiens or marigolds grown in pots
containing Sunshine LC1 media and fertigated using trickle irrigation. Runoff fl ow
rates and volume entering each cell were measured. Water samples were taken 1)
directly from the irrigation line, 2) as bench crop runoff, 3) after entering the cell,
and 4) after exiting the cell, and were analyzed for various N fractions. Preliminary
studies indicated that the cell size used in these studies was suffi cient to handle
runoff volume from each bench and could reduce overall N concentration in the
runoff. There was signifi cant variability in effectiveness between the cells, which
appears to be due to differences in cell vegetation growth and establishment.
Overall evaluation of the system and recommendations will be discussed.
272
Use Yield Ratios to Evaluate Effects of Supplemental Pollination on Crop Production
Thomas E. Ferrari *; Plant Development International, P.O. Box 81375, Bakersfi eld,
CA 93380
The environment caused large fl uctuations in almond yields from year-to-year,
which confounded analysis of pollination treatments performed in the fi eld. Following the practice of supplemental pollination, there was insuffi cient improvement in
yield to indicate that extra pollen applied to honey bees affected nut production.
However, when yield for a cultivar exposed to extra pollen was compared to an
untreated, reference cultivar grown in the same fi eld, a statistically signifi cant
increase in yield was detected. Coeffi cients of variation for yield ratios averaged
54% lower than for yields alone in each of eight orchards examined. Converting
annual yields to yield ratios mitigated the effects of the environment on analysis
of production data.
273
Growth of Container-grown Plants With and Without Azomite
Soil Amendment
Chris Ely and Mark A. Hubbard*; Agriculture Dept., College of the Ozarks, Point
Lookout, MO 65726 USA
Azomite is a mined, commercially available, hydrated sodium calcium aluminosiliclate soil amendment reported to act as a source of mineral elements.
To determine its effect on plant growth, Dendranthema ‘Connie’ rooted cuttings,
Malus seedlings, and Citrus seedlings were grown in containers in one of two
growing media: ProMix BX or ProMix BX with Azomite (1:1, v:v). Plant height was
492
monitored weekly and after 6 weeks of growth, fresh and dry plant weights of roots
and shoots were determined. There was no difference in any of the parameters
measured as a result of the addition of Azomite. Any nutritional infl uence of the
Azomite may only be evident in different conditions, e.g., fi eld soil, or over an
extended period of time. The Azomite altered the medium’s physical properties and
therefore bulk density and water-holding capacity of the Azomite were determined
for consideration.
128 POSTER SESSION 3H (Abstr. 274–281)
Breeding & Genetics—Germplasm &
Genetic Diversity
274
Use of RAPD Fingerprints for Verification of Synonyms and
Studies of Genetic Distance in Pear Genetic Resources
Richard L. Bell * and Shawn Cain; USDA, ARS, Appalachian Fruit Research Station,
45 Wiltshire Road, Kearneysville, WV 25430
Pear cultivars and clonal selections of fi ve related Pyrus species or subspecies
were “fi ngerprinted” using RAPD markers. Total DNA was extracted from young
leaf tissue usign a modifi ed cTAB procedure. Twenty oligonucleotide decamers
from Operon kits A and B were evaluated for repeatability and polymorphisms in
an initial set of six cultivars. Nine highly polymorphic primers were selected for
“fi ngerprinting” a larger set of 29 gentoypes. Dissimilarity indices were computed
from the RAPD markers, and cluster analysis performed on these genetic distance
data. ‘Jeribasma’ and ‘Vodenac’, cultivars collected in Serbia, and ‘Erabasma’
collected in Poland, were verifi ed as being synonymous genotypes. Cultivars
from Eastern Europe were not uniformly grouped separately from cultivars from
Western Europe. The results demonstrate the effi ciency of RAPD markers for
cultivar identifi cation and studies of genetic relatedness.
275
The Plumeria Germplasm Collection of the University of
Hawaii
Richard A. Criley*; Dept. of Horticulture, Univ. of Hawaii, Honolulu, HI 96822
Founded in the mid-1960s to serve as a repository for the diverse plumeria
(Family: Apocynaceae) varieties found in Hawaii, the collection has been moved
twice and now occupies an area of 0.8 ha. Since the retirement of the plant breeder
who initiated the collection, no active breeding program is in place, but the collection is augmented by donation of plumeria cuttings thought by their discoverers
to have exceptional merit. The plant material is evaluated for habit of growth,
susceptibility to rust, and for fl ower qualities including productivity, color, size,
petal overlap, fragrance, and keeping quality. Recent accessions include several
compact, evergreen plumerias with pink and yellow fl owers showing both Plumeria
obtusa and P. rubra parentage. Several plumeria cultivars developed in Texas have
demonstrated positive qualties in the more favorable growing conditons of Hawaii.
Several Hawaii accessions to be registered with the Plumeria Society of America
in 1998 will be described and illustrated in this presentation.
276
Genetic Diversity of Basil (Ocimum spp. - Lamiaceae) Based
on RAPD Markers and Volatile Oil Constituents
Roberto F. Vieira*, James E. Simon, Peter Goldsbrough, and Antonio Figueira;
Dept. of Horticulture, Purdue Univ., West Lafayette, IN 47907-1165
Essential oils extracted from basil (Ocimum spp.) by steam distillation are
used to fl avor foods, oral products, in fragrances, and in traditional medicines. The
genus Ocimum contains around 30 species native to the tropics and subtropics,
with some species naturalized and/or cultivated in temperate areas. Inter- and
intraspecifi c hybridization have created signifi cant confusion in the botanical
systematics of this genus. Taxonomy of basil (O. basilicum) is also complicated
by the existence of numerous varieties, cultivars, and chemotypes within the
species that do not differ signifi cantly in morphology. In this study we are using
RAPD markers and volatile oil composition to characterize the genetic diversity
among the most economically important Ocimum species. We hypothesize that the
genetic similarity revealed by molecular markers will more accurately refl ect the
HORTSCIENCE, VOL. 33(3), JUNE 1998
morphological and chemical differences in Ocimum than essential oil composition per se. Preliminary research using fi ve Ocimum species, four undetermined
species, and eight varieties of O. basilicum (a total of 19 accessions) generated
107 polymorphic fragments amplifi ed with 19 primers. RAPDs are able to discriminate between Ocimum species, but show a high degree of similarity between
O. basilicum varieties. The genetic distance between nine species and among 55
accessions within the species O. americanum, O. basilicum, O. campechianum,
O. x citriodorum, O. gratissimum , O. kilimandscharium , O. minimum, O. selloi ,
and O. tenuifl orum will be analyzed by matrix of similarity and compared to the
volatile oil profi le. This research will for the fi rst time apply molecular markers to
characterize the genetic diversity of Ocimum associate with volatile oil constituent.
277
Affinities ofRosa roxburghii Tratt.
David H. Byrne* and Yan Ma; Dept. of Horticultural Sciences, Texas A& M Univ.,
College Station, TX 77843-2133
Rosa roxburghii Tratt. has been placed in the monotypic subgenus Platyrhodon (Hurst) Rehd. on the basis of its exfoliating bark and prickly hips (fruits).
Several lines of evidence indicate a much closer relationship to species within the
subgenus Rosa L., particularly to the species in the sections Bracteatae Thory.,
Cinnamoneae DC. and Carolinae Crep. Unlike R. persica Michx. (subgenus Hulthemia (Dumort.) Focke.) and R. minutifolia Engelmann (Subgenus Hesperhodos
Cockerell), which inhabit deserts, R. roxburghii inhabits more mesic habitats
alongside numerous species of subgenus Rosa. Chromosome morphology and
size in R. roxburghii resemble those of subgenus Rosa, and both have a single
nucleolar organizer locus on the short arm of a relatively short submetacentric
chromosome, as revealed by fl orescent in situ DNA hybridization. Rosa roxburghii
clustered well within subgenus Rosa on the basis of alleles at putative isozyme
loci and RAPD markers. Thus R. roxburghii probably should be classifi ed as a
morphologically distinct section of the subgenus Rosa rather than as a separate
subgenus.
278
Genetic Relatedness of Pecan Cultivars Determined by Using
Random Amplified Polymorphic DNA (RAPD)
Yongling Xiao* 1, Dong Young Shin2, and Hazel Y. Wetzstein1; 1Dept. of Horticulture,
1111 Plant Science Bldg., Univ. of Georgia, Athens, GA 30602-7273, USA; 2Dept.
of Resource Plant2, Sunchon National Univ., 315 Maegok-Dong Sunchon City,
Chonnam, South Korea 540-742
Although pecan (Carya illinoinensis ) is an economically important nut and
timber crop, little is known about the nature of genetic variation among pecan
cultivars. In addition, the pedigree of many cultivars remains unknown or is
questionable. In this study, the genomic DNA of 20 pecan cultivars were analyzed
by RAPD, using 20 randomly selected oligoes as primers. Based on their genetic
similarities derived from the RAPD data, the 20 pecan cultivars were classifi ed
into different groups. Pecan cultivars within the same group displayed very
little genetic variation, whereas cultivars in different groups showed signifi cant
diversity. The putative origins for some pecan cultivars previously believed to
have unknown pedigrees were also identifi ed based on the RAPD data obtained.
Results of this study provide information useful for pecan cultivar classifi cation
and parent selection in pecan breeding programs.
279
Establishment of In Vitro Genebank of Colombian Cultivars of
Achira (Canna edulis Ker. )
Luz M. Reyes* 1, Gustavo Ligarreto2 , Germán Muñoz3, Pilar Bravo3, and Edgar
Valbuena3; 1Facultad de Agronomía, U. Nacional de Colombia. A.A. 14490;
2
CORPOICA; 3 U. Pedagógica Nacional, Bogotá, Colombia, S.A.
Clonal propagation of an Andean tuber ‘Achira’ (Canna edulis Ker.) is currently
limited to budding. A tissue-culture system to rapidly produce clonal material
would be valuable for both production and germplasm preservation. Thirteen
cultivars collected at the provinces of Cáqueza (Cundinamarca) and Garzón (Huila)
were utilized for the establishment of meristem-tips (5 mm) under in vitro conditions. Based on protocols reported for species of Musa sp., C. indica and Elletaria
cardamomun, a complete random design was implemented with 10 treatments
and six replications per clone. The analysis of variance showed no signifi cant
differences between cultivars, but signifi cant differences among treatments. The
HORTSCIENCE, VOL. 33(3), JUNE 1998
variables measured were number of shoots, aerial roots formation, roots (relative
amount), callus (absent or present) and degree of etiolation. Double disinfestation
protocol was used in this study in order to reduce the degree of contamination
of the explants during the culture. Organogenesis was obtained for the whole
cultivars, without callus formation, with treatments 9 and 10. However the best
results for shoot and root formation was detected for the treatment 10. This was
constituted by MS (1/2) supplemented with 0.1 ppm BAP; 0.5 ppm IBA; 3%
sucrose, and 2% phytagel. The explants were grown at 26 °C with photoperiod
of 16 hours and 2000 lux. After 3 weeks the shoot formation was evident, while
the rooting started after 4 weeks. Subcultures were done every 3 weeks after
plantlets formation. The 13 cultivars established under in vitro conditions were
placed at the active genebank of the Plant Genetic Resources National Program
at CORPOICA, for their conservation under low growth conditions.
280
Calculation of Genetic Correlation Coefficients Based on Offspring–Parent Relationships Using a Spreadsheet
Qiang Yao* and Shawn A. Mehlenbacher; Dept. of Horticulture, Oregon State
Univ., Corvallis, OR 97331
Genetic correlation coeffi cients can be used to compare effi ciency of direct
and indirect selection, estimate correlated response to selection and set up index
selection.Information on quantitative traits in parent and offspring can be used to
estimate genetic correlation coeffi cients for fruit and nut crops. However, existing
statistical packages do not allow easy calculation of genetic correlation coeffi cients.
In this paper, we demonstrate the use of a spreadsheet to quickly estimate genetic
correlation coeffi cients using data on parents and progeny in the OSU hazelnut
breeding program.This procedure can be extended to n traits and m crosses.
281
The Introduction, Evaluation, Escape from Cultivation, and
Ongoing Range Expansion of Ligustrum spp. On and Around
the Texas A&M University Campus
Edward McWilliams and Gretchen Rector*; Dept. of Horticultural Sciences, Texas
A& M Univ., College Station, TX 77843
For decades, the Texas A& M Univ. campus has been a center for USDA
ornamental plant introductions. Historically, horticultural nurseries on the Texas
A& M Univ. campus have served as foci from which exotic plants have dispersed
and colonized surrounding areas. Pistachia chinensis, Ulmus parvifolia, Ligustrum quihoui, Ligustrum lucidum, and Sapium sebiferum have all established
themselves on or near the campus and can be traced back to early introductions.
Many Ligustrum taxa including selections of L. quihoui were screened at Texas
A& M College in the 1930s. Clones of this species varied greatly in their ability to
naturalize. The invasion lag phase and range of expansion varied with both clone
and species. It is suggested that potential exotic ornamental plant introductions
be carefully evaluated for their potential to become non-native invasive species
as well as for their ornamental characteristics.
128 POSTER SESSION 3I (Abstr. 282–285)
Growth Regulators—Vegetable Crops
282
Involvement of Gibberellins in Phytochrome-regulated Stem
and Petiole Elongation in Watermelon Plants
N.K. Damayanthi Ranwala* and Dennis R. Decoteau; Dept. of Horticulture, Clemson
Univ., Clemson, SC 29634-0375
Phytochrome-regulated stem and petiole elongation is of great horticultural
importance due to their effects on height and compactness of plants. Although it
is believed that phytochrome action during cell elongation is controlled via gibberellin (GA) biosynthesis, conclusive evidence has not been presented. In this
study, watermelon plants pre-treated with GAs or GA biosynthesis inhibitors were
briefl y exposed to red (R) or far-red (FR) at the end of photoperiod to investigate
the involvement of GAs in phytochrome-regulated stem and petiole elongation.
Two-week-old watermelon plants were applied with either GAs, GA3 (25 ppm) or
GA4+7 (25 ppm), or GA biosynthesis inhibitors, paclobutrazol (early stage inhibitor,
493
2 ppm) or prohexadione-Ca (late stage inhibitor, 200 ppm). Following chemical
application, plants were treated with low-intensity R or FR light for 15 min at the
end of photoperiod for 8 days. The increased petiole length and increased dry
mass partitioned to petioles caused by FR were further increased when plants were
pre-treated with GA3 and GA4+7, but reduced when plants were pre-treated with
paclobutrazol or prohexadione-Ca. Pre-treatment with paclobutrazol or prohexadione-Ca further reduced the petiole length and dry mass partitioned to petioles
caused by R alone, but effects of R were reversed when plants were pre-treated
with GA3 and GA4+7. Petiole growth changes were signifi cant after 2 to 3 days
of treatments and there was no light or growth regulator effects on stem growth.
Low leaf chlorophyll content and higher photosynthesis resulted in FR-treated
plants were not observed when plants were pre-treated with paclobutrazol or
prohexadione-Ca. Prohexadione-Ca was more effective in reversing FR induced
petiole elongation than paclobutrazol, while GA4+7 was more effective than GA3 in
promoting the effects of FR and reversing the effects of R. These results provide
further evidence that phytochrome regulated growth changes in watermelon are
due to the changes in GA biosynthesis. It is also suggestive that phytochrome
has differential regulation of GA biosynthesis.
Select’ and ‘Hard Pick’) that differ in ease of separation at the calyx-pedicel separation zone were used. Individual fl owers were tagged at anthesis and intact fruit
were treated with ethephon (500, 1000 µL) 29, 32, 35, and 38 days after anthesis.
Untreated fruit were used as controls. The normal development from anthesis to
mature red is 45 to 47 days for both lines. Ethephon treatment to tabasco fruit of
both lines at 29 and 32 days after anthesis was effective in enhancing ripening by
3 to 7 days. ‘Mclhenny Select’ ethephon treated fruit 35 days after anthesis were
not affected. In contrast, ‘Hard Pick’ fruit treated with ethephon at the high rate
(1000 µL) 35 and 38 days after anthesis resulted in enhanced ripening compared
to that of the control. These results indicate that the two tabasco lines differ in
response to ethephon.
283
Influence of Methanol and Nitrogen on the Yield of Cilantro
(Coriandrum sativum)
286
Crop Residues in San Joaquin Valley Row Crop Systems
128 POSTER SESSION 3J (Abstr. 286–296)
Sustainable Agriculture—Vegetable Crops
J.P. Morales-Payan*; Dominican HortResearch Group/Sociedad Dominicana de
Investigadores Agropecuarios y Forestales (SODIAF), Dominican Republic
Treatment with short-chain alcohols such as methanol and ethanol have been
found to stimulate the performance of a number of crops. Container experiments
were conducted in the Dominican Republic to determine the effect of methanol
and nitrogen (N) treatments on the yield of cilantro (Coriandrum sativum). Plants
were individually grown in plastic containers (15 x 15 cm) fi lled with loamy clay
soil (4.3% organic matter) fertilized at planting with 20, 40, 60, and 80 kg N/ha.
Methanol was sprayed in aqueous solutions (0% , 5% , 10% , and 15 % ) when
plants reached the three true leaf stage. A randomized complete-block design
with a factorial arrangement and fi ve replications was utilized. Cilantro plants
were harvested 40 days after emergence and shoot fresh and dry weight were
determined. Resulting data was subjected to analysis of variance and regression
analysis. No signifi cant nitrogen and methanol interactions were detected. In the
range of rates tested in this study, methanol did not signifi cantly infl uence cilantro
shoot fresh or dry weight. Cilantro yields increased when N rates were increased
from 20 to 40 kg per ha, reaching a plateau at higher N rates.
J.P. Mitchell* 1, T.K. Hartz1, and G.S. Pettygrove1, D.S. Munk2, and D.M. May2;
Dept. of Vegetable Crops, Univ. of California, Davis, Kearney Agricultural Center,
Parlier, CA 93648; 2Univ. of California Cooperative Extension, Fresno County
The West Side of California’s San Joaquin Valley is one of the most productive agricultural regions of the world. The leading crops of this region include
processing tomatoes, cotton, onions, garlic, cantaloupes, and lettuce, which are
grown on over 570,000 acres annually. During the past 30 years, land use patterns
on the West Side have changed considerably. More than 60% of the acreage in
this area was typically planted to wheat, barley, and saffl ower in 1965, whereas
in 1994 these crops were grown on 7% of the area. The intensifi cation in the
production of high value crops has led to fewer additions of organic matter to
the soil and more aggressive tillage operations. In 1996–97, we quantifi ed the
amount and composition of postharvest crop residues that are returned to the
soil in typical West Side rotations. The highest amount of crop residues resulted
from corn stubble following grain harvest (10,300 lb dry matter per acre) and the
lowest amounts resulted from onions and garlic, with 517 and 700 lb dry matter
per acre, respectively. These data demonstrate the large range of organic matter
recycling that results from varous intensive cropping strategies in this region.
284
Responsiveness of Three Tayota (Sechium edule) Types to
Gibberellic Acid Treatment
287
Cover Crops for San Joaquin Valley Row Crop Production
Systems
J. P. Morales-Payan*; Dominican HortResearch Group/Sociedad Dominicana de
Investigadores Agropecuarios y Forestales (SODIAF), Dominican Republic
Container experiments were conducted in the Dominican Republic to determine
the effects of gibberellic acid applications on the ‘White’, ‘Green’, and ‘Spiny Green’
tayota (Sechium edule) Dominican types. Young plants (25 cm in length) of the
three types were sprayed with aqueous solutions of gibberellic acid at rates 0,
50, 100, 150, and 200 parts per million. A completely randomized design with
seven replications was utilized. Plant height and shoot dry weight were determined
30 days after treatment and resulting data was subjected to analysis of variance
and regression analysis. Gibberellic acid treatment signifi cantly increased tayota
shoot dry weight and stem elongation. Both variables responded with similar
patterns to gibberellic acid application. A linear regression (Y = 39.82 + 0.214 X,
r2 0.95) described stem elongation as a function of gibberellic acid rates. Results
show that gibberellic acid can be effectively used in either tayota type to promote
early stem elongation. From a practical standpoint, due to the climbing nature
of Sechium edulis, rapid stem elongation could be instrumental in a more rapid
establishment of the crop vines in the trellis system, as well as to provide the
crop with an advantage on weeds competing for light during the usually critical
early growth stages.
285
Effect of Ethephon on Tabasco Fruit Ripening
Cailiang Mao* and Carl E. Motsenbocker; Dept. of Horticulture, Louisiana State
Univ., Baton Rouge, LA 70803
The effect of ethephon on fruit maturity in tabasco pepper (Capsicum frutescens
L) was investigated in greenhouse studies. Two lines of tabasco pepper (‘McIhenny
494
1
J.P. Mitchell* , T.S. Prather, K.J. Hembree, P.B. Goodell, D.M. May, and R.L.
Coviello; Univ. of California Davis
There is currently considerable interest in the use of cover crops to improve
the productivity and sustainability of agroecosystems in California. Adoption of
cover crops into San Joaquin Valley row cropping systems has been slow, however,
largely because growth characteristics of potentially suitable cover crop species
and mixtures have not been identifi ed for the tight windows of opportunity that
exist within the region’s intensive rotations, and because of uncertainy about the
amount of water required to grow a cover crop. In 1995–96 and 1997–98, we
screened 15 potential late-summer and winter cover crop species and mixtures
planted monthly from 1 Aug. through 1 Nov. and harvested at 30-day intervals
through March. In 1995–96, Sorghum-sudan produced 36,543 lb dry matter/acre
and was the highest-producing late-summer species in a December-harvested
August planting. Triticale and Merced rye were highest-producing winter species,
yielding 19,277 and 10,155 lb dry weight/acre, respectively, during the 5-month
period from October to March.
288
Soil Nitrogen Movement under Sustainable Vegetable Production Systems
Amy M. Johnson* and Greg D. Hoyt; Dept. of Soil Science, NCSU, Mtn. Hort.
Crops Res. & Ext. Center, 2016 Fanning Bridge Rd., Fletcher, NC 28732
An experiment was established to determine the effect of different tillage
practices, vegetable crop rotations, and pest management strategies on crop yield,
plant diseases, pest and benefi cial arthropods, weed species changes over time, and
soil environmental consequences. This poster describes nitrogen movement from
HORTSCIENCE, VOL. 33(3), JUNE 1998
the various treatments over a 3-year rotation. The treatments are: 1) conventional
tillage with chemically based IPM; 2) conventional tillage with biologically based
IPM; 3) conservation tillage with chemically based IPM; 4) conservation tillage with
biologically based IPM; and 5) conventional tillage with no fertilizer or pest management. Mid-season soil analyses with depth showed chemical-fertilized plowed
and conservation-tilled treatments with more soil available nitrogen at most depths
compared to the biological-based IPM systems (soybean meal was used as a nitrogen
source). However, the biological-based systems did supply enough soil nitrogen to
produce similar yield results as the chemical-based systems. Less soil nitrate was
measured in the 30- to 90-cm depths at harvest from the biological-based systems
than chemical-based systems. Conservation-tilled systems had greater nitrate with
depth compared to conventional-tilled systems.
289
Nitrogen Assimilation and Biomass Yield of Winter Cover Crops
Used in Sustainable Horticultural Crop Production
Bharat P. Singh* , Upendra M. Sainju, and Wayne F. Whitehead; Agricultural
Research Station, Fort Valley State Univ., Fort Valley, GA 31030-3298
Cover crops are planted during winter to prevent soil erosion, improve soil
quality, and supply nutrients to the subsequent spring crops. In a 2-year study,
three winter cover crops were compared for their nitrogen assimilation and biomass
yielding ability. The experimental design was randomized complete block replicated four times with cereal rye, hairy vetch, crimson clover, and a fallow control
comprising the treatments. Cover crop roots were well distributed from 1 to 50
cm of soil depth and increased from fall to spring as temperature increased. There
was greater reduction in soil inorganic N during fall and winter in cover crop plots
compared to control. Early season soil NO3– concentration was lower in rye than
crimson clover or hairy vetch. The amount of N assimilated by hairy vetch and
crimson clover was signifi cantly greater than cereal rye or control. There was no
difference in the biomass yield of the three cover crops during the fi rst year, but
cereal rye and crimson clover produced signifi cantly greater biomass than hairy
vetch during the second year. The results suggest that cereal rye is more suited
for preventing leaching of residual N from the preceding summer crop, while the
two legumes can supply more N to the following crop.
290
Weed Control in Tomato Production using Spring-sown Cover
Crops Killed by Undercutting
Akemo Mary Christine*, Mark Bennett, and Emily Regnier; Dept. of Horticulture
and Crop Science, The Ohio State Univ., Columbus, OH 43210
A cover crop study in Spring 1996 showed that mowing did not completely kill
the cover crops. In 1997 the study was repeated with the same cover crop treatments using winter rye ‘Wheeler’ ( Secale cereale) and fi eld peas (Pisum sativum).
Cover crops were eastablished in pure stands and bi-cultures in decreasing levels
and varying proportions in early Spring 1997. They were undercut under the soil 2
months later, prior to transplanting tomato seedlings. Three controls were included
in each replicate. Tomato plants in treatments with higher seeding rates of fi eld
peas had higher leaf areas and dry weights 1 month after transplanting. Weeds,
especially dicotyledons, grew through the cover crop mulch 1.5 months after
undercutting, but by then the tomato plants were at an advanced stage of growth.
Tomato fruit yields were much higher than those of 1996 and had signifi cant
differences (P = 0.05). Highest yields were from treatments with highest rates
of 0.25 rye + 0.75 peas, 0.5 rye + 0.5 peas, pure peas, and the conventionally
hand-weeded control. Lowest yields were from the weedy checks. Undercutting
the cover crops improved yields in all plots so treated probably because the soil
was loosened and the tomato plants’ roots accessed nutrients and water better.
Spring sowing and undercutting cover crops defi nitely has a potential for weed
control.
291
Yield and Nutrient Uptake of Peppers (Capsicum annuum)
Grown with Dairy Manure Compost and Fertigated Nitrogen
Nancy E. Roe*; Texas A& M Research and Extension Center, Rt. 2 Box 1, Stephenville, TX, 76401
The use of compost as an organic source of nutrients and soil improvement
may help to increase the sustainability of intensively managed vegetables. Bell
pepper (Capsicum annuum L.) transplants were planted into silver-colored polyethylene mulched beds in a sandy loam soil amended with 0 or 22.4 Mg• ha–1
HORTSCIENCE, VOL. 33(3), JUNE 1998
dairy manure compost. Preplant P was added to all beds at 78 kg• ha–1. During
the season, N (as NH4NO3) was added about every 10 days. Total N rates for the
season were: 0, 32, 65, or 96 kg• ha–1. Percent of N in pepper leaf tissue increased
from a low of 2.7% without N to3.8% at the high N rate. Leaf P concentrations were
higher in 0 N plots than in other rates. Compost resulted in higher leaf concentrations of Ca. There was an interaction of compost and N rates for percent of culls.
Compost increased percentage of culls with 0 or 32 kg• ha–1 N, but decreased
or did not affect cull percentage at 65, or 96 kg• ha–1 N. Compost did not affect
other yield parameters measured. Marketable yields increased from 11 Mg• ha–1
with 0 N to 18 Mg• ha–1 with high N, although the regression was not signifi cant,
due to extreme variability within the fi eld.
292
Sustainable Production of Honeydew and M uskmelon in
Western Mexico
J. Farias-Larios* and A. Michel-Rosales; Facultad de Ciencias Biologicas y
Agropecuarias, Universidad de Colima, Apartado postal 36. 28100 Tecoman,
Colima, Mèxico
In Western Mexico, melon production depends on high-input systems to
maximize yield and product quality. Tillage, plasticulture, fumigation with methyl
bromide, and fertigation, are the principal management practices in these systems.
However, at present several problems has been found: pests as sweetpotato whitefl y
(Bemisia tabaci Gennadius), aphids (Myzus and Aphis), leafminer (Liryomiza
sativae); diseases as Fusarium, Verticilium, and Pseudoperenospora, and weeds
demand high pesticide utilization and labor. There is a growing demand for alternative cultural practices, with an emphasis on reducing off-farm input labor and
chemicals. Our research is based on use of organic mulches, such as: rice straw,
mature maize leaves, banana leaves, sugarcane bagasse, coconut leaves, and
living mulches with annual legume cover crop in melons with crop rotation, such
as: Canavalia, Stilozobium, Crotalaria, and Clitoria species. Also, inoculations
with mycorrhizal arbuscular fungi for honeydew and cantaloupe melon seedlings
production are been assayed in greenhouse conditions for a transplant system.
The use of life barriers with sorghum, marigold, and other aromatic native plants
in conjunction with a colored yellow systems traps for monitoring pests is being
studied as well. While that the pest control is based in commercial formulations of
Beauveria bassiana for biological control. The fi rst results of this research show that
the Glomus intraradices, G. fasciculatum, G. etunicatum, and G. mosseae reached
38.5%, 33.5%, 27.0%, and 31.0% of root infection levels, respectively. Honeydew
melons production with rice and corn straw mulches shows an benefi cial effect
with 113.30 and 111.20 kg/plot of 10 m2 compared with bare soil with 100.20
kg. The proposed system likely also lowers production cost and is applicable to
small- and large-scale melon production.
293
Conservation Tillage of Winter Broccoli in a Semi-arid Subtropical Environment
D.J. Makus*; USDA-ARS, Weslaco, TX 78596
Winter broccoli (Brassica oleracea, L. Botrytis Group) production was evaluated under three tillage systems, conventional (CT), minimum tillage (MT), and
no-till (NT), which were established in Aug. 1994. Cotton, followed by a legume,
preceded broccoli in the yearly rotation. After three growing seasons, marketable
broccoli yields were similar among tillage systems, but plant densities at harvest
were lower in the NT system compared to the CT-grown broccoli plants. No-tillgrown broccoli heads compensated for stand differences by producing slightly
larger heads (P = 0.17). The percent marketable yield was not affected by tillage
practice. Floret NO3, chlorophyll, and carotenoid concentrations were reduced
when broccoli was grown by conservation tillage (MT and NT). At the end of the
third growing season, the amount of germinable weed seeds in the upper 0-5 cm
of soil was highest in the NT soil. Total plant weed populations were higher in
conservation tilled soil. Total N, K, and Mg concentrations in the upper 30-cm soil
profi le were highest in the NT system. Total N, C, K, Mg, and P nutrient gradients
were greatest in NT soil, whereas Na concentrations were greatest in CT soils.
Min. tillage responses were generally intermediate to those of CT and NT.
294
Relationship Between Cover Crop Growth, Weed Suppression,
and Yield of No-tillage Broccoli (Brassica oleraceae L. var.
italica)
495
Ronald D. Morse* 1 and Aref Abdul-Baki 2; 1Dept. of Horticulture, Virginia Polytechnic Inst. & State Univ., Blacksburg, VA 24061-0327; 2Beltsville Agricultural
Research Center, Beltsville, MD 20705
In 1997, no-till fall broccoli was grown at the Kentland Agricultural Research
Farm (KARF), Blacksburg, Va., and the Beltsville Agricultural Research Center
(BARC), Md., to determine supplemental N requirements above the nitrogen
contribution from legume in situ mulches. Treatments were tillage systems [CT =
conventional tillage, bare soil, tilled prior to transplanting; NT-BS = untilled bare
soil; NT-SB = soybean (Glycine max L.) cover crop; and NT-CP = cowpea (Vigna
sinensis Endl.) cover crop; and nitrogen fertilizer rates (0, 84, and 168 at KARF,
and 0, 56, 112, and 168 kg• ha–1 at BARC). All plots at both sites were treated
with recommended herbicides and drip irrigated as needed to supplement rainfall.
Dry weight soybean and cowpea biomass was 6.1 and 4.3 at KARF and 4.8 and
3.5 t• ha–1 at BARC. In N-unfertilized plots at both sites, average broccoli yield
was higher in NT-SB and NT-CP than CT and NT-BS. The N contribution from
the legume mulches was inadequate to meet total crop demand, since N fertilizer
applications increased broccoli yield in all tillage treatments, including the legume
cover crops (soybean and cowpea). In N-fertilized plots, broccoli yield was similar
among tillage treatments at KARF where weed problems were not severe; however,
at BARC, yield in CT was higher than in all no-till treatments. Weed pressure was
considerably lower in CT than in no-till plots at BARC. Based on these data and
other related no-till studies, two conclusions can be drawn: a) no-till systems are
a viable option for production of broccoli when weeds are adequately controlled;
and b) uniformly distributed, high-residue levels are required for weed suppression
when weed pressure is high and herbicides are either ineffective or not applied.
295
Tillage and Mulch Effects on Yield of Bell Pepper (Capiscum
annum L. )
Aref Abdul-Baki 1 and Ronald D. Morse* 2; 1Beltsville Agricultural Research Center,
Beltsville, MD 20705; 2Dept. of Horticulture, Virginia Polytechnic Inst. & State
Univ., Blacksburg, VA 24061-0327
In 1997, three tillage/mulch pepper production systems were compared on raised
beds at the Beltsville Agricultural Research Center (BARC), Md., and at Kentland
Agricultural Research Farm (KARF), Blacksburg, Va. The tillage/mulch treatments
were no-till hairy vetch (Vicia vellosa Roth) mulch (NT-HV), black plastic mulch
on beds that were conventionally tilled and reformed before transplanting the
peppers (CT-BP), and untilled bare soil (NT-BS). ‘Camelot’ bell peppers were
planted in early June 1997 in double rows at both sites. Both the CT-BP and NTBS treatments received approximately double the nitrogen fertilizer, compared to
NT-HV. Nitrogen was applied throughout the growing season at BARC, while all
the N fertilizer was applied during the fi rst 3 weeks of plant growth at KARF. Nine
weekly harvests were made at BARC and six at KARF. Fruit yield was high in all
treatments at both sites. There were no signifi cant differences among treatments
in marketable yield or fruit weight at BARC. In contrast, yield was signifi cantly
higher with CT-BP than with NT-HV and NT-BS at KARF. Higher yield with CT-BP
at KARF possibly occurred from enhanced soil temperature and reduced N leaching
normally associated with black plastic mulch production systems.
296
Composted Chicken M anure Improves Growth and Yield of
Red Table Beets
Lydia Stivers-Young1, Anusuya Rangarajan* 2, and Frances Tucker 1; 1Cornell
Cooperative Extension, 249 Highland Ave., Rochester, NY 14620; Dept. of Fruit
and Vegetable Sciences, Cornell Univ., Ithaca, NY 14853
Six on-farm trials were conducted from 1995–1997 to test the effects of
composted chicken manure applications on stand establishment, growth, disease
incidence, and yield of red table beets (Beta vulgaris). Yields were consistently
higher (14% to 68% ) in plots where 4500 or 9000 kg• ha–1 composted chicken
manure was broadcast at planting. Compost applications improved early season
stands in 1995 and 1996; however, emergence and seedling death occured
throughout the season in all trials. The number of marketable beets at harvest
was as low as 35% of the number of seeds planted, even when yields were above
average. Applying composted chicken manure to red table beets offers a way to use
a waste product from one agricultural production system as an input in another,
thus improving effi ciency and minimizing pollution.
496
128 POSTER SESSION 3K (Abstr. 297–305)
Crop Production/Postharvest—Fruit
297
Re-evaluation of a Desiccating Surfactant for Thinning Peach
Blossoms
R.C. Ebel * 1, D.G. Himelrick1, A. Caylor2, and J. Pitts3; 1Dept. of Horticulture, 101
Funchess Hall, Auburn Univ., Auburn, AL 36849; 2North Alabama Horticulture
Substation, P.O. Box 1062, Cullman, AL 35055; 3Chilton Area Horticulture Substation, 120 County Road 756, Clanton, AL 35045
The surfactant “Surfactant WK” (dodecyl ether of polyethylene glycol) was
applied to peach trees [ Prunus persica (L.) Batsch] at full bloom over 3 years.
Blossoms died rapidly, so that within 2 days dead blossoms could be distinguished
easily from live blossoms or set fruit. There were strong (R2 > 0.87), linear correlations between concentration of “Surfactant WK” applied and percent blossoms
removed and fruit set, which were similar over the 3 years. Trees were hand-thinned
according to commercial practices after treatment. There was similar cropload,
fruit weight and yield across treatments at harvest indicating no negative effects
by the chemical on productivity. There was only slight limb damage at the highest
concentrations of “Surfactant WK”, which over thinned blossoms. We recommend
that based on the effectiveness, consistency, and lack of signifi cant phytotoxicity,
“Surfactant WK” be re-evaluated as a thinning chemical for peach trees.
298
Thinning Peaches with Dormant Applications of Soybean Oil
R.E. Moran*, D.E. Deyton, C.E. Sams, J.C. Cummins and A.L. Lancaster, Dept. of
Plant and Soil Sciences, The Univ. of Tennessee, Knoxville, TN 37901
Dormant applications of 0% to 20% soybean oil were tested as a prebloom
thinner of ‘Georgia Belle’ and ‘Redhaven’ peach fl ower buds. Five separate experiments were conducted with soybean oil applied in late Jan. or early Feb. 1992,
1993, 1995, and 1997. The number of living and dead fl ower buds was counted
on fi ve or 10 shoots per tree before and 1 month after application in Expts. 1, 2,
3, and 4. In Expt. 5, buds were counted on two to three shoots per tree before and
after a freeze of –4 °C during petal fall. Soybean oil thinned fl ower buds in all
fi ve experiments. The amount of fl ower bud death was concentration dependent
with maximum bud kill of 53% occurring with application of 12% oil. Thinning
was fairly consistent from year to year, ranging from 34% to 51% when 10% oil
was applied, but was less uniform when 5% oil was applied and ranged from 6%
to 40% . Overthinning occurred in Expt. 3 by all oil concentrations tested. Bud
death in untreated trees was 40% in this experiment indicating that no thinning
was needed. Mild to moderate spring freezes occurred in Expts. 2, 4, and 5, but
did not result in greater yield loss in thinned than untreated trees. Soybean oil
at 10% and 12% resulted in greater fl ower bud survival of a freeze in Expt. 5.
Dormant applications of soybean oil thinned fl ower buds, reduced the amount of
hand thinning and hastened fruit maturity.
299
Effect of Upright Shoot Removal on Fruit Size and Maturity of
Four-year-old ‘Braeburn’ Apple Trees
P.I. Garriz*, G.M. Colavita, H.L. Alvarez, and A.J. Alvarez; Facultad de Ciencias
Agrarias, Comahue National Univ., c.c. 85, 8303 Cinco Saltos, R.N., Argentina
The effect of upright shoot removal on the progress of maturity and fruit size
around the normal picking time were evaluated for apple fruits cv. ‘Braeburn’ at
the Experimental Farm of the Comahue National Univ., Rio Negro, Argentina, during the 1996–97 growing season. The experiment was conducted on 4-year-old
trees, spaced 4.0 x 2.3 m and trained to palmette leader. Average fruit load was
80 fruits per tree. Five trees per treatment were randomly selected; they were:
1) select cuts: water sprouts were eliminated entirely at 78 days after full bloom
(DAFB) and additional removal of newly formed shoots arising from the scaffolds
was performed at 120 DAFB; 2) control: trees received no cuts. From 158 to 184
DAFB, a sample of four fruits was taken from each tree at weekly intervals. Fruit
size and internal quality were measured. Loss of leaf surface by shoot removal
signifi cantly decreased fruit mass by 4.74% , for all data combined (P < 0.05).
There was no treament effect on maturity, although the rate of fi rmness decline
was lower for fruit from treated trees. At 172 DAFB, pressure, starch index (iodine
test) and soluble solids concentration values for control fruits were 80.55 N, 3.72
HORTSCIENCE, VOL. 33(3), JUNE 1998
and 12.35% , respectively. In the treated trees, fruit mass was 201.03 g at fi nal
harvest. It was concluded that reduction in photoassimilates following severe
upright shoot removal may be a key factor in the negative effect of this practice
on fi nal fruit size. These results suggest some goals of pruning and training for
optimizing apple yield.
a useful model in the research on anthocyanin synthesis and gene expression in
apples.
300
Evaluation of Endothall and Ammonium Thiosulfate as Potential
Bloom Thinning Compounds for ‘Delicious’ and ‘Fuji’ Apples
Lili Zhou* 1, David Christopher2, and Robert E. Paull 2; 1Dept. of Horticulture and
2
Dept. of Plant Molecular Physiology, Univ. of Hawaii at Manoa, Honolulu, HI
96822
The effect of defoliation and fruit thinning on papaya fruit set, growth, and
ripe fruit quality was determined. Three defoliation levels (0% , 50% , 75% ) and
two defoliation methods (75% leaf cut off from the oldest to the youngest vs.
75% leaves removed in a spiral from the oldest) was compared with fruit thinning
experiment on ‘Sunset’ papaya during the warm season. Removal of 75% of the
leaves signifi cantly reduced new fl ower and fruit set, and decreased TSS level in
ripe fruit. There was no signifi cant difference between 0% and 50% defoliation
in new fruit set, or ripe fruit TSS levels. Removal of leaves in a spiral reduced the
number of new fl ower and fruit set more than the defoliation from the bottom to
top. Defoliation of the ‘Kapoho’ variety increased ripe fruit number and signifi cantly
reduced ripe fruit TSS and sugar level, dry mass persentage 2 weeks after defoliation. There was no signifi cant difference between defoliated and non-defoliated
treatment in fruit production, average fruit mass, and percentage of fruit fl esh and
seed, seed mass ratio, and seed dry mass during the test period. Fruit thinning
increased new fruit set and increased ripe fruit TSS level in Line-8 and ‘Sunset’,
but not in ‘Kapoho’. However, average ripe fruit mass increased in fruit thinning
experiment in ‘Kapoho’ but not ‘Sunset’ and Line-8 varieties. Fruit thinning also
increased remaining young fruit TSS and sugar levels on the remaining fruit on
plants compared to same-aged fruit on control and defoliated plants in Line-8.
There was no effect on ‘Kapoho’ young fruit TSS and sugar levels of defoliation.
Ripe fruit TSS varied with weather conditions, plant growth conditions, and
cultivars. These results indicated that although different cultivars had different
responses to artifi cial defoliation and fruit thinning, source–sink balance and the
ratio of fruit to leaf was an important factor in controlling potential fruit production
and fi nal fruit quality.
Kathleen M . Williams* ; WSU- Tree Fruit Research and Extension Center,
Wenatchee, WA 98801
Consistent cropping of apple under Pacifi c Northwest growing conditions
depends on a reliable bloom-thinning compound. Although there are two commercially available bloom-thinning chemicals, performance of these chemicals is
not always consistent. Research on two unregistered bloom thinning compounds,
Endothall and ATS, has been ongoing for several years in commercial orchard
blocks. In 1997, multiple applications of Endothall and ATS were tested on
‘Delicious’ and ‘Fuji’. Endothall was applied at 1.0, 1.5 or 2.0 pints/100 gal per
acre rates at 40% and 80% full bloom. Endothall averaged 19 to 23% thinning
in comparison to the water control on ‘Delicious’. With ‘Fuji’, Endothall averaged
55% to 83% thinning. ATS was applied at 1.0% (v/v) on ‘Delicious’ and 1.5%
(v/v) on ‘Fuji’ at 40% and 80% full bloom. ATS thinned ‘Delicious’ an average
of 30% compared to the water control. In ‘Fuji’, ATS thinned an average of 20%
to 42% . Another experiment involved the combination of ATS or Endothall with
standard postbloom thinning regimes. Fruit quality data were collected on both
bloom and postbloom thinned blocks. Differences in fruit size and shape were
signifi cantly correlated with NAA applications. No signifi cant differences in soluble
solids, titratable acidity, skin color, or fl esh fi rmness were related to thinning
treatments.
301
Ethephon Alters the Physiology of Young Apple Fruits
Daniel Ward* and Richard Marini; Dept. of Horticulture, Virginia Tech, Blacksburg,
VA 24061
Methods are needed to quickly assess the effi cacy of chemical thinning treatments, so, if needed, additional treatments can be applied. When fruit diameter
averaged 19 mm, ‘Smoothee’ trees were sprayed with Ethrel at the rate of 3.7 ml
formulation/L to induce abscission of most fruits on the tree. The diameter of 10
fruit/tree were measured daily and fruits were sampled 2, 4, and 6 days after treatment (DAT) to evaluate fruit development. Fruit on nontreated trees increased in
diameter at the rate of about 0.7 to 0.9 mm/day. Fruit growth on treated trees was
normal for 1 day, slowed to 0.5 mm for 2 days, and grew <0.1 mm/day thereafter.
Fruit water potential was less negative for treated trees 2 DAT. Fresh and dry mass
of treated fruit ceased increasing after 4 DAT. Percent dry mass of control fruit
declined on each sampling date, but did not decline for treated fruit after 4 DAT.
Cellulase was active in the abscission zone 4 DAT for treated fruit, but not control
fruit. Compared to control fruit 6 DAT, treated fruit had elevated respiration and less
starch accumulation. Fruits began to abscise 6 DAT. Following Ethrel application.
The fi rst indication that a fruit is destined to abscise are reduced fruit growth and
changes in water potential 2 DAT.
302
Effects of Fruit Bagging on Accumulation of Anthocyanin, Flavonoid, and Simple Phenols at Harvest and on Anthocyanin
Synthesis Potential During Storage in ‘Delicious’ Apples
Zhiguo Ju*; Pomology Dept., Univ. of California at Davis, Kearney Agricultural
Center, 9240 South Riverbend Avenue, Parlier, CA 93648-9757
‘Delicious’ fruit were covered with paper bags from the early development
stage until harvest at the Horticultural Center, Univ. of Massachusetts. Bagging
did not affect fruit maturity, but signifi cantly affected phenolic composition in fruit
peel. Compared with the control, bagged fruit did not accumulate anthocyanin, but
contained low levels of procyanidin and quercetin glycosides and relatively large
amounts of simple phenolic acids. When bagged, fruit were re-exposed to light;
they started to accumulate anthocyanin quickly and anthocyanin accumulation
reached maximum after 3 days of light exposure. The potential of anthocyanin
synthesis in bagged fruit remained constant during 5 months of cold storage. Results indicate that accumulation of anthocyanin, procyanidin, quercetin glycosides,
and simple phenolic acids has different light requirement and these fruit could be
HORTSCIENCE, VOL. 33(3), JUNE 1998
303
Effect of a Single Defoliation and Fruit Thinning on Papaya
Fruit Production and Quality
304
Fruit Removal and Continual Defoliation Altered Papaya Fruit
Production and Quality
Lili Zhou* 1, David Christopher2, and Robert E. Paull 2; 1Dept. of Horticulture and
2
Dept. of Plant Molecular Physiology, Univ. of Hawaii at Manoa, Honolulu, HI
96822
The source size and sink strength were modifi ed by continual defoliation and
fruit removal in ‘Sunset’ papaya. Flower and fruit set, mature fruit mass, and TSS
was recorded weekly. Fruit at four different stages of development were harvested
at the end of the experiment. Fruit mass, respiration, sugar content, and sucrose
phosphate synthase (SPS), sucrose synthase (SS), and invertase enzyme activities were compared. Continual defoliation resulted in lower new fruit set (25% of
control), smaller fruit size (77% of control), and lower TSS (85% of control) in the
24-week experimental period. In contrast, there were 52% and 100% more new
fruit when fruit were removed than in the control within the fi rst 8 weeks and 24
weeks, respectively. Larger fruit size, earlier fruit development, lower respiration,
and higher sugar contents were observed when fruit were removed at 140, 154,
and 175 days from anthesis. No signifi cant difference was found in TSS level in the
mature fruit compared to the control. Fruit removal plus defoliation gave the same
number and mass of new fruit as the control and slightly lower TSS in mature fruit
than in the control. Fruit sugar was higher with increased fruit invertase activity
and fruit age. Data confi rmed that source–sink balance was critical for fruit set,
development, and sugar accumulation in papaya.
305
Urea Combined with 6-Benzyladenine Applied to the Foliage of
Pistachio Trees during Nut-fill Reduced Floral Bud Abscission
during the “On” Crop Year and Increased Yield the Following
“Off” Crop Year
Hassania Daoudi 1, Louise Ferguson2, and Carol J. Lovatt* 1, 1Dept. of Botany and
Plant Sciences, Univ. of California, Riverside, CA 92521; 2Cooperative Extension,
Dept. of Pomology, Univ. of California, Davis, CA 95616
Alternate bearing of pistachio (Pistacia vera L. cv. Kerman) is a signifi cant
problem in California. Excessive abscission of fl oral buds beginning in June and
497
intensifying at the time of seed development (nut-fi ll) in July during the “on” year
results in the next year’s “off” crop. While the mechanism resulting in alternate
bearing in pistachio has been identifi ed, its physiological basis has not and there
is no satisfactory horticultural practice to even out alternate bearing. Bud retention
in pistachio was increased 3-fold and 2-fold for two successive years, respectively,
on branches bearing greater than 70 nuts per cluster (an “on” crop) basal to the
shoot bearing the buds for next year’s crop with foliar applications of 0.25% N
as low-biuret urea combined with 25 mg 6-benzyladenine per liter applied in
early June and early July. In Sept. 1997, the crop produced by the buds treated
in 1996, an “on” crop year, was harvested. The untreated control trees produced
an “off” crop, 7.6 kg fruit per tree, yielding 0.5 tons split nuts (dry weight) per
acre. Trees treated with 0.25% N as urea combined with 25 mg 6-benzyladenine
per liter on June 1 and July 1 yielded 16.4 kg fruit per tree, resulting in 1.14 tons
split nuts (dry weight) per acre (P ≤ 0.05).
128 POSTER SESSION 3L (Abstr. 306–312)
Growth/Development/Nutrition—Citrus/
Subtropical
306
Citrus Carbohydrate Levels were Related to Irrigation Frequency but Not Arbuscular Mycorrhizal Fungal (AMF) Inoculum
Matthew W. Fidelibus* and Chris A. Martin; Dept. of Plant Biology, Arizona State
Univ., PO Box 871601, Tempe, AZ 85287
Sugar and starch concentrations in leaves and roots of Citrus volkameriana
Tan and Pasq were measured in response to irrigation frequency and AMF inoculum. Non-mycorrhizal seedlings were treated with a soil inoculum from one
of fi ve different communities of AMF; two AMF communities from Arizona citrus
orchard soils, and three communities from undisturbed desert soils. Plants were
assigned to frequent (soil water tension > –0.01 MPa) or infrequent (soil water
tension > –0.06 MPa) irrigation cycles and were container-grown in a glasshouse
for 4 months before tissues were analyzed. Fungal inoculum source did not affect
shoot or root carbohydrate levels. Plants grown under high irrigation frequency had
increased leaf and root starch levels and increased root sugar levels compared with
those under low irrigation frequencies. High irrigation frequency also increased
shoot mass.
307
Crease (Albedo Breakdown) can be Predicted by Peel Thickness and Peel Nutrient Status as Early as the End of the Cell
Division Stage of Fruit Development
Anwar Ali * , Leslie Summers, Grant Klein, and Carol Lovatt, Dept. of Botany and
Plant Sciences, Univ. of California, Riverside, CA 92521
Crease is a rind disorder of economic consequence to the citrus industry. The
literature suggests crease is related to the thickness of the peel at maturity and
nutrient status of the tree, especially N, P, and K, which are known to infl uence
peel thickness. Our objective was to quantify the interrelationship between the
degree of crease in an orchard at harvest and September leaf nutrient concentrations, as well as peel nutrient concentrations at maximum peel thickness. The
2-year experiment was conducted at seven California ‘Valencia’ and navel orange
(Citrus sinensis L. Osbeck) orchards with known differences in the incidence of
crease. Maximum peel thickness, which occurs at the end of cell division during
fruit development, was signifi cantly negatively correlated with percent crease at
harvest for all sites in both years. There was no signifi cant correlation between
leaf N, P, or K concentrations and maximum peel thickness or crease. There was
a signifi cant negative correlation between peel K concentration and percent crease
for all sites in both years. There was a weak correlation between the incidence
of crease and peel nitrogen content in both cultivars. Peel P concentration was
not correlated to the incidence of crease in either cultivar. These data identifi ed
threshold values for maximum peel thickness and peel K concentration at maximum
peel thickness below which the incidence of crease would be greater than 10%
for both cultivars.
498
308
Field Measurements and Simulation of Nitrogen Fate under
Citrus Production
A. Fares, A.K. Alva*, and S. Paramasivam; Univ. of Florida, Citrus Research and
Education Center, Lake Alfred, FL 33850
Water and nitrogen (N) are important inputs for most crop production. The main
objectives of nitrogen best management practices (NBMP) are to improve N and
water management to maximize the uptake effi ciency and minimize the leaching
losses. This require a complete understanding of fate of N and water mass balance within and below the root zone of the crop in question. The fate of nitrogen
applied for citrus production in sandy soils (>95% sand) was simulated using
a mathematical model LEACHM (Leaching Estimation And Chemistry Model).
Nitrogen removal in harvested fruits and storage in the tree accounted the major
portion of the applied N. Nitrogen volatilization mainly as ammonia and N leaching
below the root zone were the next two major components of the N mass balance.
A proper irrigation scheduling based on continuous monitoring of the soil water
content in the rooting was used as a part of the NBMP. More than 50% of the
total annual leached water below the root zone was predicted to occur in the the
rainy season. Since this would contribute to nitrate leaching, it is recomended to
avoid N application during the rainy season.
309
Nutrient Concentrations in Soil Solution in an Alfisol under
Grapefruit Production
Z.L. He1, A.K. Alva2* , D.V. Calvert1, D.J. Banks1, and Y.C. Li 3; 1Indian River Research
and Education Center, Univ. of Florida, Fort Pierce, FL 34945; 2Citrus Research and
Education Center, Univ. of Florida, Lake Alfred, FL 33850; 3Tropical Crops Research
and Education Center, Homestead, Univ. of Florida, Homestead, FL 33031
A fi eld experiment was conducted in a Riviera fi ne sand (Alfi sol) with 25year-old ‘White Marsh’ grapefruit trees on Sour orange rootstock to monitor
the downward transport of nutrients from fertilization practices. Fertilizer was
applied as either dry granular broadcast (three applications/year) or fertigation
(15 applications/year) at N rates of 56, 112, 168, and 336 kg/ha per year using
a N:P:K blend (1.0:0.17:1.0). Soil solution was sampled bi-weekly from suction
lysimeters, installed under the tree canopy, about 120 cm from the tree trunk, at
two depths representing above (120 cm) and below (180 cm) the hard pan. The
concentrations of K, Ca, and Mg were greater at the 180- than at 120-cm depth,
whereas, the converse was true with respect to the concentration of P in soil
solution. Over a 2-year period, the mean concentrations of P and K varied from
0.031-0.976 and 150-250 mg• L–1, respectively. Increased rate of fertilization also
appeared to increase the concentrations of Ca and Mg in the soil solution. This
could be due to effects of slight acidifi cation of the soil with increased rates of
ammonium form of N. A parallel study on pH measurements has shown evidence
of soil acidifi cation, under the tree canopy, with increased rates of ammonium
fertilization. In a bedded grove, the soil solution above the hard pan is likely to
seep into the water furrow, which is discharged into the drainage water.
310
Impact of Nitrogen Management Practices on Total Nitrogen in
the Fruits of High Productive Hamlin Orange Trees
S. Paramasivam and A.K. Alva*; Univ. of Florida, Citrus Research and Education
Center, Lake Alfred, FL 33850.
For perennial crop production conditions, major portion of nutrient removal
from the soil-tree system is that in harvested fruits. Nitrogen in the fruits was
calculated for 22-year-old ‘Hamlin’ orange (Citrus sinensis) trees on Cleopatra
mandarin (Citrus reticulata) rootstock, grown in a Tavares fi ne sand (hyperthermic,
uncoated, Typic Quartzipsamments) that received various N rates (112, 168, 224,
and 280 kg N/ha per year) as either i) broadcast of dry granular form (DGF; four
applications/year), or ii) fertigation (FRT; 15 applications/year). Total N in the fruits
(mean across 4 years) varied from 82 to 110 and 89 to 111 kg N/ha per year for
the DGF and FRT sources, respectively. Proportion of N in the fruits in relation
to N applied decreased from 74% to 39% for the DGF and from 80% to 40% for
the FRT treatments. High percentage of N removal in the fruits in relation to total
N applied at low N rates indicate that trees may be depleting the tree reserve for
maintaining fruit production. This was evident, to some extent, by the low leaf
N concentration at the low N treatments. Furthermore, canopy density was also
lower in the low N trees compared to those that received higher N rates.
HORTSCIENCE, VOL. 33(3), JUNE 1998
311
Girdling Lemons to Improve Fruit Size and Set in Southern
Arizona
Glenn C. Wright*; Univ. of Arizona, Yuma Mesa Agriculture Center, Route 1, Box
40M, Somerton, AZ 85350
Arizona lemon producers are often concerned with poor fl owering, fruit set
and fruit sizing, especially following excessively warm winter or spring weather.
‘Limoneira 8A Lisbon’ (Citrus limon Burm.) lemons were girdled over a 3-year
period to determine if girdling would improve yield or fruit size. Eight trees were
girdled each month, from November through August, using a double spiral girdle
and a 4.8-mm wide girdling knife. Fruit size measurements were taken throughout
the growing season. Trees were harvested individually, and yield; fruit packout and
fruit quality measurements were collected. For the 1995/96 harvest, trees girdled
in March and May had greater early size and greater yields. Fruit quality was
improved as well. For 1996/97 harvest year, trees girdled the previous November
and December had signifi cantly greater yield and fruit size. For trees harvested
in 1997/98, no treatment was signifi cantly better than the non-girdled trees. The
effects of girdling on the orchard profi tability will also be discussed.
312
Substrate pH and Papaya Seedling Growth
Thomas E. Marler*; College of Agriculture and Life Sciences; Univ. of Guam,
Mangilao, GU 96923
Two studies were conducted to determine the infl uence of pH on ‘Waimanalo’
papaya seedling growth and morphology. The seedlings were grown in clear, plastic
tubes with diameter of 7 cm and length of 21 cm, and substrate was silica sand.
The substrate was drenched daily with complete nutrient solution. The solution
was adjusted to pH of 3, 4, 5, 6, 7, 8, or 9. We used direct-seeded plants in the
fi rst study, and plants were harvested following 9.5 weeks of growth. We used
transplants in the second study, and plants were harvested following 4 weeks of
growth. Dry mass of plants was relatively unaffected by substrate pH within the
range of 4 to 9. In both studies; however, dry mass of plants receiving solution
with a pH of 3 was reduced. The response pattern was similar for canopy:root
ratio, total root length, root growth rate, lateral root thickness, and root tip density.
Unit leaf area per unit root length was greatly increased for plants receiving pH of
3, indicating increased susceptibility to drought conditions.
128 POSTER SESSION 3M (Abstr. 313–322)
Breeding & Genetics—Breeding for Genetics of Resistance
313
Potato Lipoxygenase POTLX-3 Gene is Expressed In Response
to Pathogens but Not Wounding
Mikhailo V. Kolomiets* , Richard J. Gladon, and David J. Hannapel ; Dept. of
Horticulture, Iowa State Univ., Ames, IA 50011-1100
Lipoxygenases are the fi rst committed enzymes in biosynthetic pathways that
produce jasmonic acid, methyl jasmonate, traumatin, fatty acid hydroperoxides,
and volatile aldehydes. These pathways often function in growth- and defenserelated processes in plants. Products of lipoxygenases may be the primary cause
of the hypersensitive response (HR) because lipoxygenase by-products such as
organic free radicals and active oxygen species are involved in cell membrane
degradation during resistance responses against pathogens. In order to study
lipoxygenase involvement in defense responses against pathogens, we have
isolated and characterized a potato lipoxygenase gene that we have designated
POTLX-3. POTLX-3 is not expressed in any potato organs, is not induced by
wounding, but is strongly induced in leaves treated with ethylene, methyl jasmonate, or inoculum of Phytophthora infestans, the causal agent of potato late
blight. In response to infection, POTLX-3 transcripts accumulate more rapidly in
resistant lines than in susceptible lines. In resistant lines, the greatest amount
of induction preceded the visual appearance of localized necrotic lesions, consistent with possible involvement of POTLX-3 in HR development. Expression of
POTLX-3 also is activated in response to inoculation with the bacterial pathogen
Pseudomonas syringae pv. phaseolicola, which causes strongly expressed HR
HORTSCIENCE, VOL. 33(3), JUNE 1998
in all potato cultivars. Thus, POTLX-3 expression is not a specifi c response to
P. infestans, but rather a common response related to HR development against a
broad range of pathogens. Pattern of POTLX-3 expression indicates that it may
have a specifi c role in defense mechanisms against pathogens.
314
Development of Five Tropically Adapted Disease Resistant
Dry Bean Varieties
E.A. Santana* 1, G. Godoy-Lutz1, J.C. Nin1, F. Saladin1, J.S. Beaver2, D.P. Coyne2
and J.R. Steadman3; 1CIAS, Apartado #145, San Juan de la Maguana, Dominican Republic; 2Univ. of Puerto Rico, Mayaguez, PR 00681; 3Univ. of Nebraska,
Lincoln, NE 68583
Diseases are a primary constraint affecting yield and seed quality of dry beans
(Phaseolus vulgaris) in the Dominican Republic. A collaborative dry bean breeding program to develop resistance to one or more diseases in different dry bean
types was conducted in the Dominican Republic (DR) under a US-AID Title XII
Bean/Cowpea CRSP involving breeders and pathologists in the Ministry of Agriculture, DR, Univ. of Nebraska, Lincoln, and the Univ. of Puerto Rico, Mayaguez.
The origin and some characteristics of the fi ve new dry bean varieties released
in 1988 are described here. The black seeded ‘Arroyo Loro Negro’ (MUS-N-4-H)
(Type II a growth habit) was derived from the cross H-270 (MSU/UPR) X XAN223 and has resistance to web blight and rust. The pedigree of the white seeded
‘Anacaona’ (L-8020) (Type II a growth habit) is (2b-5-1/2 x NEP-2/Black Turtle
Soup) X BON 355 (MSU). ‘Anacaona’ is moderately resistant to web blight. The
three red-mottled determinate Pompadour varieties were developed from the
following crosses; ‘Saladin-97’ (PC-21-SME) and ‘CIAS-95’ (PC-21-SMA) from
‘PC-50’(DR) X BAT 1274 (CIAT) and ‘JB-178’ (PR-JB-178) from ‘Jose Beta’ (DR)
X C1308 in Puerto Rico. These new high yielding Pompadour varieties have a
higher level of fi eld resistance to Andean pathotypes of rust in the DR than does
‘PC-50’ the predominate variety.
315
Gene Estimation, Associations of Traits, and Confirmation
of QTL for Common Bacterial Blight Resistance in Common
Bean
Soon O. Park* 1, Dermot P. Coyne1, and Geunhwa Jung2; 1Dept. of Horticulture,
Univ. of Nebraska, Lincoln, NE 68583; 2Dept. of Horticulture, Univ. of Wisconsin,
Madison, WI 53706
Common bacterial blight, incited by Xanthomonas campestris pv. phaseoli (Xcp),
is a serious disease of common bean(Phaseolus vulgaris L.). Gene estimation,
associations of traits, and confi rmation of QTL for resistance to Xcp were investigated in a recombinant inbred population derived from the backcross BC2F6
PC-50 (susceptible to Xcp) x XAN-159 (resistant to Xcp). One or two genes from
XAN-159 controlled leaf resistance to Xcp. One major gene from XAN-159 was
involved in controlling pod resistance to Xcp. Low (+0.24) to intermediate (+0.57
and +0.75) Pearson correlations were observed between leaf and pod reactions to
Xcp. Purple fl ower color was associated with leaf and pod resistance to Xcp but
not days to fl ower. One to 2 QTLs explained from 20 to 51% of the total phenotypic variation for leaf reactions to 5 Xcp strains. Two QTLs explained from 20 to
22% of the total phenotypic variation for pod reactions to Xcp strains EK-11 and
DR-7. A marker BC437.1050 was associated with leaf and pod resistance to 5
Xcp strains in nearly all experiments, and accounted for 13% to 45% of the phenotypic variation for these traits. A unassigned marker D13.1000 was associated
with only pod resistance to Xcp strains EK-11 and DR-7. Gene number (1 or 2)
estimations and number of QTL (1 or 2) detected for resistance to Xcp generally
agree. The confi rmed marker BC437.1050 is expected to be useful in breeding
programs for resistance to Xcp.
316
Genome M apping in Citrullus Populations Segregating for
Fusarium Wilt Resistance
Leigh K. Hawkins* 1, Fenny Dane1, and Billy Rhodes2; 1Dept. of Horticulture, Auburn
Univ., 101 Funchess Hall, Auburn, AL 36849; 2Dept. of Horticulture, Clemson
Univ., Clemson, SC 29634
Fusarium wilt, caused by the soilborne fungus Fusarium oxysporum f.sp.
niveum (FON), is one of the most economically important diseases of watermelon
(Citrullus lanatus) worldwide. FON has been divided into three races (races 0, 1,
and 2) determined by differential pathogenicity assays. Most commercial cultivars
499
are resistant to races 0 and 1; whereas none are resistant to race 2. Few morphological and isozyme variations are seen in the cultivated watermelon, but molecular
markers, such as random amplifi ed polymorphic DNA (RAPD), amplifi ed fragment
length polymorphisms (AFLPs) and simple sequence repeats (SSRs), have been
shown to generate several polymorphisms. Segregating populations, derived
from a cross between watermelon cultivar New Hampshire Midget, susceptible to
all three races of FON and the resistant C. lanatus plant introduction PI 296341,
were used to detect molecular markers linked to Fusarium wilt resistance. In a
preliminary experiment, more than 180 10-mer primers were screened against
the parents and the F1. Informative RAPD primers were identifi ed and used in
conjunction with AFLP and SSR markers to generate a genome map.
317
Molecular Markers Linked to Phytophthora fragariae Resistance Genes in Strawberry
K.M. Haymes*, S.C. Hokanson, K. Salazar, and J. Maas; Fruit Lab., Agricultural
Research Service, U.S. Dept. of Agriculture, Beltsville, MD 20705 USA
The commercial strawberry (Fragaria x ananassa Duch.) is susceptible to red
stele root rot caused by the fungus Phytophthora fragariae Hickman var. fragariae.
Characteristics of the disease are the reddened steles and “rat tail” appearance
of the roots. Infected plants are dwarfed, exhibit wilting, and eventually die. Red
stele resistance in strawberries and virulence of P. fragariae behave according to
the gene-for-gene system. Resistance genes and their corresponding avirulence
genes have been identifi ed by screening plant roots for infection. The goal of this
international research project with CPRO-DLO, The Netherlands, is to develop
highly specifi c molecular markers for various Rpf resistance genes (Rpf1, Rpf2,
Rpf3, and Rpf6) that confer resistance against P. fragariae. Bulked Segregant
Analysis was used to identify RAPD and AFLP markers putatively linked to P.
fragariae resistance genes. The bulked DNAs representing subsets of three F1
populations that segregated monogenically for either resistance or susceptibility to
P. fragariae. The map of these Rpf loci was generated using JoinMap® . The RAPD
markers linked to the resistance genes are being converted into SCAR markers,
while the AFLP markers will be used as probes for the detection of P. fragariae.
The application of the molecular markers linked to resistance genes will have
direct applicability to strawberry breeding programs. Marker-facilitated selection
of these resistance genes would allow an effi cient means in the screening and
selection of plant material containing these genes and help in the pyramiding for
resistance to P. fragariae. Genetic improvement of the strawberry by the ability
to pyramid resistance genes will contribute to the productivity of the strawberry
industry worldwide.
318
Breeding for Leafminer Resistance within the Genus Betula
William A. Hoch*, Eric L. Zeldin, and Brent H. McCown; Dept. of Horticulture,
Univ. of Wisconsin–Madison, Madison, WI 53706
The birch leafminer (Fenusa pusilla) is an important insect pest of white-barked
ornamental birches (Betula spp.). Although genetic resistance to birch leafminer
exists within this genus, it has not been identifi ed in the desirable white-barked
species. Twenty-three interspecifi c crosses were performed in an attempt to
combine ornamental white bark and leafminer resistance. The parental species
and resulting hybrid populations were assayed for resistance. All assays utilized
adult birch leafminers reared in our laboratory using a method we developed to
provide a year-round supply of fresh leafminer adults. Previous studies viewed
birch leafminer resistance as the unwillingness or inability of the female leafminer
to oviposit eggs into the leaves of resistant Betula species. Our work has shown
that female birch leafminers are unable to distinguish between suitable and nonsuitable host species. This work also has discovered two separate mechanisms
of inherent resistance to the birch leafminer: leaf chemistry and a hypersensitive
response. Two native species, B. alleghaniensis and B. lenta, kill the leafminer
larvae shortly after hatching. Analyses suggest that a specifi c compound or class
of compounds is responsible for leafminer mortality in these species and that
this resistance is reduced in F1 hybrids that include a susceptible white-barked
parent. The second resistance mechanism involves a hypersensitive response
to the deposition of the leafminer egg and results in failure of the egg to hatch.
Interestingly, this response is seen in one of our breeding lines (B. populifolia x
B. maximowicziana), but has not been observed in either parental species. These
hybrid progeny are currently in fi eld test plots for further evaluation of leafminer
resistance and ornamental characteristics.
319
Identification of a Source of Resistance to Cherry Leaf Spot
S.L. Downey*, R. Karle, A.F. Iezzoni , and A.L. Jones; Dept. of Horticulture, Michigan
State Univ., East Lansing, MI 48824
Cherry leaf spot caused by Blumeriella jaapii (Rhem) Arx. is a major fungal
disease of sour cherry in most of the world’s sour cherry production areas. This
fungus causes premature defoliation, which, in conjunction with low temperature
winter injury, can result in death of limbs and entire trees. ‘Montmorency’, the only
major sour cherry cultivar grown in the United States, is highly susceptible to this
fungus and numerous fungicides are required to prevent this disease. In 1996,
sour cherry seedlings and GI 148-1, a triploid hybrid developed in Germany from
the cross sour cherry (Prunus cerasus Schattenmorelle) x P. canescens (Schmidt
and Gruppe 1988 HortScience 23: 112), were inoculated with spores of B. jaapii
obtained from infected sour cherry leaves in the orchard. Lesion counts were
taken on days 7 and 14 and the number of lesions per cm2 was calculated. This
experiment was repeated in 1997, including a full sibling of GI 148-1, GI 148-2.
Sour cherry and GI 148-2 were highly susceptible to cherry leaf spot. Within 14
days, these selections exhibited an average of 19.4 and 5.4 necrotic lesions per
cm2 respectively, sporulation, chlorosis, and eventually leaf drop. In contrast,
GI 148-1 had signifi cantly fewer lesions on average (1.4 lesions per cm2), no
apparent sporulation, chlorosis or leaf drop. Different reactions exhibited by
siblings GI 148-1 and GI 148-2 suggest that the resistance gene(s) in 148-1 are
on the P. canescens chromosome(s), not from the sour cherry parent, and that
the P. canescens parent was not homozygous. GI 148-1 is currently being used
in a backcross breeding program to develop resistant varieties.
320
Inheritance of Resistance to the Southern Root-knot Nematode
in Capsicum chinense Jacq.
R.L. Fery* and J.A. Thies, U.S. Vegetable Lab., ARS, USDA, 2875 Savannah
Highway, Charleston, SC 29414-5334
A series of greenhouse tests were conducted to compare the level of resistance
to the southern root-knot nematode (Meloidogyne incognita) exhibited by recently
released Capsicum chinense germplasm lines to the level of resistance exhibited by
C. annuum cultivars, to determine the inheritance of the resistance in C. chinense,
and to determine genetic relationship between the resistances exhibited by C.
chinense and C. annuum. The results of a replicated test indicated that the level
of resistances exhibited by the recently released C. chinense germplasm lines
PA-353, PA-398, and PA-426 is equal to the level of resistances exhibited by
the resistant C. annuum cultivars Mississippi Nemaheart and Carolina Cayenne.
Evaluation of parental, F1, F2, and backcross populations of the cross PA-426 x
PA-350 indicated that the resistance in C. chinense is conditioned by a single
dominant gene. The results of an allelism test indicated that this dominant gene
is allelic to the N gene that conditions southern root-knot nematode resistance
in the C. annuum cultivar Carolina Cayenne. The availability of a simply inherited
source of outstanding resistance makes breeding for southern root-knot nematode
resistance a viable objective in C. chinense breeding programs. This objective
should be readily obtained by the application of conventional plant breeding
methodologies.
321
A New Virus-tolerant Southernpea
T.E. Morelock* 1, E.J. Anderson2, A.R. Gonzalez3, and D.R. Motes1, 1Dept. of
Horticulture, 2Dept. Of Plant Pathology, and 3Dept. Of Food Science, Univ. of
Arkansas, Fayetteville, AR 72701
Southernpea (cowpea), Vigna unguiculata L. Walp, is an important processing and fresh-market vegetable in the southern United States. Several varieties
are available for growers, but there are very limited numbers that combine bush
plant type, earliness, good processing quality and virus resistance. A single plant
selection from the variety ‘Excel’ offers this combination of traits. The breeding lines
87-435-68 is a singe plant selection from the variety ‘Excel’ that was made on the
basis of its reaction to blackeye cowpea mosaic virus (BLCMV). The resistance
mechanism is somewhat different than the traditional varieties with single gene
resistance to BLCMV. The reaction to BLCMV is manifested as tolerance rather
than classical single gene immunity.
322
Pathogenic Variation in Halo Blight on Common Beans
H.M. Ariyarathne1, D.P. Coyne1*, and A.K. Vidaver2; Depts. of 1Horticulture and
500
HORTSCIENCE, VOL. 33(3), JUNE 1998
2
Plant Pathology, Univ. of Nebraska, Lincoln, NE 68583
Halo blight, caused by a bacterium, Pseudomonas syringae pv. phaseolicol a
(Psp), is one of the most important bacterial diseases of common beans (Phaseolus
vulgaris L.). The objective of this study was to evaluate the pathogenic variation
of Psp strains with emphasis on those collected in Nebraska. Twenty-nine Psp
strains were inoculated on 20-day-old leaves of eight differential cultivars/lines
and a resistant check line great northern (GN) Nebraska #1 sel. 27. Two experiments were conducted in growth chambers under 20 °C and 12-h photoperiod. A
split-plot design was used with nine cultivars/lines as whole plots in a randomized
complete block design (RCBD) and strains as sub-plots in an incomplete block
arrangement. Data were analyzed as a split-plot with a RCB arrangement because
incomplete block was not signifi cant. Strains were classifi ed into fi ve races with
six, 16, and two strains classifi ed as races 1, 6, and 7, respectively. The remaining
strains were designated tentatively as new races 10 and 11. GN Nebraska #1 sel.
27 was resistant to all Psp strains tested. This information is useful to breeders
interested in developing germplasm and cultivars resistant to Psp.
128 POSTER SESSION 3N (Abstr. 323–326)
Crop Physiology/Myccorhizae—Crosscommodity
323
Alleviation of Phosphorus Stress on Capsicum annuum L. cv.
San Luis (Chile Ancho pepper) with a Mixed Glomus spp. from
Mexico and Glomus intraradices
Javed Husain*, Fred T. Davies, Jr., and Jonathan N. Egilla; Dept. of Horticultural
Sciences, Texas A& M Univ., College Station, TX 77843-2133
The effect of a mixed isolate of arbuscular mycorrhizal (VAM) fungi [ Glomus
spp. from Veracruz, Mexico] and a pure isolate of Glomus intraradices was assessed on the growth and gas exchange of ‘Chile Ancho’ (Capsicum annuum L.
cv. San Luis) under phosphorus (P) stress. The experiment was carried out under
glasshouse conditions in 1-L plastic pots containing a pasteurized mixture of 1
sand : 1 sandy loam (v/v). Plants were inoculated or noninoculated with VAM.
Plants were fertilized with a modifi ed Long Ashton nutrient solution (LANS) containing 0 or 11 (g phosphorus/ml). Gas exchange measurements were taken 21
and 70 days after the experiment was initiated. Mycorrhizal plants at both 0 and
11 (g P/ml) had greater leaf area, fruit, root, stem and leaf dry mass, and a lower
specifi c leaf area and root/shoot ratio than nonmycorrhizal plants. Nonmycorrhizal
plants not supplied with P had a higher leaf area ratio than plants colonized with
G. intraradices. Net photosynthesis and stomatal conductance were not consistent
with growth responses. There were no signifi cant differences in growth and gas
exchange between the two mycorrhizal isolates.
324
Influence of Mycorrhizal Fungi on Growth and Nutrient Uptake of
Micropropagated Guava Plantlets (Psidium guajava L. ) during
Acclimatization and Plant Establishment
Andrés A. Estrada-Luna* , Fred T. Davies Jr , and Jonathan N. Egilla; Dept. of
Horticultural Sciences, Texas A& M Univ., College Station, TX 77843-2133 USA
The effect of mycorrhizal fungi on growth and nutrient uptake during acclimatization and plant establishment of micropropagated guava plantlets (Psidium
guajava L. cv. Media China) was determined. Half of the plantlets were inoculated
with the endomycorrhizae isolate ZAC-19 and grown in a glasshouse for 18 weeks.
The isolate ZAC-19 was collected from the Chihuahuan Desert in Zacatecas State,
Mexico, and is a mixed isolate containing Glomus etunicatum and unknown
Glomus spp. Plantlets were fertilized with modifi ed Long Ashton nutrient solution containing 11 µg P/ml. Shoot length, leaf area, leaf number, and dry mass
partitioning were positively affected by mycorrhizae compared to noninoculated
plantlets; however, noninoculated plantlets had greater leaf area ratios and specifi c
leaf area. Mycorrhizal plantlets generally had increased leaf tissue mineral levels,
particularly P, Mg, Cu, and Mo. However, noncolonized plantlets had higher N,
K, and Mn. At the end of the experiment, roots of inoculated guava plantlets had
colonization levels of 94.3% .
HORTSCIENCE, VOL. 33(3), JUNE 1998
325
Effect of Mycorrhizal Fungi on Gas Exchange of Micropropagated Guava Plantlets (Psidium guajava L.) during Acclimatization and Plant Establishment
Andrés A. Estrada-Luna*, Jonathan N. Egilla, and Fred T. Davies, Jr.; Dept. of
Horticultural Sciences, Texas A& M Univ., College Station, TX 77843-2133 USA
The effect of mycorrhizal fungi on gas exchange of micropropagated guava
plantlets (Psidium guajava L.) during acclimatization and plant establishment was
determined. Guava plantlets (Psidium guajava L. cv. ‘Media China’) were asexually
propagated through tissue culture and acclimatized in a glasshouse for eighteen
weeks. Half of the plantlets were inoculated with ZAC-19, which is a mixed isolate
containing Glomus etunicatum and an unknown Glomus spp. Plantlets were
fertilized with modifi ed Long Ashton nutrient solution containing 11 (g P/ml. Gas
exchange measurements included photosynthetic rate (A), stomatal conductance
(gs), internal CO2 concentration (Ci ), transpiration rate (E), water use effi ciency
(WUE), and vapor pressure defi cit (VPD). Measurements were taken at 2, 4, 8
and 18 weeks after inoculation using a LI-6200 portable photosynthesis system
(LI-COR Inc. Lincoln, Neb., USA). Two weeks after inoculation, noninoculated
plantlets had greater A compared to mycorrhizal plantlets. However, 4 and 8
weeks after inoculation, mycorrhizal plantlets had greater A, gs, Ci and WUE. At
the end of the experiment gas exchange was comparable between noninoculated
and mycorrhizal plantlets.
326
Influence of Selected Endomycorrhizae from the Sonoran
Desert and Glomus intraradices on Growth Response and Gas
Exchange of Hibiscus rosa-sinensis L. cv. Leprechaun
Jonathan N. Egilla* and Fred T. Davies, Jr.; Dept. of Horticultural Sciences, Texas
A& M Univ., College Station, TX 77843-2133
Six endomycorrhiza isolates from the Sonoran Desert of Mexico [Desert14(18)1, 15(9)1, 15(15)1, Palo Fierro, Sonoran, and G. geosporum] were evaluated
with a pure isolate of Glomus intraradices for their effect on the growth and gas
exchange of Hibiscus rosa-sinensis L. cv. Leprechaun under low phosphorus
fertility (11 mg P/L). Rooted cuttings of Hibiscus plants were inoculated with the
seven mycorrhiza isolates and grown for 122 days. Gas exchange measurements
were made on days 26, 88, and 122 after inoculation, and plants were harvested
on day 123 for growth analysis. Plants inoculated with the seven isolates had
70% to 80% root colonization at harvest. Plants inoculated with G. intraradices
had signifi cantly higher leaf, shoot and root dry matter (DM), leaf DM/area (P ≤
0.05) than those inoculated with any of the six isolates, and greater leaf area (LA)
than Desert- 15(9)1 and 15(15)1. Uninoculated plants had signifi cantly lower
leaf, shoot, root DM, leaf DM/area and LA (P ≤ 0.05) than the inoculated plants.
There were no differences among the seven isolates in any of the gas exchange
parameters measured [photosynthesis (A) stomatal conductance (gs), the ratio
of intercellular to external CO2 (ci /ca), A to transpiration (E) ratio (A/E)]. The
relationship between inoculated and uninoculated plants in these gas exchange
parameters were variable on day 122 after inoculation.
128 POSTER SESSION 3O (Abstr. 327–334)
Extension
327
A Survey of Nursery Water Quality Best Management Practices
Cody J. White* 1, Michael A. Schnelle2, and Gerrit W. Cuperus3; Depts. of 1Environmental Science, 2Horticulture and Landscape Architecture, and 3Entomology
and Plant Pathology, Oklahoma State Univ., Stillwater, OK 74078
A survey was designed to assess high-risk areas with respect to environmental
contamination, specifi cally how it relates to water quality. Oklahoma growers of all
economic levels, retail and/or wholesale, were queried at their place of business
for their current state of implementing best management practices (BMPs) and
other strategic actions that could potentially affect current and future water quality
standards. Specifi c areas such as the physical environment of the nursery, primary
pesticides and fertilizers used, Integrated Pest Management (IPM) practices, and
501
employee safety training were covered as well as other aspects germane to preserving
and protecting current water quality and related environmental issues. More than 75
nurseries were surveyed and given the opportunity to participate in future training at
Oklahoma State Univ. Results indicated that nurseries have not fully implemented
many BMPs, but have adopted fundamental IPM approaches. The stage is set for
the implementation of the next phase of expansion and refi nement into ecologically
based programs such as propagation and sale of low pesticide input plant materials,
improved cultural practices, and the integration of environmentally sound management approaches. As an example, many growers are in the process of phasing out
calendar-based pesticide application programs in favor of aesthetic and/or economic
threshold-driven pesticide spray programs.
328
Surveys Show Extension Workshops Improve Floridians’ Adoption of Environmental Landscape Management Practices
Gary W. Knox* 1 and Glenn D. Israel 2; 1Univ. of Florida, North Florida Research
and Education Center, Monticello FL 32344; 2Univ. of Florida, Dept. of Agricultural
Education and Communication, Gainesville, FL 32611
Environmental Landscape M anagement (ELM ), an extension education
program, approaches every landscape as a “system” in which cultural practices
interact with each other and the environment. ELM guidelines integrate site
conditions, landscape design, plant selection, cultural factors, and recycling in a
comprehensive, environment-friendly strategy for managing a landscape. Use of
ELM practices by Floridians will conserve resources and protect the environment.
The ELM program was evaluated from 1992 to 1994 in 10 counties to measure the
program’s impact on participants’ landscape practices and to provide information
on ways to improve program delivery and effectiveness. The evaluation was accomplished by comparing pre-program information on the use of ELM practices
with that of a follow-up conducted 6 months after the program. Responses of
this Program Group (n = 473) were compared to those of a Comparison Group
of randomly selected Floridians (n = 186). ELM training increased the Program
Group’s adoption of most practices pertaining to pest management, irrigation,
and mowing and pruning. ELM training increased adoption of some fertilization
practices and a few recycling and wildlife practices. Energy conserving practices
were not widely used by respondents. Respondents maintaining their own yards
or those without a permanent irrigation system were more likely to adopt a wide
range of ELM practices. The Program Group generally had higher initial levels of
adoption of ELM practices than the Comparison Group.
329
Implementing Biointensive IPM Systems in Cling Peaches
Janine K. Hasey* 1, Carolyn Pickel 1, and William H. Olson2; 1Univ.of California
Cooperative Extension, Yuba City, CA 95991; 2 Univ. Of California Cooperative
Extension, 118 Ridgeview Lane, Oroville, CA 95966
A complete mating disruption program that uses pheromone confusion
technology successfully controlled oriental fruit moth and peach twig borer while
eliminating most in season insecticides in cling peaches from 1995–1997 in a
three-county area. During this 3-year period, 46 cooperators used this program
on 580 acres. Growers applied both Oriental fruit moth and peach twig borer
pheromone dispensers twice. Orchards were monitored for moths and for shoot
strikes during the season. Harvest samples were taken to determine worm damage.
A few orchards were sprayed once when shoot strike counts exceeded threshold
levels of three to fi ve strikes per tree. Along with mating disruption in 1997, 209
acres were sprayed with Bacillus thuringiensis during bloom to replace the dormant insecticide spray and improve effi cacy of pheromone confusion. Throughout
implementation, mating disruption program costs were compared with conventional spray programs. Between 1995 and 1997, the complete mating disruption
program cost decreased from $243 per acre to $216 per acre respectively. Even
with the decrease in cost, this is much higher than $104 per acre for the standard
spray program. Some growers decreased pheromone dispenser applications in
1997 for a more economic program. This program still reduced pesticide use by
33% to 67% . While most growers using this partial program had success, some
orchards had high shoot strikes indicating a potential problem. Grants from
USDA-ES-Smith-Lever IPM project, EPA Environmental Stewardship Partnership,
California Department of Pesticide Regulation and Farm Service Agency cost
share programs aided in our ability to implement these biointensive programs;
they provided the money necessary for monitoring and reducing direct costs to
the grower. The main obstacle to cling peach growers adopting the complete
biointensive program is the economics. Most growers will continue to spray or
502
use a partial mating disruption program until less expensive commercial products
become available.
330
M aryland’s Home and Garden Information Center: Helping
Residents Solve Pest, Plant, and Landscape Problems
J.H. Traunfeld*, D.L. Clement, M.K. Malinoski, and R.V. Bosmans; Home and
Garden Information Center, Univ. of Maryland, 12005 Homewood Rd., Ellicott
City, MD 21042
The Home and Garden Information Center was created by the Univ. of Maryland Cooperative Extension Service in 1989 to relieve county-based faculty of
the growing burden of client requests for help in the home horticulture area. The
Center inter-disciplinary staff includes four regional specialists, phone consultants
and offi ce support personnel. The Center’s twin goals are to educate residents to
make wise decisions regarding horticultural practices and pesticide and fertilizer
use and to help clients self-diagnose their pest and plant problems. These goals
are achieved through a variety of outreach methods and advanced technologies.
A conversant phone system allows residents toll-free access (24 hours a day) to
pre-recorded, self-help, problem diagnostic tapes. Horticulture consultants are
available Monday through Friday, 8 a.m.–1 p.m., to provide personalized phone
service to individual clients. The phone system has handled over 320,000 calls
in 8 years. A 1997 phone survey showed a client satisfaction rating of over 90% .
Center faculty produces a well-received Master Gardener Handbook with extensive
diagnostic keys and writes phone tapes and newspaper articles. The “IPM Series”
of peer-reviewed fact sheets, enables clients to use diagnostic keys to identify
and solve plant problems. Residents can also access information through the
Center’s web site which includes updated subject matter tips, and “pages” for the
Master Gardener program, Bay Issues and plant diagnostic keys. Center faculty
also helps to train phone consultants, county horticulture consultants, and Master
Gardeners.
331
Analysis of Residential Horticultural Questions Answered by
Master Gardeners
Larkin Sinnott* and Paula Diane Relf; Offi ce of Environmental Horticulture, 407
Saunders Hall, Virginia Tech, Blacksburg, VA 24061-0327
An analysis of commonly asked horticultural questions is being conducted by
the Offi ce of Environmental Horticulture at Virginia Tech in order to improve the
question and answer process between Master Gardeners and the public. Records
of questions received by Master Gardeners from a sampling of Extension offi ces
representing all growing areas of the state are being sorted and categorized to
identify the most frequently asked questions and develop a electronic resource
to assist in answering those questions quickly and with consistent IPM based
information. More than 4000 questions have been analyzed and organized in to the
following categories: Plant Questions (specifi c type or species of plant), General
Gardening Questions (composting and fertilizing, herbicides and pesticides, soil
testing etc.), Program Questions (Extension programs, Master Gardener program),
and Animal and Insect Questions. The plants questions have been further divided
into the sub-categories. The animal and insect questions have been sorted by species type with the percentage asked of each calculated. This information is posted
on a web site and is linked to additional resources for answers. The address is
www.hort.vt.edu/mastergardener/Q& A.html. The site contains useful information,
links, and opportunities for feedback via e-mail.
332
An Annotated Pest Management Database with Field Decisionmaking Guides for the Mid-Atlantic Region
W.L. Kline* 1, S.T. Kline1, J. Rabin2, J.M. Whalen3, M.P. Spellman3, and K.E.
Holmstrom 2; 1Rutgers Cooperative Extension, 291 Morton Ave., Millville, NJ
08332; 2IPM Offi ce, J.B Smith Hall, Rutgers the State Univ.of New Jersey, 176
Jones Ave., New Brunswick, NJ 08901; 3Entomology Dept., Univ. of Delaware,
Newark, DE 19717
Integrated Pest Management (IPM) information is available in various forms
to help cooperative extension agents and private consultants. Scouting forms,
manuals, fact sheets, bulletins, and books have been written over the past few
years to cover all aspects of IPM. Some of this information has not been published
or is no longer available and can only be obtained from the authors. This makes it
diffi cult to obtain historical or even new information. A Northeast Region Sustain-
HORTSCIENCE, VOL. 33(3), JUNE 1998
able Agriculture Research Education (SARE) grant was received to evaluate and
improve delivery systems for integrated crop and pest management. As part of the
grant, a searchable database was created in FileMaker Pro™ so individuals can
search for information on a specifi c crop or pest. There are 1580 entries covering
49 vegetables, 12 fi eld crops, and three small fruits. Each entry has a summary
and key words; where and how to obtain the document; crops and pests included;
the audience for the publication, e.g. extension agent, researcher, agribusiness,
gardener, etc.; and the type of publication, e.g. fact sheet, website, scouting form,
etc. All categories within the database are searchable with pull down screens
where appropriate. The database is integrated with a series of laminated fi eld
decisionmaking guides. These 2-page guides contain information on the damaging
stage of the pest, monitoring stage, sampling methods, sampling frequency and
thresholds. Information included in the fi eld guides comes mainly from research
in the mid-Atlantic region. Additional information related to the crop or pest can
be obtained by searching the database by the use of key numbers listed in the
guide. Each database entry has a key number for identifi cation. The fi eld guides
are being validated in 1998 and both will be available in late 1998.
333
Volunteer Management Reference for Local VCE Master Gardener Coordinators
Sheri T. Dorn* and Paula Diane Relf; Virginia Polytechnic Inst. and State Univ.,
Horticulture Dept., 407 Saunders Hall, Blacksburg, VA 24061-0327
Virginia Cooperative Extension’s (VCE) Master Gardener volunteer program is
available in 72 unit offi ces. The unit programs are managed by MG coordinators
who currently include 10 locally funded agents, eight locally funded technicians,
and 28 volunteers. The VCE Master Gardener Coordinator Manual, a 12-unit
resource book, was developed cooperatively with teams of MGs, coordinators,
and agents to enhance coordinators’ skills for managing the local VCE MG
program. The manual includes chapters on VCE MG components such as risk
management; job descriptions; recruitment and screening; and volunteer review,
recognition, and retention. Additional resources within the manual include a
synopsis of educational program planning, implementation, and evaluation, as
well as a copy of the current VCE Master Gardener Program Policies and the
volunteer section of the Virginia Master Gardener Handbook, which serves as
program orientation for new or prospective trainees. The VCE Master Gardener
Coordinator Manual is the basis of three local MG coordinator training sessions
in 1998. Additional resources available to coordinators for enhancing the local
MG program include a MG newsletter focused on the role of Master Gardeners
as community leaders and educators; program policies and guidelines for the
management of MG training and operation; VCE publication 426-699 Welcome
to Virginia Master Gardenering! Guide to Educational Programming and Resource
and Reference Guide; and the VCE Master Gardener Internet website at http://www.
ext.vt.edu/vce/specialty/envirohort/mastergard/master.html.
334
Instructor Attitudes toward Interactive Television for Training
Master Gardeners at a Distance
Michele R. Warmund* and Denny Schrock; Dept. of Horticulture, Univ. of Missouri, Columbia, MO 65211
Master Gardener training was delivered via interactive television (IT) or face-toface (FTF) in 1996 and 1997. Following 1997 training, instructors were surveyed to
determine if the method of program delivery infl uenced their perceptions of Master
Gardener training. Most instructors preferred FTF program delivery as compared
to IT training. More preparation time was spent in developing lecture notes, text
slides, and visual aids for IT vs. FTF training. Although instructors were more
comfortable with FTF training than IT programming, their comfort level with IT
training increased with experience. A major reason for instructor discomfort with
IT was the lack of personal contact with trainees. Although lack of interactivity was
identifi ed as a limiting factor with IT training, trainees monopolizing time during
sessions was a major constraint for FTF training. In spite of instructor preference
for FTF Master Gardener training, nearly all instructors indicated a willingness
to teach IT training again. Motivating factors for future IT training included less
night time instruction, less need to travel, job effi ciency, and the opportunity to
use new technology.
HORTSCIENCE, VOL. 33(3), JUNE 1998
26
ORAL SESSION 1 (Abstr. 335–339)
Woody Ornamentals/Landscape/Turf—
Crop Production
335
Vegetative Propagation of Woody Ornamentals Through Forcing
of Epicormic Shoots
Paul H. Henry and John E. Preece; Dept. of Plant, Soil, and General Agriculture,
Southern Illinois Univ., Carbondale, IL 62901
A propagation method is being developed that allows softwood shoots to be
generated from stem sections of dormant woody plant species. These shoots,
forced in the greenhouse during the winter, are subsequently collected and processed as softwood stem cuttings to produce clonal plant material. Many species
in the nursery industry can only be propagated using softwood cuttings, and this
technique allows propagation of these species to be initiated several months
earlier than what is typically possible. Current studies involve expanded screening of ornamental tree and shrub species to determine if commercial production
using this technique is feasible. Results demonstrate that many species may
be propagated using this method, but that some species are more prolifi c than
others with respect to number of softwood shoots produced. Additional studies
are currently in progress to determine the environmental (light regime, moisture
regime) and cultural (type of media) conditions that are optimal when producing
clonal plant material via this technique.
336
Effect of Growth Regulators on Rooting of Magnolia grandiflora
Cultivars
Ning Jiang*, Donglin Zhang, and Michael A. Dirr; Dept. of Horticulture, Univ. of
Georgia, Athens, GA 30602
Cuttings from three southern magnolia cultivars, ‘Claudia Wannamaker’,
‘Greenback™’, and ‘Little Gem’, were treated with KIBA, KNAA, and Hormodin
#3, separately and in combination, at varying concentrations. The rooting of
cuttings was cultivar-dependent, with ‘Greenback™’ responding signifi cantly to
all the treatments. Only the high KNAA and combination treatments were effective
with ‘Little Gem’ and ‘Claudia Wannamaker’. The effect of KNAA on rooting with
increasing concentration was signifi cant. No similar response was observed with
KIBA. The combination treatment with quick dip plus the talc formation produced
the greatest rooting and root quality with the three cultivars. With this treatment,
the average rooting rate of three cultivars was 67.4% , whereas the rooting rate of
control plants was only 11.8% .
337
Rooting Softwood Cuttings from Forced Stem Segments of
Adult White Ash
J.W. Van Sambeek* 1, Nadia E. Navarrete1, and John E. Preece2; 1USDA Forest
Service and 2Dept. of Plant, Soil and General Agriculture, Southern Illinois Univ.,
Carbondale, IL 62901
On 10 Apr. 1997, the smaller branch on forked Fraxinus americana L. (white
ash) trees in an 8-year-old clonal plantation were removed, cut into 25-cm-long
stem sections, and placed horizontally in perlite under seven different forcing
regimes. Sprouts from latent buds were excised 67 and 99 days later and trimmed
to retain the apical pair of leaves and terminal bud. The basal 2 cm of each cuttings was set for 30 to 60 min in one of six aqueous dilutions made from a stock
solution of 1% IBA and 0.5% NAA (Dip ‘n Grow) before placing in a 1 perlite : 1
vermiculite medium. Eight weeks after treating, cuttings data were collected. Most
cuttings treated with 3200 mg/L IBA plus 1600 mg/L NAA quickly died. Survival
(85% ) and rooting percentage (86% ) were similar for the remaining auxin-treated
cuttings and controls with water only. Cuttings treated with 1600 mg/L IBA plus
800 mg/L NAA produced the most adventitious roots (6.2 roots), the longest
adventitious root (22 cm), and longest combined sum of all adventitious roots
(51 cm); however, these rooted cuttings died when transplanted to soil. Cuttings
treated with 100 mg/L IBA plus 50 mg/L NAA or 400 mg/L IBA plus 200 mg/L
NAA had more adventitious roots (3.2 roots) and total length of adventitious roots
(370 mm/cutting) than cuttings treated with 40 mg/L IBA plus 20 mg/L NAA or
503
controls with water only (2.2 roots, 220 mm long). Results indicate softwood cuttings forced on stem segments of adult white ash readily root under mist following
a brief soak in a 400 mg/L IBA plus 200 mg/L NAA solution.
338
Propagation of Thuja x ‘Green Giant’ by Stem Cuttings: Effects
of Growth Stage, Type of Cutting, and IBA Treatment
Jason J. Griffi n*, Frank A. Blazich, and Thomas G. Ranney; Dept. of Horticultural
Science, Box 7609, North Carolina State Univ., Raleigh, NC 27695-7609
Stem cuttings of Thuja L. x ‘Green Giant’, consisting of 22-cm terminals or
20-cm laterals, were collected on three dates associated with specifi c growth
stages (softwood, semi-hardwood, and hardwood), and treated with indolebutyric
acid (IBA) in 50% isopropanol ranging from 0 to 9000 ppm and placed under
intermittent mist. Regardless of cutting type or auxin treatment, cuttings rooted in
high percentages at each growth stage. Overall rooting was highest for hardwood
cuttings (96%) followed by semi-hardwood (86%), and softwood (85%) cuttings.
Semi-hardwood cuttings were the only cuttings in which rooting was affected by
IBA or cutting type with the greatest rooting (94% ) attained using lateral cuttings
treated with 6000 or 9000 ppm IBA. Although an interaction occurred between IBA
treatment and cutting type for mean root length of hardwood cuttings, only mean
root length of semi-hardwood cuttings was infl uenced by IBA concentration alone
with the greatest length (25 mm) achieved with 6000 ppm IBA. An interaction was
noted for root count between cutting type and IBA concentrations for softwood
cuttings, whereas IBA and cutting type affected independently root count on semihardwood cuttings. Treatment with 9000 ppm IBA resulted in 18 roots per rooted
cutting whereas lateral cuttings responded with a mean of 16 roots over all IBA
concentrations. Root count on hardwood cuttings was affected by IBA treatment
only, with 9000 ppm being optimum (14 roots per rooted cutting).
339
Below-ground Pot-in-Pot (PIP) System and Substrate Moisture
Regimen Affect Growth of Two Desert Trees
Chris A. Martin* and S. Bhattacharya; Dept. of Plant Biology, Arizona State Univ.,
PO Box 871601, Tempe, AZ 85287-1601
Acacia smalli (sweet acacia) and Cercidium praecox (palo brea) trees were
grown during June–Oct. 1997 outdoors in full sun in 19-L containers positioned
either PIP or above ground on the soil surface. The 38-L PIP holder containers
were placed in the ground. Cyclic pulses of water were controlled by soil moisture
sensors interfaced with electronic solenoid irrigation valves. Rooting substrate
water potentials at 20 cm below the substrate surface and 10 cm inside the container wall were consistently maintained at either >–0.01 MPa (wet) or between
–0.02 and –0.03 MPa (dry) for both above ground and PIP container substrates.
Less than 1.25 cm of rainfall occurred during the study period. No incidences of
rooting-out were observed with PIP trees. Maximum root-zone temperatures of PIP
containers were 19 °C lower than temperatures measures in substrate of aboveground containers. Growth of both species was stimulated by the wet substrate
regimen compared with the dry regimen. Positioning trees in a below-ground PIP
confi guration under the wet substrate regimen stimulated growth of sweet acacia
compared with the PIP dry regimen. The PIP confi guration did not affect growth
of palo brea trees.
27
ORAL SESSION 2 (Abstr. 340–345)
Human Issues in Horticulture
340
Schools, Children, and Gardening: The Results of a Children’s
Garden Competition among Florida Elementary Schools
Sonja M. Skelly * and Jennifer Campbell Bradley; Dept. of Environmental Horticulture, Univ. of Florida, Gainesville, FL 32611
Children’s contact with nature is slowly diminishing as we progress towards
a more technology-orientated society. While computers and other technology
provide students with valuable skills, children are becoming more detached
from nature and the unique opportunities nature can provide. School gardens
504
offer teachers and students a “down to earth,” hands-on approach they might
not otherwise gain in the classroom. In Spring 1998, the Univ. of Florida in conjunction with the 1998 Epcot® International Flower and Garden Festival hosted
a competition for the best elementary school garden among Florida elementary
schools. The competition called for schools to construct or use an already existing
garden and for teachers to incorporate the garden in their classroom instruction.
Approximately 100 elementary schools throughout Florida participated in the
competition. From these schools a random sample of 500 students were selected
to answer an environmental attitude survey. Students completed the survey at the
beginning of the spring semester and at the completion of the competition in April
to examine the effects of the garden competition on their environmental attitudes.
In addition, teachers were asked to complete a survey detailing the use of the
garden in their classroom and the effect it had on their students. This session
will discuss the details of the competition, the fi ndings and implications of the
competition, and suggestions on how to promote student and school participation
in similar horticultural programs.
341
Studying Children’s Perceptions of Garden Benefits Using the
Internet
T.M. Waliczek* 1, R.D. Lineberger2, and J.M. Zajicek2; 1Dept. of Agriculture, Illinois
State Univ., Normal, IL 61790-5020; 2Dept. of Horticultural Sciences, Texas A& M
Univ., College Station, TX 77843-2133
A survey was designed to investigate children’s perceptions of the benefi ts
of gardening and is posted on the KinderGARDEN Web page within the Aggie
Horticulture network. The KinderGARDEN Web page was developed as a resource
for parents and teachers to help them incorporate the garden into the home and
school lives of children. The Web site additionally attracts young visitors with a
“Fun Page.” The “Fun Page” has descriptions of garden activities that children
can experiment with at home or school, garden literature for children and garden
Web links. The survey is included on this page. Children respond to the survey
via e-mail. The survey requests information about the type of gardening situations in which each respondent participates, the number of children with whom
they generally garden, what they feel they learn from gardening and what benefi ts
they feel they gain from gardening. Children responded positively on the value of
the garden to their recreation, while also mentioning educational, environmental,
aesthetic, social and economic benefi ts in the survey. Results showed that 81% of
children felt they were learning about the environment by working in the garden.
Fifty-four percent of children mentioned that the garden taught them about plants
and plant-related concepts. Other benefi ts children mentioned as important to them
included recreation and/or “having fun” (31% ) and socialization with friends and
family (15% ).
342
Plant Biotechnology Workshop for High School Students
Erika Szendrak* 1, Paul E. Read1, and Jon S. Miller2; 1Dept. of Horticulture, Univ.
of Nebraska, Lincoln, NE 68583-0724; 2Lincoln Northeast High School, Lincoln,
NE 69507
Modern aspects of many subjects (e.g., computer science and some aspects
of medical science) are now taught in many high schools, but the plant sciences
are often given short shrift. A collaboration was therefore established with a high
school biology program in which pilot workshops could be developed to enable
advanced students to gain insights into modern plant science techniques. A
successful example is the workshop on plant biotechnology presented in this
report. This workshop is simple and fl exible, taking into account that most high
school biology laboratories and classrooms are not set up for sophisticated
plant science/biotechnology projects. It is suitable for from 10 to 30 students,
depending upon space and facilities available. Students work in pairs or trios,
and learn simple disinfestation and transfer techniques for micropropagation and
potential subsequent transformation treatments. Students gain insights into: sterile
technique and hygiene; plant hormones and their physiological effects; plant cell,
tissue and organ culture; the infl uence of environmental factors on response of
cells and tissues cultured in vitro; and an understanding of the phenomenon
of organogenesis and resulting plant growth and development. This workshop
has been tested on several classes of students and following analysis, several
refi nements were included in subsequent iterations. Results of the students’
experiments have been positive and instructive, with student learning outcomes
above expectations. Further details of the workshop techniques and approach will
be presented.
HORTSCIENCE, VOL. 33(3), JUNE 1998
343
Redesigning the Master Plan for the South Carolina Botanical
Garden
Karl J. Muzii * and Mary Haque; Dept. of Horticulture, Clemson Univ., Clemson
SC 29634-0375
In 1997 the South Carolina Botanical Garden determined the need to reevaluate
and update the 1989 Botanical Garden Master Plan. The original comprehensive
plan presented recommendations for the long-term development of the site and
the facilities of the garden. Signifi cant changes and new programs have arisen
since the 1989 Master Plan was completed. Because of the new direction of
programs such as the South Carolina Heritage Corridor, Southern Living Home,
Conservatory and Outdoor Sculpture Program, it was necessary to develop an
updated design strategy to incorporate these future plans into the South Carolina
Botanical Garden. Programmatically, the idea of the South Carolina Botanical
Garden is to fi nd solace in the garden, to fi nd a retreat from the pressures of
everyday life and create a somewhat idyllic world while setting an environment
for cultural and botanical conservation. The goal was allowing visitors to move
throughout the garden without endangering the existing and established ornamental and native fl ora as well as educating its visitors. It is on this framework
that the Botanical Garden Master Plan is based. The design methodology used
in the development of the master plan began with staff meetings, research and
site analysis. Design concepts, circulation alternatives and fi nal design choices
evolved out of subsequent staff meetings and design reviews. A booklet was also
published for future development and fund raising. My presentation will outline
the goals, methodology, design decisions and concepts that shaped the fi nal
master plan for the South Carolina Botanical Garden.
344
Human Stress Recovery during Exposure to Geranium Visual
Stimuli
Eunhee Kim* and Richard H. Mattson; Dept. of Horticulture, Forestry and Recreation Resources, Kansas State Univ., Manhattan, KS 66506
Evaluating human psychophysiological responses to plant visual stimuli
provides a clearer understanding of factors within plant environments that enhance or maximize recovery from stress. Advances in physiological monitoring
technology allow continuous recording and more-refi ned data collection of human
responses to environmental stimuli. The objective of this study was to compare
effects on stress recovery by exposures to geranium visual stimuli following an
induced stressor, by measuring changes in physiological indicators and emotional
states. One-hundred-fi fty college students were randomly assigned to one of
three treatment groups: red-fl owering geraniums, non-fl owering geraniums, or
no geraniums. Each student viewed a 10-min fi lm of a stressful human situation
following a 5-min baseline, then was exposed to an assigned treatment setting
during a 5-min recovery period. Continuous physiological measurements were
taken of brainwave activities (EEG), skin conductance (EDR), and fi nger skin temperature. Self-rating scores of subjects’ feelings were taken using the Zuckerman
Inventory of Personal Reactions. Comparisons among treatment groups will be
discussed based on gender and other demographic factors.
345
Relation of Nightshades (Solanaceae) to Arthritis
Norman F. Childers* 1 and Michael S. Margoles2; 1Horticultural Sciences Dept.,
Univ. of Florida, Gainesville, FL 32611; 2Arthritis Nightshades Research Foundation, 177 San Ramon Dr., San Jose, CA 95111-3615
Diet appears to be a factor in the etiology of arthritis based on surveys of
more than 1400 volunteers during a 25-year period. Plants in the drug family,
Solanaceae (nightshades) are an important causative factor in arthritis in sensitive
people. This family includes potato (Solanum tuberosum L.), tomato (Lycopersicon
esculentum L.), eggplant (Solanum melongena L.), tobacco (Nicotiana tabacum
L.), and peppers (Capsicum sp.) of all kinds, except black pepper (family, Piperaceae). A buildup of cholinesterase-inhibiting glycoalkaloids and steroids from
consumption and/or use (tobacco) of the nightshades and from other sources
such as caffeine and some pesticides (organophosphates and carbamates) may
cause infl ammation, muscle spasms, pain, and stiffness. Osteoarthritis appears to
be a result of long-term consumption and/or use of the Solanaceae, which contain
naturally the active metabolite vitamin D3, which in excess causes crippling and
early disability (as seen in livestock). Rigid omission of Solanaceae, with other
minor diet adjustments, has resulted in positive to marked improvement in arthritis
and general health.
HORTSCIENCE, VOL. 33(3), JUNE 1998
34
ORAL SESSION 3 (Abstr. 346–352)
Woody Ornamentals/Landscape/Turf—
Biotechnology
346
Identification of Tsuga Species Hybrids Using M olecular
Markers
Margaret R. Pooler*, Susan E. Bentz, Alden M. Townsend, and Clayton B. Deming;
U.S. Dept. of Agriculture, U.S. National Arboretum, Floral and Nursery Plants
Research Unit, 3501 New York Ave., NE, Washington, DC 20002
In both urban and rural areas, landscape and forest settings, the eastern
hemlocks (Tsuga canadensis and T. caroliniana) are suffering major damage and
mortality from the hemlock woolly adelgid (Adelges tsugae). Research efforts at
the U.S. National Arboretum are focusing on the development of resistant hybrids
by crossing the East coast native species with the Asian species T. chinensis, T.
diversifolia, and T. seiboldii , which are reported to be more tolerant to damage by
the woolly adelgid. More than 2000 seedlings have resulted from these crosses and
controls. However, positive identifi cation of these putative hybrids cannot easily
be made based on visual inspections due to variation in morphological traits. We
are using molecular markers, including RAPD-PCR and Sequence Characterized
Amplifi ed Regions (SCARs) to screen putative hybrids. Our data indicate that
RAPD bands are useful to analyze the variation within a particular cross, but
are of limited use in identifying hybrids. The development of SCARs enables
fast and accurate identifi cation of hybrids using only three to four leaves from a
seedling. The production of hybrids among these fi ve species will generate novel
combinations of genes for studying adaptability, pest resistance, and horticultural
attributes, as well as broaden the genetic base of cultivated hemlocks.
347
Preliminary Investigation on Discrimination and Genetic Diversity of Cephalotaxus Taxa Using AFLP Markers
Donglin Zhang* 1, Michael A. Dirr2, Robert A. Price3, Stephen Kresovich4, and
Sharon Mitchell 4; 1Landscape Horticulture, Univ. of Maine, Orono, ME 044695722; Depts. of 2Horticulture and 3Botany, Univ. of Georgia, Athens, GA 30602,
USA; 4USDA-ARS, Plant Genetic Resources Conservation Unit, Univ. of Georgia,
Griffi n, GA 30223-1797
Cephalotaxus species and cultivars have become popular because of their sun
and shade tolerance, resistance to deer browsing, disease and insect tolerance,
and cold and heat adaptability. Unfortunately, the nomenclature and classifi cation
in the literature and nursery trade are confusing due to their extreme similarity
in morphology. To address this problem, a preliminary investigation utilizing the
AFLP technique was applied to taxon discrimination and genetic difference among
90 Cephalotaxus accessions. A total of 403 useful markers between 75- and 500-bp
fragment sizes was generated from three primer-pair combinations. The clustering
results with reference to morphological characteristics showed that 79 accessions
out of 90 can be classifi ed as three species, C. oliveri Mast., C. fortunei Hook.,
and C. harringtonia (Forbes) Koch., and one hybrid species, C. x sinensis; four
varieties, C. fortunei var. alpina, C. harringtonia var. koreana, C. harringtonia var.
nana, and C. harringtonia var. wilsoniana; and eight cultivars. Suggested names
are provided for mislabeled or misidentifi ed taxa. The Cephalotaxus AFLP data
serve not only as a guide to growers for the identifi cation and genetic differences
of a taxon, but also as a model to establish a “cultivar library” against which later
introductions or problematic collections can be cross-referenced.
348
Genetic Relationships among Cultivated Species of Rhododendron L. Section Pentanthera G. Don Based on DNA Sequence
Variation of the Internal Transcribed Spacer (ITS) Region
S.M. Scheiber* 1, R.L. Jarret2, and C.D. Robacker1; 1Dept. of Horticulture, Univ.
of Georgia; 2USDA/ARS, Plant Genetic Resources, Georgia Station, Griffi n, GA
30223
Rhododendron section Pentanthera has traditionally been viewed as a group
of closely related species due to the relative lack of distinctive morphological
characteristics separating species and numerous reports in the literature of artifi cial
505
and natural fertile hybrids that produce fertile progeny. Signifi cant variation within
species has created diffi culties in efforts to assemble these taxa into well-defi ned
groups. Genetic relationships among cultivated specimens of the 15 currently
recognized species in Rhododendron section Pentanthera were derived from
sequence comparisons of the internal transcribed spacer (ITS) region. Sequences
of the entire ITS region including ITS1, ITS2, and the 5.8S subunit were generated
by direct sequencing of polymerase chain reaction (PCR) amplifi ed fragments.
Rhododendron vaseyi A.Gray, Rhododendron section Rhodora (L.) G.Don was
used as an outgroup. Aligned sequences of the 16 taxa resulted in 690 characters.
A distance matrix of sequence divergence was calculated using Kimura’s two
parameter model. A bootstrap analysis was performed and a phenogram was
constructed using MEGA. A phenetic assay rather than a phylogenetic analysis was
performed because the ITS region contained only eight (1.16% ) phylogenetically
informative sites. The entire ITS region contained 41 variable sites (5.94% ). Five
species had identical ITS sequences. Seven additional species differed only by
one or two base pair substitutions and/or the addition or deletion of one or two
base pairs. R. luteum Sweet, R. occidentale A. Gray, R. molle (Blume) G.Don, and
the outgroup, R. vaseyi had noticeable variation (base substitutions, additions,
and deletions) compared to the other species. Divergence values among the taxa
were extremely low, ranging from 0.00% to 3.51% . This molecular data, and
previous hybridization studies, do not support the accepted taxonomic treatment
of the section.
349
In Vitro Establishment of Powdery M ildew (M icrosphaera
pulchra) on Microshoots of Flowering Dogwood
L.A. Klein, M.T. Windham, and R.N. Trigiano*; Tennessee Agricultural Experiment
Station, The Univ. of Tennessee, Knoxville, TN 37901-1071
Microshoot and callus cultures of Cornus fl orida (fl owering dogwood), which
were grown on woody plant medium amended with BA, were inoculated with
Microsphaera pulchra (an obligate plant parasite) by gently shaking infected
leaves bearing numerous conidia over the tissue. Culture dishes were sealed with
parafi lm and incubated at 24 °C with 25 mol • m–2• s–1 provided by cool fl uorescent
bulbs for 15 h. Cultures were examined with a dissecting scope every 24 h and
cultures transferred when contaminating fungi were present. Specimens were
prepared light microscopy and SEM. The fungus infected individual callus cells,
but did not sporulate. In contrast, powdery mildew was well-established (both
primary and secondary hyphae) in 70% of the microshoot cultures after 6 days
and sporulated on 20% by 7 to 8 days. The cellular relationship between host
and pathogen in vitro was similar to that found in greenhouse-grown plants. This
technique has possible applications in maintaining fungal culture collections and
studying host–pathogen relationships under more stringently controlled conditions.
350
In Vitro Screening of Azalea for Resistance to Azalea Lace
Bug
Carol D. Robacker* 1 and S.K. Braman2, 1Dept. of Horticulture, 2Dept. of Entomology, Univ. of Georgia, Georgia Station, Griffi n, GA 30223
Azalea lace bug (Stephanitis pyrioides) is the most serious pest on azalea.
Results of laboratory bioassays and fi eld evaluations of 17 deciduous azalea taxa
have identifi ed three resistant taxa: R. canescens, R. periclymenoides, and R.
prunifolium. Highly susceptible taxa are ‘Buttercup’, ‘My Mary’, R. oblongifolium,
and the evergreen cultivar ‘Delaware Valley White’. To determine whether in vitro
techniques would have potential value in screening or selecting for resistance, or
for the identifi cation of morphological or chemical factors related to resistance,
an in-vitro screening assay was developed. In-vitro shoot proliferation was obtained using the medium and procedures of Economou and Read (1984). Shoots
used in the bioassays were grown in culture tubes. Two assays were developed:
one for nymphs and one for adult lace bugs. To assay for resistance to nymphs,
‘Delaware Valley White’ leaves containing lace bug eggs were disinfested with 70%
alcohol and 20% commercial bleach, and incubated in sterile petri plates with
moistened fi lter paper until the nymphs hatched. Five nymphs were placed in each
culture tube, and cultures were incubated for about 2 weeks, or until adults were
observed. To assay for resistance to adults, fi ve female lace bugs were placed in
each culture tube and allowed to feed for 5 days. Data collected on survival and
leaf damage was generally supportive of laboratory bioassays and fi eld results.
Adult lace bugs had a low rate of survival on resistant taxa. Survival of nymphs
was somewhat reduced on resistant taxa.
506
351
Ancymidol Increases In Vitro Multiplication Rate of Hosta in
Liquid Media
J. Adelberg and M. Kroggel *; Dept. of Horticulture, Clemson Univ., Clemson,
SC 29634
The main and interactive effects of plant growth regulators were assayed to
optimize multiplication rate for Hosta in liquid media. Two varieties of Hosta were
run through three 4-week subculture cycles in shake fl asks. When Hosta ‘Blue
Cadet’ was grown on three concentrations of cytokinin (1, 2.25, and 5 µM BA),
three concentrations of auxin (0.1, 1.0, and 10 µM IAA), and four concentrations
of an anti-gibberellin growth regulator (0.0, 0.1, 0.32, and 1.0 µM ancymidol),
multiplication rates improved markedly during the fi rst two subculture cycles in
liquid, (1.7 and 3.6x, respectively) before stabilizing at third subculture. BA and
ancymidol both increased multiplication rate. IAA interacted antagonistically
with BA. An optimal multiplication medium with 2.25 µM BA, 1.0 µM IAA, and
1.0 µM ancymidol, provided a high rate of multiplication with well-defi ned shoot
morphology and minimal root growth. Media consisting of 1.0 µM BA, 10.0 µM
IAA, and 0.32 µM ancymidol was effective in producing leafy plantlets, with root
initials, ready for transfer to mist bed acclimatization. When Hosta ‘Stilletto’ was
grown on concentrations of cytokinin (1, 2.25, and 5 µM BA), auxin (0.1, 1.0, and
10 µM IAA) and ancymidol (0.0, 1.0, and 3.2 µM), multiplication rates improved
markedly during the fi rst two subculture cycles in liquid (1.9 and 2.4x, respectively)
before stabilizing at third subculture. Ancymidol increased multiplication rate at
either level; the interactive effect with BA showed highest multiplication rates at
lowest BA levels in the presence of ancymidol. Lower BA concentrations promoted
better culture morphology and lesser BA induced root inhibition.
352
Eliminating Thrips in Microshoot Cultures
Robert R. Tripepi*, Holly J. Schwager, Mary W. George, and Joseph P. McCaffrey; Plant Science Division and Entomology Division, Univ. of Idaho, Moscow,
ID 83844-2339
Two insecticides, acephate or azadirachtin, were added to tissue culture
media to determine their effectiveness in controlling onion thrips (Thrips tabaci
Lindeman.) and to determine if these insecticides could damage the plant shoot
cultures. To test for insecticide phytotoxicity, microshoots from European birch
(Betula pendula), American elm (Ulmus americana), ‘Pink Arola’ chrysanthemum
( Dendranthema grandifl ora), ‘America’ rhododendron ( Rhododendron catawbiense), ‘Golden Emblem’ rose (Rosa hybrida), and ‘Gala’ apple (Malus domestica)
were placed in 130-ml baby food jars containing 25 ml of medium supplemented
with 6.5, 13, or 26 mg/l Orthene® (contained acephate) or 0.55, 1.1, or 2.2 ml/l
Azatin® (contained azadirachtin). Control jars lacked insecticide. To test for thrips
control, 13 mg/l Orthene® or 0.55 ml/l Azatin® was added to Murashige and Skoog
medium, and 10 thrips were placed on ‘Gala’ apple microshoots in each jar. Jars
were sealed with plastic wrap. In both studies, microshoot dry weight and heights
were determined. In the second study, the total number of thrips per jar was also
determined 3 weeks after inoculation. Microshoots on Orthene® -treated media
lacked phytotoxicity symptoms, regardless of the concentration used. In contrast,
Azatin® hindered plant growth, decreasing shoot height or dry weight by up to
85% depending on the species. Both insecticides prevented thrips populations
from increasing, since less than 10 thrips were found in jars with insecticidetreated medium. Control jars, however, contained an average of almost 70 thrips
per jar. This study demonstrated that both Orthene® and Azatin® were effective
for eradicating thrips from plant tissue cultures, but Orthene® should probably
be used because Azatin® was phytotoxic to all species tested.
35
ORAL SESSION 4 (Abstr. 353–359)
Technology Applications in Extension
Horticulture
353
Factsheet Database: A Comprehensive Collection of Publications for the United States and Canada
Tim Rhodus*; Dept. of Horticulture and Crop Science, The Ohio State Univ.,
HORTSCIENCE, VOL. 33(3), JUNE 1998
Columbus, OH 43210
A full-text searchable database is available through the Internet that captures
factsheets, bulletins, and other Extension publications related to horticultural and
agronomic crop production and culture. Electronically accessable information from
Extension in 50 different colleges and universities across the United States and
Canada was indexed by a robot software program and provides clients with access
to over 14,000 publications. This database represent the most concentrated source
of plant-related information available for answering questions, developing outreach
programs, or assisting individuals to learn about plants. Information can be search
gloabally or limited to regional searches, e.g., Midwest, Northeast, Southeast,
Southwest, West (including Hawaii), North Central, and Alaska, plus Canada.
The address for the web site is: www.hcs.ohio-state.edu/factsheet.html.
354
The Development of Web-based Searchable Databases for the
Green Industry
John D. Lea-Cox1*, Tamela D. Michaels2, Ethel M. Dutky3, and Anne Bird Sinderman4; 1Dept. of Natural Resource Sciences and Landscape Architecture, 2College
of Agriculture, 3Dept. of Entomology, Univ. of Maryland, College Park MD 20742;
4
Plant Protection Section, Maryland Dept. of Agriculture, Annapolis MD 21401
Despite the explosion of resources on the World Wide Web (Web) over the past
3 years, there are still relatively few sites that provide easily accessible diagnostic
information on horticultural subjects. For members of the Green industry, (i.e.,
greenhouse and nursery growers, landscape contractors, and scouting professionals) there is a real need for Web-based resources that provide detailed information
on specifi c subjects that can be accessed at any time. The creation of diagnostic
pictorial databases with self-learning capabilities (e.g., hyperlinked glossaries to
technical terms) that are carefully designed to include expert diagnostic advice,
with methods of control specifi cally keyed to the diagnosis, will be a powerful
method to educate and inform users from the industry and in the classroom. One
such database, called Tospovirus, has been developed by the authors that can be
searched by host species and tissue type, since this important virus has a wide
host range and symptomatology. Since at the present time the only control measure
for this virus is eradication, growers can use this database to immediately identify
suspicious plants in the greenhouse or nursery before further infection occurs.
The development process of this database will be outlined to give the audience
an idea of the decision-making process involved in this rapidly evolving method
of information transfer.
355
Creation and Maintenance of a Horticultural Education Web
Site by an Extension Specialist Without HTML Programming
Skills
L. Brandenberger* 1 and D. Lineberger2; 1Texas A& M Research and Extension
Center, 2401 East Hwy. 83, Weslaco, TX 78596, 2225 Horticulture Forestry Bldg.,
TAMU, College Station, TX 77843.
Informational web sites on the World Wide Web (WWW) are another means
for extension educators to transfer information to a clientele and provide access
to new audiences. One of the problems inherent in the utilization of this new
technology is the amount of effort required by those involved in order to become
profi cient enough to accomplish their goal of sharing information through a web
site. Through the use of a HTML editor and the assistance from staff knowledgeable
about the WWW, a web site on a main campus server was created by untrained
off-campus personnel at a remote site to provide information on commercial
vegetable production. Planning of the web site included targeting potential audiences, determining what information would be shared from the site, and building a
team of extension and research personnel that would provide information and act
as reviewers for web publications. Assistance in the form of graphics and general
know how were supplied by departmental specialists. After development, the web
site was maintained and refi ned on a regular basis through the utilization of the
HTML editor and a web fi le transfer program.
356
Aggie Horticulture on Disk
R. Daniel Lineberger*; Dept. of Horticultural Sciences, Texas A& M Univ., College
Station, TX 77843-2133
The Aggie Horticulture Web site was written to CD-ROM using readily available, inexpensive equipment, supplies, and software. The CD-ROM version is
HORTSCIENCE, VOL. 33(3), JUNE 1998
accessed using the “load from fi le” option of the commonly used Web browsers
and is cross-platform compatible. Writing to CD does not allow “server-side”
functions such as cgi-based searching and forms posting and the content of the
site is fi xed at the time the CD is written. However, in situations where Web connectivity is limited in speed or where phone connections are unavailable, the CD
represents a low-cost alternative for accessing large volumes of information. Aggie
Horticulture on Disk will be demonstrated, and several precautions to be followed
to ensure an error-free transition from Web site to CD will be described.
357
Extension Program Delivery for Greenhouse Growers Using
Compressed Video Technology
Steven E. Newman* 1 and Karen L. Panter2; 1Dept. of Horticulture and Landscape
Architecture, Colorado State Univ., Fort Collins, CO 80523-1173; 2Colorado State
Univ. Cooperative Extension, 9755 Henderson Road, Brighton, CO 80601-8114
There is a need for educational programming for greenhouse growers on
effective uses of biorational pesticides and biological controls of insect and mite
pests, diseases, and alternatives to herbicide sprays in confi ned areas; however,
in many states, travel for specialists for programming and workshops is becoming
prohibitive. A series of programs outlining Best Management Practices (BMP) for
the greenhouse industry outlining techniques and practices reducing pesticide
use were conducted at multiple sites in Colorado simultaneously using interactive compressed video technology. This conferencing technology is gaining wide
acceptance in many venues and provides an opportunity for wider participation
of clientele without travel. Participants in the programs reported in post-session
evaluations that they did miss the personal interaction with the speakers, but
did acknowledge that not having to drive 5 hours to attend a seminar was quite
benefi cial.
358
Creation and Use of a Video as an Educational Tool
William H. Olson* and Carolyn Pickel; Cooperative Extension, Univ. of California,
Davis, CA 95616
Two Smith–Lever IPM Grants provided the funds to develop and disseminate
information in an educational video about Walnut Husk Fly (WHF). The video was
produced as a new way of conveying information about the techniques available
to control WHF. Helping clientele implement new information on treatment timing
was also a goal. The video was shown to 1154 clientele at 16 educational meetings. Fifteen regional trials were conducted across California to demonstrate the
techniques illustrated in the video. Three-hundred-and-twenty-four clientele took
a WHF quiz before and after viewing the video. Test results improved by 83% . A
questionnaire indicated the video was a better format than a slide presentation
for learning new information. Clientele particularly liked the review section at the
end of the video. Seventy-fi ve clientele participating in a postharvest telephone
interview indicated that the information in the video helped them control WHF.
Sixty-two percent used the new techniques described and 65% felt that the information presented improved their treatment timing. As a result of using information
presented in the video, both the average number of treatments and insect damage
was reduced. This 2-year project trained clientele representing over 40,000 acres
of walnuts. Each Cooperative Extension offi ce and IPM Advisor was given a copy
of the video. In addition, over 70 copies of the video have been sold, several to
pesticide companies for training of their pest control advisors.
359
Oklahoma Gardening— Extension Horticulture Education
Through Television
David A. Hillock and Brenda R. Simons*; Dept. of Horticulture and Landscape
Architecture, Oklahoma State Univ., Stillwater, OK 74078-6027
In an era of shrinking Extension resources the question of how to reach large
audiences with horticulture information is a pressing concern. Now in its 23rd
year, Oklahoma Gardening is an example of spreading Extension information to
large audiences through television. Oklahoma Gardening is produced cooperatively
by the Oklahoma Cooperative Extension Service, the Dept. of Horticulture and
Landscape Architecture, and the Dept. of Ag. Education, Communication, 4-H
and Youth Development. The show offers traditional how-to information about
gardening, lawn care, and landscaping, as well as up-to-date university research
on horticulture. Extension specialists from other disciplines such as entomology,
plant pathology, human environmental sciences, and soils frequently contribute
507
to the show fostering cooperation between these programs. Weekly, Oklahoma
Gardening reaches more than 175,000 viewers in Oklahoma and surrounding
states. County Extension Educators are kept informed of programming and
provided with support materials for each weekly show. They are also encouraged
to provide input as to content and needs in their particular area of the state. In
addition, consumer horticulture programming and show content are closely tied
and the show serves as a bulletin board for horticulture related events coordinated
by the extension service.
on fl owering varied by species. For example, under SD, 0% , 80% , or 100% of
Leucanthemum xsuperbum ‘Snowcap’ fl owered after 0, 3, or ≥6 weeks at 5 °C,
respectively, and time to fl ower decreased from 103 to 57 days as the duration of
cold increased from 3 to 12 weeks. ‘Snowcap’ cooled for ≥3 weeks, then forced
under LD, fl owered completely in 45 to 55 days. Flowering percentage of Lavandula
angustifolia ‘Hidcote’ reached 100 under LD or SD only when plants were cooled for
≥6 or 15 weeks, respectively. Under LD, fl owering percentage of Astilbe chinensis
pumila progressively increased from 0 to 100 as cold treatment increased from 0
to 15 weeks; fl owering percentage under SD was low regardless of cold treatment.
Additional species and fl owering characteristics will be discussed.
36
363
Lime and Lavender: The Ornamental Sweetpotato Wins Respect
in the Landscape
ORAL SESSION 5 (Abstr. 360–366)
Perennials & Poinsettias—Floriculture
Allan M. Armitage*, Dept. of Horticulture, Univ. of Georgia, Athens, GA 30602
Angelonia Humb.& Bonpl. (Angelonia), Scrophulariaceae, consists of about
30 species and has potential in amenity horticulture and as a pot plant. Selections
of A. angustifolia Benth. and hybrids occur in several fl ower colors and have been
evaluated for amenity purposes. Selected taxa were grown in different photoperiods
(8-h, 16-h and combinations), light intensity, and temperature regimes (10–30
°C) to determine optimum environments for fl owering and growth. Preliminary
studies indicate that plants are only slightly responsive to photoperiod. Plants
reached visible bud stage 4 to 10 days earlier in long-day treatments, but the
time from visible bud to fl ower was unaffected. Raceme length was longer in LD
plants. Plants fl owered more rapidly and produced more fl owers in high light and
warm temperatures. Performance of plants in a landscape situation will also be
discussed.
Wayne J. McLaurin* and Gary L. Wade; Dept. of Horticulture, Univ. of Georgia
Athens, GA 30602
Impressive its fi rst several seasons on the market, the ornamental sweetpotato
(Ipomoea batatas) provides nearly carefree cascades of fade-proof yellow-green,
purple, or variegated foliage that looks equally good on banks, in beds, or in
hanging baskets. A foil for both bright and subdued fl owering plants, such as
abelmoschus or petunias, ornamental sweetpotatoes add both dramatic color
contrasts and dimension to plantings of all kinds. As demonstrated at the 1996
Summer Olympics, large containers fi lled with ornamental sweetpotatoes, such
as ‘Margarite’ and ‘Blackie’, and the muted greys, greens, purples, and golds of
artemesia, fountain grass, and lantana create an unusual and dependable planting that holds up to heat and humidity and is generally pest-free. Cultivation
requirements are minimal. Ipomea performs best in full sun with good drainage
and regular garden soil. However, it will tolerate poor soil, dry conditions, even
semi-shade as well. In spite of its horticultural and aesthetic qualitites, Ipomea
has still to be utilized fully in home and commercial plantings. As new varieties
are introduced and the spectrum of color increases, Ipomea should become a true
mainstay of the ornamental industry.
361
Vernalization Accelerates Flowering of Lysimachia clethroides
Duby
364
Response of Poinsettia Growth and Development to Ratio of
Radiant to Thermal Energy
360
The Influence of Light and Temperature on Flowering and
Growth of Angelonia angustifolia Benth.
Pamela M. Lewis*, Alan M. Armitage, and Jim M. Garner; Dept. of Horticulture,
Univ. of Georgia, Athens, GA 30602
The effect of vernalization method and duration on off-season cut fl ower
production of Lysimachia clethroides Duby was examined. Rhizomes harvested
in October were cooled for 0, 4, 6, 8, 10 or 12 weeks at 4 ± 1 °C in crates with
unmilled sphagnum peat or in 3.75-L pots with potting media prior to forcing
in a warm greenhouse. After 6 or more weeks of cooling, shoots emerged from
crate-cooled rhizomes in higher percentages than from pot-cooled rhizomes.
However, only the duration of cooling, not the method, affected the rate of shoot
emergence, visible bud formation and anthesis of the fi rst bud in the raceme. As
cooling increased from 0 to 12 weeks, the greenhouse days required for shoot
emergence, visible bud formation and anthesis decreased linearly. The number
of fl owering fl ushes and fl owering stems varied quadratically with cooling duration, and the highest yields occurred when rhizomes received between 4 and 10
weeks of cooling. As the number of successive fl owering fl ushes increased, the
stem length increased linearly while the stem diameter decreased linearly. High
numbers of fl owers were produced rapidly after 10 weeks of cooling.
362
Cold Treatments Alter the Photoperiodic Flowering Response
of Some Herbaceous Perennial Species
Erik S. Runkle*, Royal D. Heins, Arthur C. Cameron, and William H. Carlson; Dept.
Of Horticulture, Michigan State Univ., East Lansing, MI 48824-1325
Many species of herbaceous perennials either require a cold treatment for
fl owering or exhibit enhanced and more desirable fl owering characteristics following a cold period. For some species, the photoperiodic induction of fl owering can
change following cold treatments, the parameters generally becoming less strict
as plants receive longer durations of cold until a saturation duration is reached. To
quantify the minimum and saturation durations of cold for fl owering under short
days (SD) and long days (LD), fi ve species were selected and cooled for 0, 3, 6,
9, 12, or 15 weeks at 5 °C, then forced at 20 °C under 9-h photoperiods without
(SD) or with a 4-h night interruption (LD). The effects of cold and photoperiod
508
Bin Liu* and Royal D. Heins; Dept. of Horticulture, Michigan State Univ., East
Lansing, MI 48824-1325
A concept of ratio of radiant to thermal energy (RRT) has been developed
to deal with the interactive effect of light and temperature on plant growth and
development. This study further confi rms that RRT is a useful parameter for plant
growth, development, and quality control. Based on greenhouse experiments
conducted with 27 treatment combinations of temperature, light, and plant spacing,
a model for poinsettia plant growth and development was constructed using the
computer program STELLA II. Results from the model simulation with different
levels of daily light integral, temperature, and plant spacing showed that the RRT
signifi cantly affects leaf unfolding rate when RRT is lower than 0.025 mol/degreeday per plant. Plant dry weight is highly correlated with RRT; it increases linearly
as RRT increases.
365
Quantifying the Effect of Canopy Closure on Poinsettia Stem
Elongation
James E. Faust*, Rob Klein, and Elizabeth Will ; Univ. of Tennessee, P.O. Box
1071, Knoxville, TN 37901-1071
The rate of poinsettia stem elongation is affected by several factors, including
light quality, i.e., specifi c wavelengths of irradiance. As the plants grow and the
canopy closes, the red to far-red ratio is reduced and stem elongation is promoted.
The objective of this project was to quantify the effect of canopy closure on the stem
elongation rate of pinched ‘Freedom’ poinsettias. In the fi rst experiment, individual
plants received 413, 645, 929, 1264, or 2580 cm 2 of growing area at the time of
pinch. The maximum rate of stem elongation for the fi ve spacing treatments was
2.9, 3.8, 4.3, 5.6, or 7.5 mm/day, respectively. In the second experiment, plants
were grown at a “tight” or a “wide” spacing as defi ned by the percentage of PPF
transmission measured between plants. The “wide” spacing treatments allowed
50% PPF transmission, while the “tight” spacing treatment allowed 10% PPF
transmission. A constant degree of closure was maintained by weekly adjusting
plant spacing based on the PPF transmission measurements. The maximum rate
HORTSCIENCE, VOL. 33(3), JUNE 1998
of stem elongation of the “tight” spacing was 4.6 mm/day compared to 3.1 mm/day
for the “wide” spacing treatment.
366
Photoperiod and Temperature Influence on Flower Initiation
and Development for Euphorbia pulcherrima Grown Under
Florida Conditions
C.E. Wieland*, J.E. Barrett, D.G. Clark, and G. J. Wilfret, Dept. of Environmental
Horticulture, Univ. of Florida, Gainesville, FL 32611-0670
Four poinsettia cultivars were grown in glass greenhouses in Gainesville,
Fla., in the Fall 1997 to evaluate differences in fl oral initiation and subsequent
development. Three means of regulating photoperiod were 1) natural days 2)
long-day lighting to 6 Oct. and then natural days (lights out) 3) long-day lighting
to 6 Oct., and then short-day conditions by black cloth for 15 h (black cloth).
At 2-day intervals, sample meristems were collected and examined for initiation
of reproductive development. Average minimum and maximum temperatures
during the fi rst two weeks of October were 22 and 29 °C, respectively, with an
average temperature of 25.3 °C. The overall average temperature was 23.2 °C
from planting to anthesis. Differences in anthesis dates among cultivars were
primarily due to time to initiation vs. rate of development. Under natural days,
‘Lilo’ initiated fi rst on 8 Oct. and ‘Freedom’, ‘Peterstar’, and ‘Success’, followed
by 6, 8, and 18 days, respectively. Lights out resulted in ‘Lilo’ initiating 17 Oct.,
followed by ‘Freedom’, ‘Peterstar’, and ‘Success’ initiating 7, 12, and 15 days later,
respectively. Differences between cultivars in time of initiation was reduced under
black cloth, where ‘Lilo’ initiated 14 Oct., followed by ‘Freedom’ 2 days later, and
‘Peterstar’ and ‘Success’ 7 days afterward. Initiation was positively correlated to
visible bud and anthesis. First color was positively correlated to initiation and
visible bud, with the exception of ‘Lilo’. Growth room studies conducted using
various high temperatures and photoperiods indicated similar trends.
37
ORAL SESSION 6 (Abstr. 367–374)
Undergraduate Education
367
Developing and Implementing a Field Trip Course in Public
Gardens
Jennifer Campbell Bradley*; Dept. of Environmental Horticulture, Univ. of Florida,
Gainesville, FL 32611
Public gardens, including public parks, botanical gardens, and arboreta are
signifi cant tourism destinations with increasingly popular appeal. In the United
States alone, the number of gardens is continuing to rise impressively. Undeniably, there is a need for trained and educated horticulturists who can enter the
horticulture industry, specifi cally in the area of public garden management. At the
Univ. of Florida, a new course, ORH 4932, Public Gardens was offered. This course
was designed with a fi eld trip emphasis to help students visually understand and
appreciate the value and diversity of such gardens. Students taking the course had
an opportunity to visit and tour various gardens throughout the state of Florida.
At the same time, students learned about the history, management, collections,
and importance of such institutions to society. This session will explore the value
of student experiences in the learning process, present an overview of how to
develop a fi eld trip class, and provide information to other educators interested
in offering such a course.
368
Using Extended Field Trips to Enhance the Undergraduate
Experience
Robert F. McDuffi e*; Dept. of Horticulture, Virginia Tech, Blacksburg, VA 240610327
While the use of fi eld trips is not new to undergraduate education, tailoring
a 3- to 4-day fi eld experience to enhance classroom instruction is challenging,
but rewarding, for students, faculty, and alumni. Drawing on alumni in the private
and public sectors to serve as guides has added signifi cantly to the experience
and has strengthened alumni ties to the department. Problems associated with
extended fi eld trips, such as those related to behavior and legal liabilities, can
often be avoided by proper scheduling and insurance planning. Funding can be
augmented by an industry eager to fi nd qualifi ed graduates.
HORTSCIENCE, VOL. 33(3), JUNE 1998
369
Breaking the Vegetative Cycle of Plant Materials Lectures
Michael A. Arnold*; Texas A& M Univ., Dept.of Horticultural Sciences, College
Station, TX 77843-2133
Routine lectures, even in topics as inherently appealing to students as plant
materials classes, can become monotonous. Educational games can be effective
mechanisms for breaking the classroom routine, stimulating student interaction,
and reviewing key concepts in an alternative teaching/learning style. Three plant
materials games that can be tailored to apply specifi cally to regional/local classes
were developed based on popular television game shows. Basing the formats
on games with which the students are familiar allows minimal time and effort to
learn the rules and permits students to immediately participate in the activity.
The names of the games are “Plant Pictionary”, “Plant Taboo”, and “Name That
Plant”. A brief game of each can be completed within 15 to 20 min. The games
were developed using plant morphology, taxonomy, aesthetic characteristics,
and/or site requirement terminology introduced for general concepts or specifi c
taxa covered in the course. Based on student evaluations, these activities were
well received when periodically inserted into the lecture sessions. Participation
and enthusiasm for the activities was greatest during the later half of the semester,
likely due to the greater base of knowledge that could be incorporated into the
games. The games worked best as group activities, particularly fostering good
natured competition among laboratory sections. The general concepts of the
games should be transferable to other subject matter areas.
370
IPM— A Problem-based Learning Approach
Robert P. Rice Jr.*; Environmental Horticultural Science Dept., California Polytechnic State Univ., San Luis Obispo, CA 93407
The Cal Poly philosophy of “Learn and Understand by Doing” has been
integrated with problem-based learning and the use of the latest technology to
produce a class that closely simulates real-life pest control situations. Goals of
the class, Disease and Pest Control Systems for Ornamental Plants, are to teach
students pest monitoring, control and problem solving techniques, the use of
resources including the internet and journals, and the use of the latest pest control
equipment and application techniques. Students are shown pest situations and
then work in groups to diagnose the problem, investigate management strategies,
apply control measures, and monitor results. Weekly class presentations inform
the class of the various projects and help to teach the class organization and
presentation skills. Student evaluations and test performance have demonstrated
that students achieve class objectives substantially better with the problem-based
learning approach than with the previous lecture-based approach to the class.
371
Service Learning and Environmental Education
Mary Taylor Haque* 1, Lolly Tai 2, and Brenda VanderMey3; Depts. of 1Horticulture,
2
Planning and Landscape Architecture, and 3Sociology , Clemson Univ., Clemson,
SC 29634
Service learning is a teaching method that enables college students and
faculty to learn while identifying and solving community problems. A case study
involving the creation of sustainable landscapes for a low-income community in
Clemson, S.C., will be used to illustrate the methodology necessary to complete
a successful service learning project. Clemson Univ. students from four courses
worked towards advancing their knowledge and commitment to environmental
stewardship. They enhanced their education in landscape design and implementation through a partnership with the City of Clemson, Habitat for Humanity, the
National Wildlife Federation, and others which resulted in the creation of certifi ed
backyard habitats for low-income residents.
372
Development of an Undergraduate Curriculum in Landscape
Contracting
Robert F. McDuffi e* and Robert E. Lyons; Dept. of Horticulture, Virginia Tech,
Blacksburg, VA 24061-0327
Introducing a new curriculum option has led to greater student enrollment,
more highly qualifi ed students entering the curriculum, and better relations with
and support from an expanding landscape industry. Student skills development,
and enthusiasm has been enhanced by contemporary computer facilities, retooled
instructional practices, new courses, strong ties to the industry, required internship,
509
and an active post-graduation placement program. Justifi cation for this option as
well as specifi c details will be discussed.
373
Comparisons of Field-dependent and -independent Student
Learning Preferences in an Ornamental Horticulture Class with
an Emphasis on Computer-assisted Instruction
Anthony W. Kahtz* and Gary J. Kling; Dept. of Natural Resources and Environmental Sciences, Univ. of Illinois, Urbana, IL 61801
Learning Preference differences and similarities of fi eld-dependent/-independent students were investigated with an emphasis on the usage of a computer-assisted instruction (CAI) program designed for a woody plant identifi cation class.
Qualitative interviews further investigated each participant’s cognitive learning style
after administration of the Group Embedded Figures Test instrument. The fi ndings
were congruent with the theory of fi eld dependency. In addition, results indicated
that fi eld independent students felt that using CAI was benefi cial, but may prove
to be more advantageous with provided structure. In contrast, fi eld-dependent
students did not feel there was any benefi t in using a CAI program, but, with provided structure, benefi ts may occur. However, both fi eld-dependent/-independent
students would prefer a greater usage of visuals in this CAI program.
374
Analysis of Demographics and Factors Influencing Student
Choice of Major at Five Universities
Tammy Kohlleppel * 1, Jennifer C. Bradley1, and Jayne Zajicek2; 1Dept. of Environmental Horticulture, Univ. of Florida, Gainesville, FL 32611; 2Dept. of Horticultural
Sciences, Texas A& M Univ., College Station, TX 77843
In recent years horticulture programs at universities across the United States
have experienced a decline in student numbers. Researchers at the Univ. of Florida
and Texas A& M Univ. have developed a survey to gain insight into the infl uences
on undergraduate students who major in horticulture. Five universities participated
in the survey of undergraduate horticulture programs, these include the Univ. of
Florida, Texas A& M Univ., Oklahoma State Univ., Univ. of Tennessee, and Kansas
State Univ. Approximately 600 surveys were sent to the schools during the 1997
fall semester. The questionnaires were completed by horticulture majors and nonmajors taking classes in the horticulture departments. The survey consisted of two
main sections. The fi rst section examined student demographic information, high
school history, university history and horticulture background and was completed
by all students. Only horticulture majors completed the second section, which
examined factors infl uencing choice of horticulture as a major. Results examine
fundamental predictors in promoting student interest in horticulture, demographic
variables that may infl uence student choice of major, and student satisfaction and
attitude toward current collegiate
horticulture programs. Findings from this study will provide insight into the status
of post-secondary horticulture education and assist in identifying methods to
increase student enrollment in horticulture programs across the country.
47
ORAL SESSION 7 (Abstr. 375–381)
Small Fruit & Viticulture—Crop Production/Physiology
375
Using Chlorophyll Fluorescence (Fv/Fm) as an Objective,
Sensitive, and Efficient M ethod to Determine Cane Tissue
Hardiness of Grapevines
H. Jiang* and G.S. Howell ; Dept. of Horticulture, Michigan State Univ., East
Lansing, MI 48824-1325
Determining hardiness levels of plant tissues is a prerequisite for cold hardiness research. LT50 determined by browning or regrowth tests is reliable and
the most widely used means for assessing woody vegetative tissue viability. It
is, however, time consuming and subjective. Although chlorophyll fl uorescence
(Fv/Fm) has been recently proposed to measure tissue injury for leaf and bud
tissues, there are no reports on use for assessing viability of freezing-stressed
woody tissues. We investigated the Fv/Fm changes of 1- and 2-year-old canes of
510
Concord grapevines during the cold acclimation and compared these with browning and regrowth tests. The data showed that: 1) There were statistically signifi cant,
positive relationships between Fv/Fm changes and freezing temperature treatment
that caused tissue injury. The best fi t curvilinear equations were obtained; 2) The
time of measuring chlorophyll fl uorescence post-stress was important. Immediate
assessment was not as precise in separating cold hardiness difference as when
the tissue was measured 1 week later (at the time of browning test evaluation)
or 4 weeks later (at the time of regrowth test evaluation). Assessment 20–26 h
post-stress was equivalent to the 1-week or 4-week assessment. These data suggest that chlorophyll fl uorescence (Fv/Fm) is a useful practical tool for assessing
vegetative tissue viability. Importantly, it is rapid, simple, and objective.
376
Influence of Mechanical Shoot Positioning on Fruit Exposure,
Yield, and Fruit Quality of ‘Concord’ Grapevines
Thomas J. Zabadal * 1, Gary R. VanEe2, Thomas W. Dittmer 1, and Richard L.
Ledebuhr2; 1Dept. of Horticulture and 2Dept. of Agricultural Engineering; Michigan
State Univ., East Lansing, MI 48824
‘Concord’ grapes grown in cool climates often encounter fruit maturity
problems relative to desired processor standards. Exposure of grape clusters
to sunlight may promote fruit maturity. A mechanical device for reorienting
shoots on grapevines to increase fruit exposure was evaluated on ‘Concord’
grapevines, which had been managed with Hudson River Umbrella training and
balance-pruned to retain 44 nodes per kilogram of cane prunings. Three times of
positioning and combinations of these times were evaluated for a 3-year period.
Positioning consistently increased fruit exposure. Increases in fruit soluble solids
were dependent upon the year and the time of positioning. Excessive reduction of
leaf area resulting from some treatments is suggested as a factor depressing fruit
soluble solids. The value of this approach to mechanical shoot positioning for
enhancing fruit maturity depends upon the seasonal infl uence on grapevine canopy
development. When excessive canopy develops, mechanical shoot positioning is
likely to enhance fruit maturity.
377
Quantifying the Chilling Status of Grapevines and the Response
to Dormancy-breaking Chemicals in the Coachella Valley of
California
N.K. Dokoozlian*, Dept. of Viticulture and Enology, Univ. of California, Davis,
and Univ. of California Kearney Agricultural Center, 9240 S. Riverbend, Parlier,
CA 93648 USA
A method to quantify the chilling status of grapevines grown in a desert region,
in order to better predict vine response to dormancy-breaking chemicals, was
examined. Chilling status was determined by calculating the ratio between exposure to chilling temperatures (hours ≤7C) and chill-negating temperatures (hours
≥20C) from the beginning of the dormant period (1 Nov.) to the date of pruning
(mid-December). A 6-year fi eld study (1991 to 1996) compared the budbreak of
untreated vines, and vines treated with H2CN2 (2% v/v) immediately after pruning,
exposed to a range of chill:chill negation ratios resulting from yearly variations
in environmental conditions. Budbreak was delayed, and total budbreak reduced,
when the chill:chill negation ratio was <0.5. In contrast, rapid and complete
budbreak was observed when the chill:chill negation ratio was >2. The standard
dormancy-breaking treatment in this region, 2% (v/v) H2CN2, provided acceptable
budbreak when the chill:chill negation ratio was near 1. Higher concentrations of
H2CN2 were needed when the chill:chill negation ratio fell below 1, while H2CN2
could be reduced when the chill:chill negation ratio was 2 or more.
378
Influence of Light on Fruit Set of French Hybrid Grapes
D.C. Ferree*, S.J. McArtney, and D.M. Scurlock; The Ohio State Univ., Wooster,
OH 44691
Four French–American hybrid grape cultivars grown in a greenhouse were
subjected to 5 days of 80% shade at four different times around bloom. Fruit set
of ‘Seyval’ was reduced by shade imposed before, during, or immediately after
bloom. ‘Vidal’ and ‘Chambourcin’ were less sensitive, with fruit set reduced only
by shade at bloom. Shade had little effect on fruit set of ‘DeChaunac’. In a second
study, ‘Chambourcin’ vines were exposed to ambient, ambient plus supplemental
lights, and 30% , 50% , or 80% shade for 5 weeks beginning just prior to bloom.
Fruit set was positively related to light intensity. At harvest, soluble solids, pH, and
HORTSCIENCE, VOL. 33(3), JUNE 1998
hue angle had a negative linear relationship to light level. Fruit color developed
earliest and most rapidly with the reduced light treatments applied at bloom.
Cluster weight was positively related to light intensity.
379
Influence of Pruning and Irrigation on Root Longevity of ‘Concord’ Vines
L.H. Comas* 1, D.M. Eissenstat2, A.N. Lakso3, and R. Dunst4; 1Plant Physiology
Graduate Program, 2Dept. of Horticulture, Penn State Univ., 103 Tyson Bldg.,
University Park, PA 16802; 3Dept. of Horticultural Sciences, Cornell Univ., Geneva,
NY 14456; 4Vineyard Laboratory, Fredonia, N.Y.
Improved cultural practices in grape require a better understanding of root
growth and physiology. Seasonal root dynamics were examined in mature ‘Concord’ vines with balanced or minimal-pruning, and with or without supplemental
irrigation in Fredonia, N.Y. Fine roots were continuously produced during the
growing season starting in mid-June around time of bloom. Roots began to die
in September at verasion. Minimal-pruned vines produced more roots than balanced-pruned vines, with the minimal-pruned/unirrigated vines producing the
most roots. Irrigation and pruning delayed fi ne root production at the beginning
of the growing season. Peak fi ne root fl ush was 16 June to 21 July 1997 for the
minimal-pruned/unirrigated treatment, while peak fl ush was 7 July to 2 Sept. 1997
for balanced-pruned/irrigated treatment. In minimal-pruned vines, many roots
were observed down to depths of 120 cm. In contrast, balanced-pruned vines
had very few fi ne roots deeper than 40 cm. From initial observations, median
lifespan of fi ne roots was 5 to 9.5 weeks, depending on treatment and depth in
soil. Fine roots lived longer in the top 15-cm than in the16- to 30-cm layer of
soil in all treatments. Both minimal pruning and irrigation increased root lifespan.
Fine roots had the shortest lifespan in the balanced-pruned/unirrigated treatment
and the longest lifespan in the minimal-pruned/irrigated treatment.
380
Fumigation of ‘Flame Seedless’ Grape With E-2-Hexenal Reduces Mold during Long-term Cold Storage
Douglas D. Archbold*, Thomas R. Hamilton-Kemp, Ann M. Clements, and Randall
W. Collins; Dept. of Horticulture and Landscape Architecture, Univ. of Kentucky,
Lexington, KY 40546-0091
‘Flame Seedless’ grapes were fumigated with vapor of E-2-hexenal to determine
if the compound could reduce mold during long-term cold storage. The compound
(100 or 200 µL) was placed in 1-L low-density fi lm-wrapped clamshell containers with 150 g of fruit, and the packages were stored at 2 °C. The packages were
vented at 4 and 8 weeks to prevent excessive oxygen depletion or carbon dioxide
accumulation. At 2, 4, and 8 weeks, a subset of packages were removed from cold
storage and transferred to 20 °C following removal of the over-wrapped fi lm and
remaining chemical from the containers. Mold development and quality changes
were assessed for the subsequent 13 days. The vapor phase concentration of
E-2-hexenal was at a maximum within 1 day and declined to less than 25% of
initial levels by 2 weeks of 2 °C storage. The higher volume of chemical resulted
in a higher headspace concentration, and the fruit removed a proportion of the
chemical from the headspace. There were no signifi cant effects of E-2-hexenal
on fruit weight loss, fi rmness, or total soluble solids concentration. After 2 weeks
of cold storage, fumigation with E-2-hexenal had no effect on incidence of mold.
However, after 4 and 8 weeks of cold storage, mold was signifi cantly reduced by
both rates of E-2-hexenal.
381
Prelimary Report on the Apparent Control of Pierce’s Disease
(Xylella fastidiosa) with Admire (Imidacloprid) Insecticide
Gerard Krewer* 1, Jim Dutcher2, and C. J. Chang3,1Horticulture Dept., P.O. Box
1209, Univ. of Georgia, Tifton, GA 31793; 2Entomology Dept., P.O. Box 748, Univ.
of Georgia, Tifton, GA 31974; 3Plant Pathology Dept., 1109 Experiment Street,
Univ. of Georgia, Griffi n, GA 30223
Pierce’s Disease is the major limiting factor in the production of European
and American bunch grapes in the Coastal Plain and Lower Piedmont of the
Southeastern United States. Pierce’s Disease is also a signifi cant problem in some
areas of California. The disease has been impossible to control with insecticide
sprays up to this point, because the leaf hopper vectors are xylem feeders and
have minimal plant/insecticide contact. Admire was cleared for use on grapes 3
years ago, and an experiment was started near Tifton, Ga. Cultivars of European
HORTSCIENCE, VOL. 33(3), JUNE 1998
and American bunch grapes in this experiment include ‘Flame Seedless’, ‘J.
Riesling’, ‘Cabernet Franc’, ‘Reliance’, ‘Mars’ and ‘Canadice’. Experimental design
is a randomize complete block with two replications and six vines per replication
and treatment for a total of 72 vines in the experiment. Treatments are untreated
control and vines treated with Admire (3.26 g/vine per application) in an aqueous
solution of 1 to 2 L applied as a basal drench. Vines were planted in Mar. 1996
and applications of Admire have been applied in the early spring and mid summer
of each year. Apparent Pierce’s Disease symptoms became evident on some of
the control vines in mid-summer 1997. By Fall 1997, some of the control vines
were dead. This trend has continued in Spring 1998. Some vines treated with
Admire show slight Pierce’s Disease symptoms, but rate of disease development
is much slower than in the control vines. Based on company research with virus
transmission on other crops, even better results can be expected when large blocks
are treated with Admire. Current results on this experiment will be presented.
Larger scale experiments are underway as well as experiments to determine the
effect of Admire on the development of phony peach disease and plum leaf scald
disease.
48
ORAL SESSION 8 (Abstr. 382–389)
Woody Ornamentals/Landscape/Turf—
Crop Physiology
382
Temperature Response of Whole-plant CO2 Exchange Rates of
Magnolia (Magnolia grandiflora L. )
Marc W. van Iersel* and Orville M. Lindstrom; Dept. of Horticulture, Georgia
Station, Univ. of Georgia, Griffi n, GA 30223.
Photosynthesis and respiration temperature-response curves are useful in
predicting the ability of plants to perform under different environmental conditions. Whole crop CO2 exchange of two groups of magnolia ‘Greenback’ plants
was measured over a 26 °C temperature range. Net photosynthesis (Pnet) increased
from 2 to 17% C and decreased again at higher temperatures. The Q10 for Pnet
decreased from ≈4 at 6 °C to 0.5 at 24 °C. The decrease in Pnet at temperatures
over 17 °C was caused by a rapid increase in dark respiration (Rdark) with increasing temperature. The Q10 for Rdark was estimated by fi tting an exponential curve
to data, resulting in a temperature-independent Q10 of 2.8. Gross photosynthesis
(Pgross), estimated as the sum of Rdark and Pnet, increased over the entire temperature
range (up to 25 °C). The Q10 for Pgross decreased with increasing temperature, but
remained higher than 1. The data suggest that high respiration rates may be the
limiting factor for growth of magnolia exposed to high temperatures, since it may
result in a net carbon loss from the plants. At temperatures below 5 °C, both Pnet
and Rdark become low and the net CO2 exchange of the plants would be expected
to be minimal.
383
Heat Tolerance of Selected Provenances of Atlantic White
Cedar
Laura G. Jull*, Frank A. Blazich, and Thomas G. Ranney; Dept. of Horticultural
Science, North Carolina State Univ., Raleigh, NC 27695-7609
Uniform seedlings of six provenances (Escambia Co., Ala.; Santa Rosa Co.,
Fla.; Wayne Co., N.C.; Burlington Co., N.J.; New London Co., Conn.; and Barnstable Co., Mass.) of Atlantic white cedar [Chamaecyparis thyoides (L.) B. S. P.],
were transplanted in Apr. 1997 into 0.95-L plastic containers with a medium of 1
peat : 1 perlite : 1 vermiculite (v/v). Plants were acclimatized at 26/22 °C under a
16-hr photoperiod for 2 weeks before treatment initiation. Fourteen seedlings per
provenance were then transferred to each of fi ve growth chambers maintained at
16/8 hr thermoperiods of 22/18 °C, 26/22 °C, 30/26 °C, 34/30 °C, or 38 /34 °C
with a 16-hr photoperiod of 550–600 µmol • m–2• s–1. Seedlings were arranged in a
split-plot design with a 5 x 6 factorial arrangement of treatments (5 temperatures x
6 provenances). Plants were harvested 12 weeks after treatment initiation and data
recorded. Temperature had a signifi cant effect on overall growth with responses
to temperature varying according to provenance. There was a highly signifi cant
(P ≤ 0.0001) temperature x provenance interaction for height, stem caliper (measured below the lowest leaf), and foliar, stem, root, and shoot (foliar dry weight +
stem dry weight) dry weights. Top and root dry weights were maximized for the
511
northern provenances (Connecticut and Massachusetts) at 22/18 °C. At 26/22
°C and 30/26 °C, the northern provenances (Connecticut and Massachusetts)
had the lowest top and root dry weights. However, the southern provenances
(Alabama, Florida, and North Carolina) had the greatest top dry weights at 26/22
°C. At 30/26 °C, the southern provenances (Alabama and Florida) and the New
Jersey provenance had the greatest top dry weights but they were not signifi cantly
different from 26/22 °C. Root dry weights were not signifi cantly different between
26/22 °C and 30/26 °C for the Alabama and New Jersey provenances, but were
signifi cantly different for the North Carolina and Florida provenances. Regardless
of provenance, dramatic reductions occurred for all growth measurements when
temperatures exceeded 30/26 °C. For top and root dry weights, there were no
signifi cant differences among the six provenances at 34/30 °C and 38/34 °C. All
plants at the highest temperatures of 38/34 °C did not survive by week 8.
384
Media Temperature in Above-ground and In-ground Pot-in-Pot
Container Systems
Jason B. London* 1, R.T. Fernandez1, Roy E. Young2, Jerry D. Christenbury2; 1Dept.
of Horticulture and 2Dept. of Agricultural & Biological Engineering, Clemson
Univ., Clemson, SC 29634
In-ground, pot-in-pot (PNP) systems control container blow-over and buffer
media temperatures. At least two nursery container manufacturers have recently
introduced above-ground, PNP systems to reduce installation cost, overcome land
use infl exibility, and eliminate root growth into drainage systems. Above-ground,
PNP systems eliminate some of the problems associated with an in-ground PNP
system, but little is known about how it compares with in-ground PNP’s attributes;
specifi cally media temperaturee buffering. Fifteen-gallon containers of Ligustrum
japonicum var. ‘Repandens’ were installed in May 1997 at a nursery in Moncks
Corner, S.C. In-ground PNP; conventional pot placement; and two, commercial,
above-ground PNP systems were used as treatments with 12 replications. Four of
the replications contained six thermocouples in each treatment. Thermocouples
were placed in the top and middle of the container media at three orientations:
East–northeast, south, and center. During hot weather studies the two aboveground PNP confi gurations buffered media temperature deviation ranges slightly
when compared to conventional pot production, but not nearly as much as the
in-ground PNP confi guration. Media temperatures rose more slowly during the
daylight hours in the above-ground PNP systems than in conventional pots, but
eventually approached similar temperature peaks. Neither above-ground PNP
treatment cooled to the low temperature levels of the conventional treatment
overnight. The in-ground PNP treatment experienced less temperature deviations
than the other three treatments and rarely exceeded 32 °C (90 °F). Measurements
of biomass and growth were not different among the above-ground pot-in-pot
and the conventional pots, yet the in-ground treatments had a larger growth index
and biomass weight. Data for cold weather is currently being collected and will
be available for this presentation.
385
Critical Heat Thresholds for Root Tissue of Two Golden Barberry
Cultivars
B.H. Murphree* 1, J.L. Sibley1, D.J. Eakes1, and J.M. Ruter2; Dept. of 1Horticulture,
101 Funchess Hall, Auburn University, AL 36849, and 2Dept. of Horticulture, Univ.
of Georgia, CPES, Tifton, GA 31793
Limited information exists for container production of golden barberry
cultivars. The objective of this study was to evaluate root thermostability of
container-grown Berberis thunbergii ‘Monlers’ (Gold Nugget™) and Berberis sp.
‘Bailsel’ (Golden Carousel™). Bare root cuttings were planted in 2.7-L containers in an amended 6 pinebark : 1 sand (v/v) substrate in Apr. 1997. Plants were
grown under overhead irrigation for 6 months in a completely randomized block
design. Young, unsuberized root tips (1.0–2.5 cm), were subjected to temperature
treatments from 20 to 63 °C in a thermostatically controlled water bath prior to
electrolyte leakage determinations. ‘Golden Carousel’ was more heat-tolerant
(critical temperature midpoint = 49.4 ± 0.3 °C) than ‘Monlers’ (critical temperature
midpoint = 48.0 ± 0.4 °C). Implications of these differences for container production will be discussed.
386
Annual Evapotranspiration and Crop Coefficients of Ligustrum
japonica Growing in Three Container Sizes
512
R.C. Beeson, Jr.*; Central Florida Research and Education Center, IFAS, Univ. of
Florida, Sanford, FL 32711
The objective of this study was to determine crop coeffi cients (KC) for Ligustrum
japonica growing in three container sizes using the Penman equation to calculate
reference evapotranspiration (ETR). Rooted cuttings were transplanted into 3-liter
containers and upcanned as needed into 10- and 23-L containers. Production
was scheduled such that a series of plants in each container size were about 2
months from commercial marketable size every 4 months. Beginning 1 Jan. 1995
until 31 Dec. 1996, three uniform plants of each size were suspended in weighing
lysimeters and surrounded by similar size plants fi lling an area 3.7 by 4.9 m.
Plants within each area were overhead irrigated at 2000 h as needed, based on a
30% moisture allowed defi cit. Plants were exchanged every 4 months such that
the annual mean size was that of a marketable plant. Actual evapotranspiration
(ETA) was calculated from half-hour measurements of each plant’s weight and
adjusted for rainfall. From these and daily calculated ETR, KC were determined for
each size of container. KCs ranged from 1.06 to1.50 when ETA was converted to
mm/day based on allocated bed space. Comparisons of volumes of supplemental
irrigation to ETA and effects of assumptions required in converting ETA to mm/day
will be discussed.
387
Overwinter Survival of Plants in Closed, Insulated Rootzone
Containers
A.M. Shirazi* 1 and J.L. Green2; 1The Morton Arboretum,4100 Illinois Route 53
Lisle, IL 60532; 2Dept. of Horticulture, Oregon State Univ., Ag & Life Sci Bldg.
4017, Corvallis, OR 97331
Growth and overwinter survival of tree–shrub–groundcover plant combinations
in above-grade closed, insulated rootzone containers (CIRCs) are being evaluated
at Morton Arboretum where winter air temperatures below –11.1 °C (12 °F) are
not uncommon. Two-inch-thick extruded polystyrene foam board insulating liner
enclosed the rootzone compartment. Triple expanding foam applied where the top
insulating board surrounds the above-container plant stems completed the seal
preventing heat-moisture transfer and separating the root and shoot environments.
Water reservoirs (6-inch depth) in the base of the containers provide additional
volume heat capacity. Three plants (tree, shrub, groundcover) were installed in
each CIRC. In this preliminary experiment, two 300-gal CIRCs are planted with
Picea glauca ‘Conica’ (Dwarf Alberta Spruce), Pinus mugo pumilio (Dwarf Mugo
Pine), and Potentilla fruiticosa ‘Goldfi nger’. The two 200-gal CIRCs are planted with
Acer ginnala ‘Mondy’ TM (Red Rhapsody Maple), and Hedera helix ‘Bulgaria’ and
‘Silver Dust’. Control plants are in a fi eld nursery. Within the insulated containers,
temperature fl uctuations are less extreme than outside. Temperatures within the
CIRC have not been below –2.22 °C (28 °F) even when exterior temperatures have
hovered at below –11.1 °C (12 °F). Shoot cold hardiness of plants in the closed,
insulated containers and of control plants in the fi eld nursery will be compared.
388
Stem Cold Hardiness, Leaf Heat Tolerance, Growth, and
Performance of Six Japanese M aples (Acer palmatum) in
Northern Illinois
A.M. Shirazi*, The Morton Arboretum ,4100 Illinois Route 53 Lisle, IL 605321293
Six different Japanese Maples (Acer palmatum) cultivars ‘Water Fall’, ‘Burgundy Lace’, ‘Crimson Queen’, ‘Oshio-Beni’, ‘SangoKaKu’, and ‘Bloodgood’ from
Monrovia Nursery were planted in a randomized block design on 4 June 1997 at
the The Morton Arboretum. Leaf heat tolerance was evaluated by measuring ion
leakage of the leaf tissue at 25–60 °C in July, Aug., and Sept. 1997. The LT50 (the
temperature at which 50% of the tissues were injured) of all the cultivars were
higher in July (≈53 °C) and were lower in September (≈47 °C). Water content
of the leaf tissues were higher in July compare to August and September and
were not related to heat tolerance of most cultivars. Stem cold hardiness was
performed by artifi cial freezing tests in Oct., Dec., and Feb. 1997/98. The Lowest
Survival Temperature (LST) for the most hardy to least hardy cultivars in October
and December were: ‘Burgundy Lace’ (–15, –27 °C), ‘Bloodgood’ (–18, –24 °C) ,
‘Oshio-Beni’ (–15, –24 °C), ‘Crimson Queen’ (–15, –18 °C), ‘Water Fall’ (–9, –18
°C) and ‘SangoKaKu’ (–9, –12 °C), respectively. Growth, dormancy development,
spring budbreak and performance of these cultivars will be compared.
HORTSCIENCE, VOL. 33(3), JUNE 1998
389
Membrane Thermostability for Root Tissue of Red and Freeman Maple Cultivars
J.L. Sibley1*, J.M. Ruter2, and D.J. Eakes1; Dept. of 1Horticulture, 101 Funchess
Hall, Auburn University, AL 36849; 2Dept. of Horticulture, Univ. of Georgia, CPES,
Tifton, GA 31793
Six red (Acer rubrum ‘Autumn Flame’, ‘Fairview Flame’, ‘Franksred’, ‘Landsburg’, ‘Northwood’, and ‘October Glory’) and three Freeman (A. x freemanii ‘Armstrong’, ‘Celzam’, and ‘Jeffersred’) maple cultivars originating in different parts of
the United States were grown in containers in 1995 and 1996 prior to laboratory
procedures to determine root cell membrane thermostability. Electrolyte leakage
from excised root tissue exposed for 30 min to temperatures ranging from 20 to 63
°C, was used to assess cellular injury of unsuberized, current season, fi ne roots.
The critical killing temperatures of root tissue of cultivars evaluated ranged from
52.0 ± 0.8 °C to 53.3 ± 0.5 °C, indicating minimal differences in root membrane
thermostability among the selections evaluated. Critical temperatures for cultivars
selected from the northern part of the native range did not differ from cultivars
originating elsewhere. Implications of these differences for container production
will be discussed.
49
ORAL SESSION 9 (Abstr. 390–396)
Fruits—Flowering/Abscission/Thinning
390
Effects of AVG, NAA, Ethephon, and Summer Pruning on Preharvest Drop and Fruit Quality of ‘McIntosh’
E.W. Stover1*, C.B. Watkins2, M.J. Fargione3, and K.A. Iungerman4; 1Indian River
Research & Education Center, Univ. of Florida, Ft. Pierce, FL 34945; 2Dept. of
Fruit & Vegetable Science, Cornell Univ., Ithaca, NY 14853; 3Dept. of Horticultural
Science, Cornell Univ., P.O. Box 727, Highland, NY 12528; 4Cornell Cooperative
Extension, Ballston Spa, NY 12020.
Ethylene production increases dramatically during maturation and ripening
of ‘McIntosh’ apples, frequently resulting in preharvest drop and accelerated fruit
softening. As harvest approaches, commercial growers must balance the need
for color development with minimizing fruit softening and drop. The effects of
plant growth regulators and summer pruning on this balance were evaluated in
this study. Treatments were applied to trees in the Mid-Hudson in 1995 and 1996
and a subset of growth regulator treatments was applied in the Champlain Valley
in 1996. NAA (naphthalene acetic acid) signifi cantly reduced drop on only one
sample date in only one of the three trials. Ethephon (2-chloroethylphosphonic
acid) at 150 ppm plus 10 ppm NAA, accelerated ripening and permitted harvest
before substantial drop occurred, but earlier harvest resulted in smaller fruit size.
AVG (aminoethoxy vinyl glycine) at 124 gram a.i./ha, on otherwise untreated trees,
signifi cantly delayed drop compared to the controls in two of three trials and
resulted in better fruit fi rmness out of storage. Use of ethephon on AVG-treated
trees signifi cantly enhanced red color but also accelerated drop, although drop was
reduced compared to ethephon only treatment. Late summer pruning signifi cantly
accelerated red color development, drop and ripening in both years. Pruning
16 Aug. 1996 signifi cantly accelerated drop compared to pruning 1 Aug. 1996.
Combining AVG application and pruning on 16 Aug. 1996 resulted in improved
color without increasing drop compared to controls.
391
Interaction Between CPPU and NAA on Fruit Thinning and Fruit
Development in Selected Apple Cultivars
Martin J. Bukovac* 1, Jerome Hull, Jr.1, John C. Neilsen1, Michael Schroeder2,
and Georg Noga2; 1Dept. of Horticulture, Michigan State Univ., East Lansing,
MI 48824, and 2Univ. of Hohenheim Research Station, Bavendorf, D-88213
Ravensburg, Germany
NAA is used extensively for fruit thinning of apples to increase fruit size and
to promote return bloom. In some cultivars, even if thinning is achieved, fruit size
at harvest may be less than expected based on crop load. CPPU, N-(2-chloro4-pyridinyl)-N.-phenylurea, has been shown to increase fruit growth in apples,
grapes, and kiwi. We evaluated combinations of NAA and CPPU on thinning, fruit
growth and return bloom in Redchief ‘Delicious’, ‘Elstar’, and ‘Gloster’. CPPU was
HORTSCIENCE, VOL. 33(3), JUNE 1998
applied at 5 mg• L–1 (based on 0 to 10 mg• L–1 response curve) in combination
with 15 mg• L–1 NAA as high-volume sprays at 7 to 10 mm KFD. Yield and fruit
size distribution (on total yield) were used as index of response. In ‘Delicious’,
CPPU (3-year study) increased % large (70 mm+) fruit, but in the presence of
NAA % large fruit was reduced 2 of the 3 years. CPPU did not induce signifi cant
thinning. There were no signifi cant effects on color or soluble solids; fi rmness
was increased slightly and seed number reduced. The L/D ratio was increased
and uneven lobe and carpel development was common. CPPU had no signifi cant
effect on return bloom in presence or absence of NAA, but NAA increased bloom
in both the presence and absence of CPPU. With ‘Elstar’ (2-year study) there was
no signifi cant thinning with either chemical, but CPPU increased mean fruit size
and % large (70–80 mm) fruit over nonthinned, but not signifi cantly greater than
NAA alone. There were no signifi cant differences in fi rmness, color, soluble solids
or seed number. NAA + CPPU did not inhibit fruit growth or cause excessive
uneven carpel development. Frost damage reduced crop load in ‘Gloster’ where
results were similar to ‘Elstar’ except seed number was reduced by the NAA +
CPPU combination.
392
Effect of Seed Number on Preharvest Drop and Fruit Mass of
Three Apple Cultivars
Daniel L. Ward*, Richard P. Marini , and Ross E. Byers; Dept. of Horticulture,
Virginia Tech, Blacksburg, VA 24061
The factors controlling preharvest drop are poorly understood. The number of
viable seeds in apple fruit has been associated with fruits retained following June
drop. Three experiments were conducted to determine the effect of seed number
on time of preharvest drop. In two experiments treatments were imposed to induce
variability in seed numbers. Trees of ‘Redchief Delicious’ were covered with 92%
shade fabric for 0, 1, 2, or 3 days when fruits averaged 13 mm in diameter. In
a second experiment ‘Redchief Delicious’, ‘Smoothee’, and ‘Commander York’
fl owers had 0, 1, 2, 3, 4, or all 5 stigmas excised at early “popcorn” stage and the
remaining stigmas were hand-pollinated. The third experiment investigated drop
of the same three cultivars as affected by the natural variability in seed number.
Fruits were gathered from under the trees daily from 26 Aug. until all the fruits had
fallen from the trees. Fruits were weighed and the number of fi lled, large aborted
and small aborted seeds were counted. Neither total number of seeds, number of
fi lled seeds, total number of aborted seeds, number of large aborted seeds nor
number of small aborted seeds explained any appreciable amount of the variation
in date of drop (R2 < 0.13). Fruit mass was positively related to seed number for
‘Delicious’, but not for ‘Smoothee’ or ‘York’.
393
Effect of Split Applications of GA3 on Flowerbud Density of
Mature Peach Trees
S. Howard* and B.H. Taylor; Dept. of Plant and Soil Science, Southern Illinois
Univ., Carbondale, IL 62901
The effect of divided GA3 applications on fl owerbud density was investigated
using mature ‘Redhaven’ and ‘Sweet Sue’ peach trees treated at 6,12, and 24
g/acre in 1994 and ‘Redhaven’ and ‘Loring’, treated at 12, 24, and 48 g/acre in
1995. Flowerbud densities were found to be reduced, except in the cultivar Sweet
Sue, which had poor vegetative vigor. The reduction averaged 10% for the 48
g/acre, single, and 32% for the split application of the same rate. For both ‘Loring’ and ‘Redhaven’, it was the basal most 10 cm that showed the largest effect
of the split applications, fl owerbud density was 86% (single) vs. 28% of control
(split) for ‘Loring’ and 94% vs. 42% for ‘Redhaven’. For the rest of the shoot the
differences were not as marked, but were larger for the younger, more vigorous
‘Loring’. Vegetative bud densities were found to be increased in all cultivars, with
the split applications showing a larger effect. The increases were most marked
in the distal most 10 cm of the shoots, at the 48 g/acre rate densities were 127%
vs. 195% of control for ‘Loring’ and 159% vs. 233% for ‘Redhaven’. Other growth
characteristics (node and blind node density, shoot length) were also evaluated,
but signifi cant changes were rarely found. Comparing the number of fl ower- and
vegetative buds per node revealed that the GA3 applications were effective on nodes
that had formed 10 to 15 nodes prior to the number of nodes present at spray
application. The effect of split GA3 applications was visible on a larger number of
nodes, showing that split applications were able to affect a larger portion of the
continuously elongating shoot.
513
394
Thinning Peaches by Heat
A. Erez* , R. Korcinski , and Z. Yablowitz; A.R.O. The Volcani Center, Inst. of
Horticulture, P.O.B. 6, Bet-Dagan, 50250 Israel
Flower buds in their last stages prior to opening, open fl owers and small
fruitlets are the most sensitive organs to frost damage. Such effect of low temperature is well-known as it poses an economical hazard in growing stone fruits
in many countries. Heat effect on fl ower buds and fl owers is less known simply
because it is not common at time of bloom in most locations where such species are grown. Many of the low-chill early maturing peaches and nectarines set
very heavily in subtropical climate and require a major input of manual thinning
in order to obtain marketable fruit. As the level of fruitset is usually very high,
thinning is been carried out during full bloom. With increase in costs of manual
labor, this element becomes the critical one in producing such fruits economically.
Up till now, no chemical or physical mean can replace hand-thinning in these
early cultivars effectively. During our work with greenhouse-grown stone fruits
we came across the enormous sensitivity of non-dormant fl ower buds as well
as fl owers to high temperatures. Avoiding excessive heat close to, and during
bloom, became number one concern in the practice of growing stone fruits in
greenhouses. By using container-grown peaches and temperature-controlled
chambers in a phytotron, we were able to quantify the effect of heat on fl ower buds
with the potential of obtaining controlled damage leading to the required level of
thinning. Trials with potted and with orchard grown trees will be reported.
395
Bloom Thinning of Peaches with Gibberellic Acid in the
Southeast
Michael L. Parker* ; Dept. of Horticultural Science, North Carolina State Univ.,
Raleigh, NC 27695
Thinning peach fruit in the spring of the year is one of the most labor- and
capital-intensive operations for peach growers in the southeast. In addition, fruit
size can be negatively affected if peach thinning is delayed. The objective of this
study was to evaluate the application of gibberellic acid (4% GA3, Ralex— Abbott
Labs) in June to reduce peach bloom the following spring. Ralex was applied
in June 1995 and 1996 to ‘Contender’ peaches. Bloom density was evaluated in
Spring 1996 and 1997 from long and short shoots from the higher and lower
portions of the tree’s canopy. Applications in 1995 were to trees with a crop
load while applications in 1996 were to trees without a crop due to a spring
freeze. Bloom densities in 1997 were 300% greater than bloom densities in
1996. The fi ve rates of material evaluated were 0, 59, 79, 99, and 119 g/ha. In
1996, bloom density was signifi cantly reduced with Ralex applications with the
greatest reduction with the 99 and 119 g/ha application rates. However, in 1997
only slight differences were detected between all treatments with no difference
between the control and 79-g/ha rate.
396
Control of Dormancy and Budbreak in Sweet Cherry (Prunus
avium L. ) cv ‘Bing’ with Surfactant + Calcium Ammonium
Nitrate and Hydrogen Cyanamide
K.G. Weis1, S.M. Southwick* 1, J.T. Yeager1, M.E. Rupert1, and W.W. Coates2;
Pomology Dept., Univ. of California, Davis CA 95616; 2Univ. of California
Cooperative Extension, San Benito County, Hollister, CA 95023
Continuing trials (1995–present) advanced budbreak and fl owering with
a surfactant and calcium ammonium nitrate (CAN17), and in 1997, hydrogen
cyanamide (HCN). Chilling in 1996–1997 was marginal in San Joaquin County
(SJ, 830 chill hours, 18 Feb.), and low in San Benito County (SB, 612 chill hours,
21 Feb.). When we used the “45 °F” chilling model, the most effective surfactant
+ nitrate treatment timings for both locations were similar by chill accumulation
(≈72 % to 82% of required chilling for ‘Bing’ = 850–880 chill hours), although
the two locations differed in total chill accumulation and date of effective treatment.
Full bloom (FB) was advanced by 1 week with 4% HCN in SJ, followed by 2%
surfactant + 25% calcium ammonium nitrate applied on 21 Jan. (700 chill hours),
compared to the untreated control. Bloom duration (full bloom to petal fall) was
compressed most by surfactant and CAN17. Bloom in SB was also most advanced
by HCN, followed by 2% surfactant + 25% CAN17 applied on 21 Feb. (612 chill
hours). Fruit set was improved in SB by surfactant and CAN17 in mid-February; set
was too low, however, for real impact. In SJ and SB, HCN advanced fruit maturity
most, followed by surfactant and CAN17 applied 21 Jan.; these fruits were softer.
1
514
We believe that, in order for treatments to be effective in advancing budbreak and
full bloom, some minimum amount of chilling must be accumulated prior to application (perhaps 60% to 75% of chilling requirement). We have also determined
that where chilling is well below minimum requirement, higher rates of CAN (25%)
are necessary to advance bloom. A further advantage of using Armobreak + CAN
is improved N level in buds and bark after treatment (1997).
58
ORAL SESSION 10 (Abstr. 397–401)
Vegetable Crops—Breeding & Genetics
397
The Characterization of Jalapeno ( Capsicum annuum)
Germplasm Based on RAPD Markers and M orphology
Julie M. Villand* and James Nienhuis; Dept. of Horticulture, 1575 Linden Dr.,
Univ. of Wisconsin, Madison, WI 53706
Characterization of germplasm collections is often criticized due to the lack of
relevance given to “unadapted” germplasm by commercial breeders. Within Capsicum , only specifi c pod types are commercially important. Jalapeno peppers are
becoming increasingly important due to the increase in sale of Capsicum -based
food products. Unfortunately, few Jalapeno cultivars are available to growers. A
Capsicum is classifi ed as a Jalapeno based largely on pod shape, rendering a
liberal defi nition of a Jalapeno. Curators and breeders with knowledge of pepper
collections submitted accessions characterized as a Jalapeno. These accessions
were grown at two locations to cull accessions not included in the Jalapeno
market class. Accessions were characterized for traits important to commercial
breeders at both locations. In addition, accessions were characterized using a
set of RAPD markers dispersed throughout the genome in a separate mapping
population. A subset, created from RAPD marker-based estimates of genetic
distance, was created to represent the range of genetic diversity available among
all Jalapeno accessions analyzed. These accessions will add genetic diversity to
a breeding program without changing pod type expectations. The comparison
between Jalapeno accessions and currently grown Jalapeno cultivars was examined based on differences in RAPD marker frequency. In addition, differences in
marker frequencies were used to compare Jalapenos and other C. annuum market
types also characterized with RAPD markers. The characterization of Jalapenos
will assist breeders in their future efforts to diversify their Capsicum breeding
base.
398
AFLP-derived, Codominant M arkers for Locus-specific Applications
James M. Bradeen* and Philipp W. Simon; USDA-ARS and Dept. of Horticulture,
Univ. of Wisconsin, 1575 Linden Drive, Madison, WI 53706 USA
The amplifi ed fragment length polymorphism (AFLP) is a powerful marker,
allowing rapid and simultaneous evaluation of multiple potentially polymorphic
sites. Although well-adapted to linkage mapping and diversity assessment,
AFLPs are primarily dominant in nature. Dominance, relatively high cost, and
technological diffi culty limit use of AFLPs for marker-aided selection and other
locus-specifi c applications. In carrot the Y2 locus conditions carotene accumulation in the root xylem. We identifi ed AFLP fragments linked to the dominant Y2
allele and pursued conversion of those fragments to codominant, PCR-based
forms useful for locus-specifi c applications. The short length of AFLPs (≈60 to
500 bp) precludes development of longer, more specifi c primers as in SCAR
development. Instead, using sequence information from cloned AFLP fragments
for primer design, regions outside of the original fragment were amplifi ed by
inverse PCR or ligation-mediated PCR, cloned, and sequenced. Differences in
sequences associated with Y2 vs. y2 allowed development of simple PCR assays
differentiating those alleles. PCR primers fl anking an insertion associated with
the recessive allele amplifi ed differently sized products for the two Y2 alleles in
one assay. This assay is rapid, technologically simple (requiring no radioactivity
and little advanced training or equipment), reliable, inexpensive, and codominant.
Our PCR assay has a variety of large scale, locus-specifi c applications including
genotyping diverse carrot cultivars and wild and feral populations. Efforts are
underway to improve upon conversion technology and to more extensively test
the techniques we have developed.
HORTSCIENCE, VOL. 33(3), JUNE 1998
399
M olecular Markers Linked to Quantitative Trait Loci for Anthracnose Resistance in Tomato
John R. Stommel * and Yiping Zhang; USDA–ARS, Vegetable Lab., Plant Sciences
Inst., Beltsville, MD 20705 USA
Random amplifi ed polymorphic DNA (RAPD) and amplifi ed fragment length
polymorphism (AFLP) markers linked to quantitative trait loci (QTL) involved
in tomato anthracnose resistance were identifi ed in an F2 population of tomato
(Lycopersicon esculentum ) segregating for anthracnose resistance. The F2 population was developed from the cross of an unadapted and small-fruited, but highly
anthracnose-resistant L. esculentum accession and an adapted, but anthracnosesusceptible processing type tomato. Resistance to anthracnose caused by the
fungal pathogen Colletotrichum coccodes is estimated to be controlled by at least
three genes or chromosomal regions in this cross. One-thousand RAPD random
primers and 64 AFLP primer pairs were screened for polymorphisms between
the parental lines. Primers or primer pairs which differentiated the anthracnose
resistant and susceptible parents were utilized to screen the F2 population for
detection of QTL. Using single-factor analysis of variance, a number of markers,
including six unmapped RAPD markers were identifi ed that were signifi cantly
associated with resistance. Mapping of marker loci and their potential use in
marker assisted breeding will be discussed.
400
Identification of Molecular Markers Linked to Tomato Mottle
Virus Resistance Genes
P.D. Griffi ths* and J.W. Scott; Univ. of Florida, Gulf Coast Research and Education
Center, IFAS, 5007 60th St. E. Bradenton, FL 34203
Tomato mottle virus (ToMoV) is a whitefl y transmitted geminivirus threatening
the Florida fresh-market tomato (Lycopersicon esculentum Mill.) industry. ToMoV
resistance was identifi ed in Lycopersicon chilense accessions LA 1932, LA 1938,
LA 1969, and LA 2779, and introgressed into tomato breeding lines. Inheritance
studies of populations derived from resistant accessions of LA 1932 and LA 1938
suggest that introgressed resistance is largely additive and multigenic. RAPD
polymorphisms were identifi ed using 800 arbitrary primers (decamers), and 88
polymorphisms with good repeatability were identifi ed. Of these, 45 polymorphisms were identifi ed in breeding lines derived from two or more of the four
accessions. Analysis of segregating F2 populations has resulted in association
of RAPD markers with geminivirus resistance genes, and markers have been
identifi ed that are common to different L. chilense resistance sources. Linkage
of several markers to each other and to the self pruning (sp) and ß-carotene (B)
loci on chromosome 6 was also determined.
401
Identification of PCR-based Molecular Markers Linked to B,
A Carotenoid-related Gene in Tomato
Yiping Zhang* and John R. Stommel ; USDA–ARS, Plant Science Inst., Vegetable
Lab., Beltsville, MD 20705 USA
β-carotene is the principal provitamin A caroteniod found in tomato fruits
and makes a signifi cant contribution to the fruits nutritional value. The dominant
B gene conditions high levels of β-carotene in ripe tomato fruits. PCR-based
molecular markers, including random amplifi ed polymorphic DNA (RAPD) and
amplifi ed fragment length polymorphism (AFLP), were used to identify marker
linkage to the B locus. The study was conducted using a near-isogenic line (NIL)
of the cultivar Rutgers isogenic for the B locus and bulk segregant analysis of
an interspecifi c F2 population segregating for the B locus, which was derived
from the cross of Lycopersicon cheesmanii accession LA 317 x L. esculentum
cv. Floradade. Sixty-four AFLP primer pairs and 1018 arbitrary RAPD primers
were screened for polymorphism between the pair of NILs and between the two
bulks. A number of amplifi ed RAPD and AFLP products were identifi ed that were
present in one line or bulk but not the other. Marker linkage with the B locus
was confi rmed by checking individual samples from the F2 and BC populations.
Two RAPD markers were confi rmed tightly linked with the B phenotype using
the interspecifi c F2 population. Similarly, a single AFLP marker was identifi ed
with close linkage to the B phenotype using the NIL F2 population. The markers
identifi ed in this study can be useful in breeding programs with marker assisted
selection and, if very tightly linked, as a starting point to isolate the gene.
HORTSCIENCE, VOL. 33(3), JUNE 1998
59
ORAL SESSION 11 (Abstr. 402–406)
Woody Ornamentals/Landscape/Turf—
Nutrition
402
Rate of Fertilizer Application and Pot-in-Pot Production Increase Growth of Heritage River Birch
John M. Ruter*; Dept. Horticulture, Coastal Plain Experiment Station, Univ. of
Georgia, Tifton GA 31793-0748 USA
A study was conducted to compare the effects of three rates of fertilizer (High
N–Southern Formula, 23N–1.7P–6.6K at 1.3, 1.7, and 2.0 kg N/m 3) and two
production systems [pot-in-pot (PIP) or conventional above-ground (CAG)] on
the growth of Heritage river birch (Betula nigra L. ‘Cully’) in 26 L (#7) containers.
Plants grown PIP had higher shoot dry weight (20% ), root dry weight (31% ), total
biomass (27% ) and root:shoot ratios (12% ). Fertilizer rate increased shoot dry
weights but decreased root:shoot ratios. Rate of fertilizer application infl uenced
foliar Mg, Zn, and Fe while production system had no effect. The foliar P:Zn ratio
increased linearly as rate of fertilizer increased. Soluble salts and NO3-N in the
leachate increased linearly as rate of fertilizer increased at 15 and 60 days after
application (DAA), whereas the response was curvilinear at 120 DAA. When different, nutrient concentrations in the leachate were greater for plants grown CAG.
Fertilizer longevity was greater when the PIP system was used, presumably due
to lower substrate temperatures during the experiment period.
403
Fertilizer Placement Effects on Growing M edium Nutrient
Distribution and Root Growth of Roses
Raul I. Cabrera* and Pedro Perdomo; Dept. of Plant Science, Rutgers Univ., 59
Dudley Road, New Brunswick, NJ 08901
The effect of localized controlled-release fertilizer (CRF) topdressing applications on medium nutrient distribution and root growth was evaluated in containerized roses (20-L pots with peat-based medium). Small samplers were used to
monitor the soil solution nutrient status in four vertically oriented quadrants of the
medium profi le. Average electrical conductivity (EC) and nitrogen concentrations
([N]) found in quadrants beneath the localized CRF supplies were signifi cantly
higher (from 1.6 up to 5.8 times) than in the rest of the quadrants. Nutrient distribution patterns in pots receiving evenly distributed CRF applications were affected
by the placement of irrigation spray-stakes, with higher EC and [N] in quadrants
receiving the least water. After a 12 week experimental period no signifi cant differences in average new root mass and length densities were observed for pots
receiving either localized or evenly distributed CRF applications. Reductions in
root growth parameters were, however, observed in those quadrants farther away
from the irrigation spray-stakes. Results from pots irrigated with a Hoagland
nutrient solution applied with either a 360-degree spray-stakes or localized drippers showed a more prominent effect of water and nutrient localization on root
growth.
404
Lime and Micronutrient Additions to Pine Bark Affect Growth
of Nine Landscape Tree Species
Amy N. Wright*, Jody K. Fanelli, Alex X. Niemiera, J. Roger Harris, and Robert D.
Wright; Dept. of Horticulture, Virginia Tech, Blacksburg, VA 24061-0327
Although the practice of amending a pine bark substrate with lime and micronutrients is common in the nursery industry, the effect of these amendments on the
growth of container-grown landscape trees has not been documented. The objective
of this study was to determine the lime and micronutrient preferences for a wide
range of landscape trees grown in pine bark. Approximately 10 seedlings per pot
for each of nine species of trees were greenhouse-grown in pine bark-fi lled 3-gal
containers. Initial pH of the bark was 4.7. Preplant bark treatments were: unamended
(control), dolomitic lime only (3.57 kg• m–3), micronutrients only (Micromax™,
0.89 kg• m–3), or lime plus micronutrients (previously stated rates). All seedlings
except one per pot were harvested at week 12, and shoot height was determined.
Remaining seedlings were grown until week 19, at which time fi nal shoot height
515
was determined. Bark solutions were extracted (pour-through method) at week
7. Adding micronutrients increased height for all species by week 19. Adding
lime either had no effect on height or supressed height. Micronutrient additions
increased solution concentrations of Ca, Fe, Mn, Cu, and Zn, but in the presence
of lime these increases were diminished. Under the conditions of this experiment,
amending pine bark with micronutrients is essential for maximum height of these
tree species, while a lime amendment is unnecessary.
405
The Effect of Media and Lime Incorporation on Growth of Three
Azaleas
Patricia R. Knight*, John M. Anderson, and Ralph A. Parks; Mississippi State
Univ., P.O. Box 193, Poplarville, MS 39470
The infl uence of media and lime incorporation was investigated for a satsuki
(Rhododendron eriocarpum ‘Pink Gumpo’), a kurume (Rhododendron obtusum
‘Girard’s rose), and a Southern indica azalea (Rhododendron indicum ‘Formosa’).
Uniform liners of each cultivar were planted into 2.8-L containers on 11 Apr. 1997
and placed under shade. Media evaluated included 4 pine bark (pb):0 coconut coir
pith (cc), 3 pb:1 peatmoss, 3 pb:1 cc, 2 pb:2 cc, 1 pb:3 cc, and 0 pb:4 cc. Dolomitic
limestone was incorporated at 0 or 1.2 kg/m 3, and Micromax was incorporated
at 0.6 kg/m3. Data collected included pH and electrical conductivity and growth.
Liming increased pH for 4 pb:0 cc and 4 pb:1 peatmoss treatments compared
to unlimed 4 pb:0 cc and 4 pb:1 peat moss treatments 0 DAT, respectively, but
electrical conductivity measurements were similar. By 240 DAT, pH measurements
for all treatments were similar. Medium composed of 4 pb:0 cc and dolomitic
limestone had higher conductivity compared to all other treatments. Growth of
Formosa was only impacted when plants grown in 3 pb:1 peat moss or 2 pb:2
cc with no dolomitic limestone were compared to plants grown in 4 pb:0 cc and
dolomitic limestone. Addition of dolomitic limestone did not infl uence growth
within any media. Growth of Girard’s rose was higher for plants grown in 1 pb:3
cc regardless of dolomitic limestone amendment, and growth was lower for plants
grown in 4 pb:0 cc with no dolomitic limestone although there were similarities
between other treatments. Incorporation of dolomitic limestone increased growth
when plants were grown in 4 pb:0 cc. Growth of pink gumpo was not infl uenced
by media.
406
Influence of Nitrogen and Potassium on Three Zoysiagrasses
James N. McCrimmon* ; Dept. of Horticulture, Louisiana State Univ., Baton
Rouge, LA 70803-2120
Zoysiagrass has great potential for use in the Gulf Coast states as a turfgrass.
There has been minimal research on the nitrogen (N) and potassium (K) fertility
response of zoysiagrass and the effect on turf color, quality, and nutrient content. The
objective of this study was to evaluate the effects of N and K fertility on zoysiagrass. A
study was conducted on three zoysiagrasses: Zoysia japonica x Z. tenuifolia Willd.
ex Trin. (‘Emerald’); Z. japonica Steud. (‘Meyer’); and Z. matrella. The N and K
treatment combinations consisted of high (H) and low (L) rates of N and K at the
following levels: N levels of 454 and 227 g N/92.9 m2 per month and K levels of
454 and 227 g N/92.9 m2 per month. The treatment combinations were (N and
K): HH, HL, LH, and LL and were applied in two split applications monthly from
July through November. The study was a randomized complete-block design with
three replications. All plots received two applications of a micronutrient fertilizer
(late June and August), were irrigated as needed, and maintained at a height of
3.8 cm. Color, density, texture, uniformity, and quality were determined visually
for each month. Plant tissue samples were collected (September) and analyzed for
macronutrient and micronutrient contents. There were signifi cant differences for
color, density, and quality in the following months: September (color and density);
October (quality); and November (color and quality). There were differences in
leaf texture for all months. There were signifi cant differences for N, magnesium
(Mg), and K contents but there were no differences for any micronutrient. This
study indicated that all three zoysiagrasses provided acceptable color and quality
during the summer and fall, and that N and K rates affected N, K, and Mg contents
in the plant.
516
60
ORAL SESSION 12 (Abstr. 407–411)
Small Fruit & Viticulture—Genetics
407
Intersubgeneric Hybridization between Muscadinia and Euvitis
Species
Jiang Lu* and Lloyd Schell; Center for Viticultural Sciences, Florida A& M Univ.,
Tallahassee, FL 32310, USA
The genus Vitis contains two subgenera: Euvitis Planch. (with the common
name bunch grapes) and Muscadinia Planch. (with the common name muscadine
grapes). The muscadine grapes (V. rotundifolia) are originated and limited to
the southeastern United States and are distinguished from the Euvitis species
morphologically and cytologically. They are characterized by high disease and
pest resistance, and unique muscat fl avor. Bunch grapes, with a total of 60-plus
species, are grown world-wide and can be grouped into the American species, the
Asiatic species and the European grape (V. vinifera) according to their geographical
origination. V. vinifera, which is known for good fruit quality, is the predominant
commercial species. Attempts to produce rotundifolia–vinifera hybrids to combine
good fruit quality and disease resistance of both into F1 hybrids have been made
by grape breeders for many years. Limited success was only reported when the
V. vinifera was used as seed parents and it failed vice versa. This study extended
the crosses between the V. rotundifolia and other Euvitis species originated from
North America and East Asia to see if hybrids could be produced from any of these
crosses. Results indicated that a limited success were achieved in a few crosses
[muscadine (female) x Euvitis species] while failure occurred in most others.
These hybrids may be used as bridges to carry the viticulturally important genes
over to the muscadine grapes from V. vinifera. Microscopic study also revealed
that the diffi culty of hybridization between Muscadinia x Euvitis is due to the
pre-fertilization barriers.
408
Unknown Cultivars of Cold-hardy Grape Can Be Successfully
Identified by Their Simples Sequence Repeat (SSR) Fingerprints
Warren F. Lamboy* 1, Christopher A. Alpha2, and David V. Peterson3; 1USDA-ARS
Plant Genetic Resources Unit and Dept. of Horticultural Sciences, Cornell Univ.,
Geneva, NY 14456;2Laboratory for Stable Isotope Research and Analysis, The
Boyce Thompson Inst. for Plant Science Research, Ithaca, NY 14853; 3Swedish
Hill Vineyard, Romulus, NY 14541.
Simple sequence repeat DNA fragments (SSRs) have been suggested as the
method of choice for DNA fi ngerprinting of grape cultivars. Nevertheless, the
use of SSRs as a practical fi ngerprinting method is not without its pitfalls. For
example, when the polymerase chain reaction is used to amplify SSR sequences,
potentially confusing “stutter” bands may occur, or there may be non-template
directed addition of an “A” to the end of synthesized fragments, or other artifactual
amplifi cation products may be produced. Since we would like to fi ngerprint our
entire cold-hardy grape collection of ≈1300 cultivars, we decided to conduct a
blind test to determine if SSR fi ngerprinting actually would be practical in our
circumstances. First, SSR fi ngerprints were established for 45 commercially
important cool-climate grape cultivars, the known standards. Then, SSR fi ngerprints were produced for 44 “unknown” cultivars grown in the Finger Lakes
Region of New York. The identities of these were known only to the third author.
To independently identity these “unknowns,” their fi ngerprints were compared to
those of the known standards. By this means, 42 of the 44 “unknowns” were immediately correctly identifi ed. The identity of one of the two remaining unknowns
was truly not known to the vineyard owner; it was identifi ed as Cabernet Franc, a
grape commonly grown in the region. The fi nal “unknown” was a plant of Pinot
Blanc, whose fi ngerprint matched those of both the known and the unknown Pinot
Gris and Pinot Noir plants, but did not match that of the Pinot Blanc plants used
as standards. This was surprising, since all three Pinot’s varieties are simply
fruit color mutants of the same genotype. Further investigation revealed that
the known plants of “Pinot Blanc” had been misidentifi ed, and actually were the
cultivar Melon. Thus, identifi cation of the “unknown” Pinot Blanc as Pinot Noir
or Pinot Gris was correct, as were the identifi cations of the 43 other ‘unknowns.”
HORTSCIENCE, VOL. 33(3), JUNE 1998
This study confi rmed that SSR fi ngerprinting is a practical method for identifying
cool-climate grape cultivars.
409
Herbicide Tolerance Of Transgenic ‘Stevens’ Cranberry Plants
Depends on the Test Environment
Eric L. Zeldin*, Rodney A. Serres, and Brent H. McCown; Dept. of Horticulture,
Univ. of Wisconsin, Madison, WI 53706
‘Stevens’ cranberry was genetically engineered to confer tolerance to the
broad spectrum herbicide glufosinate. Initially, herbicide tolerance was verifi ed
by spraying greenhouse plants with the commercial formulation Liberty. Although
one transformant showed signifi cant tolerance, the tolerance level was below that
required to kill goldenrod, a common weed of cranberry beds. This transformant
was propagated and the plants established outdoors in a coldframe, yielding a
growth form more typical of fi eld-grown plants than that of greenhouse-grown
plants. These plants, as well as untransformed cranberry and goldenrod plants,
were sprayed with various levels of the herbicide. The transformed plants were
not killed at glufosinate concentrations up to 1000 ppm, although delayed growth
did occur. Some runner tip injury was observed at 500 ppm as well as widespread
shoot tip death at higher levels. The above-ground parts of goldenrod plants were
killed at 400 ppm with signifi cant injury at 200 ppm. Untransformed cranberry
plants were killed at 300 ppm and had extensive tip death even at 100 ppm.
Transformed cranberry plants with confi rmed “fi eld” tolerance were re-established
in the greenhouse and new vegetative growth was forced. When these plants were
sprayed with glufosinate, signifi cant shoot tip injury was observed at levels as low
as 100 ppm. The degree of herbicide tolerance of transformed cranberry appears
to be modulated by the growth environment, which may affect the expression of
the inserted genes or the physiological sensitivity of the impacted tissues.
410
M olecular Responses of Strawberry Fruit to High Carbon
Dioxide
Jianzhi Jenny Zhang* and Chris Watkins; Dept. of Fruit and Vegetable Science,
Cornell Univ., Ithaca NY 14850 USA
Postharvest strawberry fruit respond benefi cially to 20% CO2 treatment as
indicated by enhanced fruit fi rmness and reduced decay. However, the CO2 treatment also can cause detrimental effects, such as off-fl avor, depending on concentration and length of exposure to CO2, temperature, and cultivar. To characterize
molecular responses of the fruit to high CO2 treatment, mRNA differential display
technique has been used to identify and clone genes differentially expressed in
CO2-treated fruit compared with air-treated fruit at both cold storage (2 °C) and
room (20 °C) temperatures. Forty-eight differentially displayed cDNA bands have
been selected and grouped into four families: CO2-induced at both temperatures,
CO2-induced only at low temperature, CO2 induced at room temperature, and
CO2-repressed ripening cDNAs. These cDNAs are being cloned and sequenced.
Genebank database research indicates that alcohol dehydrogenase, spermidine
binding protein, and rbcl gene are being induced, and ripening-associated genes
such as ACC synthase and ACC oxidase are found to be repressed by the CO2
treatment. Full length of the genes are being obtained by 5’RACE/cDNA library
screening methods. Possible function(s) of the genes in responses of strawberry
fruit to CO2, and in relation to other kinds of stress-induced gene expression, will
be discussed.
411
Response of Dehydrins to Drought, Low Temperature, and
ABA Treatment in Whole Plants and Cell Suspension Cultures
of Blueberry
G.R. Panta*, C.M. Parmentier, and L.J. Rowland; USDA/ARS, Fruit Lab., Beltsville,
MD 20705 USA
Previously, three dehydrins of 65, 60, and 14 kDa were identifi ed as the
predominant proteins present in cold-acclimated blueberry fl oral buds. Levels
were shown to increase with cold acclimation and decrease with deacclimation
and resumption of growth. Recently, a dehydrin cDNA clone was isolated and sequenced, and shown to hybridize to messages likely to encode all three dehydrins.
In the present study, expression of dehydrins was examined in blueberry cultivars
in response to drought and low-temperature treatment and in cell suspension
cultures in response to low temperature and ABA treatment. During 32 days of
drought stress, relative shoot water content dropped to 51% to 90% , depend-
HORTSCIENCE, VOL. 33(3), JUNE 1998
ing upon cultivars. For cold stress experiments, cultivars with different chilling
requirements and levels of cold hardiness were kept at 4 °C for 5 weeks. Cell
suspension cultures were held at 4 °C for up to 2 weeks. For ABA experiment,
ABA concentrations ranging from 10-3 to 10-7 M were used. Dehydrins were
monitored in response to various treatments at RNA and proteins levels using the
cDNA clone and antisera raised against the dehydrins. Interestingly, a previously
uncharacterized 30 kDa dehydrin was found to be the major low temperature and
ABA-responsive protein in cell suspension cultures.
61
ORAL SESSION 13 (Abstr. 412–419)
Herbs/Medicinals
412
Multiple Harvest Yield Response of Microirrigated Herbs to
N and K Rates
A.A. Csizinszky* ; Univ. of Florida, IFAS, Gulf Coast Research and Education
Center, Bradenton, FL 34203
Italian parsley (parsley), Petroselinum crispum; summer savory (savory),
Satureja hortensis; sweet marjoram (marjoram), Origanum majoranna; and thyme,
Thymus vulgaris, were evaluated for their yield potential in multiple harvest during
the fall–winter–spring (Nov.–June) 1995–96 and (Dec.–June) 1996–97. The
herbs were grown with the full-bed polyethylene mulch-micro (trickle) irrigation
system at 1x and 2 x N and K rates (1x = 0.86 N and 0.71 K, kg/ha per day). Phosphorous was applied pre-plant at 21 kg• ha–1 P with both N and K rates. Parsley,
savory, and thyme yields in the fi rst harvest were similar with both N and K rates.
Marjoram yields were higher (4.30 t• ha–1) with the 2x than with the 1x N and K
rate (2.55 t• ha–1) (P < 0.05). For the season, parsley, marjoram, and thyme yields
in 1995–96, and parsley and thyme yields in 1996–97 were higher with the 2x
than with the 1x N and K rate. Savory yields in both years were similar with the
1x or the 2x N and K rate. Residual concentrations of macro- and micronutrients
in the soil at the end of the season were similar with both N and K rates. In the
shoots, macro and micronutrient concentrations for the same herb were similar
with the two N and K rates. Very high concentrations of Cu, Fe, and Zn were found
in the savory shoots at both N and K rates. Zinc concentrations were very high
in parsley shoots.
413
The Effect of Mild Water Deficit on Basil Yield and Quality
Jennifer Warner and Albert H. Markhart, III*; Dept. of Horticultural Science, Univ.
of Minnesota, St. Paul, MN 55108
Secondary compounds, essential oils, and fl avor components of leaf tissue
often increase in response to environmental stress. The objective of this study is
to determine if a simple measure of soil matric potential could be used to generate
mild plant water stress in sweet basil, which would improve the fl avor components
of the foliage. Sweet basil was grown in Universal Soil Mix with adequate water
and fertilization in greenhouses supplied with 18 h of high-pressure sodium
supplemental lighting until the third pair of leaves was fully expanded. Aquaprobe
matric potential sensors were installed in the center of the pot and soil matric
potentials recorded daily. Water was withheld from stressed plants until the soil
water potential reached –4 bars. Treatments consisted of one or two stress cycles.
Plants were harvested 24 h after rewatering and fresh and dry weights determined.
The youngest two fully expanded leaves were placed in zip log bags and used in a
taste test. The two water stress treatments decreased leaf fresh weight by 10% and
16% , respectively, decreased total plant dry weight by 6% and 10% , respectively,
and had moderate effect on fl avor intensity as rated by our taste test panel. The
substantial decrease in yield suggests that –4 bars was too severe a stress to be
used commercially. The Aquaprobe sensor was an easy to use economical way
to monitor soil water and could be useful in regulating watering in a greenhouse
environment.
414
Influence of Planting Stock Clove Size, Nitrogen Rate, and
Planting Method on Elephant Garlic Production
Jeanine M. Davis*; Dept. of Horticultural Science, North Carolina State Univ.,
MHCREC, 2016 Fanning Bridge Rd., Fletcher, NC 28732
517
To produce large elephant garlic ( Allium ampeloprasum L.) bulbs in the
southeastern United States, stock cloves must be planted in the fall. During
extremely cold winters, however, winter survival rates can be very low. A 2-year
study was undertaken to examine practices to increase winter survival rates. Two
clove sizes (≤20 g or >20 g), three nitrogen rates (112, 224, and 336 kg/ha), and
three planting methods (fl at, mulched, and hilled) were tested in a RCB design
with four replications. For all planting methods, cloves were set in a shallow trench
and covered with soil to ground level. This was also the fl at treatment. For the
mulched treatment, 7 cm of straw was spread on top. For the hilled treatment, soil
was mounded 10 to 15 cm high over the ground level. Cloves were planted in early
October and harvested in mid-June. Use of large planting stock cloves increased
winter survival rates during the harsh winter, but had no effect during the mild
winter. Both years, winter survival was reduced with the fl at treatment. Yields of
marketable bulbs were 4 to 5 times higher when >20 g cloves were planted than
when ≤20 g cloves were used. Nitrogen rate and planting method had no effect
on yields. The >20 g cloves also produced larger bulbs than the smaller cloves.
Of the three planting methods, the fl at treatment produced the smallest bulbs.
Bulbs were much larger following the mild winter than the harsh winter.
415
Comparative Study of Various Hypericum perforatum Cultivars
under Organic Cultivation
W. Letchamo* 1, V.S. Krutilina2, and T. Kireeva3; 1Flora Labs. Inc., & Trout Lake
Farm Co., WA 98650 USA; 2Moscow Agr. Academy, Soil Science Dept., Timiriazevskaja Str. 49, Moscow U-550 Russia; 3Edmyrtia State Univ., Dept. of Botany
and Physiology, Ezchevsk, Russia
St. John’s Wort (Hypericum perforatum L.), a perennial from Hypericaceae, is
one of the highly esteemed medicinal plants since ancient times. The tops are used
for its soothing, calming antidepressant effects, wound healing, antispasmodic,
and antiviral effects. Recently it has been found to be a natural substitute for
“PROZAC™”. So far, most of the commercial supply of St. John’s Wort originates
from wild collections. Five different cultivars of Hypericum perforatum originating
from Germany (‘Due-1’, ‘Due2’) Canada (‘Quebec’), United States (‘TLF-1’), and
Russia (‘Russia’) were grown under commercial organic cultivation. H. perforatum
of Canadian origin (Quebec) and ‘TLF-1’ from the United States (Washington
and Oregon) were of a recent selection, while the German (Due-1, Due-2) and
Russian cultivars were selected for higher yield and better concentration of the
active constituents (essential oil, hypericin, and other related fl avonoids). Seeds
obtained from these cultivars were directly sown in the fi eld, using animal manure,
in Trout Lake Farm, Wash. There was a signifi cant difference among the cultivars
in morphology, fl owering period, yield, and content of the essential oil. Cultivars
Due-1, Due-2, and Russia showed an erect growth, with uniform fl owering time
and pattern, indicating the suitability of these cultivars for mechanical harvesting
and better exposure of the fl owers to sunlight. The highest herb yield was obtained
from ‘TLF-1’, while the lowest was obtained from ‘Quebec’. Cultivar TLF-1 came
to fl owering the latest, while ‘Due-1’ was recorded to fl ower earliest and had the
lowest shoot yield. The essential oil content of ‘Due-1’, ‘Due-2’ and ‘Russia’ was
signifi cantly higher than ‘Quebec’ and ‘TLF-1’ cultivars.
416
Variability in Yield, Essential Oil Content and Seed Germination
of Lometium dissectum
W. Letchamo1 and V.S. Krutilina* 2; 1Trout Lake Farm Co. & Flora Laboratories
Inc., 42 Warner Road, WA 98650, USA; 2Moscow Timiriazev Agricultural Academy,
Dept. of Soil Sciences, Timiriazevskaja Str. 49, Moscow U-550 Russia
Lomatium dissectum (Torrey & Gray) Mathias & Constance, a perennial from
the Apiaceae, has been among important traditional medicinal plants of the native
North Americans for thousands of years. Preparations from the tuber are used
to improve the general well-being, immune system, and adaptation. Its formulations with other herbs is used in cosmetics for skin regeneration, and treatment
of psoriasis. L. dissectum is normally collected from the wild for commercial
processing. As the demand for the raw material is increasing, there is a growing
danger of genetic erosion of the wild species. In addition to this, wild collection
does not guarantee regular availability, quality, and exact botanical identity. The
objective of this investigation was, therefore, to study the variability in tuber and
seed yield, essential oil content, and fi nd effective method of increasing seed
germination and develop improved cultivars, suitable for commercial cultivation.
We found signifi cant variations in tuber and seed yield/plant, and essential oil
content in the tubers. The color of the oil varied from pale green to deep green.
518
The intensity and composition of the aroma of the oil obtained from individual
plants was also found to vary signifi cantly. We carried out investigations with
microbial seed pretreatment under laboratory and fi eld conditions, with varying concentrations and length of seed soaking. The microbial (RIBAV™) seed
pretreatment for 20 min, at a concentration of 20% under laboratory conditions
resulted in a 99.2% germination, while control variants had only 18% to 26%
seed germination. Pretreated seeds took signifi cantly less time for germination
compared to the control. Similar results were recorded for seeds sown under fi eld
conditions. Seedlings from pretreated seeds showed vigorous growth and better
fi eld establishment, compared to the control variants.
417
Gamma-linolenic Acid Levels of Native Species of Evening
Primrose (Oenothera)
Sandra A. Balch*, Cynthia B. McKenney, and Dick L. Auld; Dept. of Plant and Soil
Science, Texas Tech Univ., Lubbock, TX 79409-2122
Gamma-linolenic acid (GLA) is an essential fatty acid that serves as a precursor
for prostaglandin biosynthesis in humans. GLA was fi rst extracted from the seed
oils of evening primrose, and currently Oenothera biennis is the major commercial
source of evening primrose oil. In this study, native species of the Onagraceae
family occurring in semiarid regions of Texas were surveyed. Seeds from these
native populations were collected and oil extracted for analyzation of fatty acid
composition. Gamma-linolenic acid levels ranged from less than 1% to 8% and
was species specifi c. GLA levels from fi eld-grown plants from native seed were
compared with GLA levels from corresponding native populations. Two species
of native Oenothera were evaluated for relative levels of GLA over several harvest
dates.
418
Developmental Variations in the Content of Active Substances
and Nutrients in Echinacea purpurea
W. Letchamo* 1 and V.S. Krutilina2; 1Flora Labs. Inc., & Trout Lake Farm Co., 42
Warner Road, Trout Lake WA 98650 USA; 2Moscow Agr. Academy, Soil Science
Dept., Timiriazevskaja Str. 49, Moscow, Russia
Echinace from the Asteracea family has been among the top 10 marketed herbs
in North America and Europe. So far, only a limited amount of Echinace originate
from commercial cultivation. Echinacea purpurea has been commercially cultivated
in the United States since the mid 1970s, in Russia since 1935, while in Europe
since the 1960s. However, there has been no published information in the English
language on methods of cultivation, expected yields, limiting factors, nutrient
requirements, and the optimum plant development stage to obtain maximum yield
and concentration of the biologically active substances for pharmaceutical and
cosmetic processing. The objective of this investigation was, therefore, to study
the general distribution of major nutrients and biologically active substances and
the relationship between the two groups, and the pattern of the accumulation of
cichoric acid, echnacoside, isobutylamides (tetraenes) and essential oil in commercially cultivated Echinacea purpurea. There was a signifi cant variation in the
content of essential oil, cichoric acid, and isobutylamides (tetraenes) in different
organs and stages of the plant development. Similarly, the difference in the distribution of N, P, K, Ca, Mg, and Fe in different organs and developmental stages
is demonstrated. The correlation between the content of the active substances and
nutrients is demonstrated, while recommendations for an optimum harvesting
stage and date are made.
419
Response of Plant Tissue Cultures to Various Light Spectra and
Ultra-high Levels of Carbon Dioxide
Brent Tisserat*; USDA-ARS, National Agricultural Utilization Research Center,
Peoria, IL 61604
Growing plant tissue cultures under specifi c light quality treatments (e.g.,
white, red, blue, yellow, or orange light) has been conducted to study altered
morphogenesis. Characteristic differences in leaf shape, rooting, axillary shooting and fresh weights may be obtained depending on the light quality treatments
employed. However, light quality treatments also results in a reduction of available
light intensity provided to the culture which can be detrimental. Long-term treatments (i.e., 8 weeks) with certain light treatments may result in severe stunting
in growth or even culture death. This situation can be corrected by increasing
the light intensity for each light quality treatment employed or reducing the time
HORTSCIENCE, VOL. 33(3), JUNE 1998
of treatment exposure. As an alternative, this study was conducted to determine
if coupling colored light treatments with enhanced ultra-high CO2 levels (e.g.,
10,000 L• liter–1 CO2) could result in growth rates comparable to that occurring
in white light treatments. The growth results of employing several species (i.e.
lettuce, thyme, citrus) shoot cultures under various light quality treatments with
and without ultra-high CO2 levels are presented. Ultra-high CO2 levels enhanced
culture growth regardless of the light treatment employed. In some cases, cultures
that were given ultra-high CO2 levels with several light treatments exhibited growth
rates that exceeded that obtained from white light treatments. Based on these
results, ultra-high CO2 levels may play a role in testing and obtaining a benefi cial
effect from light quality treatments on plant tissue cultures.
71
ORAL SESSION 14 (Abstr. 420–424)
Floriculture—Molecular Biology
420
Variability of Clonal Selections of Poinsettia ‘Eckespoint
Monet’
Gary J. Wilfret*; Gulf Coast Research & Education Center, IFAS, Univ. of Florida,
5007 60th Street East, Bradenton, FL 34203
The introduction of poinsettia (Euphorbia pulcherrima) cultivar Eckespoint
Monet in 1994 provided a novelty bract color that promised to be a welcome addition to the array of poinsettia colors available. The light tan bracts of ‘Monet’ are
splashed with fl ecks of medium rose, with the fl ecks concentrated on the margins.
In warm growing areas, the bracts’ base color appears faded and the rose fl ecks
are not intense, which delays time to market and reduces consumer acceptance.
Plants with darker rose fl ecks were observed in 1994 and clonal selections were
saved that had a range of very light to very dark rose fl ecks. Further selections
within these clones were made in 1995 based on bract color and consistency. A
cultivar trial in 1996 evaluated 26 of these clones compared to the true ‘Monet’ and
a ‘ Dark Monet’ from the Ecke Ranch. Single plants were grown in 20-cm containers and pruned twice. Data were recorded on plant height and diameter, days to
fi rst bract color, marketable, and anthesis, the percentage of mutant laterals, and
bract color. Plant height and diameter and days to anthesis were not signifi cantly
different among the selections but the clones with darker bracts were marketable
up to 5 days earlier than ‘Monet’. Selections with darkest rose fl ecks occasionally
mutated to solid red but these laterals could be easily rogued in propagation beds
by using the dark red petioles as a selection criterion. These selections can be
too dark when grown in cool climatic areas but are more intense and acceptable
in warm regions of the United States.
421
Changes in Responsiveness to Ethylene at the Molecular Level
during Carnation Petal Development
Sven Verlinden * and William R. Woodson ; Purdue Univ., West Lafayette,
IN 47907
Differences in responsiveness and sensitivity to plant hormones between tissues and in specifi c tissues during development have been observed. Increased
sensitivity to ethylene during development has been demonstrated in fruits and
fl owers. In order to study the molecular changes in responsiveness to ethylene
during fl ower development carnation petals of three developmental stages were
treated with 0.1, 1, 10, 100, pr 1000 ppm of ethylene for 0, 0.5, 1, 3, 6, 9, 15, or
24 h. Northern blot analysis was performed on total RNA extracted from these
treatments. Hybridizations were carried out with the senescence related cDNAs
SR5, SR8, SR12, DCACO1, DCACS1, and DCCP. The respective transcripts
showed distinct patterns of accumulation in response to ethylene. SR5 transcripts,
encoding for a putative β-glucosidase, accumulated signifi cantly faster and at
lower ethylene concentrations than all the other transcripts. DCACS1, an ACC
synthase, on the other hand showed a delay in the accumulation of its mRNA
when compared to the other genes. As the petals develop each mRNA also
showed a unique pattern of increased responsiveness to ethylene. This increase
in responsiveness is expressed as a decrease in the ethylene-time constant. The
ethylene-time concept, similar to degree-days, states that it takes a certain time
for a given ethylene concentration to induce a response, 50% maximum transcript
HORTSCIENCE, VOL. 33(3), JUNE 1998
level in this study. This allows for a quantitative assessment of changes in ethylene
responsiveness during petal development.
422
Biological Control of Bacterial Blight of Geranium with H-Mutant Bacteriophages
Brent K. Harbaugh* 1, Jeffrey B. Jones1, Lee E. Jackson2, Gail Somodi 1, and Joseph
E. Flaherty1; 1Univ. Of Florida, Gulf Coast Research and Education Center, 5007
60th St. East, Bradenton, FL 34203; 2AgriPhi, Inc., 160 North Main, Logan, UT
84321
Bacterial blight, caused by Xanthomonas campestris pv. pelargonii (XCP), is
considered the most serious disease of geraniums ( Pelargonium x hortorum ). A
novel approach that uses bacteriophages (phages, viruses that kill bacteria) for
the biological control of geranium blight will be presented. Phages were once
abandoned as biological control agents due to the emergence of bacterial mutants
resistant to the phages employed. However, our approach utilizes a mixture of three
to eight different phages including host-range mutants (H-mutants). H-mutants
are spontaneously derived from their wild-type parent phages and lyse not only
parent wild-type bacteria, but also phage-resistant mutants originating from parent
bacteria. Two phages specifi c for XCP initially were isolated from soil samples
from Florida and California. These phages produced virulent reactions in six of
30 XCP strains, and lysogenic reactions in 22 strains. After selection of these
phages for increased virulence and additional phages were isolated from MN and
UT, 17 phages were evaluated for sensitivity to 21 XCP strains from around the
world. Four to 14 phages produced virulent reactions in the 21 XCP strains. Five
phages produced virulent reactions in at least 17 XCP strains. A mixture of fi ve
phages tested against the 21 XCP strains produced virulent reactions for all 21
XCP strains. Geraniums in 10-cm pots were inoculated with XCP and placed on
a greenhouse bench in the middle of 5 non-inoculated plants. After 2 weeks of
daily spraying plants with a phage solution (109 pfu phage/ml) or water, there was
a 71% reduction in the number of bacterial lesions on phage-treated plants.
423
Effects of an Autoregulatory Senescence-inhibitor Gene Construct on Nicotiana alata Link and Otto.
Kenneth R. Schroeder* and Dennis P. Stimart; Dept. of Horticulture, Univ. of
Wisconsin, 1575 Linden Dr., Madison, WI 53706
Nicotiana alata Link and Otto. was transformed via Agrobacterium tumefaciens
encoding a senescence-specifi c promoter SAG12 cloned from Arabidopsis thaliana
fused to a Agrobacterium tumefaciens gene encoding isopentenyl transferase
(IPT) that catalyzes cytokinin synthesis. This was considered an autoregulatory
senescence-inhibitor system. In 1996, we reported delayed senescence of intact
fl owers by 2 to 6 d and delayed leaf senescence of transgenic vs. wild-type N.
alata. Further evaluations in 1997 revealed several other interesting effects of
the SAG12-IPT gene construct. Measurement of chlorophyll content of mature
leaves showed higher levels of both chlorophyll a and b in transgenic material
under normal fertilization and truncated fertilization regimes. At 4 to 5 months of
age transgenic plants expressed differences in plant height, branching, and dry
weight. Plant height was reduced by 3 to 13 cm; branch counts increased 2 to
3 fold; and shoot dry weight increased up to 11 g over wild-type N. alata. These
observations indicate the system is not tightly autoregulated and may prove useful
to the fl oriculture industry for producing compact and more fl oriferous plants.
424
The Effect of a pH Gene on the Color of Petunia Flowers
R.J. Griesbach*; Floral and Nursery Plant Research, U.S. National Arboretum,
USDA, ARS, Beltsville, MD 20705
An in vivo system was developed to determine the effects of pH on naturally
occurring, pigment complexes within cells. The in vivo system was based upon a
controlling element inserted into the Ph6 gene. The controlling element mutation
was crossed into a genetically marked Petunia line expressing known fl avonoid
pigments. Flowers expressing the controlling element were variegated with the
mutant background lighter in color than the revertant sectors. In the progeny,
several individuals were found that had sectors that were a different fl ower color
than the background. In these fl owers, the background had a higher pH than
the sectors. An increase in pH less than 0.5 unit changed the color from red to
blue.
519
77
ORAL SESSION 15 (Abstr. 425–430)
Subtropical/Tropical Fruits—Postharvest
425
The Influence of Gibberellic Acid (GA) on Postharvest Pitting
of Citrus
Peter D. Petracek* 1, Huating Dou1, and Ed Stover2; 1Florida Dept. of Citrus, 700
Experiment Station Road, Citrus Research and Education Center, Lake Alfred, FL
33850; 2Univ. of Florida, Research and Education Center, 2199 South Rock Road,
Fort Pierce, FL 34945
Postharvest pitting is a citrus peel disorder that is characterized by the physiological breakdown of oil glands and is caused by high temperature storage waxed
fruit. Pitting can be controlled by low temperature storage (>10 °C) or application of
waxes with high gas permeability. However, refrigeration is costly and often diffi cult
to implement while waxes with higher gas permeabilities have gloss values that
are considered to be insuffi cient for consumer acceptance. Consequently, packers
would like to control or predict pitting incidence prior to postharvest stress. Pitting
incidence within a grove can vary dramatically within a season despite comparable
postharvest handling. Thus, peel susceptibility may be not only variable, but alterable. Peel physiology is readily altered by early-season application of GA, a method
currently used to retard peel maturation. Since the infl uence of GA on postharvest
pitting is not known, we examined the effect of early-season foliar-applications of
GA on peel quality of ‘Fallglo’ tangerines and white grapefruit. Fruit were harvested
throughout the season, washed, coated with shellac-based wax, and stored at 21
°C and 93% RH. GA applied with a silicone surfactant retarded peel maturation as
indicated by greener, fi rmer peels. Pitting incidence was typically less for GA-treated
fruit during the initial days of storage. However, GA suppression of pitting did not
always persist throughout storage. GA did not affect internal levels of O2, CO2,
ethanol, or acetaldehyde or weight loss. While the effectiveness of GA was not
consistent, the results suggest that GA application strategies could be developed
to suppress pitting. Also, GA treatments may help defi ne factors that determine
fruit susceptibility to postharvest pitting.
426
Navel Orange Pitting Stimulated by Waxing and High Storage
Temperature
Huating Dou*, Peter D. Petracek, and Craig Davis; Florida Dept. of Citrus, 700
Experiment Station Road, Citrus Research and Education Center, Lake Alfred,
FL 33850
Navel oranges are reportedly susceptible to postharvest peel disorders, including chilling injury and aging/stem end rind breakdown. These and other physiological disorders are sometimes given the common term “navel rind breakdown.”
California citrus industry reports on recent incidences of navel rind breakdown
suggested that some instances of this disorder were similar to “postharvest pitting,”
a disorder that we have observed in a number of Florida citrus varieties. Thus, we
decided to defi ne the morphology and etiology of pitting of ‘Washington’ navel
orange (Citrus sinensis L.) peel. The disorder was characterized by the collapse of
clusters of oil glands and was stimulated by wax application and high temperature
(≥13 °C) storage. Internal ethanol levels of waxed fruit stored at high temperature
(13 or 21 °C) were signifi cantly higher among fruit that developed pitting than
those that did not. The pitting observed in these studies is comparable to previously observed navel orange disorders that have occurred without known cause.
Navel orange pitting is morphologically and etiologically distinct from chilling
injury and aging/stem end rind breakdown, but is similar to postharvest pitting
of Florida citrus fruit.
427
Postharvest Quality of ‘Valencia’ and Navel Oranges after High
Temperature Forced-air Treatments
B.S. Patil 1* , J.R. Sievert2, M.R. Williamson3, P.M. Winkelman4, and M.L. Arpaia2;
1
Citrus Center, Texas A& M Univ.–Kingsville, Weslaco, TX 78599; 2Dept. of Botany
and Plant Science, Univ. of California, Riverside, CA 92521; 3Dept. of Agricultural
Engineering, Univ. of Hawaii, Honolulu, HI 96822; 4Dept. of Agricultural Engineering, Univ. of Calgary, Calgary, Alberta, Canada
‘Valencia’ and navel orange (C. sinensis L. Osbeck) fruit quality was evaluated
520
following exposure to either a cold treatment (21 days below 2.2 °C) or a hightemperature forced-air (HTFA) treatment (ramped: fruit center end point, 47.2 °C;
and constant: 46 °C for 310 min). These treatments are approved as disinfestation
measures against selected fruit fl ies (APHIS, 1996). Fruits were stored at either
5 or 1 °C (cold treatment) for 14 days followed by 10 days at 11 °C and 7 days
at 20 °C. Fruits were obtained six times during the commercial ‘Valencia’ and
navel orange season (three grower lots/time). Fruits exposed to HTFA (ramped
and constant) treatments had signifi cantly lower appearance ratings, total soluble
solids, titratable acidity as compared to control or cold treated fruits. Cold treated
fruits had signifi cantly higher L* values. Fruits were also presented to an untrained
sensory evaluation panel. Both ramped and constant temperature treated fruits
were rated signifi cantly inferior in taste. Although statistically signifi cant, these
differences were slight. This research demonstrates the potential deleterious quality
attributes of ‘Valencia’ and navel oranges due to HTFA; however, we believe that
cold treatment may be the effi cacious quarantine treatment method for distant
export market. The potential for HTFA treatments for CA citrus, in light of these
results is discussed.
428
Hydrothermic Treatment Effects on Some Ripening Changes
on Mango Fruits (Mangifera indica L) Crillo de Bocado’ during
Storage: I. Physical Parameters
Oswaldo Valor* and Juan E Manzano; Posgrado de Horticultura, Decanato de
Agronomía-UCLA . P.O. Box 815 , Barquisimeto -Lara State - Venezuela , South
America
Mango fruits ‘Criollo de Bocado’ harvested at the mature-green stage were
treated with a hydrothermic treatment of 55 °C for 3 min and stored for 20 days
to temperatures of 10 ± 2, 15 ± 2, and 28 ± 2 °C. A randomized design 2 x 3 x 4
with three replications was used. Physical parameters such as color (L*, a* , b*
), fi rmnness, and fresh weight loss were studied . Results reported that mango
fruits stored at 10.2 and 15.2 °C showed the highest fi rmness values. Skin color
changed very fast during the fi rst storage days, while pulp color required more
time to achieve mature ripe color. Fresh weight loss tended to increase with storage
time and with high storage temperature. The lowest storage temperture retarded
softening in mango fruits and fi rmnness reached the highest values.
429
Hydrothermic Treatment Effects on Some Ripening Changes on
Mango Fruits (Mangifera indica L) ‘Crillo de Bocado’ during
Storage: II. Chemical Parameters
Juan E Manzano* and Oswaldo Valor; Posgrado de Horticultura, Decanato de
Agronomía-UCLA, P.O. Box 815 , Barquisimeto -Lara State - Venezuela, South
America
Mango fruits ‘Criollo de Bocado’ harvested at the mature-green stage were
treated with a hydrothermic treatment of 55 °C for 3 min and stored for 20 days
at temperatures of 10 ± 2 , 15 ± 2 and 28 ± 2 °C . A randomized design 2 x 3 x 4
with three replications was used. Some chemical parameters were analyzed, such
as total soluble solids content (% TSS) , pH , tritatable acidity, and TSS/tritatable
acidity ratio. TSS content increased with storage time at low temperature. The pH
increased measurably with storage temperature, while tritatable acidity values
results had inconsistent data.
430
Purification and Characterization of 5'-Deoxy-5'-methylthioadenosine Nucleoside from Avocado Fruits
Chunlin Xiao* and Mosbah M. Kushad; Dept. of Natural Resources and Environmental Sciences, Univ. of Illinois, Urbana, IL 61801
The polyamine and ethylene biosynthetic pathways utilize methionine as
substrate for their biosynthesis. However, methionine pool in fruits and other
plant tissues is very limited and is not suffi cient to accommodate the amount of
ethylene or polyamines that are synthesized during development and senescence.
To compensate for the insuffi cient amount of methionine, plant tissues have
evolved a mechanism to salvage 5'-deoxy-5'-methylthioadenosine (MTA), a byproduct of polyamine and ethylene biosynthesis, back into methionine. The fi rst
enzyme involved in this salvage pathway is MTA nucleosidase. Purifi cation of MTA
nucleosidase from mature avocado fruits showed that there are two isozymes of
MTA nucleosidase. In this study we will report on the purifi cation of one of the
isozymes, MTA nucleosidase I. Using ammonium sulfate fractionation, DEAE-
HORTSCIENCE, VOL. 33(3), JUNE 1998
Sepharose, Sephadex G-100 gel fi ltration, and hydroxyapatite chromatography,
the isozyme was purifi ed 3712-fold yielding about 11% protein. The isozyme
migrated as a single band of 40 kDa molecular weight on SDS-polyacrylamide gel
electrophoresis. MTA nucleosidase I exhibited an optimum pH of 7.2 and optimum
temperature of 55 °C. The Km value of the isozyme for its substrate MTA is 7.69
µM and the Vmax is 58.82 x 10–6 µmol • min-1. Incubation of MTA nucleosidase I
with analogs of MTA, 2.5 mM ethylthioadenosine and 2.5 mM 5'-S-isobutyl-5'deoxyadenosine, completely blocked its activity. The isozyme activity was also
inhibited by putrescine, spermidine, and spermine.
86
ORAL SESSION 16 (Abstr. 431–435)
Woody Ornamentals/Landscape/Turf—
Crop Production
431
Evaluation of Square Funnel Containers for Container Nursery
Production
Claire M. Brooks* 1, Thomas H. Yeager1, Richard C. Beeson, Jr.1, and Dorota Z.
Haman2; Depts. of 1Environmental Horticulture and 2Agricultural and Biological
Engineering, Univ. of Florida, Gainesville, FL 32611
A series of experiments was conducted to evaluate the infl uence of square
funnel and round containers on overhead irrigation water collection. Square
funnel containers, constructed by attaching a 30.5-cm square plastic extruded
funnel surface to the 15.9-cm opening of a conventional round 3-L container, were
placed edge-to-edge on a white gravel surface. Conventional round containers
were spaced on 30-cm centers. Both container types contained a 2 pine bark: 1
Canadian peat: 1 sand substrate (by volume) in which temperatures were monitored
daily at 1600 HR in the center of substrate. Temperatures during August for funnel and conventional containers averaged 34 and 41 °C, respectively. In another
experiment, both container types received overhead irrigation either without plants
or with small or large (3853 cm2 or 5187 cm2 leaf area, respectively) Viburnum
odoratissimum Ker-Gawl. Square funnel containers without plants collected 4.3
times more water than conventional containers; whereas, with plants 1.3 times
more water was collected by square funnel containers. Volume of water collected
in square funnel and conventional containers with plants was not different due
to plant size. Additional information on NO3- N leaching as infl uenced by water
collection and substrate temperature will be presented.
432
Irrigation Management Practices in Ohio
Cassandra C. Sheaffer* and Mary Ann Rose; Dept. of Horticulture and Crop Science, The Ohio State Univ., Columbus, OH 43210
Expanding urbanization in Ohio has made the availability of quality water an
emerging issue of great importance to the state’s nursery industry. This development necessitates an examination of nurseries’ use and management of water. This
study surveyed 600 Ohio nursery growers with a mail questionnaire to determine
the frequency of irrigation and water-saving techniques across the state. The 21question questionnaire covered topics including water sources, irrigation practices,
water testing and information needs. The mailing list used was the Ohio Dept. of
Agriculture’s licensed nursery operators list. Nonrespondents received a postcard
reminder and a second copy of the survey within 3 months of the initial mailing,
yielding a 45% response rate. Data was analyzed using SPSS software. Responses
indicate approximately 57% of Ohio nurseries used irrigation in the 1997 growing
season. For fi eld production, 64%of nurseries used overhead irrigation for at least
half of their irrigated production; for container production, 91% . Nearly 41% of
respondents using irrigation reported capturing runoff for reuse this past year.
The most common irrigation sources for Ohio nurseries were wells (79% ) and
ponds (62% ). Additional goals for the project include raising awareness of water
management and water quality issues, identify common water quality problems,
and to obtain direction for future research and extension efforts.
HORTSCIENCE, VOL. 33(3), JUNE 1998
433
Effect of Weed Control Methods Upon Soil Physical Properties
and Plant Growth
Paul H. Henry*, She-Kong Chong, and Amy O’Leary; Dept. of Plant, Soil, and
General Agriculture, Southern Illinois Univ., Carbondale, IL 62901
There has been speculation in trade journals that landscape fabrics, while
doing a excellent job of weed control, may have a detrimental effect upon growth
of landscape plants. A study is in progress to investigate the manner in which
applied landscape fabric affects soil aeration, soil temperature, and water infi ltration
rate over a period of 18 months. The experimental design is a split-plot with main
plots specifi ed as composted or non-composted areas. Within each main plot, the
design is a randomized complete-block with four blocks and four treatments per
block (control, bark mulch, landscape fabric, landscape fabric + bark mulch). Each
plot has been planted with herbaceous species so as to allow analysis of treatment
effects upon plant growth. Re-dox potential is recorded weekly as a measure of
soil oxygen status. Infi ltration rate is measured biweekly, and soil temperatures
within plots are monitored on a continuous basis. Preliminary results suggest
that landscape fabrics limit oxygen exchange and that this may adversely affect
plant growth. As the study progresses, an attempt will be made to contrast any
adverse effects of landscape fabric with the obvious benefi ts offered by increased
weed control.
434
Pre-plant Solarization Affects Bedding Plant Quality and Fresh
Weight
Michelle L. Bell * 1, Robert J. McGovern1, and Robert McSorley2; 1Gulf Coast
Research and Education Center, IFAS, Univ. of Florida, Bradenton, FL 342039324; 2Dept. of Entomology and Nematology, Univ. of Florida, Gainesville, FL
32611-0630
A solarization study was initiated in Central West Florida whereby fi eld plots,
comprised of EauGallie fi ne sand known to be infested with Rhizoctonia solani
and phytoparasitic nematodes, were covered with a double layer of 1.0-mil clear,
low-density polyethylene mulch. The split-plot design consisted of 10 plots, fi ve
which were solarized for 6 weeks and fi ve left untreated. Each plot was further
subdivided into four 1.5 x 1.5-m subplots. On 14 Oct. 1997, 16 Impatiens wallerana ‘Accent Burgundy’ were planted to each subplot. Pre- and post-plant drench
treatments included the fungicide, fl udioxonil; two biological control agents; and
an untreated control. Individual plants and whole subplots were rated for stunting,
chlorosis, and incidence of disease from R. solani (stem lesions, crown and shoot
blight) twice weekly. Two months after planting, plant fresh weight by subplot was
measured, plant quality was determined, roots and crowns were plated on selective
media and visually evaluated for disease and root-knot nematode symptoms. Soil
cores were taken prior to solarization, at planting, and at termination of the study
for nematode identifi cation and enumeration. Data presented will be limited to the
combined plant fresh weights of subplots and to plant quality; disease symptoms
were incorporated in quality ratings. Solarized plots had a 250% greater combined
fresh weight than non-solarized plots. The lowest mean quality ratings for any
subplot treatment within the solarized plots was signifi cantly greater than the
highest ratings of plants from any subplot treatment within the non-solarized
treatment.
435
Low-maintenance AlternativeTurfgrass
Mary H. Meyer * ; Minnesota Landscape Arboretum, 3675 Arboretum Drive,
Chanhassen, MN 55317
Thirteen materials and two controls were evaluated for 3 years at two locations
for color, cover, and overall rating as acceptable turf or lawn. 10’ x 16’ plots were
maintained at 2”, 4”, and no mowings; two, one or no fall fertilizations; with no
pesticide or irrigation. Best color ratings were the fi ne fescues; best cover a traditional mix of Kentucky bluegrass, fi ne fescues and perennial ryegrass (Sunnylawn
mix); dryland ecology mix and fl eur de lawn;best overall rating was Sunnylawn
mix, fi ne fescue blend, and Ram I. Materials evaluated included: 378 and 45-3
buffalograss; ‘Alma’ bluegrama;”No Mow” ;’Azay’ sheep fescue; ’Discovery’ hard
fescue;dwarf sheep fescue; fi ne fescue blend; fl eur de lawn; Dryland Ecology Mix;
native grass and forb mix; Flowers and Flowers Elite;Super Short Mix ; creeping
alfalfa; Sunnylawn mix and ‘Ram I’ KBG were used as controls.
521
87
ORAL SESSION 17 (Abstr. 436–443)
Floriculture—Growth Regulators/Nutrition/Irrigation
436
Effects of Plant Growth Retardants and Application Timing after
Shearing on Growth and Flowering of Coreopsis verticillata
‘Moonbeam’
J. Raymond Kessler, Jr.* and Gary J. Keever; 101 Funchess Hall, Auburn University,
AL 36849-5408
Coreopsis verticillata ‘Moonbeam’ is a herbaceous perennial that may grow
too tall in small containers under greenhouse conditions for market acceptance,
and therefore may benefi t from plant growth retardants. Rooted terminal cuttings
produced under short days were given a terminal pinch and transplanted to 10cm pots. Cuttings were sheared to 6 cm above the pot rim 4 weeks later. Growth
retardant treatments consisting of ancymidol drench at 0, 0.125, 0.25, or 0.375 mg
a.i./pot; paclobutrazol drench at 0, 0.125, 0.25, or 0.375 mg a.i./pot; daminozide
spray at 0, 2550, 5100, or 7650 mg• L–1; paclobutrazol spray at 0, 12, 24, 36, 48,
or 60 mg• L–1; or fl urprimidol spray at 0, 25, 50, 75, 100, 150, or 200 mg• L–1
were applied 10 days after shearing. Night-breaking lighting using incandescent
bulbs was started the same day. The highest rate of ancymidol, paclobutrazol
drench, daminozide, and fl urprimidol decreased plant height compared to controls
by 36, 30, 21, and 36% , respectively. Paclobutrazol sprays were not effective. A
market quality rating of four or higher (good, salable) was given to plants treated
with daminozide at 5100 or 7650 mg• L–1 or fl urprimidol at 150 or 200 mg• L–1. A
second experiment was conduced to determine application timing. A daminozide
spray at 0, 2550, 5100, or 7650 mg• L–1 was applied 0, 3, 6, 9, 12, or 15 days
after shearing. Plant height, growth index and lateral shoot length were least and
market quality rating highest when 5100 or 7650 mg• L–1 of daminozide was
applied between 6 and 9 days after shearing.
437
Chemical Growth Retardant Application to Scaevola
Terri Woods Starman* and Millie S. Williams; Dept. of Ornamental Horticulture
and Landscape Design, Inst. of Agriculture, Univ. of Tennessee, Knoxville, TN
37901-1071
Fan fl ower (Scaevola aemula L.) has become a popular specialty bedding and
hanging basket plant in the United States. The genus contains several species from
Australia and the Indo-Pacifi c region and there exists a wide diversity of growth
habits and fl ower colors, including blue, violet, pink and white. Our objective
was to measure the effect of type of growth retardant, method of application,
and chemical concentration on S. aemula ‘New Wonder’, ‘Mini Pink Fan’, ’Purple
Fan’, and ‘Royal Fan’, S. albida ’White Fan’, and S. striata ‘Colonial Fan’. Variables
measured included days to fl ower, plant width, fl ower stem number, fl ower stem
length, and fl ower number per stem. Uniconazole applied as a media drench to
S. aemula ‘New Wonder’ at 1.0 and 2.0 mg• L–1 decreased plant width and fl ower
stem length without affecting time to fl ower or fl ower number. Therefore, number
of fl owers per cm of stem length on S. aemula ‘New Wonder’ was increased, resulting in attractive, compact clusters of fl owers on pendulus stems. Paclobutrazol
drench (4.0 and 8.0 mg• L–1) was also effective. Daminozide spray (5000 mg• L–1)
reduced plant width but fl ower number was reduced. Ancymidol foliar sprays and
media drenches (all rates) had no effect on the parameters measured. Ethephon
(500 and 1000 mg• L–1) reduced plant width, but delayed fl owering and reduced
fl ower number. Uniconazole drenches were benefi cial in improving the quality of
S. aemula. ‘New Wonder’ grown in hanging baskets, but the growth control was
not long-lived. The effect of uniconzole on plant growth varied with Scaevola
species and cultivars.
438
Growth Response and Carbohydrate Status of Gibberellintreated Spectral Filter-grown Chrysanthemum Plants
Anuradha Tatineni *, Sonja L. Maki and Nihal C. Rajapakse; Dept. of Horticulture,
Clemson Univ., Clemson, SC 29634
Interest in the use of non- (or less) chemical methods to reduce the height
of ornamental crops has increased tremendously. Manipulation of greenhouse
522
light quality is one alternative for plant growth regulation. We have shown that
eliminating far-red light from the greenhouse environment with liquid CuSO4
spectral fi lters is effective in reducing the height of a wide range of plants though
plant carbohydrate status is also altered under CuSO4 fi lter. In previous studies,
application of GA3 reversed both the reduction of plant height and carbohydrate
status of CuSO4 spectral fi lter grown plants. It has been proposed that GAs enhance
the activity of the enzyme sucrose phosphate synthase to regulate carbohydrate
levels. In the present study the role of exogenously applied GA19, GA1, and GA3
in overcoming the reduction of plant height and carbohydrate levels was investigated. Chrysanthemum plants were treated weekly for 4 weeks with saturating
doses of GA19, GA1 and GA3 (25 µg) or the growth retardants paclobutrazol
and prohexadione. GA1 was also applied with paclobutrazol and prohexadione
to assess whether response to GAs is altered under CuSO4 fi lter. GA1 and GA3
promoted growth similarly under control or CuSO4 fi lter. GA19 was least effective
in promoting growth under CuSO4 fi lter. In summary, these results suggest that
gibberellin physiology is altered under spectral fi lters with the conversion of GA19
a possible point of regulation. The correlation between the carbohydrate status
and the growth of the plants will be discussed.
439
Irrigation of Geraniums with an Automatic Controlled Water
Table System
J.W. Buxton*, D.L. Ingram, and Wenwei Jia; Dept. of Horticulture and Landscape
Architecture, Univ. of Kentucky, Lexington, KY 40546
Geraniums in 15-cm pots were irrigated automatically for 8 weeks with a
Controlled Water Table (CWT) irrigation system. Plants were irrigated with a
nutrient solution supplied by a capillary mat with one end of the mat suspended
in a trough below the bottom of the pot. The nutrient solution remained at a
constant level in the trough. Nutrient solution removed from the trough was immediately replaced from a larger reservoir. The vertical distance from the surface
of the nutrient solution and the bottom of the pot determined the water/air ratio
and water potential in the growing media. Treatments consisted of placing pots
at 0, 2, 4, and 6 cm above the nutrient solution. Control plants were irrigated as
needed with a trickle irrigation system. Geraniums grown at 0,2 and 4 CWT were
≈25% larger than the control plants and those grown at 6 CWT as measured by
dry weight and leaf area. Roots of plants grown at 0 CWT were concentrated in
the central area of the root ball; whereas roots of plants in other treatments were
located more near the bottom of the pot. Advantages of the CWT system include:
Plant controlled automatic irrigation; no run off; optimum water/air ratio.
440
Growth of Dracaena marginata and Spathiphyllum ‘Petite’
in Spaghnum Peat and Coconut Coir Dust-based Growing
Media
Robert H. Stamps* 1 and Michael R. Evans2; 1CFREC, IFAS, Univ. of Florida, 2807
Binion Road, Apopka, FL 32703-8504; 2Dept. of Horticulture, Iowa State Univ.,
Ames, IA 50011
Dracaena marginata Lam. and Spathiphyllum ‘Petite’ were grown in three
greenhouse growing media made with Philippine coconut (Cocos nucifera L.)
coir dust (CD) or Canadian sphagnum peat (SP). Three soilless media [Cornell,
Hybrid, Univ. of Florida #2 (UF-2)] were prepared using CD or SP and pine bark
(PB), vermiculite (V), and/or perlite (P) in the following ratios (percent by volume):
Cornell = 50 CD or SP:25 V:25 P; Hybrid = 40 CD or SP:30 V:30 PB; UF-2 =
50 CD or SP:50 PB. When most of the plants of each genus were of marketable
size, plant root and top masses and grades were determined as well as plant top
growth indices. For dracaena, there were interactions between medium component
(CD/SP) and medium type for everything except mass and grades of roots. For
Cornell mix, plant top growth index and grades were higher for SP- (SPM) than
the CD-containing medium (CDM). However, masses were not different due to
component. For Hybrid mix, only top mass was affected (CDM 12% > SPM). For
UF-2, top plant index and top and total plant masses were higher for CDM than
SPM by 10, 19 and 15% , respectively. Overall, plant masses were the same for
all three mixes containing CD; however, top plant index and grades were higher
for the Hybrid and UF-2 mixes than for Cornell. Using SP, plants in Cornell and
Hybrid mixes generally outperformed those in UF-2. For spathiphyllum, there
were no interactions and medium component only affected root ratings (CDM >
SPM). Plant top, root and total masses and root ratings were higher for Cornell
and Hybrid than for UF-2.
HORTSCIENCE, VOL. 33(3), JUNE 1998
441
Application of Processed Fiber for Nursery Crop Production
A.M. Shirazi * 2 and L.H. Fuchigami 1; 1Dept. of Horticulture, Oregon State Univ.,
Ag & Science Bldg. # 4017, Corvallis, OR 97331; 2The Morton Arboretum, 4100
Route 53, Lisle, IL 60532
Composted Tillamook Methane-digested dairy manure (processed fi ber) plus
woodwaste from landfi lls at Tillamook, Ore., was compared with Langerwerf,
Calif., processed fi ber amended with woodwaste from Tillamook, a mixture of
peatmoss and pumice, and two commercial mixes from Black Gold Inc., Hubbard,
Ore. Electrical conductivity, water-holding capacity, pH, cation exchange capacity, and mineral contents of Tillamook processed fi ber with a mixture of wood
waste were within the acceptable range for production of some nursery crops.
Tillamook processed fi ber with a mixture of wood waste media were favorable for
the germination and growth of the lettuce and radish cultivars. The performance
for seed germination was comparable to the performance of both Black Gold
media and better than the other media. The growth of marigold ‘Bonanza Yellow’,
petunia ‘Plum Maddness’, and salvia ‘Purple Sizzler’ in Tillamook processed fi ber
wood media, supplemented with weekly feeding of fertilizer , was comparable to
their growth in Black Gold media and better than the other media. The growth of
‘Double Delight’ rose plants in Tillamook processed fi ber wood media was similar
to their performance in Black Gold media.
442
Phosphorus Fertilization in Ebb and Flow Production of Bedding Plants
Erin James* and Marc van Iersel ; Dept. of Horticulture, Georgia Station, Univ. of
Georgia, Griffi n, GA 30223-1797
The quantity and quality of available water in the Southeastern United States
continues to decline as demands on limited resources increase. Growers will soon
be forced to comply with legal limitations on water consumption and limits on
nutrient runoff from their operations. A lack of information on standard growing
practices using alternative irrigation systems such as ebb and fl ow is hindering
their acceptance and implementation. We are currently conducting a series of
experiments to establish basic growing guidelines for the use of ebb and fl ow in
the greenhouse in bedding plant production. In the third of these experiments,
Petunia x hybrida Hort. Vilm.-Andr. ‘Blue Frost’ and Begonia x hiemalis Fotsch.
‘Ambassador Scarlet’ were grown for 5 weeks on ebb and fl ow tables with fertigation
solutions (225 ppm N) containing three different levels of phosphorus (0, 50, and
100 ppm). Three soilless media were also used, which varied in their percentage
content of vermiculite, perlite, pine bark and coconut coir. For both the begonias
and petunias dry mass of the shoot was greatest in plants grown with higher
levels of phosphorus. In comparison to plants grown with 0 ppm phosphorous,
petunias and begonias grown with 50 or 100 ppm P were 44% and 25% greater
in mass, respectively. However, begonias had 38% more fl owers when fertigated
with the higher levels of phosphorous while petunias fl owered earlier with 0 ppm
P fertigation solution. The electrical conductivity of the media did not change
signifi cantly over the course of the growing period, but the pH dropped by an
average of 1 over the same time interval.
443
Nitrogen Demand of Cut Chrysanthemums in Relation to Shoot
Height and Planting Date
Siegfried Zerche*; Inst. for Vegetable and Ornamental Crops, Großbeeren/Erfurt
e.V. Kühnhäuser Straße 101, D-99189 Erfurt-Kühnhausen, Germany
Refi ned nutrient delivery systems are important for environmentally friendly
production of cut fl owers in both soil and hydroponic culture. They have to be
closely orientated at the actual nutrient demand. To solve current problems, express analysis and nutrient uptake models have been developed in horticulture.
However, the necessity of relatively laborious analysis or estimation of model input
parameters have prevented their commercial use up to now. For this reason, we
studied relationships between easily determinable parameters of plant biomass
structure as shoot height, plant density and dry matter production as well as amount
of nitrogen removal of hydroponically grown year-round cut chrysanthemums. In
four experiments (planting dates 5.11.91; 25.3.92; 4.1.93; 1.7.93) with cultivar
‘Puma white’ and a fi xed plant density of 64 m 2, shoots were harvested every 14
days from planting until fl owering, with dry matter, internal N concentration and
shoot height being measured. For each planting date, N uptake (y) was closely
(r2 = 0.94; 0.93; 0.84; 0.93, respectively) related to shoot height (x) at the time
HORTSCIENCE, VOL. 33(3), JUNE 1998
of cutting and could be characterized by the equation y = a * x b . In the soilless
cultivation system, dry matter concentrations of N remained constant over the
whole growing period, indicating non-limiting nitrogen supply. In agreement with
constant internal N concentrations, N uptake was linearly related (r2 = 0.94 to 0.99)
to dry matter accumulation. It is concluded that shoot height is a useful parameter
to include in a simple model of N uptake. However, in consideration of fl uctuating
greenhouse climate conditions needs more sophisticated approaches including
processes such as water uptake and photosynthetically active radiation.
88
ORAL SESSION 18 (Abstr. 444–451)
Vegetable Crops—Culture & Management
(Sustainable Agriculture)
444
Impact of Narrow Row Production on Yield Recovery, Nitrogen
Use Efficiency, and Weed Competition in Sweet Corn
Vincent A. Fritz*, Carl J. Rosen, and Roger L. Becker; Depts. of Horticultural
Science, Soil Water and Climate, and Agronomy and Plant Genetics, Univ. of
Minnesota, St. Paul, MN 55108
The processing industry is beginning to adopt narrow row confi gurations
for sweet corn production thinking that plants spaced more equidistant will
compete less with each other and weeds, improving yield potential and production effi ciency. However, empirical knowledge relating to whether these proposed
benefi ts change with hybrid, N fertility, and planting date is lacking. Narrow row
(56 cm apart) sweet corn production was evaluated for improved production effi ciency over the “traditional” row confi guration (76 cm apart) at identical plant
populations (60,000/ha). Yield from seed planted in narrow rows on 1 May was
signifi cantly higher than traditional row confi guration. Increasing N fertilizer rate
(0, 68, 136 kg N/ha) also yielded a positive linear response in yield across the
three hybrids. As planting date progressed later into the season (27 May and 19
June), narrow row confi guration benefi ts observed earlier began to diminish.
Although increased N fertilizer rates continued to show a positive yield response
across all planting dates, the degree of the slope decreased as planting date was
progressively delayed suggesting a greater rate of N mineralization from the
soil. Plant leaf samples were collected from each plot at silking for N analysis
and determination of N use effi ciency. Degree of canopy closure was dependent
on plant architecture of the hybrid and N fertilizer rate; and may be related to
postemergence weed competition and yield potential. The decision to convert
to narrow row production would require a signifi cant capital investment in new
equipment. An economic assessment of the equipment required in addition to
more detailed information on yield response to the narrow row confi guration will
help the processor make an informed choice when considering conversion.
445
Evaluation of Tillage Methods and Cover Crops for Sweetpotato
Production
Lewis W. Jett*; Louisiana State Univ. Sweet Potato Research Station, Chase LA
71324-0120
The marketable yield of the sweetpotato [ Ipomoea batatas (L.) Lam.] can
be limited by environmental variation. Cover crops may ameliorate water and
temperature stress encountered during the growing season while reducing soil
erosion and weed competition. The objective of this research was to investigate
the commercial production of sweetpotatoes with cover crops in a conventional
or conservation tillage system. Rye, ryegrass, wheat, and triticale were broadcastseeded in Fall 1995 and 1996. Three weeks before transplanting, the cover crops
were plowed-in or retained as an in situ mulch. Uniform slips of ‘Beauregard’
sweetpotato were transplanted in May and June of each year, and standard cultural
practices (with the exception of cultivation) were performed. In 1996 and 1997,
conservation tillage increased marketable yield of sweetpotato 15% with a noticeable improvement in quality. Ryegrass produced the largest quantity of biomass
and was effective in reducing soil temperature during storage root initiation and
development. Conservation tillage resulted in a signifi cantly higher root set relative
to the control. Conservation tillage seems to have advantages as an alternative
tillage method for sweetpotato production.
523
446
Swine Effluent for Tomato in a Plasticulture Production System
Kent Cushman* and Thomas Horgan; North Mississippi Research and Extension
Center, Verona, MS 38879
Tomato was grown in Fall 1997 with swine effl uent or commercial soluble
fertilizer in a plasticulture production system. Four cultivars, ‘Mountain Delight’,
‘Celebrity’, ‘Equinox’, and ‘Sunbeam’, were transplanted to raised beds with plastic
mulch and drip irrigation. Preplant fertilizer was not applied. Effl uent from the
Wiley L. Bean Swine Demonstration Unit’s secondary lagoon was fi ltered through
in-line screen fi lters and applied directly to the plants through the irrigation system.
Toward the end of each application, sodium hypochlorite was injected in the line to
achieve a free chlorine concentration of ≈1% . Clogging of fi lters or drip emitters
did not occur. Control plants received 100 ppm N from soluble fertilizer injected
in irrigation lines supplied by a municipal water source. Number and weight of
tomatoes from plants receiving swine effl uent were equal to that of plants receiving
soluble fertilizer. No differences in fruit quality were evident between treatments.
Plant dry weight was also equal for three out of four cultivars. No differences in
soil characteristics were detected between treatments after the study. Chemical
analysis of the effl uent showed a pH of 7.8 and nutrient concentrations of ≈110
ppm NH4-N, 57 ppm P2O5, 150 ppm K2O, and trace amounts of Cu and Zn.
Though no differences in yield were detected in this study, the effl uent’s high pH
and high NH4-N content need to be managed more closely for commercial tomato
production.
447
Effect of Compost Applications on the Yield of Several Vegetables in Long-term Organic Farming Experiments Conducted
in the Tropics
H.R. Valenzuela* and C. Crosby; Dept. of Horticulture, Univ. of Hawaii at Manoa,
Honolulu, HI 96822-2279
Experiments conducted over 5 years evaluated the effect of compost applications on the yield of several vegetable crops grown under organic farming
conditions in the tropics. The yield of organically grown lettuce, basil, Filipino
spinach (Corchorus olitorius L.), and zucchini after application of 20 MT compost/ha per crop was compared to yields obtained with standard synthetic fertilizer
applications (150 kg N/ha per crop), and with a combination of several compost
: synthetic fertilizer ratios. Treatments consisted of 10 by 1.30-meter raised beds
replicated four times. Data collected included soil nutrient analysis prior to
planting and after the last harvest, tissue analysis of macro- and micronutrients,
canopy dimensions, and yields. The tissue nutrient levels collected from crops
receiving composts alone were at or above those levels recommended to achieve
commercially acceptable yields. Yields of plants receiving composts alone were
comparable to those obtained by plants receiving synthetic fertilizer applications.
However, the greatest yields were obtained with 20 MT• ha–1 of compost plus
supplemental synthetic N applications, depending on the length of the harvesting period. After 5 years cumulative yields ranged from 110 to 124 MT• ha–1 for
vegetables receiving compost plus supplemental N, compared to 75 for controls,
and to about 100 MT• ha–1 for treatments receiving either synthetic N or compost
applications alone.
448
Effect of Poultry Compost on Productivity and Quality of
Beets
Anusuya Rangarajan* 1, Lydia Stivers2, and Steve Reiners3; 1Dept. of Fruit and
Vegetable Science, Cornell Univ., Ithaca, NY 14853; 2Cornell Cooperative Extension, 3Dept. of Horticulture, Cornell Univ., Geneva, NY 14456
One characteristic of compost that might provide greater incentive for use
by vegetable growers is suppression of soil-borne diseases in crops grown on
compost-amended soils. The mode of action of low rates of compost on vegetable
growth may include stimulation of microbial activity for suppression of soil-borne
diseases, enhanced plant resistance, and improved nutrient availability. Preliminary
research on beets demonstrated that higher stands and decreased loss to root rot
diseases in poultry compost-amended plots contributed to marketable yields which
were twice that of the control plots. This presentation will summarize research
results from studies to determine if compost reduced disease severity by changing in soil microbial activity or if these products primarily improved plant growth
as a result of increased nutrient availability. Three fi eld experiments explored
524
impact of two commercially available poultry compost products (2 to 5 T/A) and
two rates of chemical fertilizer, on growth and disease incidence on beets. Soil
microbial activity was estimated using an enzyme assay, and soil nitrate-N and
ammonium-N concentrations were also measured, three times over the season.
Results indicated that these composts act primarily through a nutrient affect to
enhance beet yield. Neither compost affected microbial activity in the top 8 inches
of soil. Both products had signifi cant, opposite effects on available soil nitrogen.
One product signifi cantly increased the amount of available soil nitrogen over the
season and beet yields. The different methods of production of the two poultry
composts tested in this research had signifi cant implications for potential use in
either greenhouse or fi eld systems. The effects of these composts on crop fertility
and composition will be discussed.
449
Tomato Growth and Yield Response to Cover Crop and Fertilizer Nitrogen
Wayne F. Whitehead* and Bharat P. Singh; Agricultural Research Station, Fort
Valley State Univ., Fort Valley, GA 31030-3298
The goal of this study was to evaluate how tomato yield, vegetative dry matter,
leaf area index (LAI), and photosynthesis (Pn) responded to winter cover crop and
recommended fertilizer N rates. The following winter/spring fertility treatments
were applied using randomized complete block design with four replications: 1)
0 N winter /0 N spring, 2) 0 N winter/90 kg• ha–1 N spring, 3) 0 N winter/180
kg• ha–1 N spring, 4) 0 N winter + abruzi rye/0 N spring, 5) 0 N winter + hairy
vetch/0 N spring, and 6) 0 N winter + crimson clover/0 N spring. In Spring 1997,
‘Mountain Pride’ tomatoes were transplanted in all plots. Whole plant dry matter,
LAI and Pn were measured at fl owering, fruiting and prior to senescence, while
seasonal yield was compiled over 6 weeks. Tomatoes preceded by Vetch produced
highest plant dry matter (243.0 g/plant) prior to senescence, highest LAI (3.07)
at fruiting and highest Pn (8.98 µmol CO2/m2 per s) during fl owering. Total yield
were highest (60.9 Mg• ha–1) at 180 kg• ha–1 N and lowest (35.3 Mg• ha–1) in
control. Supplemental N from legume and grain cover crops affected plant dry
weight, LAI, Pn, and yield comparable to those receiving synthetic N. Results of
this study indicate that cover crop treatments were as effective as N fertilizer in
supporting tomato yield, vegetative growth, LAI, and photosynthesis.
450
Evaluation of Summer Cover Crops for Vegetable Production
in South Florida
Herbert Bryan* and Yuncong Li ; Tropical Research and Education Center, Univ.
of Florida, 19805 SW 280 Street, Homestead, FL 33031
Cover crops are used for weed control and to retain nutrients during the heavy
summer rains and have become an integral part of vegetable production practices
in south Florida. Moreover the use of cover crops will continue to increase as
farmers seek to improve soil quality and reduce chemical inputs. A wide variety
of plants are used as cover crops in south Florida. Obviously legumes contribute
more nitrogen by fi xing N compared to nonlegumes such as sorghum–Sudan
grass, which is a common cover crop in this area. We have evaluated 10 cover
crops, and fi ve of them are legumes. The sunn hemp, Crotalaria juncea L, stands
out from other tested cover crops. Sunn hemp produced 8960 kg dry weight per
ha and fi xed up to 336 kg N/ha. We have strongly recommended sunn hemp
as a cover crop for vegetables and tropical fruits in south Florida. A large fi eld
demonstration will be conducted in a grower’s fi eld in the summer rainy season
of 1998.
451
Living Mulch Strips as Habitats for Beneficial Insects in the
Production of Cucurbits
Jean-Pierre Amirault* and John S. Caldwell ; Dept. of Horticulture, Virginia
Polytechnic Inst. & State Univ., Blacksburg, VA 24061
Effects of cover crops managed as living mulch habitats on populations of
cucumber beetles Acalymma vittatum Fabricius and Diabrotica undecimpunctata
howardi (Barber) (Coleoptera: Chrysomelidae) and arthropod predators were assessed at the Virginia Tech Kentland experimental farm and a local farmer’s fi eld
in 1994 and 1995. In 1994, spring-planted strips of two living mulch mixtures,
oats/vetch (Arvena sativa/Vicia atropurpurea) and oats/white clover (A. sativa/
Trifoliium repens), and straw mulch between rows of cucumber cv. Pointsett and
an heirloom pumpkin cultivar were compared to non-mulched plots in a random-
HORTSCIENCE, VOL. 33(3), JUNE 1998
ized complete-block design. Counts of the predator Pennsylvania leatherwing,
Chauliognathus pennsylvanicus (Coleoptera: Cantharidae) on yellow sticky traps
were 2.7 to 10 times greater in living mulch treatments, compared to plots with
cucurbits alone or with straw mulch (P = 0.0040 in 1994 and P = 0.0085 in 1995).
In 1995, counts of Harpalus spp. (Coleoptera: Carabidae) in buckwheat Fagopyrum
esculentum (Moench) living mulch treatments were twice those in the plots with
the crop alone, and cucumber beetle counts were 60% lower (P = 0.0165) in the
mulched habitats. Crop yields were depressed in living mulch treatments, but a
twin-row planting system (5:3 crop: habitat ratio) with buckwheat gave yields 4.8
times greater than the single-row system (3:5 crop: habitat ratio) initially used in
1994. These yields were 72% of yields in the control using conventional practices.
These results indicate that strip cropping has the potential to maintain cucumber
beetle populations below threshold levels, but that more management research
is needed to obtain economically viable yields.
99
ORAL SESSION 19 (Abstr. 452–458)
Vegetable Crops—Crop Protection/Pest
Management
452
Yield of ‘Superior’ Potatoes following Nematode-suppressive
Cover Crops
Alan W. McKeown* 1 and J.W. Potter2; 1Univ. of Guelph, Horticultural Research
Inst. of Ontario, P.O. Box 587, Simcoe, Ontario N2Y 4N5 Canada; 2Agriculture
and Agri-Food Canada
‘Superior’, the common early potato in Ontario, has developed early dying and
low yield problems along the Lake Erie Counties. A series of experiments were
planted in 1993 to 1996 to evaluate nematode-suppressive cover crops as a means
of soil management, improving yield of potatoes, and reduction of plant parasitic
nematodes. Sorghum NK557 as a nematode host, reported suppressive species
Sordan 79, Trudan 8 sorghum-sudan hybrids, Domo and Cutlass mustard, Forge
canola, and ‘Norlee’ fl ax were compared to either Telone IIB or Vorlex-Cp ( 225
L/ha) fumigants applied with a deep shank applicator to 30 cm. Fertility and pest
management practices followed Ontario recommendations. Northern root lesion
nematodes, Pratylenchus pentrans Cobb, populations were monitored prior to
planting potatoes, during the season, and after harvest. Fumigation resulted in the
highest total yields in all 3 years and marketable yield in 1994 and 1995. There
was no difference in marketable yield in 1996. Yield was similar among cover
crops treatments. Suppressive crops, while useful in soil management, were not
as effective as fumigants.
453
Metam Sodium Combined with Chloropicrin as an Alternative
to Methyl Bromide Fumigation for Tomato
S.J. Locascio*1 and D.W. Dickson2; Depts. of 1Horticultural Sciences and 2Entomology and Nematology, Univ. of Florida, Gainesville, FL 32611
In past work, dichloropropene + 17% Pic (1,3-D + Pic) at 327 L• ha–1 plus
pebulate provided good control of nematode, soil fungi, and nutsedge in mulched
tomato (Lycopersicon esculentum Mill.) and is considered the best alternative for
methyl bromide (MBr) + chloropicrin (Pic), which is scheduled for phase-out in
the United States by Jan. 2001. Metam-sodium did not provide acceptable pest
control. In the present study, metam-Na (295 L• ha–1 combined with Pic (168
kg• ha–1) + 4.5 kg• ha–1 pebulate, and 1,3-D + 35% Pic at 168 and 225 L• ha–1 +
pebulate were compared to MBr-Pic (98-2% at 345 kg• ha–1 and 67-33% at 505
kg• ha–1). Fumigants were injected into the bed except metam-Na and pebulate
were surface-applied and incorporated and drip tubing and mulch were applied.
Marketable yields with MBr-Pic, 225 L• ha–1 1,3-D + Pic, and metam-Na + Pic
were higher than with the check. Yields with metam-Na alone or with additional
water before transplanting were similar to the check. Nutsedge was controlled with
MBr-Pic and all treatments with pebulate. Nematode root-gall ratings were high
on tomato grown without fumigants (8.9 rating on a scale of 0 to 10 with 0 = no
galling), low with MBr-Pic (0.33), and intermediate with all other treatments (2.2 to
5.5) except with 168 L• ha–1 1-3-D + Pic (8.3). This study indicates that metam-Na
+ Pic + pebulate also is a possible alternative to MBr- Pic for tomato.
HORTSCIENCE, VOL. 33(3), JUNE 1998
454
Use of the Biological Compound Ret-flo Px357 to Increase
Yield and Improve Fruit Quality of Tomato and Banana Grown
in a Greenhouse
A. Ait-Oubahou* and M. El-Otmani ; Institut Agronomique et Vétérinaire Hassan
II, Complexe Horticole d’Agadir BP. 18/S, Agadir 80.001, Morocco
In the past few years, there has been a high demand for the use of new generations
of biological products in modern agriculture. Several of these products are friendly to
the environment and guarantee good yield and quality of many horticultural products.
Pesticide residues resulting from heavy applications of a wide range of chemicals
to control various pests is becoming a serious problem for exports, as well as for
local consumption, of many products. This study was initiated to examine the effect of Ret-fl o Px-357 a biological compound from EIBOL Co., Spain, developed to
induce resistance to nematode infestation on several plants. ‘Daniella’ tomato and
‘Grande naine’ banana grown in plastic greenhouses were used to evaluate these
effects. Two ground applications of Px357 at the rate of 20 L• ha–1 were used at
4-month intervals in Oct. 1996 and Feb. 1997. These treatments have stimulated
root formation, stem diameter, and plant height. In tomato plants, the number of
fl owers and fruits per cluster was greater in treated than in non-treated plants.
After harvesting eight clusters from the tomatoes, the number, size, individual
fruit weight and total production of fruits from treated plants were greater than for
the control plants. Similar results were observed in banana plants, which showed
larger pseudo-stem and heavier fruit bunches at harvest. Variation in nematode
population as well as plant nutrition during plant growth will be discussed, and
results related to fruit quality will be presented and commented upon.
455
Assessment of Chemical Induction of Acquired Resistance to
Pythium Fruit Rot in Field-grown Cucumber
Priscilla M. Hockin* and Irvin E. Widders; Dept. of Horticulture, Michigan State
Univ., East Lansing, MI 48824
Systemic acquired resistance (SAR) is a physiological defense response
in plants conferring broad spectrum resistance to pathogens. SAR is inducible
through infection by necrotizing pathogens or chemical inducers and involves
the systemic activation of defense related genes. The objectives of this study
were to evaluate resistance expression to Pythium soft rot in fruit of cucumber in response to foliar applications of 2,6-dichloro isonicotinic acid (INA),
benzo(1,2,3)thiadiazole-7-carbothioc acid S-methyl ester (CGA 245704), or
beta-amino-butyric acid (bABA). Excised leaves from three cucumber cultivars,
Vlaspik, Sumpter and SMR 58, exhibited a resistance response to foliar applications of INA (50 ppm) and CGA 245704 (25 ppm) when challenge inoculated with
Colletotrichum lagenarium. However, the reduction in lesion incidence by INA was
99% in Vlaspik and only 11% and 18% in Sumpter and SMR 58, respectively.
bABA did not enhance resistance in vegetative tissues. Multiple foliar applications
of INA and CGA 245704 prior to fruit set were found to be more effective than
a single application. Harvested cucumber fruit, 3.0 to 5.0 cm in diameter, were
wounded and challenge inoculated with Pythium sp.; no statistically signifi cant
differences in infection were observed between controls and fruit from chemically
treated plots. In Vlaspik, however, INA and BTH did reduce the rot infection rate in
fruit when foliar applications were made early in plant ontogeny, at the four-leaf
stage. In addition, larger more mature fruit (4-5 cm diameter) exhibited slower
lesion growth than less developed fruit (>3 cm). It is unclear if these differences
were attributable to changes in physiological or anatomical factors. These fi ndings
indicate that the level of physiological resistance achievable through chemical
induction in cucumber is a function of the specifi c pathogen and the plant organ
being infected, i.e., leaves or fruit.
456
Two-cluster Tomatoes Require Less Pesticide per 1000 kg of
Salable Fruit than Eight-cluster Tomatoes
B.A. Kratky*, Richard Cupples, and Gaillane Maehira; Univ. of Hawaii CTAHR,
Beaumont Agricultural Research Center, 461 W. Lanikaula St., Hilo, HI 96720
Tomatoes were grown in plastic-covered rainshelters at a cool, moist 1300m elevation. Plants were placed in aluminum beverage cans fi lled with growing
medium and immersed in a a 0.6-m wide tank containing 5 cm of non-circulating nutrient solution. Tomatoes were pruned such that only two, four, or eight
clusters were harvested. Two-cluster ‘Vendor’ tomatoes yielded 49% and 73%
more salable tomatoes per day than eight-cluster tomatoes in two experiments,
525
respectively. Two-cluster ‘Lenor’ tomatoes yielded 47% and 92% more salable
tomatoes per day than eight-cluster tomatoes in two experiments, respectively.
Two-cluster tomatoes required 347 g of pesticide to produce 1000 kg of salable
fruit compared to 708 g pesticide for eight-cluster tomatoes in the fi rst experiment. Fungal pressure increased in the second tomato experiment such that the
two-cluster tomatoes required 1112 g of pesticide to produce 1000 kg of salable
fruit, whereas the eight-cluster tomatoes required 2075 g of pesticide. Most of
the pesticides applied were fungicides.
457
The Effects of American Black Nightshade (Solanum americanum) Interference in Bell Pepper (Capsicum annuum)
Debbie L. Roos* 1, W.M. Stall 1, D.G. Shilling2, S.R. Kostewicz1, and M.E. Swisher3;
1
Horticultural Sciences Dept., 2Agronomy Dept., 3Dept. of Family, Youth, and
Consumer Sciences, Univ. of Florida, Gainesville, FL 32611
Information about the effects of weed interference on crop yields can help
growers make appropriate management decisions. Such information is particularly useful in horticultural crops such as pepper, where the number of registered
herbicides is limited. Bell pepper is the second most-valuable vegetable crop
grown in Florida, and American black nightshade (Solanum americanum) is one
of the primary weeds in Florida pepper production. Additive experiments were
conducted in 1997 in Florida to determine the effects of American black nightshade interference on bell pepper yield. One additive experiment was conducted
in Gainesville, Fla., in the spring and two additive studies were conducted in the
fall in Gainesville and Live Oak, Fla. A randomized complete-block design with
four replications was used. Double rows of ‘Capistrano’ peppers were transplanted
into white polyethylene mulched beds with 1.22-m centers. Peppers were planted
at an in-row spacing of 0.3 m. Weeds were propagated in the greenhouse in
polystyrene fl ats and transplanted at the two-leaf stage simultaneously with
the peppers. Overhead irrigation was used and monitored with tensiometers.
Fertilizers and pesticides were applied based on Extension recommendations.
Weed densities in the spring trial were 0, 2, 4, 8, 12, 16, and 20 plants/m2. Weed
densities of 0, 0.5, 1, 1.5, 2, 3, 4, and 8 plants/m2 were planted in the fall. Crop
and weed heights were recorded weekly, and fruit number, grade, and weights
were recorded at each harvest. Crop and weed dry weights were obtained at fi nal
harvest. Data were subjected to analysis of variance and regression. There was
an interaction by season, but there was not an interaction by location for the fall
season; therefore, the fall data were combined. In all trials, S. americanum had a
signifi cant effect of bell pepper fruit yield. In the spring, the biological threshold
of weed interference occurred at a density of four S. americanum/m2, but only
caused a 50% yield loss. In the spring, the critical density causing 20% yield loss
was calculated from the regression model to occur at 0.36 S. americanum/m2. A
calculated density of 0.58 S. americanum/m2 caused 20% yield loss in the fall.
Plant height and dry weight data indicated that the pepper initially grew more
quickly in the fall than in the spring.
458
The Effect of Rhizosphere Competence on Colonization of Sweet
Corn Roots by Biocontrol Fungi in Differing Soils
Thomas Björkman*, Lisa Blanchard, and Gary E Harman; Dept. of Horticultural
Sciences, Cornell Univ., Geneva, NY 14456
To be effective, biocontrol agents, fungi need to colonize roots under a wide
range of conditions. The ability do so is called rhizosphere competence. A common
benefi cial fungus, Trichoderma harzianum, has been bred to produce a new strain,
T-22, that has exceptionally high rhizosphere competence. In fi eld experiments,
we have demonstrated that T-22 was resistant to edaphic conditions that reduce
colonization by indigenous Trichoderma species, so that it can provide protection against root pathogens. Well-drained sand, stone or gravel soils supported
lower populations of wild Trichoderma than did loams (100.5 vs 10 3.3 cfu/g), but
populations of T-22 were high in all soils (>104 cfu/g). In a multivariate analysis
of soil characteristics affecting colonization, only soils with low Ca and low pH
had reduced populations. No other measured soil characteristics were correlated
with colonization. When sown in the fi eld at different initial soil temperatures
ranging from 10 to 27 °C, T-22 populations were unaffected by temperature,
having a population from 104.6 to 105.4 cfu/g. Indigenous strains were 103 in cold
soils, peaked at 104 at 15 °C, declining in later sowings due to higher biological
competition. Differences in microbial competition had little effect. Roots were
equally colonized in the differing soil microfl ora in three management systems at
the Rodale Farming Systems Trial. Invading an existing soil microbial community
526
is the most diffi cult thing to achieve with a biocontrol organism. These data show
that T-22 is the fi rst to consistently do so.
100 ORAL SESSION 20 (Abstr. 459–464)
Nuts—Breeding & Genetics
459
Final Results of Propagation Experiments to Show Distribution
of Noninfectious Bud-failure in ‘Carmel’ Almond
D.E. Kester*, K.A. Shackel, T.M. Gradziel, W.C. Micke, and M. Viveros; Univ. of
California, Davis, CA 95616
The distribution of the potential for noninfectious bud-failure (BFpot) was shown
for the entire ‘Carmel’ almond cultivar by propagating from single buds on single
budsticks on individual trees of separate source blocks of commercial nurseries.
Approximately 2700 progeny trees were grown at the same test site. The gradual
increase in the expression of BF (Bfexp) in progeny trees from individual source
trees shows a continuous range of latent BFpot among individual source trees directly correlated to fi ve (or six) consecutive generations of vegetatively propagated
source orchards. This pattern shows a continuous gradient in expression (vertical
variation). A continuous gradient in expression also exists among progeny trees
originating from the same source tree (horizontal variation). Individual source trees
were identifi ed whose progeny produced little or no BFexp when grown for 5 or
more years in a high temperature test site. These studies confi rm that noninfectious
bud-failure (and probably other genetic disorders) represent persistent variants of
a specifi c gene(s) whose genepot changes during vegetative growth sequences to
bring about differential expression over time (“age”) and developmental patterns.
These represent a class of clonal variants which are “age-related” and include
“phase changes”, “juvenility–maturity” phenomena, and can affect morphology,
thorniness, ease of rooting, etc. BF is related to a gene that affects environmental
adaptation of the almond. Control is through the selection, maintenance and
management of foundation clones.
460
Endocarp Structural Components of Insect Resistance in
Almond
M. Freeman*, C. Walters, M.A. Thorpe, and T. Gradziel; Dept. Of Pomology, Univ.
of California, Davis, CA 95616
Almond, as with other stone fruit, possesses a highly lignifi ed endocarp or
shell. The dominant hard-shelled trait (D-) is positively associated with greater
resistant to insect infestation than nuts expressing the paper-shelled (dd) trait.
Hard-shelled genotypes have undesirable effects, including a lower kernel meatto-nut crack-out ratio, greater kernel damage during mechanical shelling, and a
reduction in plant energy available to kernel development. Histogenic analysis
shows that the almond endocarp, unlike peach, has a tri-partite structure. Insect
feeding studies have subsequently demonstrated that the inner endocarp layer,
which is similar in both hard and paper-shelled types, is the most important
structural barrier to insect infestation. Shell-seal integrity and X-ray studies
have confi rmed that discontinuities at the inner endocarp suture seal are the
primary , though not the sole site of entry for insect pests. Paper-shelled almond
selections with highly lignifi ed and well-sealed inner endocarps show resistance
levels comparable to hard shelled types but with crack-out ratios 30% to 40%
higher. Pseudo-paper-shelled types have also been selected, in which a highly
lignifi ed outer endocarp is formed, but is retained by the fruit hull at dehiscence.
An understanding of endocarp morphology and development is thus important in
breeding for insect resistance as well as the commercial utilization of both kernel
and hull.
461
Genetic Diversity of Castanea pulia var. ozarkensis
Fenny Dane* 1, Shona Harrison1, and Hongwen Huang2; 1Dept. of Horticulture,
Auburn University, AL 36849; 2Wuhan Inst. of Botany, Chinese Academy of Sciences, Wuhan, Hubei, P.R. China
The genus Castanea includes several species, some of which, like the American
chestnut (C. dentata) and chinkapin (C. pumila), are susceptible to chestnut blight,
HORTSCIENCE, VOL. 33(3), JUNE 1998
caused by the Asian fungus Cryphonectria parasitica. Blight spread throughout
the natural range of the American chestnut, destroying several billion trees within
the past 50 years. Although the plight of the American chestnut is well-known,
the chinkapin has been neglected. Taxonomic studies indicated two varieties, the
Ozark chinkapin, var. ozarkensis, limited to the Ozark Highlands of Arkansas,
Missouri, and Oklahoma, and the Allegheny chinkapin, var. pumila, found from
New Jersey to Florida and Texas. The genetic diversity within and between 11
geographic populations of the Ozark chinkapin was evaluated to provide baseline
genetic information pertinent to the conservation and restoration of this species.
Nuts or dormant buds of chinkapin trees were evaluated for isozyme and RAPD
polymorphism. The genetic variability of the Ozark chinkapin populations was
relatively high when compared to the American chestnut, and most of the diversity
resides within the populations. Conservation considerations for restoration of the
Ozark chinkapin will be discussed.
462
Breeding and Improvement of Seguin Chestnut (Castanea
segunii)
J.D. Norton* 1 and Hongwen Huang2; 1Dept. of Horticulture, Auburn University,
AL 36849; 2Wuhan Inst. of Botany, Chinese Academy of Sciences, Wuhan, Hubei,
Peoples Republic of China
The seguin chestnut, commonly called Maoli in China, is one of the three
chestnut species (C. mollissima, C. seguinii , and C. henryi ) native to southeastern
and central China. Seguine is a valuable germplasm resource for horticultural
traits such as precocity, everbearing, high yield, blight resistance, and dwarfi sm.
A recurrent selection breeding program was initiated in 1989. Since seedlings
fl owered as early as 3 weeks, selections were made annually for seven generations. Improvement in precocity, everbearing, yield, quality, blight resistance, and
dwarfi sm is sought. The everbearing and high-yielding plants should provide an
abundant source of food for wildlife on a continuing yearly basis. Incorporation
of the precocious and dwarf traits into commercial chestnut species can enhance
the development of high-density chestnut production.
463
AFLPs in Pecan Genetics Research
L.J. Grauke* , T.E. Thompson, and A.S Reddy; USDA, ARS, Pecan Breeding,
Somerville, TX 77879; Crop Biotechnology Center, Texas A& M Univ., College
Station, TX 77843
Procedures were refi ned for extraction and amplifi cation of DNA from pecan
[ Carya illinoinensis (Wangenh.) K. Koch] leaf tissue. Genomic DNA was extracted
from leaf tissue from multiple inventories of ‘Wichita’ and ‘Pawnee’ and processed
for Amplifi ed Fragment Length Polymorphism (AFLPs). Using only four AFLP
primers, 26 polymorphisms were identifi ed, verifying the reproducibility and
consistency of amplifi cation. The application and limitation of the procedure
for separating genotypes will be discussed. Twenty-four cultivars and seedlings
representing the geographic range of the species were analyzed using 10 primer
combinations. Despite the small sample size, polymorphic bands apparently associated with geographic origin were apparent. Individuals from selected controlledcross families of the Pecan Breeding Program were bulked according to disease
reaction and screened using 64 primers. Primary primers were selected on the
basis of polymorphisms observed in bulked samples of resistant and susceptible
genotypes. Eighteen primer combinations were selected for use on all individuals
in the test. The candidate markers were evaluated to verify that parental lines were
polymorphic for the trait, reducing to one the number of appropriate primers. That
primer was used to screen 84 progeny samples phenotypically rated for disease
resistance levels. The data were analyzed for linkage to scab resistance in the
population. Factors limiting the utility of AFLPs as tools for selection of disease
resistant genotypes, and their use in developing markers for heterodichogamy (a
simple dominant genetic system) will also be discussed.
464
A Phenotypic and Molecular Evaluation of Field-grown Trees
Derived from Somatic Embryogenic Cultures
Wagner A. Vendrame* 1, Darrell Sparks1, Gary D. Kochert2, and Hazel Y. Wetzstein1;
Dept. of 2Horticulture or 2Botany, 1111 Plant Science Bldg, Univ. of Georgia,
Athens, GA 30602-7273 USA
Somatic embryogenic protocols have been developed for pecan, Carya illinoinensis (Wangenh.) C. Koch, in which high multiplication rates and effi cient
HORTSCIENCE, VOL. 33(3), JUNE 1998
plant regeneration can be obtained. Regenerated plants were transferred into the
fi eld in 1995. Phenotypic and genetic comparisons were made of trees from two
tissue culture lines to assess if plants derived from somatic embryogenic cultures
maintain clonal fi delity and exhibit true-to-type characteristics. Genetic changes
were examined using AFLP (Amplifi ed Fragment Length Polymorphism) analyses.
Shoot growth, leaf morphology, and the occurrence of scab (Cladosporium caryigenum) lesions and Phylloxera galls were evaluated. AFLP could readily detect
differences between the tissue culture lines, which exhibited a higher number of
polymorphic loci relative to comparisons within culture lines. Phenotypic characteristics differed between lines, but were generally consistent in trees within a
culture line.
101 ORAL SESSION 21 (Abstr. 465–471)
Vegetable Crops—Breeding & Genetics
465
New Hybrid Tomato For Summer Season In Bangladesh
A.K.M. Matiar Rahman*, S.M.M. Hossain, and Md. Shahidul Islam; Division of
Olericulture, Horticulture Research Center, BARI, Gazipur-1701, Bangladesh
Tomato is a winter vegetable in Bangladesh. The production of tomato in
summer is limited because of high temperature, heavy rainfall and severe infestation of diseases. Recently Bangladesh Agricultural Research Inst. developed two
varieties of tomato that can set fruits in summer with the application of Tomatotone
(Parachloro phenoxy aceticacid) but, the yield is poor (24 t/ha). Hence, a program
was initiated to develop hybrid tomatoes that can set fruits at high temperature
without Tomatotone. In 1995 winter season half dialel crosses were made between seven selected inbred lines. Hybrid seeds of all crosses were collected
and tested in 1996 summer season along with the parents. All the hybrids gave
higher yield over the parents. The hybrid line TM0832 was the highest yielder
and produced 424.7% higher yield over the better parent. Selected hybrids were
further put into regional yield trial in Summer 1997 with the control variety BARI
Tomato-4. TM0832 performed better in all the locations and produced 146.45%
higher yield over the control. The distinguishing morphological characters of the
hybrids are dwarf plants with less foliage coverage and profuse bearing (70–75
fruits/plant). Fruits of TM0832 matured in 60–65 days after transplanting and
harvesting continued for a month. Fruits are globose, medium in size, solid and
developed uniform red colour at maturity. Fruits have shelf life of 20 days at an
ambient summer environment. The plants showed high degree of tolerance to
bacterial wilt.
466
Evaluation of Tomato Varieties for Resistance to Alternaria
Fruit Rot
Joseph O. Kuti *; Dept. of Agronomy & Resource Sciences, Hort. Crops Research
Lab., Texas A& M Univ.–Kingsville, Kingsville, TX 78363
Alternaria alternata (Fr.:Fr.) Keissl. (syn. A. tenuis Ness.) causes severe rot of
tomato fruits and reduction in yield under fi eld conditions in south Texas. Several
fungicidal control measures have been tried against the disease and incorporation
of genetic resistance has been found to be economically feasible. The objective
of this study was to evaluate resistance and susceptibility of fruits of different
tomato cultivars to Alternaria rot. Twenty-fi ve tomato varieties were grown in
the fi eld in a randomized complete-block design. Subsequently, the plants were
inoculated two times at mature-green stage with A. alternata conidia suspension
(104 per ml) to promote moderate to severe fruit rot epidemics. Uninoculated fruits
served as controls. Fruit rot incidence was measured by recording numbers of
rotted fruit/plant per block and disease severity were rated on a scale of 0 to 3
at red-ripe stage. Three tomato varieties ‘Celebrity’, ‘Golden Boy’, and ‘Colonial’
had little or no fruit rot symptoms, with disease severity indices of less than 1.0.
These varieties were regarded as resistant. The tomato varieties ‘Duke’, ‘GH 761’,
‘Quick-Pick’, and ‘Heat-wave’ had disease severity ratings greater 1.5 and were
regarded as relatively resistant. The remaining tomato varieties with disease
severity ratings greater than 1.5 were regarded as susceptible.
467
The ffs Allele Conditions Flower Stem Fasciation in Red Beet
527
I.L. Goldman*, Dept. of Horticulture, Univ. of Wisconsin–Madison, Madison,
WI 53706
A fasciated fl ower stem character arose spontaneously during development
of the red beet (Beta vulgaris L.) inbred line W411. The fasciated character is
manifest by a fl attened fl ower stem with petioles coalesced into a twisted, ribbonlike appearance. No fasciation is present in the vegetative stem or petioles. An
inheritance study was conducted to determine the genetic control of fl ower stem
fasciation. The inbred line W411 was used both as a male and female parent in
crosses with four red beet inbred lines. Segregating progenies in both the BC1 and
F2 generations were developed and scored for the fasciated fl ower stem character.
Variable expression of the fasciated fl ower stem phenotype was observed in these
progenies; however, the presence of fl attened fl ower stems at the stem/hypocotyl
junction was unequivocal. Chi-square goodness-of-fi t tests in both the BC1 and
F2 generations did not deviate signifi cantly from expected ratios for a monogenic
recessive character for each genetic background. No reciprocal differences were
detected for any cross in this group of four inbred lines, which suggests the lack of
maternal effect for the fasciated character. The symbol ffs is proposed to describe
the genetic control of the fasciated fl ower stem phenotype.
State Univ., East Lansing, MI 48824 USA
A number of pure fl avonoid compounds have been isolated and identifi ed from
seedcoats of bean (Phaseolus vulgaris) with known genotypes for seedcoat color.
Kaempferol-3-O- -D-glucopyranoside was found to be the major seedcoat fl avonol
of the “brown” genotypes yellow brown (P C J G b v), mineral brown (P C J G B
v), mat mineral brown (PC j G B v), buffy citrine (P C J g B v). This kaempferol
glycoside was also found in a yellow bean (‘prim’ P C j G b v) of the manteca
market class, but the diglycoside kaempferol-3-O- -D-glucopyranoside-(2 1)- D-xylopyranoside was another major fl avonol found in manteca. The “brown”
genotypes also contained proanthocyanidins that are currently being characterized,
but no tannins or proanthocyanidins were found in the manteca bean. Three main
anthocyanins have been found in the three “black” genotypes, mat black, 5-593
and dark brown violet. Preliminary identifi cation of the anthocyanins indicates the
presence of delphinidin, petunidin and malvidin. Further work on identifi cation of
the minor anthocyanins is underway.
468
Genetics and Breeding of Miniature Iceberg Lettuce
W.Y.L. Poon and I.L. Goldman*; Dept. of Horticulture, Univ. of Wisconsin–Madison, Madison, WI 53706
Previous studies have shown the lack of pigmentation in carrot root is dominant
to the production of pigment. However, the rp allele causes a 92% reduction in
total carotenoid pigmentation in roots of W266rprp. When homozygous recessive, the rp allele also appears to alter the carotenoid quality of carrot roots. The
primary focus of this study was to investigate the effect of rp on the composition
of carotenoids in two near-isolines of carrot, W266RPRP and W266rprp. Field
experiments during 1996 and 1997 revealed that accumulation of total carotenoid
concentration in W266RPRP and in W266rprp was 12.7 and 1.3 µg/g dry weight,
respectively. HPLC analyses showed W266rprp contained no α-carotene, whereas
W266RPRP contained both α- and β-carotene. HPLC analyses of W266rprp also
showed no accumulation of phytoene nor lycopene and due to the absence of
α- carotene in W266rprp, thus it was hypothesized that the rp gene may cause
a lesion in the β and/or ε cyclases. HPLC analyses also provided evidence that
the rp gene is associated with a greater synthesis of a product that has a high
absorbance at 296 nm and an elution time ≈28.6 min in W266rprp. MALDI mass
spectroscopy of HPLC-generated fractions eluting at 28.6 min revealed differences
between W266rprp and W266RPRP, suggesting differential carotenoid composition
between the two near-isolines.
Edward J. Ryder*; U.S. Agricultural Research Station, USDA-ARS, 1636 E. Alisal
St., Salinas, CA 93905
Miniature vegetables have become mildly popular in the United States and
elsewhere. These include small forms of carrot, pumpkin, bok choi, tomato, potato,
corn, eggplant, squash, and watermelon. Some of the miniature vegetables are
based upon harvest of immature edible portions. Others are genetically reduced in
size. Miniature lettuce forms include romaine and butterhead cultivars, as well as
young leaves harvested for mesclun, or baby leaf mixes. Miniature iceberg lettuce
was derived from crosses of early fl owering dwarf forms with standard iceberg
lettuce cultivars. Three slow-bolting miniature cultivars, Ice Cube, Mini-Green,
and Blush, were released from this program. Another miniature iceberg cultivar,
LeCup, was developed by Asgrow Seed. Co. Crosses among these types and
normal size iceberg cultivars showed that the two miniature types were based
on two different single recessive genes with an epistatic relationship. Further
breeding goals in the program will include earlier maturing miniature cultivars
with variations in color, including green, red, and yellow.
469
Inheritance of Pod Calcium Concentration in Snap Beans
(Phaseolus vulgaris L. )
J.M. Quintana* 1, H.C. Harrison1, J. Nienhuis1, J.P. Palta1, K. Kmiecik1, and E.
Miglioranza2; 1Dept. of Horticulture, Univ. of Wisconsin–Madison , Madison WI
53706; 2Departamento de Agronomia, Universidade de Londrina-PR, 86051,
Brazil
Signifi cant variation for pod Ca concentration among snap bean genotypes
was previously observed. To evaluate and better understand the genetics that
control calcium concentration of pods in snap bean, two populations of snap
beans were evaluated during the summers of 1995 and 1996 at Hancock, Wis.
These populations were Ca2 (‘Top Crop’ x ‘Evergreen’) and Ca3 (‘Slimgreen’
x ‘Evergreen’), therefore forming a half-sib structure. The experimental design
used in this experiment was an 8 x 8 double lattice repeated each year. No calcium was added to the plants, which were grown in a sandy loam soil with 1%
organic matter and 600 ppm Ca. To ensure proper comparison for pod calcium
concentration among cultivars, only commercial sieve size number 4 pods (a
premium grade, 8.3 to 9.5 mm in diameter) were sampled and used for calcium
extractions. After calcium was extracted, readings for calcium concentration of
extracts were made using an atomic absorption spectrophotometer. Statistical
analyses resulted in distinct differences among genotypes and between years for
pod calcium concentration (P = 0.01) in both populations. No signifi cant year
x genotype interactions were observed. To assess the power of selection for pod
calcium concentration in snap beans, variance components and heritabilities are
estimated and discussed.
470
Identification of Flavonoids from the Seedcoats of Phaseolus
vulgaris L. Beans of Known Genotype for Seedcoat Color
C.W. Beninger* and G.L. Hosfi eld; USDA Agricultural Research Service, Michigan
528
471
The rp Allele Alters Carotenoid Accumulation and Composition
in Carrot Roots
102 ORAL SESSION 22 (Abstr. 472–479)
Small Fruits—Crop Production
472
Source–Sink Relations in Non-dormant and Dormant Blueberry
Production Systems
Peter A.W. Swain* and Rebecca L. Darnell ; Horticultural Sciences Dept., Univ. of
Florida, PO Box 110690, Gainesville, FL USA.
Two cultivars of southern highbush blueberry ( Vaccinium corymbosum
interspecifi c hybrid) were grown in containers under the traditional dormant production system or the non-dormant production system. Plants in the non-dormant
production system were maintained by continuous N fertilization throughout the
year. The fi rst objective was to determine when source limitations to reproductive development in blueberry occurred. The second objective was to determine
if source limitations could be alleviated by the non-dormant production system,
since photosynthesis and therefore carbohydrate accumulation continue later into
the season. In order to determine when source limitations occurred, reproductive
manipulations were applied to three groups of plants, either after fl ower bud differentiation in the fall, or after fruit set in the spring. After fl ower bud differentiation,
80% of the fl ower buds were removed from one plant group. After fruit set, 80%
of individual fruits or 80% of fruit clusters were removed from two other plant
groups. Average fruit dry weight was higher in the fl ower bud removal treatment
than in the fruit removal or control treatments in the dormant production system,
indicating a source limitation occurs prior to anthesis. No pre-anthesis source
limitation was found in the non-dormant system; this is probably due to insuffi cient
HORTSCIENCE, VOL. 33(3), JUNE 1998
fruit and fl ower removal, and/or continued fl ower bud initiation prior to anthesis in
this system. However, both fruit number and total yield were signifi cantly higher
in the non-dormant than the dormant production system.
473
Establishment of a Non-dormant Blueberry (Vaccinium Corymbosum Hybrid) Production System in a Warm Winter Climate
Rebecca L. Darnell* 1, J.G. Williamson1, and T.A. Obreza2; 1Horticultural Sciences
Dept., Univ. of Florida, Gainesville, FL 32611; 2SWFREC, Univ. of Florida, Immokalee, FL 34142
A high-density planting of three southern highbush cultivars was established
in 1994 in southwest Florida to test the feasibility of a non-dormant blueberry
production system. A non-dormant system involves continuous application of
nitrogen throughout fall and winter, which enables the plants to avoid the normal
dormancy cycle and the concomitant chilling requirement. Three nitrogen fertilizer rates and two organic soil amendments (muncipal solid waste compost and
acidic peat) were evaluated for effects on maintaining plant growth in this system.
In general, increasing N rates from 84 to 252 kg• ha–1 increased plant canopy
volume, leaf retention, and rate of new vegetative budbreak. Plant height and
volume were consistently greater for plants grown in the compost compared to
the peat amendment, but there were no differences in leaf retention or vegetative
budbreak between the two soil amendments. Flower bud density and fruit yield
were increased in plants grown in the compost compared to the peat, while N
rate had no effect on either. Plants in this non-dormant system have shown no
deleterious growth effects, suggesting that establishing a blueberry planting in a
warm winter climate is feasible under the described conditions.
474
Budbreak of Rabbiteye Blueberry Enhanced by Hydrogen
Cyanamide
Melvin R. Hall* and Max E. Austin, Dept. of Horticulture, Univ. of Georgia Coastal
Plain Experiment Station, Tifton, GA 31793
Few fl ower buds on pot grown ‘T-227’ rabbiteye blueberry (Vaccinium ashei
Reade) advanced past stage 1 (tight bud) when exposed to 0 or 200 h of chilling
temperatures (4 °C), regardless of treatment with hydrogen cyanamide. However,
0.25% , 0.5% , 1% , and 2% sprays on plants chilled 400 h advanced fl ower bud
development through stage 6 (open). Sprays were less effective on plants chilled
for 600 h or longer, and 1% and 2% sprays caused some phytotoxicity regardless
of chilling.
475
Hydrogen Cyanamide Increases Leafing and Reduces Fruit
Development Period of Southern Highbush Blueberry
J.G. Williamson*, B.E. Maust, and R.L. Darnell; Horticultural Sciences Dept.,
IFAS, Univ. of Florida, Gainesville, FL 32611-0690
Mature, fi eld-grown ‘Misty’ southern highbush blueberry plants were sprayed
to drip with 0, 20.4, and 10.2 g• L–1 concentrations of hydrogen cyanamide in
north-central Florida on 20 Dec. and 7 Jan. 1996–97. Plants were dormant and
leafl ess, with slightly swollen fl ower buds, at the time of spray applications. All
hydrogen cyanamide sprays increased the extent and earliness of vegetative
budbreak and canopy establishment. The number of vegetative budbreaks per
centimeter of shoot length increased linearly with increasing spray concentration of
hydrogen cyanamide. Hydrogen cyanamide-treated fruit had greater average fresh
weights and shorter average fruit development periods than non-treated fruit. On
15 Apr., 40% ti 60% of hydrogen cyanamide-treated fruit were ripe compared to
about 10% of control fruit. Some fl ower bud damage and subsequent fruit thinning was observed from the 20.4 g• L–1 spray, especially at the later spray date.
Hydrogen cyanamide shows potential for increasing early fruit maturity and fruit
size of some southern highbush blueberry cultivars in Florida.
476
Lowbush Blueberry Response to Different Phosphorus/Nitrogen
Ratios
J.M. Smagula* W. Litten, and S. Dunham; Horticulture Program, Univ. of Maine,
Orono, ME 04469-5722
Lowbush blueberries (Vaccinium angustifolium Ait.) in three commercial
fi elds were treated with 67.2 kg P/ha from triple super phosphate (TSP), monoammonium phosphate (MAP), or diammonium phosphate (DAP) and compared to
HORTSCIENCE, VOL. 33(3), JUNE 1998
a control in a randomized complete-block design with 12 blocks. Correction of P
defi ciency by fertilizers with different ratios of P to N was assessed by leaf nutrient
concentrations. Samples of stems collected in July from three 0.03-m2 quadrats
per treatment plot indicated MAP and DAP had no effect on dry weight of stem
tissue, but increased average dry weight of leaf tissue. P and N Leaf concentrations
were raised to higher levels by MAP and DAP than by TSP. TSP had no effect on
leaf N concentrations but raised leaf P concentrations compared to controls. Stem
length, fl ower buds per stem and fl ower bud density were increased by both MAP
and DAP, but not TSP. MAP and DAP increased fruit yield by about 340 kg/ha
compared to the control.
477
Affect of Pre-plant Amendment, Mulch, and Nitrogen Level
on Mature Highbush Blueberry Root Growth and Mycorrhizal
Infection Intensity
Barbara L. Goulart*, Kathleen Demchak, and W.Q. Yang; Horticulture Dept., The
Pennsylvania State Univ., University Park, PA 16802
The affect of pre-plant rotted sawdust amendment (with and without), mulch
(with and without), and nitrogen level (four levels, ranging from 0 to 160 g/plant)
were evaluated for their affects on highbush blueberry root and mycorrhizal
infection intensity in a fi eld study that was instigated in 1992 at the Russell E.
Larson Agricultural Research Center in Rock Springs, Pa. Over the years, mycorrhizal infection intensity was affected interactively by these treatments, however
in general, it was negatively correlated with nitrogen level, mulch, and pre-plant
amendment. Plants were excavated in Oct. 1998, and it was found that fi ne feeder
roots constituted a much higher percentage of total root mass in unmulched plants,
as well in high nitrogen plants, however there was an interaction between nitrogen
level and mulching, such that non-mulched high N plants had a higher proportion
of feeder roots. Total root mass was unaffected by mulch and pre-plant amendment; however it was increased by nitrogen. Root systems were also sampled for
mycorrhizal infection intensity from different locations on the root system and are
currently being analyzed.
478
Calcium Sulfate Soil Amendment Reduces Incidence of Phytophthora Root Rot in Raspberry
K.E. Maloney1, M.P. Pritts2*, and W.F. Wilcox3; 1Dept. of Horticultural Science,
Dept. of Plant Pathology, Cornell Univ., Geneva, NY 14456; 2Dept. of Fruit and
Vegetable Science, Cornell Univ., Ithaca, NY 14853
Phytophthora is a debilitating root disease of many crops, and limits raspberry
production in much of the world. Two fungicides are labeled for use against Phytophthora on raspberries in North America, but they are not effective when disease
pressure is severe. We were interested in the effect of preplant soil amendments
such as composts, fertilizers, gypsum and limestone on the incidence of Phytophthora in red raspberries. Various amendments were incorporated simultaneously
at two sites prior to planting raspberries. Both sites had identical soil, but one had
a known history of P. fragariae var. rubi and the other had no history of raspberry
production. Differences in survival and plant growth of ‘Heritage’ among fertilizer
(ammonium nitrate, phosphorus acid), compost, gypsum and lime (calcitic or
dolomitic) treatments were small in the uninfested site, whereas differences were
large in the infested site. Gypsum (CaSO4) treated plots had higher yields and
greater cane diameter, density, and height compared to control plots after 2 years.
Plants in compost amended plots exhibited the most severe disease symptoms;
liming had little effect. In a second fi eld experiment, various sources of calcium
and sulfate were compared in an infested site. As before, plants in calcium sulfateamended plots performed better than plants in control plots or in plots amended
with sulfur or potassium sulfate. In a greenhouse experiment using infested soil
and artifi cial fl ooding, calcium sulfate also reduced disease incidence in ‘Titan’
compared to unamended soil. Data from these three experiments suggest that
gypsum could be used in an integrated approach to Phytophthora management
in raspberries, and perhaps other crops as well.
3
479
Physiological Evaluation and Field Assessment of Floricane
Productivity of Cold-damaged Red Raspberry in a “Recovery”
Year
Chuhe Chen*, J. Scott Cameron, and Stephen F. Klauer; Washington State Univ.
Research and Extension Unit, 1919 N.E. 78th St., Vancouver, WA 98665
529
The two test sites paired perennially cold-damaged portions of fi eld vs. controls
were monitored and assessed the same as last season. The winter of 1996–97 did
not produce the same level of winter injury as the previous winter, thus this season
was an opportunity to evaluate the effects of a “recovery” year. The overall cane
lengths and bud number per cane were higher in the previously winter injured plots
of both fi elds compared to the control. It showed the previous injured plants with
a reduced crop load in 1996 were able to devote more energy into developing the
1997 crop. However, damaged plots still had higher cane dieback, percentage of
cane dieback, number of dead or dormant buds per cane, and percentage of dead
or dormant buds in both sites, especially at site 2, even in a mild 1996–97 winter.
The control plots had greater average lateral length, total lateral length, and higher
berry numbers per lateral, especially in laterals from primary buds at both sites.
Thus, a mild winter reduced productivity of the fl oricanes and its laterals in the
cold damaged plots. The differences in fruit yield and its components between the
check and the cold-damaged ones were not signifi cant this season. Leaves on the
cold damaged fl oricanes had greater photosynthetic activity after harvesting than
the control. The winter-injured plants with a reduced leaf area may show higher
demand for photosynthate.
103 ORAL SESSION 23 (Abstr. 480–487)
Extension Horticulture
480
Researching Alternative Cash Crops for Small Scale Farmers
in Southern Ohio
Brad Bergefurd* 1 and Gary Gao2; 1OSU Extension–Enterprise Center, 1864 Shyville
Road, Piketon, OH 45661; 2OSU Extension-Clermont County
Speciality crops are great alternative cash crops for small scale farmers.
Small scale farmers are constantly searching for viable economic crops to grow.
We have been conducting applied research on the production and marketing of
culinary herbs, oriental vegetables, colored peppers, and muskmelons to name a
few. These crops show excellent potential for southern Ohio. Field demonstration,
seminars, and surveys were used to gather and disseminate information on these
speciality crops. More than 230 people attended our seminars on alternative cash
crops. More than 150 people attended our fi eld days. In addition, we had identifi ed many chefs that are willing to purchase from local speciality crop growers.
It will be a win-win situation for both chefs and growers. Growers will be able
to maximize their profi tability while chefs will receive fresh and unique produce.
As a result of our research, we were able to show small scale growers what they
can grow successfully and how they can market their crops for most profi t. These
applied research projects received a combined funding of $10000.00 from OSU
Extension-Innovative Grant program. These projects are a great way to establish
credibility among clients. We would also like to demonstrate how other extension
agents can help their clients. A lecture utilizing slides and overhead transparencies
will be the format of the seminar.
481
Colorado Commercial Greenhouse Needs Assessment Survey— 1997
Karen L. Panter* 1 and Steven E. Newman2; 1Colorado State Univ. Cooperative
Extension, 9755 Henderson Road, Brighton, CO 80601-8114; 2Dept. of Horticulture and Landscape Architecture, Colorado State Univ., Fort Collins, CO
80523-1173
Greenhouse crop producers in Colorado were surveyed in the fall of 1997 to
determine their educational, extension, and research needs and expectations. Four
mailings were made to a mailing list of 180: pre-letter, cover letter and survey,
follow-up post card, and post-letter with another survey sent only to those who
had not responded after the third mailing. One hundred and six usable surveys
were returned for a rate of 59% . The survey itself consisted of fi ve sections:
Educational Programming Topics, Educational Programming Delivery Methods,
Research Needs, Extension Needs, and Personal/Business Data. Results were
tabulated via simple frequencies. In the area of Educational Programming Topics,
66% of respondents wanted to learn more about non-chemical pest control and
63% were interested in production of perennials. In Educational Programming
Delivery Methods, 76% preferred workshops with the most favorable months for
attendance being January, September, and October. In the area of Research Needs,
530
64% wanted explorations into new crops in general and 73% were interested
in new insect management strategies. In the Extension Needs section, 76%
expected a fi eld visit from extension personnel on an as-needed basis and 51%
were familiar with services offered by extension greenhouse specialists. Finally,
in the Personal/Business Data section, 43% reported that they held a bachelor’s
degree, 50% had 16 or more years experience in the industry, and 50% worked
in greenhouses less than 50,000 square feet in size.
482
Extending Biologically Integrated Farming Practices within the
San Joaquin Valley’s West Side
J.P. Mitchell * 1, P.B. Goodell 1, R.L. Coviello1, T.S. Prather1, D.M. May1, T.K. Hartz1,
G.S. Pettygrove1, K.J. Hembree1, D.S. Munk1, T. O‘Neill 2, and J. Diener2, 1Univ.
of California; 2Five Points, Calif.
The West Side On-Farm Demonstration Project is a large-scale extension
program consisting of farmers, researchers, extension advisors from the Univ. of
California, and other private and public agency consultants who are evaluating
biologically integrated soil-building and pest management practices within a
participatory and on-farm demonstration context. Modeled after the Biologically
Integrated Orchard Systems (BIOS) Projects that were originally sponsored by the
Community Alliance with Family Farmers, the goals of this project are to facilitate
information exchange among West Side farmers, consultants and researchers on
soil-building practices and options for reduced reliance on agrichemical inputs, to
monitor and evaluate on-farm demonstrations of soil-building practices, including
cover cropping and organic soil amendments, and to determine the extent to which
IPM practices are utilized in row crops on the West Side and identify constraints
preventing further adoption of biologially intensive pest management practices.
The Project has generated several adjunct research activities and considerable
regional attention. A summary of ongoing impact assessment efforts will be
presented.
483
Consumer Perceptions of Plant Quality
T.E. Bilderback, T.E. Glasgow*, T. Johnson, K.B. Perry, and C.D. Safl ey; Dept. of
Horticultural Sciences, North Carolina State Univ., Raleigh, NC 27695.
Plant quality has been identifi ed as one of the most important factors in
determining where retail customers shop and which plants they buy. A better
understanding of what customers actually mean by “plant quality” can enhance the
industry’s ability to give customers what they want, and improve the competitive
position of individual nursery/garden center businesses. Five common woody
ornamentals— fl owering dogwood (Cornus fl orida), red maple (Acer rubrum),
azalea (Rhododendron spp.), nandina (Nandina domestica) and ‘Compacta’ holly
(Ilex crenata ‘Compacta’)— were selected for a three-part study of consumer
perceptions of plant quality. The fi rst component of the study was comprised of
three focus groups, conducted during Summer 1995 in New Bern, N.C., and Fall
1996 in Raleigh, N.C. The purpose of the focus groups was to learn more about
the specifi c quality attributes customers use in evaluating trees and shrubs in
the garden center. The second component consisted of fi ve different intercept
surveys conducted in 1997 and 1998 in Virginia, North Carolina, South Carolina,
Florida, Georgia, Alabama, and Tennessee. Purchase intent, rank order, paired
comparison, dollar metric and constant sum scales, accompanied by photographs
of plant material, were used to interview retail customers in independently-owned
garden centers. These studies focused primarily on azaleas and dogwoods. The
third component was a hedonic study focusing on azaleas and ‘Compacta’ holly,
conducted in the Raleigh, N.C., area in Apr. 1998. Using standard regression
analysis techniques, hedonics examines prices and levels of selected attributes
to provide an estimate of the marginal implicit price a consumer is willing to pay
for an additional unit of a particular attribute.
484
U. S. –Hungarian Horticultural Research Program for Stresstolerant Ornamental Plants
Erika Szendrak1,2, Paul E. Read1*, Gabor Schmidt2, Donald H. Steinegger1, and
Todd M. Morrissey3; 1Univ. of Nebraska–Lincoln, Dept. of Horticulture, Lincoln,
NE 68583-0724; 2Univ. of Horticulture and Food, Budapest, Hungary; 3Nebraska
Statewide Arboretum, Lincoln, NE 68583-0715
Pollution has become one of the most important problems in urban and
industrial environments and plants are considered to be one of the best means
HORTSCIENCE, VOL. 33(3), JUNE 1998
for diminishing its harmful effects. Installation of landscape plants is probably
the cheapest and one of the most effective ways to reduce the adverse effects of
polluted or stressful environments. Resistance or tolerance of various plant species
against environmental stresses (e.g., pollution, drought, high salt content and poor
aeration of soil, human damage) varies dramatically with type of plant species and
cultivar. Nebraska and Hungary have many similarities in climate and geographical
characteristics and researchers have accumulated considerable results in the fi eld
of plant environmental stress and pollution tolerance. However, time and history
have prevented cooperative work until recently. Excellent connection and cooperation with the Univ. of Horticulture and Food, Budapest and several Hungarian
nurseries was established by the Dept. of Horticulture, Univ. of Nebraska–Lincoln
and the Nebraska Statewide Arboretum ,which was an optimal foundation for this
research project. Our overall goal was to mutually utilize the rich genetic materials
and experience which have accumulated in these two regions during the past 5
decades. This continues to be accomplished by a systematic germplasm-exchange
program and testing pollution- and stress-tolerant tree, shrub and herbaceous
perennial cultivars, along with investigations of the physiological mechanisms
of their stress reactions and biotechnological methods for mass-propagation.
The presentation will highlight the main results of this several years long joint
program.
485
Contract Growing for the Export-oriented Cut Flowers Industry
in Turkey
Robin G. Brumfi eld* 1, Burhan Ozkan2, and Osman Karagüzel 2; 1Dept. of Agricultural Econ. & Marketing, Rutgers, The State Univ. of New Jersey, 55 Dudley Rd.,
New Brunswick, NJ 08901-8520 USA; 2Univ. of Akdeniz, Faculty of Agriculture,
Turkey
Thirty cut fl ower businesses were surveyed in 1997 to examine the production
structure and main problems of export-oriented contract growing in Turkey. The
survey was conducted in Antalya province, which is the center of export-oriented
cut fl ower production in Turkey. The results of the research provided insight
into how Turkish cut fl ower-contracted growers were managing some of the key
areas of their operations. The study also provided the opportunity for growers
to highlight their concerns about contract growing for export-oriented cut fl ower
production. The survey showed that contract growers do not use specifi c performance indicators relevant to cut fl ower production. The product price received
by the contract growers was determined by the export companies. These export
companies receive fl owers from growers mainly on consignment. After exporting
the products, exporters periodically pay the grower, subtracting a commission
for their services and other marketing expenses. Contract growers are essentially
price takers in the transactions. The business procedure from production to price
setting and marketing was not in the hands of the contract growers. Therefore, the
trading risks are essentially borne by the contract growers. The main concerns
raised by contract growers were the current consignment system, cost of the plant
materials, and the late payment for the sold products.
486
Development of REDCAHOR— a Vegetable Research and Development Network in Central America
J. Nienhuis* ; Dept. of Horticulture, Univ. of Wisconsin,1575 Linden Drive,
Madison, WI 53706
REDCAHOR is the Spanish acronym for “Central American Vegetable Network.” Vegetables have traditionally been an important source of nutrients and
vitamins in the diet in Central America. Vegetable production in this region is now
changing as local consumers are demanding increased diversity and quality and
international markets are expanding with “non-traditional” vegetable exports. The
present restraints to expanded research and production of vegetables in the region
include i) need for cultivars with increased insect and disease resistance, ii) poor
and excessive use of pesticides, and iii) inadequate postharvest technology. In
addition, there are few vegetable researchers in the region and response to their
activities have not been coordinated. The goal of REDCAHOR is to develop a
regional network of national institutions that can prioritize agendas and cooperate to maximize the impact of available resources. Establishment of a system of
regional trials and cooperative regional programs in integrated pest management and plant breeding are currently under development. A series of regional
workshops are planned, including integrated pest management, maintenance
and use of genetic resources, organic production, and greenhouse production.
In addition, REDCAHOR, in collaboration with the Escuela Agricola Panamerica
HORTSCIENCE, VOL. 33(3), JUNE 1998
in Honduras, will offer regional short-course training in vegetable breeding and
genetics as well as vegetable production and management, including integrated
pest management.
487
Implementing a Tomato Disease Forecast System in Northern
New Jersey
M.H. Maletta*, W.P. Cowgill, Jr., W. Tietjen, S.A. Johnston, T. Manning, and P.
Nitzsche; Rutgers Cooperative Extension of Hunterdon County, 4 Gauntt Place,
Flemington, NJ 08822-9058
After 4 years of research trials with TOM-CAST, an early blight and anthracnose
forecaster for tomatoes, forecast information was made available to northern
New Jersey growers in 1997. Rutgers Cooperative Extension provided 20 tomato
growers with information and training on using TOM-CAST to schedule fungicide
applications. Rutgers Cooperative Extension set up and maintained six weather
stations in a three-county area. Rutgers personnel downloaded weather data twice
weekly from May to late October and generated and published disease severity
values (DSV) by phone and fax. Growers obtained DSVs for their site from the
nearest weather station(s) and used them to determine their spray schedule. A
survey to determine grower use of and attitudes about the system were mailed
in Oct.1997. Four growers used the system to schedule fungicide applications.
Growers reported the following perceived advantages of using TOM-CAST: cost
savings and savings to environment; disease forecasting being “the future” of
disease management; knowing for sure when to spray. Growers reported the following perceived disadvantages: risk to crop; inconvenience of an irregular spray
schedule; concern about other diseases. Growers who did not use the system in
1997 were queried about the reasons they did not use it and whether they would
consider using TOM-CAST in 1998.
116 ORAL SESSION 24 (Abstr. 488–492)
Fruits—Breeding & Genetics
488
Evaluating Transgenic Apple for Resistance or Tolerance to
Apple Replant Disease
Dorcas Isutsa*, Ian Merwin, and Bill Brodie; Fruit and Vegetable Science Dept.,
Cornell Univ., Ithaca, NY 14853-0327
Apple replant disease (ARD) causes serious problems in most fruit-growing
regions worldwide. It is associated with nematodes, fungi, bacteria, and other
deleterious factors. Its symptoms range from severe stunting to death of replants
in old orchards. We evaluated effects of antibacterial (cecropin-, attacin- and hen
egg white lysozyme-encoding) and antifungal (chitinase-encoding) transgenics,
obtained from the apple-rootstock breeding program at Geneva, N.Y., on ARD.
Transgenics were tested in a composite soil collected from New York orchards with
known replant problems. The ARD-infested fi eld soil (FS) had ≈675 Pratylenchus
penetrans (root-lesion nematodes, RLN) and ≈75 Xiphinema americanum (dagger nematodes) per liter pot; soil for controls was steam-pasteurized. Height,
biomass, nematode vermiforms and eggs were recorded after ≈60 days under
optimal growing conditions in the greenhouse. There was signifi cant variation in
growth and Pratylenchus counts among transgenics (P < 0.00), most of which
were susceptible to ARD. However, endoparasitic RLN accounted for <50% of
the variation in biomass, suggesting that other factors were important in affecting plants. Conversely, RLN signifi cantly increased root necrosis (P < 0.00; R2
= 80% ). Eggs were observed in diseased chitinase-encoding lines, probably
because of low-gene expression. There was no signifi cant difference in eggs
among the lines (P ≤ 0.3). Apparently, good growth was inconsistent and due to
confounding factors such as mild ARD. These results suggest that single-gene
therapy and low-gene expression may not protect apple against ARD complex,
instead gene-pyramiding and high-gene expression should be tested.
489
Advanced Selections of Summer Apples from the Arkansas
Apple Breeding Program
Curt R. Rom*, R.C. Rom, J.N. Moore, and J.R. Clark; Dept. of Horticulture, PTSC
531
316, Univ. of Arkansas, Fayetteville, AR 72701
An apple breeding program was begun in Arkansas in 1966 with objectives
including the development of early maturing cultivars adaptable to warm environments. Several advanced selections have achieved this objective and are briefl y
described here prior to possible introduction as new cultivars. AA-50 (PCR3-120 x
PCR4-56) mature 65–75 days after bloom, are moderate size (120–160 g), round,
tart, juicy; red over green/white ground color. Fruit are similar to ‘Jonathan’.
AA-63 (Jersey Mac x AA-11) mature 70–85 days after bloom, are moderate size
(130–180 g), round, somewhat tart but with good sugars for maturation season,
are dark red/purple striped with pronounced lenticels on a green/white ground
color. AA-18, aka ‘Arkcharm’ (NJ123249 x NJ136055) ripen 85–100 days after
bloom, are medium to large size (165–195 g), slightly conic, bright red on green
ground/yellow color, are very crisp and fi rm, tart with good fl avor, good shelf-life
for season (7–21 days) and extended harvest period (two to three harvests). AA44 (NJ674016 x NJ40), mature 90–105 days after bloom, are large (180–210
g), round, red with some dark red striping with green ground color; fruit have
moderate acid content and are relatively sweet, require two to three harvests and
have a storage life of 2–4 weeks. AA-64 (SpurGold x AA-26) mature 110–120 days
after bloom, are yellow, conic, russet free, often have a pink blush, are moderate
to large size (160–200 g), fi rm, subacid, and sweet.
490
Transfer of Plum Pox Virus Coat Protein Genes from a Plum
Pox-resistant Transgenic Clone of Prunus domestica Plum to
Its Progeny through Hybridization
Ralph Scorza1*, Laurene Levy2, Vern Damsteegt3, Ann Callahan1, Kevin Webb1,
Michel Ravelonandro4; 1USDA-ARS Appalachian Fruit Research Station, 45
Wiltshire Rd., Kearneysville, WV 24530; 2USDA-APHIS, PPQ, Plant Methods
Development Laboratory, Bldg 580, Beltsville, MD 20705; 3USDA-ARS Foreign
Disease-Weed Science Research Unit, Fort Detrick, Frederick, MD 21702; 4Station
de Pathologie Vegetal, INRA, Centre de Recherches de Bordeaux, BP 81 33883
Villenave d’Ornon, France
Sharka or plum pox virus (PPV) is a major disease of stone fruit and causes
severe economic losses in Europe. There is little resistance to PPV in most Prunus
species, thus genetic engineering represents a potentially useful approach to
obtain resistant germplasm. Transgenic plums containing the PPV coat protein
(CP) or the related papaya ringspot virus (PRV)-CP gene were produced through
Agrobacterium tumefaciens-mediated transformation. These transgenic plum
clones were then evaluated for resistance to PPV infection in the greenhouse by
graft or aphid inoculation with PPV. While symptoms of PPV appeared in most
transgenic clones, all plants of PPV-CP transgenic clone C5 were symptomless
and ELISA and immunocapture-reverse transcriptase PCR negative for over three
years following inoculation with two strains of PPV (Ravelonandro et al., Plant Dis.
81:1231-1235, 1997). Clone C5, which contains multiple copies of the PPV-CP
gene, was hybridized with PRV-CP transgenic plants or untransformed plum
cultivars. Progeny were obtained containing no transgenes, only the PPV-CP,
only the PRV-CP, or both the PRV-CP and PPV-CP transgenes. Seedlings were
inoculated with PPV. At 5 and 11 months post-inoculation, seedlings containing
the PPV-CP genes from C5 were symptomless and ELISA negative. Seedlings
containing only PRV-CP transgenes or non-transformed controls showed symptoms of PPV infection and were ELISA positive. These results indicate that the
PPV-CP transgenes can be transferred to progeny through hybridization and that
these genes can impart resistance to PPV in transgenic seedlings. The inheritance
of the multicopy inserts of the PPV-CP and PRV-CP transgenes is being analyzed.
The combined effects of both transgenes on resistance to PPV and the stability
of PPV resistance in the progeny of the resistant C5 transgenic line are currently
under evaluation.
491
An S-locus Receptor Protein Kinase from Peach is Expressed
Predominantly in Fruit and Responds Differently to Various
External Stresses
C.L. Bassett*, M. Nickerson, T.A. Artlip, M. Wisniewski, A. El Gaouth, and C. Wilson; USDA, ARS, Appalachian Fruit Research Station, Kearneysville, WV 25430
A receptor-like protein kinase (RLK) isolated from December peach bark
(Ppsrlk1) was previously shown to have considerable homology to the S-locus
class of RLKs associated with reproductive self-incompatibility. Unlike those
RLKs, transcripts arising from Ppsrlk1 were not detectable in standard RNA
532
blots. To determine the pattern of expression of this gene, RNAs from various
peach tissues, some of which had been subjected to different stress treatments,
were surveyed using Reverse Transcript-PCR (RT-PCR). Based on these results,
select RNAs were further quantitated by Competitive PCR (C-PCR). RT-PCR of
RNAs from seasonal peach bark revealed little change in the relative abundance
of Ppsrlk1, although a slight decrease was noted in the RNAs from October and
December bark. Expression of Ppsrlk1 in developing peach fruit peaked at stage
II and declined thereafter from stage III and in the later stages of ripening. Ripe
peach fruit subjected to 10 min UV treatment or wounding followed by application of a yeast biocontrol agent showed a further decline in Ppsrlk1 expression;
C-PCR analysis of the wounded fruit indicated a fi ve-fold difference in expression
between wounded water controls and wounded fruit treated with the biocontrol
agen 48 h after treatment. In bark and xylem tissues under water defi cit conditions
expression of Ppsrlk1 declined. In contrast, levels of Ppsrlk1 in leaves and roots
increased. C-PCR of the root samples revealed a 50-fold increase in the transcript
in response to water defi cit.
492
Mapping Cold Tolerance QIL in Citrus grandis (L. ) Osb. x Poncirus trifoliata (L. ) Raf. Hybrids: A Three-pronged Approach
Courtney Weber*, Wayne Sherman, and Gloria Moore; Horticultural Sciences
Dept., IFAS, Univ. of Florida, Gainesville, FL 32611
A pseudo-testcross population of Citrus grandis selection DPI6-4 x Poncirus
trifoliata cv. Rubideaux, cold-sensitive and cold-tolerant parents, respectively, is
being used to map quantitative trait loci (QTL) for cold tolerance using bulked
segregant analysis (BSA), selective genotyping, and interval mapping. A population
of 500 young trees was frozen under controlled conditions to –9 and –15 °C to
select contrasting bulk segregant populations from the distributional extremes of
cold tolerance. A randomly selected subset of 61 individuals from this population
was used to construct a linkage map for interval mapping. The pseudo-testcross
population allows mapping of both the C. grandis and P. trifoliata genomes
through the identifi cation of parental origin of marker alleles. Screening of random
10-mer primers is ongoing and, to date, ≈100 primers have produced eight markers showing differences in mean stem dieback between the bulked populations.
MAPMAKER-QTL was used to analyze all markers (122 presently) on the linkage
maps for correlation to QTL for cold tolerance or susceptibility, and two regions
of interest have been identifi ed. Also, markers linked to those identifi ed through
BSA are being analyzed for association with QTL through selective genotyping.
The goal of this research is to identify genomic regions and associated markers
relating to QTL for cold tolerance for future use in Citrus cultivar improvement.
117 ORAL SESSION 25 (Abstr. 493–498A)
Fruits—Fruit Development/Postharvest
493
Characterization of α-Farnesene Synthase from ‘Delicious’
Apples
H.P.V. Rupasinghe* 1, G. Paliyath2, and D.P. Murr1; Depts. of 1Horticultural Science
and 2Food Science, Univ. of Guelph, Guelph, Ontario, Canada N1G 2W1
α-Farnesene metabolism is associated with the occurrence of superfi cial scald
in pome fruits. Trans,trans- α-farnesene synthase, which catalyzes the terminal
step of α-farnesene biosynthesis viz. conversion of farnesyl pyrophosphate to
α-farnesene, has been characterized in the extract from skin tissues of ‘Delicious’
apples (Malus domestica Borkh.). The total and specifi c activities of the enzyme
were the highest in the cytosolic fraction when compared to that in membrane
fractions. The enzyme possessed a pH optimum of 5.6 and required a divalent
metal ion (Mg+2 and Mn+2 were preferred). The activity was highest between 10
and 20 °C, although 50 % of the activity was still retained at 0 °C. The presence
of thiol reagents, pyridine dinucleotide effectors, anaerobic conditions or antioxidants did not signifi cantly affect enzyme activity. α-Farnesene synthase activity
was similar in the extract of skin tissue from scald-developing and non-scalddeveloping apples. The enzyme activity was not correlated to the inherent nature
of scald-susceptibility or resistance in eight different apple cultivars tested.
HORTSCIENCE, VOL. 33(3), JUNE 1998
494
Components of Apple Fruit Epicuticular Wax and Growth of
Sooty Blotch Disease
Robert D. Belding1, Turner B. Sutton2, Sylvia M. Blankenship3, and Eric Young3;
1
Rutgers Univ., Rutgers Agricultural Research and Extension Center, 121 Northville
Road Bridgeton NJ, 08302; 2North Carolina State Univ., Dept. of Plant Pathology, Box 7616, Raleigh, NC 27695; 3Dept. of Horticultural Science, Box 7609,
Raleigh, NC 27695
Sooty blotch severity varied among: ‘Smoothie Golden Delicious’, ‘Coop-17’,
‘Liberty’, ‘NY65707-19’, and ‘NY61356-22’, apple cultivars surveyed In this study,
Peltaster fructicola Johnson, Sutton et Hodges, and Leptodontidium elatius (F.
Mangenot) Hoog were grown on compounds that make up the epicuticular wax of
the fruit in order to determine if one or more wax compound acted as a substrate
for growth, or if a growth modifi er could be identifi ed. There were no relationships
between the major epicuticular wax components of each cultivar and the severity
of the disease. P. fructicola and L. elatius, two of the most important sooty blotch
fungi, did not grow on any of the fi ve major components of the epicuticular wax.
SEM studies showed that mycelia of P. fructicola grew on the surface of the wax
and did not appear to degrade it. In view of the fact that conidia germination
requires pre-treatment with dilute apple juice and the fact that SB does not grow
on fruit cuticles where russet creates an impermeable layer. We conclude that the
SB fungi are epiphytic and obtain their nutrients primarily from fruit leachates
and not from components of the cuticle.
495
Developing a Quality Index for New Cherry Cultivars Growing
in the San Joaquin Valley
Gayle M. Crisosto*, Carlos H. Crisosto, Steve Southwick, and David Garner;
Univ. of California, Davis, Pomology Dept., Kearney Agricultural Center, 9240 S.
Riverbend Ave., Parlier, CA 93648
Sensory evaluation studies including trained panel and consumer in-store
acceptance tests were carried out to develop a quality index for early cherry cultivars. A trained taste panel was used to study how cherry physical parameters are
related to the perception of sweetness, sourness, and cherry fl avor. Based on this
information, we conducted an in-store consumer test. In the in-store consumer
test, ‘Brooks’ cherries with a SSC ≥17% were accepted by signifi cantly more
consumers than ‘Brooks’ cherries with an SSC of ≤16% . ‘Brooks’ cherries with
a SSC of 17 to <20% were “liked” by 74.2% of the consumers tested. When the
SSC was ≥20% , 96% of the consumers tested “liked” them, while only 12.6%
acceptance for cherries with a SSC <16% . There were no signifi cant differences
in acceptance of cherries with SSC ≥17% between genders. However, when the
SSC was ≤16% , signifi cantly more female than male consumers “liked” them,
17.5% vs. 2.6%, respectively. A 4-year orchard survey on the relationship between
skin color and SSC is also discussed.
496
Developing a Quantitative M ethod to Evaluate Peach and
Nectarine Flesh Mealiness
Carlos H. Crisosto, Zhiguo Ju*, and David Garner; Univ. of California, Davis,
Pomology Dept., Kearney Agricultural Center, 9240 S. Riverbend Ave., Parlier,
CA 93648
A quantitative method to measure peach and nectarine fl esh mealiness was
developed. To measure “free water”, ≈30 to 40 g of fruit tissue was wrapped with
four layers of cheesecloth (20 x 20 cm) and subjected to 17.4 N of force using a
prototype press. After the fruit tissue was pressed for 1 min, the force was released.
Pressing of the fruit tissue was repeated four times, after which no further juice
or pectins were released. The juice was collected and centrifuged at 6,000 xg for
10 min. The residue was discarded and the supernatant was weighed and used to
represent “free water” from the tissue. The percentage of “free water” had a higher
correlation to mealiness perception by a trained taste panel and visual observation than the percentage of juice. This “free water” measurement is an objective
and reliable method to evaluate genetic material, physiological changes during
storage, and any treatment’s effect on mealiness.
497
Thermal Blast Shelling of Nuts
D.A. Smith* 1, H. Harris2, and J.D. Norton2; 1Dept. of Horticulture, Univ. of Nebraska–Lincoln, Lincoln, NE 68583; 2Dept. of Horticulture, Auburn University,
AL 36849
HORTSCIENCE, VOL. 33(3), JUNE 1998
Thermal blast shelling has proven effective in removing the shells from fi lberts,
chestnuts, almonds, pecans, and coconuts. Shells were completely removed from
nuts and the nuts were blanched in a single operation. Thermal Blast shelling was
accomplished with an apparatus that confi ned nuts in a pressure vessel, supplied
intense heat for a short duration, then instantly opened the vessel to atmospheric
pressure. The result was an explosion that blew the product from the vessel and
simultaneously exploded the shell from the nut. Blanching was complete with all
testa removed from kernel convolutions during the shelling of fi lberts, chestnuts,
and almonds. Pecans required conditioning to an optimum moisture level and a
heating medium comprised of superheated steam and air to avoid kernel damage.
498
Commodity Heating Medium and Mexican Fruit Fly Mortality
Krista C. Shellie*; USDA, ARS, 2301 S. International Blvd., Weslaco, TX 78596
The objective of this research was to investigate whether the medium used to
transfer heat to a commodity infl uenced the mortality of Mexican fruit fl y larvae.
A similar 2-h heat dose was delivered to grapefruit via immersion in a variable
temperature water bath or via exposure to a rapidly circulating gas. The concentration of oxygen and carbon dioxide inside the grapefruit was analyzed at 30-min
intervals and grapefruit center temperatures recorded every 60 s during heating.
The mortality of larvae located inside grapefruit during heating in a controlled
atmosphere or in hot water was signifi cantly higher than that of larvae located
inside grapefruit heated in air. The internal atmosphere of grapefruit heated in a
controlled atmosphere or in hot water contained signifi cantly higher levels of
carbon dioxide and lower levels of oxygen than grapefruit heated in air. Larval
mortality was compared after larvae were heated in media by rapidly circulating
air or by an atmosphere containing 4 kPa of oxygen and 18 kPa of carbon dioxide
to evaluate whether the altered atmosphere or a heat-induced fruit metabolite was
responsible for enhanced mortality. The signifi cantly higher mortality of larvae
heated in media in the presence of an altered atmosphere suggested that the
altered atmosphere enhanced larval mortality. Results from this research suggest
that reducing oxygen and or increasing the level of carbon dioxide during heating
can enhance mortality of the Mexican fruit fl y and potentially reduce the heat dose
required for quarantine security.
498A
Effects of UV-B Irradiance on Blueberry Storageability, Quality,
and Shelf Life
Fouad M. Basiouny*; Dept. of Agricultural Scciences, Tuskegee Univ., Tuskegee,
AL 36088
Blueberry fruits (Vaccinium ashi Reade cv. ‘Tifblue’), divided into two groups,
were subjected to UV-B irradiance (between 280 and 310 nm) to evaluate fruit storeability and shelf-life under cold conditions. Two Westinghouse FS40 sunlamps
were mounted above the fruits of each group as the source of UV-B rediation. The
emission from the FS40 lamps was fi ltered through 0.005 mm cellulose acetate
(+UV-B) and through 0.005 mm mylar (–UV-B) and served as a control. UV-B
lamps were turned on for 6 h daily and fi lters were changed every week to avoid
solariztion. Storeability, quality, and shelf-life of blueberry fruits stored under UV-B
radiation were better than similar fruits stored under the same conditions without
UV-B radiation. Fruit quality parameters varied between the two treatments.
118 ORAL SESSION 26 (Abstr. 499–505)
Vegetable Crops—Breeding & Genetics
499
Ploidy of Regenerated Broccoli Derived from Microspore Culture Versus Anther Culture
Min Wang* and Mark W. Farnham; U.S. Vegetable Lab., 2875 Savannah Hwy,
Charleston, SC 29407
Anther and microspore culture are commonly utilized to produce doubled-haploid (diploid), homozygous lines in broccoli (Brassica oleracea L. Italica Group).
It is well-documented that doubled-haploid regenerants are produced by means of
polyploidization during anther culture. However, polyploidization may not occur at
all, or it may involve a tripling or quadrupling of the chromosome complement. As
533
a consequence, regenerated populations from anther culture contain diploids, but
also haploids, triploids, and tetraploids. Microspore culture represents a simpler
and more direct method for producing doubled-haploids. Although a similar mix of
ploidy types is likely to be observed among regenerants derived from microspore
culture, the actual ploidy levels of such regenerants have not been documented
for broccoli. Thus, the objectives of this study were to compare ploidy levels of
regenerants developed using both anther and microspore culture in broccoli, and
to examine phenotypic variation in ploidy makeup of populations developed from
both anther and microspore culture using different F1 hybrids. Broccoli regenerants
were derived simultaneously from both anther and microspore cultures using the
same four F1 hybrids, including Everest, Patriot, Greenbelt and Major. Ploidy level
was determined by fl ow cytometry. A majority of regenerants derived from both
anther and microspore culture, were determined to be diploids or tetraploids.
Signifi cant differences in ploidy makeup of populations were observed among
hybrid varieties for both culture techniques. Regardless of the culture method
used, ‘Everest’ produced a greater percentage of diploids and a lower percentage
of tetraploids than ‘Patriot’ did. Haploids were observed more frequently from
microspore culture than from anther culture when ‘Everest’ and ‘Major’ served as
parents.
500
Environmental and Genetic Factors Affects Frequency of Tetraploid Regenerants from Immature Cotyledons of Melon
J. Adelberg* and J. Chen; Dept. of Horticulture, Clemson Univ., Clemson SC
29634
Immature cotyledons of three inbred melon genotypes, Cucumis melo
L., and all hybrid cross-combinations were placed for a 1-week treatment on
liquid/membrane system prior to 5-week regeneration culture on a MS medium
containing 10 µM benzyladenine. Moving plants from agar to liquid/membrane
culture system altered the frequency of tetraploid regenerants. The frequency of
tetraploidy was also effected by sucrose level during the 1-week liquid treatment.
The most stressful conditions, those where the least regenerants were found, had
the highest number frequency of tetraploidy. Genotypic variation in the modes
of genetic control was observed in the different environments. Tetraploid variation can be manipulated by one week treatment of immature cotyledons prior to
regeneration.
501
Resistance to Lettuce Infectious Yellows Virus in Melon
James D. McCreight*; U.S. Dept. of Agriculture, Agricultural Research Service, U.S.
Agricultural Research Station, 1636 East Alisal Street, Salinas, CA 93905 USA
Yellowing of melon (Cucumis melo L.) incited by lettuce infectious yellows
virus (LIYV) reduces yield and fruit quality of infected plants. LIYV is transmitted
only by the sweetpotato whitefl y (Bemisia tabaci Genn.). Two naturally infected
fi eld tests indicated several potential sources of resistance to LIYV. PI 124112
and ‘Snake Melon’ had mild symptoms in both fi eld tests whereas PI 313970
was asymptomatic in the test in which it was included. In greenhouse tests using
controlled inoculation, PI 313970 was asymptomatic, had negative ELISA assays
for LIYV, and was negative for LIYV in serial transfers to Chenopodium. ‘Top Mark’
and ‘PMR 5’ were symptomatic, had positive ELISA assays for LIYV, and were
positive for LIYV in serial transfers to Chenopodium in these greenhouse tests.
Limited data indicate that resistance in PI 313970 is conditioned by a single,
dominant gene.
502
Disease Resistance and Yields of Transgenic and Traditional
Summer Squash
Brent Rowell*, William Nesmith, and John C. Snyder; Dept. of Horticulture and
Landscape Architecture; Dept. of Plant Pathology, N-318 Ag. Science North, Univ.
of Kentucky, Lexington, KY 40546-0091.
Kentucky vegetable growers exploiting a fall-harvested market window for summer squash (Cucurbita pepo L.) usually encounter severe virus and fungal disease
pressure resulting in serious yield and quality reductions. Twenty-fi ve summer
squash varieties or advanced breeding lines (9 zucchini, 8 yellow straightneck, and
8 crookneck entries) were evaluated in a late summer planting for yield, quality,
and disease resistance at the Univ. of Kentucky South Farm in Lexington. Both
genetically engineered virus-resistant materials and new resistant/tolerant varieties from traditional breeding programs were compared with our recommended
534
hybrids. Border rows of a virus-susceptible variety were planted alongside and
between each of the four blocks to enhance virus spread throughout the trial. Virus
incidence was determined visually before and after fi nal harvest and leaf samples
were collected for virus assays. Virus symptoms were absent or diffi cult to see on
zucchini squash plants during most of the trial but became obvious near the fi nal
harvest date. Varieties from traditional breeding programs having virus tolerance
were among the highest yielding zucchini types. Traditionally-bred cultivars with
the precocious yellow gene and two transgenic lines were in the highest yielding group of yellow straightneck squash— in spite of high virus incidences in
precocious yellow cultivars. Transgenic cultivars were clearly superior in terms
of yields among yellow crooknecks with yields nearly double those of the lowest
yielding traditional hybrids. Cultivars and breeding lines varied considerably in
color, shape, overall appearance, and potential marketability.
503
Field Screening for Onion White Rot Resistance
Ronald Voss* , Kent Brittan, Herb Phillips, Donald Kirby, W. Michael Davis,
Warren Gabelman, Irwin Goldman, and Michael Havey; Univ. of California, Davis
CA 95616; Univ. of Wisconsin; and USDA-Madison, WI 53706
Onion white rot disease (Sclerotium cepivorum) is a serious production
problem throughout the world. Very low pathogen level in the soil can cause
signifi cant loss. Generic integrated pest management programs include clean
seed, site selection, sanitation, crop rotation, biological and chemical controls,
crop resistance to the pest, and other components. Onion white rot disease
management currently does not have crop resistance as a component. The lack of
resistant germplasm and/or the inability to identify and screen potentially resistant
germplasm are primary reasons. Research was conducted to determine if fi eld
screening for resistance is feasible, to defi ne fi eld screening methodology, and to
identify and/or quantify resistance. Disease incidence was inconsistent from year
to year. In some years, disease expression was high; in others, disease was low.
Uniform pathogen level and disease expression throughout the experimental fi eld
were required for successful screening. Results provide evidence that “resistant”
or “tolerant” germplasm does exist, and that disease “resistance”, “tolerance”, or
“susceptibility” can vary from slight to strong, suggesting multigenic involvement.
“Resistance”/”tolerance” was identifi ed in long-day yellow hybrids and inbreds.
‘Southport White Globe’ selections and derivatives had much higher disease
susceptibility than yellow or brown skin lines screened.
504
Genetic Analysis of Chinese Cucumber Collections in the U. S.
National Germplasm Collection
J. Staub*, Felix Sequen, Tom Horejsi, and Jin Feng Chen; USDA-ARS and Univ.
of Wisconsin, Horticulture Dept., 1575 Linden Dr., Madison, WI 53706
Genetic variation in cucumber accessions from China was assessed by examining variation at 21 polymorphic isozyme loci. Principal component analysis
of allelic variation allowed for the depiction of two distinct groupings of Chinese
accessions collected in 1994 and 1996 (67 accessions). Six isozyme loci (Gpi,
Gr, Mdh-2, Mpi-2, Pep-gl, and Pep-la) were important in elucidating these major
groups. These groupings were different from a single grouping of Chinese 146
accessions acquired before 1994. Allelic variation in Chinese accessions allowed
for comparisons with other accessions in the U.S. National Plant Germplasm
System (U.S. NPGS) collection grouped by continent and sub-continent. When
Chinese accessions taken collectively were compared with an array of 853 C.
sativus U.S. NPGS accessions examined previously, relationships differed between
accessions grouped by country or subcontinent. Data indicate that acquisition of
additional Chinese and Indian cucumber accessions would be strategically important
for increasing genetic diversity in the U.S. NPGS cucumber collection.
505
Taste and Quality of Burpless and Bitterfree Cucumbers
Todd C. Wehner*; Dept. of Horticultural Science, Box 7609, North Carolina State
Univ., Raleigh, NC 27695-7609
Burpless cucumbers (Cucumis sativus L.) are listed in many seed catalogs
as being milder for eating than the standard American slicing type. It has been
suggested that burpless cucumbers 1) are genetically bitterfree, 2) cause less
burping when eaten, or 3) are the marketing term for Oriental trellis cucumbers.
The objective of this experiment was to determine whether burpless cucumbers
are bitterfree, and whether they cause less burping when eaten. Bitterness of
HORTSCIENCE, VOL. 33(3), JUNE 1998
the plants was determined by tasting a cotyledon of six seedlings per cultivar.
Burpiness of the fruits was determined in the fi eld using two seasons (spring
and summer) and two replications. Six judges evaluated three cultivars over two
harvests by eating one half of a fruit of the three cultivars on three consecutive
days (in random order). Burpiness was rated 0 to 9 (0 = none, 1–3 = slight, 4–6
= moderate, 7–9 = severe). ‘Marketmore 76’ and ‘Tasty Bright’ were normal-bitter, and ‘Marketmore 80’ was bitterfree. Burpiness ratings were not signifi cantly
different for ‘Marketmore 76’ (3.0), ‘Marketmore 80’ (2.6), and ‘Tasty Bright’ (2.5).
Burpless cucumbers appear to be the American marketing term for Oriental trellis
cucumbers.
such as a Mycosphaerella brassicae (ringspot). Micropropagation of caulifl ower
is well-established and is used routinely by many breeding companies of both
F1 and OP varieties for multiplying clones of parental lines. It is clear however,
that the true micropropagation potential of caulifl ower has never been realized
since the curd has been estimated to bear up to 5 million meristems (Kieffer et
al., 1997), yet yields of shoots per head are typically 10 to 100 plants. A new
micropropagation schedule for caulifl ower has recently been described (Kieffer
et al, 1996; Kieffer et al., in press), and it is clear that this schedule does offer a
new technology for production of many thousands of plants from a single curd.
This paper will explore the potential of the technique as an alternative to F1 hybrid
seed for growers particularly focusing on the limiting processes in the schedule
and its cost-effectiveness.
119 ORAL SESSION 27 (Abstr. 506–512)
Vegetable Crops—Culture & Management
509
Comparison of Mother Stalk Culture and Clear-cut Harvesting
for Spring Production and Forcing in Late Summer
506
Findings from a Three-year Crop Nutrient Study with Four
Vegetable Crops in Dade Country, Florida
Mary Lamberts* 1, Stephen K. O’Hair2, Edward Hanlon3, and George Hochmuth4;
1
Univ. of Florida, Dade Co. Extension Service, 2Tropical Research & Education
Ctr., Homestead, FL 33030; 3Univ. of Florida, SW Florida Research & Education
Ctr., Immokalee, FL 33934; 4Univ. of Florida, Gainesville, FL 32611
A 3-year replicated fertility trial with four vegetable crops was begun in the
1993–94 season to: a) determine crop nutrient requirements for four vegetable
crops (bush bean, malanga (Xanthosoma caracu), potato, and sweet corn, and
b) to develop and calibrate a soil testing procedure for the local calcareous soils.
Soils were found to test medium to high for both phosphorus and potassium.
Responses to nitrogen varied by crop. Specifi c results and follow up trials with
growers will be discussed.
507
Presidedressing Soil Nitrate Testing (PSNT) Effective in Reducing N Fertilizer Use in Vegetable Production
T.K. Hartz1* and W.E. Bendixen2, 1Dept. of Vegetable Crops, Univ. of California,
Davis, CA 95616; 2UC Cooperative Extension, Santa Barbara County
The utility of PSNT in determining N sidedress requirement of cool-season
vegetables (broccoli, caulifl ower, celery and lettuce) was evaluated in a total
of 20 trials conducted in commercial fi elds in California in 1996–97. Fields
were selected which had soil NO3-N concentration >20 mg• kg-1 at the time the
cooperating grower made the fi rst sidedress N application. The grower’s fertility
program was compared with two reduced N treatments, established by skipping
either the fi rst, or the fi rst and second, sidedress N application. There were four
replications of each N treatment, in a randomized block design. All fi elds were
conventionally irrigated (sprinkler and/or furrow). Crop and soil N status was
evaluated throughout the season. No yield or quality differences were observed in
any fi eld by skipping the fi rst N sidedress; in only three fi elds was yield reduced
by skipping two sidedress applications. Total crop N uptake varied little among N
treatments in most fi elds, despite differences in seasonal N application of as much
as 200 kg• ha–1. These results indicate that PSNT can reliably identify fi elds in
which sidedress N application can be delayed or eliminated. A soil NO3-N “quick
test” was evaluated and proved to be a practical on-farm method to determine soil
NO3-N status.
508
Cauliflower Microshoots— A Potential Alternative to F1 Hybrid
Seed?
M.P. Fuller* 1, M.L.Kieffer2, and A.J. Jellings1; 1Dept. of Agricultural and Food Studies, Seale-Hayne Faculty, Univ. of Plymouth, Devon, TQ12 6 NQ, UK; 2Dept. of Plant
Biotechnology and Biochemistry, Univ. of Leeds, Leeds, West Yorkshire, UK
Caulifl ower is produced all year round in the United Kingdom, with winter
production confi ned to relatively frost-free areas such as Cornwall in the southwest peninsula. Most production zones now take advantage of F1 hybrid varieties
although winter production a complete suite of varieties is not yet available and
growers must rely on open-pollinated varieties bred locally, which, although being variable, do have locally adapted resistance to prevalent wet weather diseases
HORTSCIENCE, VOL. 33(3), JUNE 1998
Robert J. Dufault* , Clemson Univ. Coastal Research Center, 2865 Savannah
Highway, Charleston, SC 29414
Short lifespan is a major problem with asparagus grown in coastal South
Carolina. The Taiwanese system of mother stalk culture may enhance asparagus
longevity and yield. The objective was to determine if mother stalk culture improves
survival and yields in the spring harvests or late summer forcing compared to
conventional spring clear-cut harvesting or to non-conventional forced clearcut summer harvesting. ‘Jersey Giant’ asparagus was harvested for 3 years
(1993–1996) using: 1) SCC–spring clear-cut (normal emergence in February in
this location), 2) SMSuM–spring mother stalk followed by summer mother stalk
(mow fern in August and establish new mothers), 3) SM–spring mother stalk
only, 4) SuCC-summer clear-cut only (mow fern in August and harvest), and 5)
SuM–summer mother stalk only. All mother stalk plots produced 40 mother stalks
per 12 m of row length before harvesting. All plots were harvested for 8 weeks.
Traditional SCC yielded poorly for a 3-year total of 1,651 kg/ha with a 94% stand
reduction after 3 years. SM yielded only 793 kg/ha for all years with a 98% stand
loss. SMSuM yielded 1985 kg/ha total for 3 years with an 81% stand loss. SuCC
yielded 4073 kg/ha for 3 years with 43% stand loss. SuM yields and stand loss
were similar to SuCC. Stand loss in an unharvested controls was 34% . Mother
stalk culture did not improve longevity any time. Spring harvesting systems failed
because by mid summer, aged fern depleted crown carbohydrates and repeated
yearly, this eventually killed the plants. Summer forcing removed aged fern just
about the time the fern became ineffi cient and new effi cient fern produced sugars
for root storage well into the fall, making recovery successful and sustaining plant
longevity compared to traditional spring harvesting.
510
Precision Planting for sh2 Sweet Corn Stand Establishment
Amy Barr and Mark Bennett*; Dept. of Horticulture and Crop Science, The Ohio
State Univ., 2021 Coffey Rd. Columbus, OH 43210 USA
The impact of soil type and planting depths on the emergence of three hybrids
of shrunken 2 sweet corn with varying seed vigor was investigated. Two fi eld trials
were completed (planted on 18 Sept. 1996 and 6 May 1997) in a fi eld containing
Crosby and Kokomo soil types in Columbus, Ohio. Three sh2 hybrids (‘Starship’,
‘Skyline’, and ‘Confection’) were planted at 1.3-, 2.5-, and 5.1-cm depths with
six replications on each of the two soils in the fall study. The same hybrids were
planted the following spring with an adjustment to 2-, 4-, and 6-cm planting
depths over the same soil types, and the addition of a transition soil. The use
of data loggers in 1997 allowed for continual monitoring of soil temperatures at
each of the planting depths throughout the fi eld, and calculation of soil heat units
throughout the emergence period. There were no signifi cant differences between
depths for average temperatures or soil heat units. Minimum temperatures were
signifi cantly colder on the lighter color soil and had a linear relationship with
emergence counts. Soil tests were carried out at all sites for P, K, Mg, and Ca.
Although signifi cant differences were found with the Kokomo soil having higher
nutrient levels than the transition or Crosby soil, levels throughout the fi eld were
more than adequate for emergence. Compaction and soil moisture measurements
were taken with a neutron probe. Dry density was signifi cantly higher on the lighter
color soils, while soil moisture percentage climbed from 18% on Crosby to 25%
on the Kokomo. In both years, there were signifi cant differences in emergence
indices based not only on hybrid and planting depth but also on location. Emergence ranged from below 50% to nearly 100% depending on the treatment and
fi eld location. Each of the 108 sampling points was located with a GPS receiver
535
and the use of ArcView software allowed for data layers to be stored and mapped
so that prescriptions could be made for best stand establishment.
511
Seed-piece Spacing Influences Yield, Size Distribution, Net
Returns, and Stem and Tuber Density of Three Processing
Potato Cultivars
Stephen L. Love* and Asunta Thompson-Johns; Univ. of Idaho, Aberdeen R& E
Center, Aberdeen, ID 83210
Seed-piece spacing is an important economic consideration in the production
of potatoes and optimum varies by cultivar and intended market. A study was
designed to determine the infl uence of seed-piece spacing on yield, tuber size
distribution, net returns and stem and tuber density of three processing potato
cultivars. Seed tubers of cvs. Russet Burbank, Frontier Russet and Ranger Russet
were planted 8, 15, 23, 31, 46, 61, 76, or 91 cm apart at two locations in 1988
and 1989. Total, marketable (U.S. No. 1), and mid-size (226–452 g tubers) yield,
yield of fi ve incremental size categories, net profi ts from a typical processing
contract, and stem and tuber density (number per m of row) were determined.
All three cultivars achieved highest total yields at the narrowest (8 cm) spacing.
Marketable and mid-size yield were optimized between 15 and 31 cm depending
on the cultivar. The size distribution of tubers shifted from a predominance of
small tubers at the narrow spacing treatments to a predominance of large tubers
at the wide spacing treatments. The rate of shift across spacing treatments was
cultivar dependent. Russet Burbank showed a bimodal response to spacing for net
returns with optimums at the 23- and 46-cm spacing treatments. Frontier Russet
and Ranger Russet showed optimums at 23 cm. All three cultivars gave maximum
mid-size yields at a stem density of 10.5–12.1 per m of row and a tuber density
of 23.9–24.9 per m of row.
512
Effect of In-row Plant Spacing on Yield of ‘Beauregard’ Sweetpotato
S. Alan Walters* 1 and Jonathan R. Schultheis2; 1Dept of Plant, Soil, and General
Agriculture, Southern Illinois Univ., Carbondale, IL 62901-4415; 2Dept. of Horticultural Sciences, North Carolina State Univ., Raleigh, NC 27695-7609
Several in-row plant spacings (15, 23, 31, and 38 cm) of ‘Beauregard’ sweetpotato [ Ipomoea batatas (L) Lam.] were evaluated to determine which spacing
produced higher yields under North Carolina growing conditions.The 15 cm
spacing (the closest spacing evaluated) gave the highest root yields.With closer
plant spacings, the yields of No. 1 grade roots increased compared to wider plant
spacings.The No. 1 grade is the most desired and gives the grower the greatest
monetary return.Jumbo grade root production increased with wider plant spacings
due to less plant-to-plant competition compared to those at closer spacings.In
most cases, the widest spacing tested for ‘Beauregard’ (38 cm) produced lower
yields (except for jumbo grade yields) to the other spacings tested.
120 ORAL SESSION 28 (Abstr. 513–520)
Floriculture—Postharvest/Growth &
Development
513
Hormone Sprays and Supplemental Light Prevent Cold-storage-induced Postharvest Leaf Chlorosis and Abscission in
‘Stargazer’ Hybrid Lilies
Anil P. Ranwala* and William B. Miller; Dept. of Horticulture, Clemson Univ.,
Clemson, SC 29634
Rapid leaf chlorosis and abscission limits the use of cold storage for postproduction short-term holding of potted lilies. We investigated the effects of
storage temperature, storage irradiance and pre-storage foliar sprays of gibberellin
and/or cytokinin on postharvest leaf and fl ower quality of Lilium sp. ‘Stargazer’
hybrid lilies. Storage of “puffy bud” stage plants at 4, 7, or 10 °C in dark for 2
weeks induced leaf chlorosis within 4 days in a simulated consumer environment, and resulted in 60% leaf chlorosis and 40% leaf abscission by 20 days.
Cold-storage also reduced the duration of fl ower bud opening, infl orescence
536
and fl ower longevity, and increased fl ower bud abortion. Providing light up to 40
µmol • m–2• s–1 during cold-storage at 4 °C signifi cantly delayed leaf chlorosis
and abscission and increased the duration of fl ower bud opening, infl orescence
and fl ower longevity. Foliar sprays of ProVide (100 mg• L–1 GA4+7) and Promalin
[100 mg• L–1 GA4+7 and 100 mg• L–1 benzyladenine (BA)] effectively prevented leaf
chlorosis and abscission at 4 °C, while ProGibb (100 mg• L–1 GA3) and ABG-3062
(100 mg• L–1BA) were not effective. Accel (10 mg• L–1 GA4+7 and 100 mg• L–1 BA)
showed intermediate effects on leaf chlorosis. Flower longevity was increased and
bud abortion was prevented by all hormone formulations except ProGibb. The
combination of light (40 µmol • m–2• s–1) and Promalin (100 mg• L–1 GA4+7 and
100 mg• L–1 BA) completely prevented cold-storage induced leaf chlorosis and
abscission and signifi cantly improved fl ower opening and overall plant quality.
514
Effect of the Stages of Floral Development and Postharvest
Temperatures to Flowering of Eremurus in Israel
Rina Kamenetsky*; Dept. of Ornamental Horticulture, the Volcani Center, Bet
Dagan, 50250, Israel
The infl uence of postharvest temperature on the fl owering response of Eremurus was studied. The plants were harvested at four different stages of development
and were separated into three groups. The fi rst group was immediately exposed
to 2 °C, the second group to 20 °C followed by 2 °C, and the third group to 20
°C followed by 32 °C and, subsequently, 2 °C. Scanning electron microscopy
(SEM) was used for concurrent morphological analysis of fl oral development.
Application of 2 °C to the plants in the initial stage of fl oral development caused
plant destruction and death, while the same treatment applied at the stage of full
differentiation promoted normal fl owering. Temperatures of 20 °C and, especially,
32 °C, signifi cantly improved fl owering of the plants harvested in the early stages
of fl orogenesis, whereas the same treatment applied to the plants harvested at the
end of fl ower differentiation did not affect the fl owering process. A developmental
disorder, which we term “Interrupted Floral Development” (IFD), was observed
only in the plants harvested when the racemes were fully differentiated. This was
probably caused by the very high air and soil temperatures that prevail in Israel
during the summer. The extent of fl oral differentiation has a determinant role in
subsequent scape elongation and fl owering.
515
Photoperiod Affects Growth, Dry Weight and Fructan Partitioning in Dahlia ‘Sunny Rose’ Seedlings
Garry Legnani * and William B. Miller; Dept. of Horticulture, Clemson Univ.,
Clemson SC 29634
Photoperiod can be an important environmental variable for dahlia seedling
(plug) production. During a 7 week plug production scheme, long days provided
by a 4-h night interruption with ≈10 fc of incandescent light inhibited tuberous
root development while increasing shoot fresh and dry weight, fi brous root dry
weight, leaf area, and height. Night interruption reduced plug production time
by 1 to 2 weeks and plugs grown under long days showed superior growth following transplanting to 10-cm pots. No signifi cant difference in total plant fresh
and dry weight was observed between long-day and short-day plugs, indicating
that growth differences were a result of photoperiod alterations in carbohydrate
partitioning. Tuberous roots of short-day-grown plugs showed a 156% increase in
fructan concentration (mg/g dry wt. basis) over long-day plugs. The carbohydrate
status of long-day (night interruption) tuberous root tissue was characterized by
high glucose concentration. The accumulation of glucose (a product of fructan
synthesis), in plugs grown with night interruption is believed to be the result of
slower rates of cell wall formation in long-day plugs compared to short-day plugs.
HPAEC-PAD separation of fructans showed a maximum degree of polymerization
of ≈30 in short-day tuberous roots and 27 for long-day tuberous roots. Effects
of photoperiod on fructan metabolism in dahlia tuberous roots and the practical
use of photoperiod in dahlia plug production are discussed.
516
Zantedeschia aethiopica and Z. ‘Green Goddess’ Responses to
GA3 and Bonzi for Cut Flower Calla Lily Production in Florida
Ramona A. Reiser*; R& R Expectations, 6932 Clark Rd., Sarasota, FL 34241
Zantedeschia aethiopica, the large white calla lily, and Z. ‘Green Goddess’,
which is white with a unique green blush on the lip, are two cultivars popular in the
fl oral cut fl ower trade. Both were treated with gibberellic acid (GA3) for increased
HORTSCIENCE, VOL. 33(3), JUNE 1998
fl ower development, a technique routinely successful for potted calla production
but not previously reported effective on cut fl owers. Two winter trials in successive
years were replicated under Florida growing conditions. A preplant bulb dip of GA3
ranged from 100 to 250 ppm. Z. aethiopica control plants averaged 1.3 fl owers
per plant, which increased to 3.4 with GA3 in the fi rst trial and from 1.6 to 2.5 in
the second trial. ‘Green Goddess’ went from 1.3 to 3.8 fl owers per plant and 0.9
to 3.3, respectively. Bonzi was applied at either a short (10.2–12.7 cm) or tall
(30.5–38.1 cm) height, with greater effect when shorter. A drench application of
2 mg a.i. per pot shortened foliage more than fl ower height with 32% reduction
on foliage and 12% on fl owers for Z. aethiopica and 44% and 33% respectively
on ‘Green Goddess’. Results favor use of GA3 on cut fl owers for increased fl ower
production, but discourage Bonzi because shortened heights are normally undesirable for cut fl owers.
517
Floral Ontogeny of Pelargonium xdomesticum
Marietta M. Loehrlein* 1 and Richard Craig2; Agriculture Dept., Western Illinois
Univ., Macomb, IL 61455; 2The Pennsylvania State Univ., University Park, PA
16802
Floral ontogeny of Pelargonium xdomesticum was examined for two cultivars
grown under identical environmental conditions. Apical meristems of ‘Duchess’
and ‘Jennifer’ were vegetative at the commencement of the experiment. Meristems
were examined every fi ve days over an experimental period lasting 85 days. Floral
ontogeny was the same for both cultivars, although the timing of fl oral initiation
of the meristem, fl oral organ initiation, and fl oral organ development differed.
The vegetative meristem was convex with leaf primordia initiated on either side
in an alternate pattern. Early fl oral initiation was characterized by formation of a
cleft towards one side of the meristem, followed quickly by a second cleft on the
other side. Between the clefts new meristems developed. New meristems lacked
leaf primordia. Proliferation of meristems continued until numerous meristems
were organized in a cluster arrangement at the apex of the shoot. Proliferation
of meristems at the apex continued until multiple infl orescences had developed.
Infl orescences were subtended by bracts. Floral organ primordia were initiated in
a succession of four whorls: sepals, petals, androecia and gynoecium. Petals and
androecia appeared to develop simultaneously soon after sepal primordia were
visible. Petal primordia remained small while the androecia continued to grow.
The gynoecium fi rst formed a conical shape, with carpels protruding from the
base in a bulbous fashion. At the distal end of the gynoecium, divisions appeared
which developed into stigmatic lobes. As the gynoecium elongated, stigmatic
lobes became more pronounced. Petal elongation concurred in synchrony with
elongation of the gynoecium. On one experimental unit of ‘Duchess’ two fl orets
had opened at 750 total cumulative moles. No ‘Jennifer’ fl orets had opened by
termination of the experiment.
518
Occurrence and Development of a Dorsal Gland in the Leaves
of Twelve Cultivars of Ficus benjamina L. (Weeping Fig)
Svoboda V. Pennisi * 1, Dennis B. McConnell 1, and Richard W. Henley2; 1Dept. of
Environmental Horticulture, Univ. of Florida, Gainesville, FL 32611-0670; 2Central
Florida Research and Education Center, Apopka FL 32703-8504
Ficus benjamina plants are an integral part of most modern interior landscapes. Reports from growers and interiorscape managers have drawn attention
to a specifi c problem related to large F. benjamina plants, namely the occurrence
of a dark oval spot on the abaxial surface of the leaf base. Twelve cultivars of F.
benjamina were examined: Christine, Citation, Florida Spire, Kelly, Kiki, Midnight,
Monique, Stacey, Wintergreen, Dwarf Nikita, Spearmint, and Starlight. Anatomically, the dorsal gland consisted of one to several layers of densely stained,
columnar cells. Positive colorimetric reaction for phenolics was obtained in the
glandular cells. Developmentally, the gland cells could not be distinguished from
the regular epidermal cells until ≈30% of fi nal leaf size was reached. The cells
of the outermost glandular layer changed shape from rectangular with long axis
parallel to the leaf surface to elongate with long axis perpendicular to the surface.
In a mature leaf, the thickness of the glandular layer was between 20 and 30 µm.
Externally, at this stage, no dark spot, indicative of the gland’s location, could be
observed. In older leaves, however, an accumulation of phenolic substances led to
appearance of dorsal dark spot. All cultivars possessed glandular layer. However,
this area did not darken in all cultivars; Christine, Citation, Florida Spire, Kelly,
Kiki, and Stacey developed small dark spots, while Dwarf Nikita and Starlight had
numerous, well-pronounced glandular regions. This study showed that the dark
HORTSCIENCE, VOL. 33(3), JUNE 1998
spots in F. benjamina cultivars were a normal morphological feature. Although the
gland was present in every cultivar, only a few cultivars developed a dark color.
519
Calcium Oxalate Cuticular Crystals in the Epidermis of Dracaena— A Taxonomic Feature of the Genus
Svoboda V. Pennisi and Dennis B. McConnell *; Dept. of Environmental Horticulture, Univ. of Florida, Gainesville, FL 32611-0670
The genus Dracaena has been placed in Agavaceae by most taxonomists.
Recent work, however, has justifi ed the placement in a separate family, Dracaenaceae. This study was initiated to examine the extracellular crystalline deposits
in Dracaena and the possibility of this feature as a taxonomic trait of the genus.
Fresh epidermal peels of fi ve Dracaena species were observed under polarized
light. Extracellular epidermal crystals were evident in all of them. The deposits
were found between the cuticle and the outer primary epidermal cell wall. The
crystal size varied from less than 1 µm to 5 µm along the long crystal axis. The
size and quantity of the deposits varied between the species with largest and
most numerous crystals in the cuticle of D. marginata and D. sanderiana. Dracaena deremensis, D. fragrans, and D. surculosa had smaller and less numerous
crystals. The optical properties of the crystals were indicative of calcium oxalate
monohydrate form which exhibited interference colors of second and third order.
For comparison species of three members of Agavaceae were examined - Cordyline
terminalis, Sansevieria trifasciata, and Yucca sp. No extracellular crystal deposits
in the proximity of the epidermal wall were detected. Based on our observations,
the genus Dracaena possessed an anatomical feature which could be used for
identifi cation. The existence of calcium oxalate crystals embedded in the cuticle
was readily observable in fresh epidermal peels under polarized light.
520
Effects of Irridiance Levels during Flasking and Greenhouse
Production on Growth and Flowering of the Phalaenopsis
Orchid
Elise A. Konow* and Yin-Tung Wang; Dept. of Horticultural Sciences, The Texas
A& M Univ. System, 2415 East Hwy. 83, Weslaco, TX 78596
Four-month-old, aseptically raised Phalaenopsis Atien Kaala ‘TSC 22’ seedlings 1.0 cm in leaf spread were transferred (Nov. 1995) 25 per polycarbonate
box to an agar medium and placed under 10, 20, 40, or 80 mol • –2• s–1 PPF
from cool-white fl uorescent tubes. In June 1996, plants grown under 40 or 80
mol • –2• s–1 PPF had greater mass, wider leaves, and more roots than those under
the two lower PPF. Plants were then transplanted and grown in a greenhouse (GH)
under 340, 170, or 85 mol • –2• s–1maximum PPF. In May 1997, plants previously
produced under 40 mol • –2• s–1 PPF had longer, wider, and thicker leaves than
those under 10 mol • –2• s–1 PPF when grown under the two higher GH PPF. Under
the low GH PPF, however, plants were equally small, regardless of the previous
fl asking PPF levels. Plants under the high, medium, and low GH PPF had an
average of 61, 37, and 17 g of fresh mass, respectively. By September 1997,
plants had increasingly larger leaves and higher concentrations of malic acid,
sugars, and starch as GH PPF increased. Each doubling in GH PPF resulted in
more than a two-fold increase in plant fresh mass. Under the low GH PPF, plants
previously produced under 80 mol • –2• s–1 PPF during fl asking were 13% larger
than those under 10 mol • –2• s–1 PPF. Plants grown under the high, medium, and
low GH PPF had 100% , 79% , and 0% fl owering, respectively. Those under the
high GH PPF bloomed earlier and had longer infl orescences, bearing many more
and larger fl owers, than those under the medium GH PPF.
121 ORAL SESSION 29 (Abstr. 521–528)
Small Fruit—Crop Production/Physiology
521
Strawberry Transplant Propagation in Elevated Horizontal
Troughs
Eric B. Bish*; Dept. of Horticultural Science, North Carolina State Univ., Raleigh,
NC 27695-7609
Commercial strawberry cultivars are vegetatively propagated in fi eld nurseries.
Mother plants produce daughter plants on stolons in response to long photo-
537
periods and high temperatures. The daughter plants are primarily removed from
the fi eld as a bare-root transplant. These bare-root transplants can be extremely
stressed in this digging process, resulting in plant variability and pathogen
infestation. A strawberry transplant production system has been developed that
uses micropropagated disease free mother plants in elevated horizontal culture.
The mother plants are grown in suspended plastic troughs (10-cm width by 10-cm
depth) with a soilless medium consisting of vermiculite and perlite. The mother
plants are subfertigated via drip tubing to avoid leaf wetness. Stolons produced
by the mother plants hang over the trough and continue to grow down toward
the ground. The stolon tips‚ are harvested and rooted in plug trays. This study
compared proliferation rates of several strawberry cultivars. The benefi ts of the
elevated system were: disease-free plants, high-density daughter plant production,
all the runners could be removed at one time and separated for propagation, and
the daughter plants had active root tips that established quickly.
522
Factors Influencing Strawberry Plug Plant Performance
T.D. Crawford, D.G. Himelrick*, and J.L. Sibley; Dept. of Horticulture, 101 Funchess Hall, Auburn University, AL 36849
Three studies evaluating production of strawberry (Fragaria x ananassa Duch.)
plug plants were conducted. The infl uence of runner tip plantlet size, container
size, and chilling on the fi eld performance of ‘Chandler’ plug plants were evaluated over a 2-year period in central and southern Alabama. Plantlet size did not
signifi cantly infl uence yield following transplanting; therefore, grading of plantlets
prior to propagation appears to be an unnecessary expense for successful yields
from plug plants. There were no signifi cant differences in yields of plug plants
from 60-cell vs. 72-cell packs; therefore, growers could produce more plug plants
in the same area without compromising total yield, early yield, or berry size when
propagating plug plants in 72-cell packs. The infl uence of 1, 2 or 3 months of
runner tip cold storage prior to rooting in cell packs was also investigated.
523
Soil M oisture and Soil Salinity Distribution in Strawberry
Beds
W.E. Bendixen* 1 and B.R. Hanson2; 1Univ. of California Cooperative Extension,
624 West Foster Rd., Santa Maria, CA 93455; 2Dept. of Land, Air and Water
Resources, Univ. of California, Davis, CA 95616
Strawberries in the Santa Maria Valley are grown on beds 25.2 cm wide with
four rows of strawberries and two lateral drip tapes. Previous strawberry production was on beds 15.7 cm wide with two rows of strawberries and one lateral drip
tape. The two strawberry production systems were evaluated on several grower
fi elds for water emission uniformity, soil moisture, and soil salinity. The salinity
was evaluated for placement in the bed, type of salts, and nitrate concentration.
At one side, the effect of banded slow-release nitrogen fertilizers as a source of
nitrogen in addition to that applied through fertigation was investigated. Results
showed that the EUs ranged between 80% and 96% , with an average of 89% . A
variety of distributions were found for soil moisture, soil salinity, and soil nitrate,
depending on the water and fertilizer management and time of sampling with
respect to irrigation and fertigation. Distributions of soil moisture content made
3 to 4 days after an irrigation indicated excessive drying of the soil between irrigations. Distributions of soil salinity revealed high salt concentrations near the
drip tape, where leaching was insuffi cient, and relatively low concentrations near
the tape, where leaching was adequate. Nitrate concentrations in and below the
rootzone were smaller where no slow-release fertilizers were used.
524
Phenological Aspects of Strawberry Growth Influencing Gray
Mold Development in Annual Systems
L.M. Butler Carver* 1, G.E. Fernandez2, and F.J. Louws1; Depts. of 1Plant Pathology,
and 2Horticulture, North Carolina State Univ., Raleigh, NC 27695
Strawberry (Fragaria xananassa) plant phenology was evaluated at two sites in
North Carolina in order to assess the relationship of plant growth and the development of gray mold fruit rot (Botrytis cinerea). Site 1 consisted of three cultivars:
Camarosa (CA), Chandler (CH), and Sweet Charlie (SC) from a single nursery; site
2 consisted of cultivar CH obtained from three distinct sources. Weekly records
were kept of leaf senescence, leaf emergence, fl owering, and fruit set, as well as
a monthly whole-plant analysis. Leaf senescence and emergence was uniform
for all treatments, with >90% of transplant foliage senescing between November
538
and December. Analysis of leaf area and plant weights reveal an increase in dry
mass beginning in February and continuing through April. Although fi rst bloom
appeared in December, primary fl oral development occurred in late February for
cultivar SC and in March for cultivars CA and CH, with blooms continuing through
late May. Marketable yield was lower in cultivar SC throughout harvest, with the
exception of early fruit development in March. Non-marketable yield varied, with
increases in gray mold following periods of heavy rainfall. Statistical analysis
of all data shows no consistent differences in plant growth or disease among
treatments. Analysis of foliage revealed latent infections on transplants as the
primary source of gray mold inoculum. Patterns of plant growth and
corresponding disease development found in this study provide tools necessary
for phenology-based control practices for the integrated management of gray
mold.
525
Chill Requirements to Break Dormancy of Wisconsin Cranberry:
Conventional Models may Not be Applicable
Beth Ann A. Workmaster* and Jiwan P. Palta; Dept. of Horticulture, Univ. of
Wisconsin, Madison, WI 53706
Conventional chilling models developed primarily for deciduous fruit crops
such as apple and peach are based on the accumulation of optimal chilling
temperatures between ≈4 and 7 °C. Cranberry (Vaccinium macrocarpon) is a
perennial evergreen woody vine that requires chilling temperatures to overcome
its dormancy. Periodic collections of budded stems (uprights) from cranberry
beds (cv. Stevens) in central Wisconsin throughout the fall and early winter were
forced to determine when dormancy requirements were met in the fi eld. For this
purpose excised uprights were placed in deionized water in test tubes at 24 °C
and 16-h day (cool-white fl uorescent). In both 1996 and 1997 it was observed
that uprights were able to break bud and grow in late fall and early winter only
after experiencing (in addition to chilling) a prolonged period of temperatures
slightly below freezing. As an evergreen plant, cranberry may be receiving critical
environmental cues at its leaves. Additionally, the existence of the native cranberry
plant in harsh winter environments may have resulted in the need for freezing
temperatures during dormancy to ensure survival.
526
Ripening Stages of Cranberry Fruit Have a Dramatic Influence
on Its Postharvest Shelflife: Physiological and Morphological
Explanation
Mustafa Özgen*, Jonathan D. Smith, Beth Ann A. Workmaster, and Jiwan P. Palta;
Dept. of Horticulture, Univ. of Wisconsin, Madison, WI 53706
Cranberries ripen in late fall. The fruit develops color in the outer two cell layers
in response to low temperatures and incident light. Berries at the top of the canopy
generally develop full red color, whereas fruits lower in the canopy (especially
under dense canopies) can remain white even at harvest time. This is especially
true for Wisconsin-grown cranberries. Wet-harvested cranberries are stored for 1
to 2 months and sold at Thanksgiving and Christmas time. We investigated if the
storage quality of fruit is dependent on ripening state. Wet-harvested fruits were
sorted into four different ripening stages and rated for quality after 4 and 7 weeks
of storage. In addition, fruit CO2 and ethylene production, as well as anthocyanin
content, were measured after 4 weeks of storage. The amount of rotten fruit
among red, light red, blush, and white were 12% , 14% , 23% , 38% respectively.
Thus, white fruits had three times greater incidence of rot than the red fruits.
Although the ethylene production by various categories of fruit was nearly same,
white fruits had 70% higher respiration than red fruits. We also found that as the
fruit developed color cuticle thickness increased. For example, cuticle thickness
averaged 1.6 µm for white fruit and 2.3 µm for red fruit. In addition, the calyx end
opening of red fruit was impregnated with more wax than white fruit. Furthermore,
a compact cell layer accumulated anthocyanin under the calyx opening in red fruit
only. Our studies suggest that white berries have poor shelf-life as compare to
red fruit because: i) white fruits have higher respiration rates, ii) thicker cuticle
and wax accumulation (especially at the calyx end) on red fruits retard the entry
of microorganisms into the fruits during wet harvest.
527
Sepal Color Change Relates to Fruit Quality, Firmness, and
Detachment Force in Erect and Semi-erect Thornless Blackberry Cultivars
HORTSCIENCE, VOL. 33(3), JUNE 1998
Herbert D. Stiles* and W. Malcolm Tilson; VPI& SU, Virginia Tech, Southern
Piedmont Agricultural Research and Extension Center, Route 3, Box 60, Blackstone, VA 23824
Black coloration occurs before the inception of horticultural maturity, so other
cues (sheen, drupelet shapes, drupelet sizes, and fruit detachment force) have been
employed as indicators of physiological and horticultural maturity among erect
and semi-erect thornless blackberry cultivars. A more distinct visual cue might,
however, allow reductions in the variability of quality, fi rmness, and shelfl ife among
manually harvested berries. Such a maturity indicator would allow researchers to
select more-uniform materials for genetic and physiologic studies of blackberry
fruit ripening and quality development. Our 1996 and 1997 data confi rm earlier
observations of sepal color relationships to fruit quality attributes (soluble solids, pH, titratable acidity, and sugar/acid ratio) among semi-erect cultivars, and
they show that such relationships exist among erect cultivars. These data also
demonstrate relationships among sepal color, fruit detachment force, and berry
fi rmness in both phenotypes.
528
Control of Weeds, Insects, and Diseases on Cranberry with a
Spring Flood
Carolyn DeMoranville* 1, Anne Averill 2, Frank Caruso1, Hilary Sandler1, and Mary
Jane Else3; 1Cranberry Experiment Station, Univ. of Massachusetts, East Wareham,
MA 02538; 2Dept. of Entomology and 3Dept. of Plant and Soil Sciences, Univ. of
Massachusetts, Amherst, MA 01003
An intensive study of the use of spring fl ooding to control pests and reduce
chemical inputs in cranberry production began in 1995, following preliminary
studies in 1993 and 1994. This 4-week fl ood, known as late water (LW), has been
shown to suppress some insects, mites, and fungi, and to stimulate plant growth.
We demonstrated that pesticide use could be reduced or eliminated in the year
of the fl ood and to a lesser extent in the year following the fl ood. With the use
of LW in from 1993 to 1996, cranberry grower participants in our study reduced
insecticide sprays by 24% and reduced fungicide applications by 30% compared
to standard practice bogs without effect on crop quality. LW increased mortality of
Rubus sp. weeds so that their spread in a cranberry bed was checked. However,
the weed population did not decrease over time. Effects of the fl ood on cranberry
growth and productivity were examined. With changes in rate and timing of fertilizer inputs, growth was similar to that on control beds. However, following an
abnormally mild winter and drought conditions in 1995, crops on LW bogs were
reduced , sometimes severely, compared to the controls. Crop was not affected in
1993, 1994, or 1996. On a LW bog, it is possible to reduce insecticide use by up
to 60% , fungicide use by up to 50% , and nitrogen use by 30% . Reductions and
outcomes vary depending on seasonal conditions but, with careful management
and weather monitoring, this practice remains a strong option for a sustainable
cranberry production system.
130 ORAL SESSION 30 (Abstr. 529–535)
Woody Ornamentals/Landscape/Turf—
Stress Physiology
529
Photosynthesis and Growth of M agnolia x soulangiana in
Response to Consecutive Drought Stress
R.T. Fernandez* 1 and R.E. Schutzki 2; 1Dept. of Horticulture, Clemson Univ., Box
340375, Clemson, SC 29634-0375, USA; 2Dept. of Horticulture, Michigan State
Univ., East Lansing, MI 48824-1325, USA
Responses of Magnolia x soulangiana ‘Jane’ to consecutive short-term drought
stresses were evaluated in this study. Plants were received from a commercial
nursery in 19-L containers in a 4:1 pine bark:sand media. In Oct. 1997, plants
were exposed to one, two or three consecutive 3-day drought stress periods, each
separated by one rewatering period. There were 48 total plants with eight replicates
per treatment for each stress period. Following each stress period, a group of
eight control and eight stressed plants were planted in the fi eld and well-watered
to monitor recovery from each stress duration. Whole-plant photosynthesis, leaf
photosynthesis, shoot growth, and soil moisture content were measured approximately every 2 days during the stress periods. Leaf photosynthesis, shoot growth,
HORTSCIENCE, VOL. 33(3), JUNE 1998
and leaf defoliation rate were monitored for recovering plants. Few differences in
growth were noticed except more rapid defoliation with onset of autumn for the
three 3-day stressed plants. Whole-plant and leaf photosynthesis were reduced
by day 3 of the fi rst 3-day stress for drought-stressed plants and remained lower
while plants were under stress. After release from stress, photosynthesis returned
to control levels for plants receiving one and two 3-day stress treatments in ≈1
week, while it was more than 3 weeks until recovery for plants receiving three
3-day stress treatments. Plants will be evaluated in Spring 1998 for bloom and
growth characteristics.
530
The Influence of Drought on Growth and Gas Exchange in
Fraxinus species
R.E. Schutzki * 1 and R.T. Fernandez2; 1Dept. of Horticulture, Michigan State Univ.,
East Lansing, MI 48824-1325; 2Dept. of Horticulture, Clemson Univ., Box 340375,
Clemson, SC 29634-0375
Fraxinus americana, F. pennsylvanica, and F. nigra were subjected to short-term
drought of 4, 8, and 16 days. Seedlings were obtained from a commerical nursery
and grown in 4:1 pine bark:sand media for 3 months prior to the onset of the
stress. Seventy-two trees with six replicates per stress treatment were arranged in a
completely randomized design. Following each stress period, the appropriate trees
were well watering and monitored through recovery. Leaf photosynthesis, shoot
growth, leaf emergence, terminal bud set, trunk caliper and soil moisture content
were measured through the stress and recovery periods. Drought suppressed
shoot growth and leaf emergence in all species; however, Green Ash maintain
active growth at higher rates than either White or Black. Leaf photosynthesis was
reduced in both White and Black following 4 days of drought whereas Green ash
was not adversely effected until day 10. Trees were harvested following recovery
and dry weight fractions of leaves, stems, and roots recorded.
531
Effect of Biostimulants on Drought Tolerance of Ornamental
Annuals
S.A. Geer*, T.J. Smalley, and M.W. Rieger; Dept. of Horticulture, Univ. of Georgia,
Athens, GA 30602
This study determined the effect of the granular humate Earthgreen (Menefee
Mining Corp., Dallas) and the biostimulant ROOTS2™ (LISA Products Corp.,
New Haven, Conn.) on drought tolerance of the ornamental annuals Impatiens
wallerana ‘Accent White’ and Salvia splendens ‘Red Hot Sally’. Earthgreen was
incorporated into the soil and ROOTS2™ applied as a root drench at transplanting
and 30 days after transplanting, Transplants were established in greenhouse beds
under irrigated conditions for 8 weeks, then subjected to a fi ve week drought.
Data indicates rates of 43.9 and 87.9 g• m–2 of Earthgreen or 300 ml of 1% or
2% ROOTS2™ per plant had no signifi cant effect on Salvia shoot dry weight or
chlorophyll content of Salvia or Impatiens at the end of the 8-week establishment
period. However, Salvia fl ower dry weight was signifi cantly increased with the
higher rate of Earthgreen. During the 5-week drought, Earthgreen or ROOTS2™
did not signifi cantly affect xylem pressure potential of Salvia or relative water
content of Impatiens. After the 5-week drought no signifi cant effect of either
product on shoot dry weight of Salvia or Impatiens or fl ower dry weight of Salvia
was observed.
532
Effects of Drought and Post-drought Recovery on Katsura
Tree
Michael S. Dosmann* and Jeffery K. Iles; Dept. of Horticulture, Iowa State Univ.,
Ames, IA 50011-1100
Katsura tree (Cercidiphyllum japonicum Sieb. & Zucc.) is appreciated because
of its stately form and brilliant autumnal leaf color. One problem of the species,
however, is its reputed intolerance to drought. While data either refuting or substantiating this claim are lacking, anecdotal references abound. To understand
this issue better, a study was designed to measure the effect of drought and
post-drought relief on growth and development of katsura. Two-year-old trees
were container-grown in a greenhouse and subjected to one of three irrigation
treatments (comprised of four irrigation phases) that simulated either drought or
conditions where moisture was not limiting. In treatment one (control), plants in
each phase were irrigated daily with the amount of water lost the previous 24 h.
Plants in the second treatment experienced an initial drought phase (irrigation
539
withheld until soil moisture content decreased to a predetermined level) followed
by three non-drought phases. In the third treatment, plants were subjected to two
drought phases, each followed by a non-drought phase. Destructive harvests were
performed at the beginning of the study and at the conclusion of each phase. Due
to abscission, trees subjected to one and two drought phases underwent a 38%
and 63% reduction in lamina mass, respectively. Stem diameter in trees exposed
to both drought phases was 16% less than that of controls. Net assimilation rates
of trees within each treatment indicate that plants recovering from drought may
be more effi cient as assimilating systems than controls. Based upon our results,
we fi nd that katsura is a drought avoider, responding to drought by defoliating.
Refoliation once water is available does occur and may lend itself to recovery.
533
The Effects of Drought on Leaf Gas Exchange and Growth of
Three Species of Herbaceous Perennials
K.J. Prevete* and R.T. Fernandez; Dept. of Horticulture, Clemson Univ., Clemson,
SC 29634-0375
Three species of herbaceous perennials were tested on their ability to withstand and recover from drought stress periods of 2, 4, and 6 days. Eupatorium
rugosum and Boltonia asteroides ‘Snowbank’ were chosen because of their
reported drought intolerance, while Rudbeckia triloba was chosen based on
its reported drought tolerance. Drought stress began on 19 Sept. 1997. Plants
were transplanted into the fi eld the day following the end of each stress period.
The effects of drought on transpiration rate, stomatal conductance, and net photosynthetic rate were measured during the stress and throughout recovery using
an infrared gas analysis system. Leaf gas exchange measurements were taken
through recovery until there were no differences between the stressed plants and
the control plants. Transpiration, stomatal conductance, and photosynthesis of
Rudbeckia and Boltonia were not affected until 4 days after the start of stress.
Transpiration of Eupatorium decreased after 3 days of stress. After rewatering, leaf
gas exchange of Boltonia and Rudbeckia returned to non-stressed levels quicker
than Eupatorium. Growth measurements were taken every other day during stress,
and then weekly following transplanting. Measurements were taken until a killing
frost that occurred on 3 Nov. There were no differences in the growth between the
stressed and non-stressed plants in any of the species. Plants will be monitored
throughout the winter, spring, and summer to determine the effects of drought on
overwintering capability and regrowth.
534
Transplanting Shock and Water Relations in Urban Tree Species
Amy J. Barton* and Christopher S. Walsh; Dept.of Natural Resource Sciences and
Landscape Architecture, Univ. of Maryland, College Park MD 20742-4552 USA
Large-caliper trees transplanted into urban settings show low survivability.
A 1-year transplanting experiment was conducted using Acer ginnala and Acer
truncatum. Trees were blocked by species and size, with three blocks of four trees
per species. Three trees of each species were left in their original location for
purpose of comparison. A 2 x 2 factorial was used to assign treatments (water,
water and top prune, top prune, and transplanted control). Using a Schollander
Pressure Bomb, predawn and midday water potential measurements were recorded
biweekly from early May through September. The fi rst 8 weeks following transplant,
all transplanted trees of both species had signifi cantly (P ≥ 0.05) more negative
midday water potentials than those not transplanted. During periods of stress,
predawn water potentials of transplanted trees did not recover overnight. By September, irrigated trees had water potentials not signifi cantly different from those
of trees not transplanted. Canopy closure was measured on the same schedule
using a Li-Cor Canopy Analyzer. Leaf area index of transplanted trees was nearly
half that of non-transplanted trees. Trees treated with water did have slight, but
signifi cantly greater leaf area indexes than those of other treatments. It appears
that the most notable effect of transplanting is the inhibition of leaf expansion
resulting from early spring water stress. This leads to an open canopy for the
whole season following transplant.
535
Urban Influences on Local Plant Hardiness Zones
Derald A. Harp* and Edward L. McWilliams; Dept. of Horticultural Sciences, Texas
A& M Univ., College Station, TX 77843-2133
The combination of concrete, asphalt, large buildings, lack of surface water,
540
and heat inputs from industry, automobiles, and poorly insulated buildings result
in warmer temperatures in urban environments. This effect is most pronounced
in winter minimum temperatures and may cause changes in local plant hardiness
zone designations. We obtained minimum temperatures for the years 1974–96
from NOAA and the Offi ce of the State Climatologist of Texas for all recording
stations in the counties in and immediately adjacent to the Dallas/Fort Worth, Texas
(D/FW), metroplex to compare to the 1990 USDA plant hardiness zone map. These
data were averaged and analyzed in two groups, 1974–86, which correspond to
the 1990 USDA map, and the subsequent years, 1987–96. Stations that did not
include a minimum of 15 years of data or anomalies that could be attributed to
microclimatic phenomena were discarded. Minimum temperatures were averaged
and a contour map was created using TNT Lite software. This map was overlaid
on a TIGER map that included county lines and major roadways. The 1974–86
map illustrated only one discrepancy with the 1990 USDA map, the inclusion of
8a temperatures for most of the Tarrant county. Changes in the 1987–96 map
included the further expansion of 8a westward into Parker county and an 8b zone
in the downtown/Love Field area of Dallas. These changes corresponded well with
increased construction and human activity in these areas over the past decade.
These changes also help explain variations in low-temperature damage of several
ornamental plant species reported in previous studies.
131 ORAL SESSION 31 (Abstr. 536–543)
Fruits—Photosynthesis/Growth & Development/Water Relations
536
Prohexadione-Ca— A New Plant Growth Regulator for Apple
with Interesting Biochemical Features
W. Rademacher* 1, J.B. Speakman1, R.R. Evans2, J.R. Evans2, S. Roemmelt3, S.
Michalek3, A. Lux-Endrich3, D. Treutter3, T. Iturriagagoitia-Bueno4, and P. John4;
1
BASF Agricultural Center, 67114 Limburgerhof, Germany; 2BASF Corporation,
P.O.Box 13528, Research Triangle Park, NC 27709-3528, USA; 3Inst. for Fruit
Production, Munich Technical Univ., 85350 Freising, Germany; 4Plant Science
Laboratories, The Univ. of Reading, Reading RG6 6AS, United Kingdom
Prohexadione-Ca is currently developed as an inhibitor of excessive vegetative growth in apple. In addition to the control of shoot growth, distinct effects on
the incidence of fi reblight are observed that are not due to any bactericidal effect
of the compound. Further, the compound often causes a delay of senescence.
It is known that prohexadione-Ca acts as a structural mimic of 2-oxoglutarate
thereby inhibiting dioxygenases, which catalyze distinct steps in gibberellin (GA)
biosynthesis. As a result, levels of growth-active GAs are lowered and, hence,
longitudinal shoot growth is reduced. Prohexadione-Ca also induces changes in
fl avonoid metabolism, which may also be related to the inhibition of dioxygenases
involved in this pathway. Preliminary evidence is available that this effect is related
to a lowered susceptibility of apple tissue towards infection with fi reblight. ACC
oxidase, another dioxygenase, which catalyzes the conversion of aminocyclopropane-carboxylic acid into ethylene, is also affected by prohexadione-Ca and related
compounds. Lowered levels of ethylene may account for a delay of senescence.
537
Whole Plant Measurement of Photosynthesis and Development
of Apple Trees in Relation to Pest Damage
Sarah Breitkreutz* and James Flore; Dept. of Horticulture, Michigan State Univ.,
East Lansing, MI 48824
The objectives of this study were to determine the relationship of whole-plant
photosynthesis (WPP) and overall growth of apple trees to the damage caused
by insects and disease. This project was part of a larger experiment involving a
pest control system consisting of different control strategies, with integrated pest
management being one. WPP was measured seven times during the 1997 growing
season on 16 single-tree replicates of apple trees from two varieties, ‘Empire’ and
‘Liberty’, on M-9 rootstocks at the Clarksville Horticulture Experiment Station.
WPP was measured on trees subjected to six pesticide and fungicide treatments
that were part of the established study. In addition to these measurements, the
leaf number and area were determined at the time of the measurement. At three
times during the growing season, an estimation of insect damage to the fruit
HORTSCIENCE, VOL. 33(3), JUNE 1998
and foliage were determined. At harvest, the total number, size distribution, and
weight of the apples from each tree was measured. In addition, an estimation of
pest and disease damage to the fruit was conducted. Results showed a decrease
in the rate of WPP as the season progressed. All of the treatments had higher rates
of photosynthesis than the control trees. In addition, the soft chemical treatments
had higher rates of photosynthesis than the conventional IPM treatments, 1.8 and
1.5 mmol CO2/cm2 trunk cross sectional area per s, respectively. Further details
of these results and the relationships between foliage damage, photosynthesis
and tree yield will be presented.
538
Light Absorption and Partitioning in Response to Nitrogen in
Apple Leaves
Lailiang Cheng*, Leslie H. Fuchigami, and Patrick J. Breen; Dept. of Horticulture,
ALS 4017, Oregon State Univ., Corvallis, OR 97331
Bench-grafted Fuji/M26 apple trees were fertigated with different concentrations of nitrogen by using a modifi ed Hoagland solution for 6 weeks, resulting
in a range of leaf N from 1.0 to 4.3 g• m–2. Over this range, leaf absorptance
increased curvilinearly from 75% to 92.5% . Under high light conditions (1500
(mol • m–2• s–1), the amount of absorbed light in excess of that required to saturate
CO2 assimilation decreased with increasing leaf N. Chlorophyll fl uorescence
measurements revealed that the maximum photosystem II (PSII) effi ciency of
dark-adapted leaves was relatively constant over the leaf N range except for a slight
drop at the lower end. As leaf N increased, non-photochemical quenching under
high light declined and there was a corresponding increase in the effi ciency with
which the absorbed photons were delivered to open PSII centers. Photochemical
quenching coeffi cient decreased signifi cantly at the lower end of the leaf N range.
Actual PSII effi ciency increased curvilinearly with increasing leaf N, and was
highly correlated with light-saturated CO2 assimilation. The fraction of absorbed
light potentially used for free radical formation was estimated to be about 10%
regardless of the leaf N status. It was concluded that increased thermal dissipation
protected leaves from photo-oxidation as leaf N declined.
539
The Effect of Water Shortage on Potted Peach Trees in Relation
to Ecophysiological Parameters and Infra-red Thermometry
Rita Giuliani* and James A. Flore; Dept. of Horticulture, Michigan State Univ.,
East Lansing, MI 48824
Potted peach trees grown outdoors during the 1997 season were subjected
to drought and subsequent rewatering to evaluate their dynamic response to soil
water content. The investigation was primarily focused on the early detection
of plant water stress to prevent negative effects on the growth. Leaf chlorophyll
fl uorescence and canopy temperature estimates (by infra-red thermometry) were
conducted. Drought effect on physiological processes were detected through by
estimates of canopy development rate, leaf gas-exchange measurements; while
leaf water potential was measured to characterize plant water status. A decrease
in the canopy’s development rate was found 1 week after irrigation was stopped,
which also coincided with a more-negative leaf water potential, whereas a decrease
of the gas-exchange activities occurred several days later. No signifi cant differences between the stressed and control plants were recorded by the chlorophyll
fl uorescence parameters (Fo, Fm, Fv and the ratio Fv/Fm), whereas the infra-red
estimates of canopy temperature detected a slight increase of the canopy surface
temperature (connected to the change of leaf energy balance and in relation to
partial stomatal closure) on the non-irrigated plants 1 week after the beginning
of the trial.The use of infra-red thermometry for early detection of water shortage
is discussed.
540
Carbohydrate Metabolism of Vegetative and Reproductive Sinks
in the Late-maturing Cultivar Encore
Riccardo Lo Bianco1, Mark Rieger* 1 and Shi-Jean S. Sung2; 1Dept. of Horticulture,
Univ. of Georgia, Athens, GA 30602 USA; 2Inst. of Tree Root Biology, Southern Research Station, USDA-Forest Service, 320 Green Street, Athens, GA 30602 USA
Activities of major sorbitol and sucrose metabolizing enzymes and carbohydrate contents were followed during the growth season of ‘Encore’ peach fruits and
developing shoot tips. In fruit fl esh, sucrose synthase (SS) was present during
stage I of growth, when cells are actively dividing, and NAD+-dependent sorbitol
dehydrogenase (SDH) during stage III, when cells enlarge actively. Acid invertase
HORTSCIENCE, VOL. 33(3), JUNE 1998
(AI) revealed the best correlation with relative growth rate (RGR) of fruits during
the entire season. Activities of all carbohydrate metabolizing enzymes were not
detectable in fruit fl esh during seed fi lling and pit hardening, when RGR of fruits
was the slowest. The highest content of sucrose was in concert with low levels
of sucrose metabolizing enzyme activities toward the end of fruit development.
In shoot tips, SDH had low activity at the beginning and end of the season when
vegetative growth was slowest and a 2:1 sorbitol : sucrose ratio was present.
Mid-growing season was, on the other hand, characterized by an increase in
SDH activity and a 1:1 sorbitol : sucrose ratio. In ‘Nemaguard’ seedlings, only
SDH activity showed a positive correlation with shoot growth. Also, in root tips
of ‘Nemaguard’ seedlings SDH exhibited its highest activity, even higher than AI
activity in the same roots. We concluded that in peach sucrose may represent the
major carbon form used for fruit growth, while sorbitol seems to play a predominant
role in vegetative growth.
541
Soil Organisms Influence Fine Root Lifespan in Peach
Christina Wells* 1, David Eissenstat2, and Michael Glenn3; 1Intercollege Program in
Plant Physiology, 2Dept.of Horticulture, The Pennsylvania State Univ., University
Park, PA 16802; 3USDA-ARS Appalachian Fruit Research Station, Kearneysville
WV 25430
Damage to the root system by soil insects and pathogenic fungi is diffi cult
to assess and often goes unnoticed until a tree exhibits signifi cant decline above
ground. In this study, below-ground imaging technology was used to quantify
fi ne root turnover in peach and to determine what percentage of root death may be
caused by soil pests in an apparently healthy orchard. The study was conducted on
six 15-year-old ‘Loring’ peach trees on Halford rootstock in Kearneysville, W.Va.
Five root observation tubes were placed in the soil beneath each tree in Apr. 1996.
Each tube was randomly assigned one of fi ve soil drench treatments: Lorsban
4E insecticide, Ridomil 2E fungicide, a combination of both pesticides, 1/10th
strength Hoagland’s solution, or water. A portable VCR and camera system were
used to record images of fi ne roots (<1 mm diameter) growing along the tubes
at biweekly intervals from May 1996 through Nov. 1997. The images were used
to construct a database of life history information for more than 1500 individual
roots. Peach root survivorship was infl uenced by root diameter and pesticide treatment. Fine roots on tubes receiving either of the pesticide treatments had higher
survivorship than roots on control tubes for all diameter classes. The effect was
most pronounced for white roots <0.5 mm in diameter, whose survivorship during
the growing season was increased by 45% when both insecticide and fungicide
were applied. These results suggest that a substantial fraction of fi ne root death
may be caused by interactions with the soil fauna.
542
Winter Bud Cold-hardiness of Interstem Peach Trees
Gregory L. Reighard* and David R. Ouellette; Dept. of Horticulture, Clemson
Univ., Clemson, SC 29634
Large fl uctuations in annual peach production is a chronic problem in the
southeastern United States. Winter and spring cold injury to fl owers reduces the
potential peach crop almost every year in the Southeast. A bloom delaying peach
interstem has consistently delayed phenology in the Southeast, but its effect on
bud hardiness is unknown. Nine varieties (650–1050 chill hours) budded to ‘Ta Tao
5’ (P.I. 101667) interstems on Lovell rootstock or budded to only Lovell rootstock
(i.e., controls) were sampled monthly from November or December to late February in 1996–97 and 1997–98 from an interstem test established in 1993 near
Clemson, S.C. High-chill varieties such as ‘Contender’, ‘Encore’, and ‘Redhaven’
were 1 to 2 °C more cold-hardy on interstem trees in late winter. General trends
showed that varieties were slightly more cold-hardy on interstems in 1996–97, but
no differences were observed from Nov.1997 through early Jan. 1998. Signifi cant
varietal differences in cold-hardiness were found on each sampling date, but no
trends were observed.
543
Leaf Gas Exchange and Growth Responses of Young, Containergrown Annona Trees to Flooding
Roberto Núñez-Elisea, Bruce Schaffer*, Jonathan H. Crane, and Angel M. Colls;
Univ. of Florida, Tropical Research and Education Center, 18905 SW 280th Street,
Homestead, FL 33031
Commercial Annona species such as sugar apple and atemoya, are sensitive to
fl ooding. Annona glabra (pond apple) is a non-commercial species that grows well
541
in fl ooded soils and may have potential as a fl ood-tolerant rootstock for commercial
Annonas. The effects of fl ooding on net CO2 assimilation (A), stomatal conductance (gs), and vegetative growth of 2-year-old, container-grown Annona trees
were studied under glasshouse conditions. Seedlings of A. glabra, A. muricata,
and A. squamosa, and plants of ‘49-11’ [a cross between atemoya (Annona. spp.
hybrid cv. Gefner) x A. reticulata] grafted onto A. glabra or A. reticulata rootstock
(‘49-11’/ A. glabra; ‘49-11’/ A. reticulata) were exposed to 50 days of continuous
fl ooding. Non-fl ooded (control) plants were irrigated daily. Flooded soil became
anaerobic from day 3 of initiating the fl ooding treatment. Seedlings of A. glabra
and A. muricata, and trees of ‘49-11’/ A. glabra, produced more vegetative growth
during fl ooding than A. squamosa and ‘49-11’/ A. reticulata. Flooding decreased A
and gs of A. squamosa and ‘49-11’/ A. reticulata, and caused tree mortality (80% )
of A. squamosa. Morphological adaptations of A. glabra (seedlings and rootstock)
to fl ooding included adventitious root formation into fl ood water, development of
hypertrophied (swollen) lenticels on trunk and adventitious roots, and development
of trunk aerenchyma. All seedling trees of A. glabra and A. muricata, and all grafted
trees of ‘49-11’/ A. glabra survived 120 days of continuous fl ooding. A. glabra
rootstock imparted fl ood tolerance to the ‘49-11’ scion and may therefore impart
fl ood tolerance to other Annona species. A. muricata seedlings may withstand
extended periods of waterlogging under fi eld conditions.
132 ORAL SESSION 32 (Abstr. 544–551)
Vegetable Crops—Crop Physiology
544
Effect of Volatile Reduction on Growth and Development in
Closed Atmospheric Chambers
G.W. Stutte* 1 and R.M. Wheeler2; 1Mail Code DYN-3, 2Mail Code JJ-G, Kennedy
Space Center, FL 32899
Plants produce and respond to a broad spectrum of volatile chemical compounds. The concentration and duration of volatile exposure during long-duration
space missions will be higher than typically experienced by plants. The effects
of using fi lters to reduce volatile organic compound (VOC) exposure on growth
and development of several species has been studied in the Biomass Production
Chamber (BPC) at Kennedy Space Center. The VOC composition of the BPC
was determined weekly using a modifi cation of EPA Method TO-14 with mass
spectrometry. Ethylene concentration was monitored every 8 h using FID gas
chromatography. Experiment durations were 84 days for wheat, 105 days for
potato, 104 days for rice, and 90 days for tomato. In all cases, non-biological
sources including siloxanes, Freon’s, solvents and hydrocarbons were the primary
VOC constituents. The primary biogeneic compounds detected include ethylene,
acetaldehyde, pinene, isoprene, and carbon disulfi de. Species-specifi c compounds
detected included various terpenes, esters, furans, alcohols, aldehydes, and ethers.
Filtering the atmosphere through activated carbon fi lters typically reduced the
overall VOC concentration by at least 50% . Filtering the atmosphere through
potassium permanganate pellets generally maintained ethylene concentrations
<25 ppb. Concentration difference between fi ltered and unfi ltered treatments
varied according to species, stage of development and specifi c compound. By
reducing the overall VOC exposure, several species-specifi c morphological and
development changes were observed, including: an increase in internode length
of wheat, potato and rice, delayed anthesis of wheat and tomato, delayed tuber
initiation in potato, delayed ripening of tomato, earlier anthesis of rice, and larger
leaf area in potato. No phytotoxicity per se was noted during these experiments.
545
Low-level Irradiance during the Dark Period Prevents Photoperiodic-induced Tuberization of Potato
N.C. Yorio* 1, G.W. Stutte1, R.M. Wheeler2, and L.M. Ruffe1; 1Dynamac Corporation;
NASA Biomedical Operations Offi ce, Kennedy Space Center, FL 32899
The threshold irradiance during the dark portion of a photoperiod required
to inhibit tuberization of potato (Solanum tuberosum L.) was investigated. Two
cultivars of potato (cv. Norland, an early maturing variety; cv. Russett Burbank, a
late-maturing variety) were grown using nutrient fi lm technique hydroponics in
separate tests within a walk-in growth chamber under a normally tuber-inductive
2
542
photoperiod (12-h light/12-h dark). Light period photosynthetic photon fl ux (PPF)
was provided by either daylight fl uorescent lamps (providing 150 µmol • m–2• s–1
PPF) or a combination of daylight fl uorescent and metal halide lamps (providing 300 µmol • m–2• s–1 PPF). The chamber was confi gured with vertically hung
shadecloth and a pair of 15-W cool-white fl uorescent lamps mounted at one end
of the chamber to provide a range of low irradiance during the dark period. The
low irradiance treatments averaged 3.65, 0.43, 0.06, and <0.01 µmol • m–2• s–1
PPF for the entire 12-h “dark” period. Results showed that tuberization occurred
around 23 DAP, regardless of cultivar or light period PPF for plants grown with
0.06 and <0.01 µmol • m –2• s–1 PPF during the dark period. Tuberization also
occurred at around 30 DAP for cv. Norland grown with 0.43 µmol • m–2• s–1 PPF
during the dark period. No tubers were formed for either cultivar grown with 3.65
µmol • m–2• s–1 PPF during the dark period. These results indicate that light levels
<0.43 µmol • m–2• s–1 PPF do not infl uence photoperiodic induction of tuberization
in potato.
546
Does Ethanol-induced Chilling Tolerance Affect the Antioxidant
Systems of Cucumber Seedling Roots?
Windy A. Boyd* and Paul H. Jennings; Dept. of Horticulture, Forestry and Recreation Resources, Kansas State Univ., Manhattan, KS 66506
Previous experiments have shown that chilling-stressed cucumber seedlings
treated with ethanol have greater chilling tolerance when compared to untreated
seedlings. This chilling tolerance persists for a limited time (2-4 h) and, once lost,
chilling tolerance can be re-induced by a second ethanol treatment. In all cases,
greater chilling tolerance was measured as an increase in root growth and a decrease
in lipid peroxidation and electrolyte leakage. This study was undertaken to determine
whether antioxidant systems, which may help plants survive some environmental
stresses, are affected by ethanol and/or chilling treatments. The relative activities of
glutathione reductase (GR) and peroxidase (POX) of chilled and/or ethanol-treated
seedlings were compared. GR activity was suppressed by the combination of any
ethanol treatment and chilling when compared to the control. Upon re-warming, all
ethanol treated groups exhibited higher GR activity than before chilling. POX activity
was affected by the chill plus re-warming treatment in which a signifi cant increase
was seen in all treatment groups. Any group treated with ethanol had a lower POX
activity than the control. POX activity stains, using non-denaturing PAGE, showed
the appearance of three new bands in all treatment groups after the chill and rewarming. The increased intensity of the stain in the re-warmed groups supports the
enzyme activity data mentioned above. Since ethanol treatment generally suppressed
the enzyme activity after chilling, ethanol’s possible role as a scavenger of reactive
oxygen species will be discussed.
547
Calcium Uptake and Whole-plant Water Use Influence Pod
Calcium Concentration in Green Bean Plants
Kirk W. Pomper* and Michael A. Grusak; USDA-ARS, Children’s Nutrition Research Center, Dept. of Pediatrics, Baylor College of Medicine, 1100 Bates St.,
Houston, TX 77030
Understanding the mechanisms that regulate xylem transport of calcium (Ca)
to green bean pods could allow approaches to increase pod Ca concentrations
and enhance the nutritional value of edible pods. Using the green bean cultivars
‘Hystyle’ and ‘Labrador’, that exhibit high and low pod Ca levels respectively, we
wished to determine whether observed differences in Ca concentration of stem
xylem-sap were related to differences in whole-plant water uptake and Ca import.
Well-watered greenhouse-grown plants, selected at fl owering and at two stages of
pod development, were placed in a growth chamber at a constant light intensity.
Pot weight loss was measured to determine whole-plant water use and stem xylem
exudate was subsequently collected from the severed base of the shoot. ‘Hystyle’
displayed 50% higher Ca concentration in exudate than ‘Labrador’ during pod
development. Labrador showed 35% greater total water transport through the
stem than ‘Hystyle’. Additional plants were used to determine total, long-term
Ca uptake. No signifi cant differences in total Ca were seen between cultivars at
the three harvest dates. With whole-plant Ca uptake being equivalent, the results
suggest that higher water uptake in ‘Labrador’ led to a dilution of Ca in the xylem
stream and thus less total Ca was transported to developing pods, relative to that
in ‘Hystyle’. These results reveal that green bean varieties with low whole-plant
water use have the potential to yield edible pods with elevated Ca content.
HORTSCIENCE, VOL. 33(3), JUNE 1998
548
Endo-β-mannanase Activity and Seed Germination of Thermosensitive Lettuce Genotype in Response to Temperature
and Seed Priming
Warley M. Nascimento*, Daniel J. Cantliffe, and Donald J. Huber; Horticultural
Sciences Dept., Univ. of Florida, 1251 Fifi eld Hall, PO Box 110690, Gainesville,
FL 32611-0690
Under high temperatures (above 30 °C) in the greenhouse (transplant industry)
or fi eld, lettuce germination can be erratic or completely inhibited. Seed priming
circumvents thermodormancy of lettuce seeds and allows germination at higher
temperatures. Weakening of the endosperm layer of lettuce seeds is a prerequisite
to radicle protrusion at high temperatures. Enzyme-mediated degradation of
endosperm cell walls may be a crucial factor for lettuce seed germination at high
temperatures. Softening of the endosperm could occur during seed priming and
result in improved germination. A single-seed assay for endo- β-mannanase was
used to follow the activity of this enzyme during priming in lettuce seeds. We also
investigated the effects of seed priming on seed germination and mannanase
activity at both inhibitory and non-inhibitory temperatures for seed germination
in a thermosensitive lettuce cultivar Dark Green Boston. Seeds were primed for 3
days at 15 °C with constant light in aerated solutions of polyethylene glycol (PEG)
at an osmotic potential of –1.2 MPa. Afterward, seeds were rinsed and redried at
10 °C and 45% RH for 3 days. Primed and nonprimed seeds germinated 100% at
20 °C. At 35 °C, primed seeds germinated 100% , whereas nonprimed seeds did
not germinate. During priming, endo- β-mannanase activity increased between 24
and 72 h after the beginning of osmotic imbibition. Mannanase activity persisted
in primed seeds, even following seed drying. Radicle protrusion did not occur
under the priming conditions used in this study. Higher enzyme activity was
observed in primed seeds compared with nonprimed seeds. The results suggest
that priming overcomes the inhibitory effect of high temperature in thermosensitive
lettuce seeds by weakening of endosperm due to increased endo- β-mannanase
activity.
549
Low- temperature Storage of M icropropagated Broccoli
Plantlets under Varying Light Quality
Sandra B. Wilson1, Nihal C. Rajapakse1, and Roy E. Young2; 1Dept. of Horticulture
and 2Dept. of Agricultural and Biological Engineering, Clemson Univ., Clemson,
SC 29634
Micropropagation is often associated with mass production at a competitive price. Since labor accounts for a large portion of micropropagation costs,
alternative measures to distribute labor costs are necessary. One such method of
distributing labor costs is the use of storage systems to hold micropropagated
plantlets until market availability. Broccoli (Brassica oleracea L. ‘Green Duke’)
plantlets were cultured photoautotrophically (without sugar) or photomixotrophically (with sugar) on cellulose plugs in liquid media in vitro for 3 weeks at 23
°C and 150 µmol • m–2• s–1 photosynthetic photon fl ux (PPF). To determine the
conditions that yield a zero carbon balance, plantlets were subsequently stored for
3 d under different temperatures (1, 5, 10, 15 °C), different light intensities (1.6,
4.1, 8.6 PPF), and different light spectra (provided by white or blue fl uorescent
bulbs or red Light Emitting Diodes). Plantlets under 3 PPF and 1 °C maintained
a zero carbon balance. Subsequently, plantlets were stored for 4, 8, or 12 weeks at
1 °C under darkness or 3 PPF of white, red, or blue light. Prior to low temperature
storage, photomixotrophic plantlets were characterized by increased chlorophyll,
dry mass, total soluble sugars (TSS), leaf starch, and net photosynthetic rate (NPR).
Illumination during storage was necessary to maintain dry mass, TSS, NPR, and
regrowth potential of photoautotrophic plantlets. When sucrose was provided
to the media, dark stored plantlets survived up to 12 weeks of storage. During
storage, the quality of broccoli plantlets was best maintained under red light. Red
light increased chlorophyll, TSS, and dry matter accumulation into leaves during
storage. In addition, photoautotrophic plantlets stored for 8 or 12 weeks under red
light had higher survival rates once acclimatized to the greenhouse when compared
to photoautotrophic plantlets stored in darkness or under white or blue light.
550
Reproductive Responses of Capsicum annuum to High Temperatures
Ami N. Erickson* and Albert H. Markhart III.; Dept. of Horticulture Sciences, Univ.
of Minnesota, St. Paul, MN 55108
HORTSCIENCE, VOL. 33(3), JUNE 1998
Fruit yield reduction due to high temperatures has been widely observed in
Solanaceous crops. Our past experiments have demonstrated that Capsicum annuum cultivars Ace and Bell Boy completely fail to produce fruit when grown at
constant 33 °C. However, fl owers are produced, continually. To determine which
stages of fl ower development are sensitive to high temperatures, pepper buds,
ranging in size from 1 mm to anthesis, were exposed to high temperatures for
6 hr, 48 hr, 5 days, or for the duration of the experiment. Fruit set for each bud
size was determined. Exposure to high temperatures at anthesis and at the 2-mm
size stage for 2 or more days signifi cantly reduced fruit production. To determine
whether inhibition of pollination, inhibition of fertilization, and/or injury to the
female or male structures prevents fruit production at high temperatures, fl owers
from pepper cultivars Ace and Bell Boy were grown until fl owers on the 8th or
9th node were 11 mm in length. Plants were divided between 25 °C and 33 °C
constant growth chambers for 2 to 4 days until anthesis. At anthesis, fl owers
from both treatments were cross-pollinated in all combination, and crosses were
equally divided between 33 or 25 °C growth chambers until fruit set or fl owers
abscised. All fl ower crosses resulted in 80% to 100% fruit set when post-pollination temperatures were 25 °C. However, post-pollination temperatures of 33
°C signifi cantly reduced fruit production. Reduced fruit set by fl owers exposed
to high temperatures during anthesis and pollination is not a result of inviable
pollen or ovule, but an inhibition of fertilization or initial fruit development.
551
Flower Development and Yield of Cucurbita in Four Locations
Differing in Temperature
H.C. Wien* 1, S. Cady2, D.N. Maynard3, C. McClurg4, and D. Riggs5; 1Dept. of Fruit
and Vegetable Science, Cornell Univ., Ithaca, NY 14853; 2Hillsborough County
Coop. Extn. Seffner, FL 33584; 3Univ. of Florida, Bradenton, FL 34203; 4Dept. of
Horticulture, Univ. of Maryland, College Park, MD 20742; 5Cornell Coop. Extn.,
Albany, NY 12207
Preliminary greenhouse experiments indicated that Cucurbita pepo, when
grown at high temperatures, shows a high incidence of female fl ower bud necrosis,
preventing those fl owers from reaching anthesis and thus delaying fruit set. This
can lead to reduced yield in areas with short growing seasons. To determine if
delayed fruit set also occurred under fi eld conditions, replicated cultivar trials were
conducted during the summer seasons of 1996 and 1997 in Ithaca and Albany,
N.Y.; Wye, Md., and Bradenton, Fla. Mean growing season air temperatures were
20, 21, 24, and 28 °C, respectively, at the four locations. Delay in fruit set was
indicated by the main stem node number at which the fi rst fruit formed. In Ithaca
and Albany, the six cultivars grown in both years formed their fi rst fruit at node 17,
while this was shifted to node 24 at Wye, and to node 26 or more at Bradenton. Fruit
yields among the C. pepo cultivars ranged from 45 to 85 mt• ha–1 in all locations
except Bradenton, where they ranged from 7 to 35 tons. Among C. pepo cultivars,
‘Appalachian’ showed least yield decrease at Bradenton, and ‘Howden’ and ‘Baby
Bear’ the most, in the hotter 1996 season. The C. maxima ‘Prize Winner’ yielded
well in all locations. The results indicate that delayed fruit set occurred most often
in the highest temperature locations. There is scope for selecting for improved
high temperature female fl ower development among C. pepo cultivars.
133 ORAL SESSION 33 (Abstr. 552–559)
Vegetable Crops—Postharvest Physiology
& Food Science
552
Distribution of Glucosinolates and M yrosinase Activity in
Cruciferous Vegetables
M. Kushad* 1, A. Brown1, H.-Y. Baik2, A. Kurilich1, J. Juvik1, M. Wallig3, B. Klein2,
and E. Jeffery2; Depts. of 1Natural Resources and Environmental Sciences, 2Food
Science and Human Nutrition, and 3Vet. Pathobiology, Univ. of Illinois, Urbana,
IL 61801
A diet rich in curciferous vegetables has been associated with inhibition
of chemically induced carcinogenesis in laboratory animals and humans. The
underlying mechanism(s) for this inhibition is not completely clear; however,
cruciferous vegetables are rich in sulfur-containing glucosides called gluco-
543
sinolates. Myrosinase-mediated breakdown of glucosinolates has been shown
to produce compounds with anti-cancer activity. About 100 forms of glucosinolates have been identifi ed, mostly in the Cruciferae family. In this study, we have
developed a unique data set of glucosinolate types and amounts in 51 broccoli,
three caulifl ower, fi ve Brussels sprouts, fi ve cabbage, and two kale lines. The
types of glucosinolates and their concentrations were variable among the different
genotypes and within each genotype. The dominant glucosinolates in broccoli
were glucoraphanin, gluconapin, and glucobrassicin. Glucoraphanin concentration in broccoli ranged from 0.1 µmol • g–1 dry weight in EV6-1 to 21.7 µmol • g–1
dry weight in Brigadier. Concentrations of the other types of glucosinolates in
broccoli also showed wide range of variability. In cabbage, Brussels sprouts,
caulifl ower, and kale, the dominant glucosinolates were sinigrin (7.8, 8.9, 9.3, and
10.3 µmol • g–1 dry weight, respectively) and glucobrassicin (0.9, 3.2, 1.3, and 1.2
µmol • g–1 dry weight, respectively). Brussels sprouts also has signifi cant amounts
of gluconapin (6.8 µmol • g–1 dry weight). Myrosinase activity, using sinigrin as
substrate, was signifi cantly higher in cabbage, Brussels sprouts, caulifl ower, and
kale than in broccoli. Wide variations in glucosinolates, glucosinolates content,
and myrosinase activity among cruciferous genotypes and within each genotype
suggest differences in the health-promoting properties of these vegetables.
553
Thermal Blast Peeling of Sweetpotatoes
D.A. Smith* 1 and H. Harris2; 1Dept. of Horticulture, Univ. of Nebraska–Lincoln,
Lincoln, NE 68583; 2Dept. of Horticulture, Auburn University, AL 36849
Thermal blast peeling is a process whereby peels and blemishes are effi ciently
removed from produce by holding the produce for a brief period in a heated, closed
vessel fi lled with superheated steam under elevated pressure while supplemental
radiant heat is supplied by the vessel wall. This intense, dry heat superheats a
fi lm of moisture immediately underlying the peel tissue. The pressure within the
vessel is then instantaneously reduced by opening the vessel. Steam within the
vessel expands blowing the produce free of the vessel and simultaneously the
superheated water in and immediately underlying the peel fl ashes to steam thus
cleanly exploding the peel tissues from the produce. Different size grades and
cultivars of sweetpotatoes were peeled by the Thermal blast process, hot caustic
immersion, or by high-pressure saturated steam. Thermal blast-peeled sweetpotatoes had higher product recoveries, less heat penetration into the tissue, and
better color than caustic or saturated steam-peeled potatoes.
554
Thermal Blast Peeling of Peppers
D.A. Smith1 and H. Harris* 2; 1Dept. of Horticulture, Univ. of Nebraska–Lincoln,
Lincoln, NE 68583; 2Dept.of Horticulture, Auburn University, AL 36849
The skins of peppers are tightly attached to the fl esh and do not readily
separate by moderate scalding or steaming. In commercial canning operations,
skin separation is achieved by immersion in hot caustic or by fl aming. These
treatments remove a substantial portion of edible pod tissue and cause tissue
collapse and loss of product quality. Thermal blast peeling is a process whereby
peels and blemishes are effi ciently removed from produce by holding the produce
for a brief period in a heated, closed vessel fi lled with superheated steam under
elevated pressure while supplemental radiant heat is supplied by the vessel wall.
This intense, dry heat superheats a fi lm of moisture immediately underlying the
peel tissue. The pressure within the vessel is then instantaneously reduced by
opening the vessel. Steam within the vessel expands blowing the produce free
of the vessel and simultaneously the superheated water in and immediately
underlying the peel fl ashes to steam thus cleanly exploding the peel tissues from
the produce. Pimiento peppers and jalapeno peppers were peeled by the Thermal
blast process and compared to caustic peeled peppers. Product yields, Instron
texture analysis, and color were compared in both the raw peeled fruit and in the
canned peeled product. Volatile fl avor profi les were analyzed by head space gas
chromatography. Thermal blast-peeled peppers had fi rmer texture, thicker pod
walls, and better color than caustic-peeled peppers. Thermal blast-peeled peppers
had head space volatiles similar to unheated raw peppers.
555
Nondestructive Quality Evaluation of Tomatoes
A. Hakim* 1, A. Purvis1, E. Pehu2, I. Voipio2, and E. Kaukovirta2; 1Dept. of Horticulture, Univ. of Georgia, Coastal Plain Station, P.O.Box 748, Tifton, GA 31793;
2
Dept. of Plant Production, Horticulture Section, 00014, Univ. of Helsinki,
544
Helsinki, Finland
Both external and internal quality of fruits such as tomatoes can be evaluated by
different methods, but all most all of the methods are destructive. For this reason,
there is a need to reassess some of the alternative techniques. Nondestructive
quality evaluation is an attractive alternative. The principles of different nondestructive quality evaluation techniques such as optical, physical, and fl uorescence
techniques applied to tomato fruit is explained. Successful application of these
techniques that could be used for evaluation of different quality attributes are
illustrated. The advantages of nondestructive quality evaluation techniques are
that they are very fast, easy, labor- and time-intensive, and inexpensive. These
techniques could also be useful to evaluate the quality of other vegetables.
556
Apoplastic pH and Mineral Composition during Ripening of
Tomato Pericarp
Domingos P.F. Almeida* and Donald J. Huber; Horticultural Sciences Dept., Univ.
of Florida, Gainesville, FL 32611
Ionic conditions and pH affect the catalytic activity of polygalacturonase and
other cell wall enzymes, as well as non-enzymic pectin solubilization. Despite its
potential role in regulating fruit ripening, apoplastic pH and mineral composition
in ripening fruit are poorly documented. A pressure-extracted fl uid was obtained
from tomato pericarp, using a constant pressure of≈0.6–0.7 MPa for immature
and mature-green fruit and 0.3–0.5 MPa for pink and red fruit. The osmolality of
the pressure-extracted fl uid ranged from 66 to 138 mmol • kg–1 compared with
268 to 293 mmol • kg–1 for the bulk pericarp homogenate, which attests to the
putative apoplastic origin of the fl uid. The pH of the apoplastic fl uid was 6.7 at the
immature and mature-green stages and dropped to 4.4 by the ripe stage, whereas
bulk pericarp pH dropped from 4.6 to 4.3. [K+] in the apoplast increased from
13.2 mM at the mature-green stage to 37.3 mM at the ripe stage, whereas the bulk
tissue [K+] ranged from 44 to 49 mM without relation with ripening stage. [Mg2+]
declined from 11.9 mM in immature fruit to 8.7 mM in mature-green fruit and
then increased to 12.9 mM in ripe fruit. [P] increased from 1.5 to 4.8 mM during
ripening, and [Cl – ] remained around 3.8 to 4.0 mM until the pink stage, increasing
to 6.5 mM at the ripe stage. [Na+] remained constant at 6.2 to 6.5 mM, whereas
[Ca2+] ranged from 3.5 to 4.9 with no consistent relationship with ripening stage.
The changes in pH and ionic composition of the pericarp apoplast may affect the
binding and catalysis of cell wall hydrolases and physical interactions between
structural polysaccharides.
557
Sugar Changes, Respiration, and Decay Control of Sweet-potatoes in Consumer Packages
Anthony W. Kilili * , David H. Picha, and Yuehe Huang; Dept. of Horticulture,
Louisiana State Univ., Baton Rouge, LA 70803
Cured ‘Beauregard’ sweetpotatoes [ Ipomoea batatas (L.) Lam] were either
treated with a fungicide (300 ppm, 2,6-dichloro-4-nitroaniline), hot water (55
°C for 5 min), a combination of the two treatments, or untreated. The roots were
shrink-wrapped in 2.3-kg consumer packs using a Clysar D 955 heat-shrinkable
fi lm. The packs were kept at room temperature, which ranged from 18 to 22C,
for 4 weeks. The average CO2 concentration in the packages was 18% after the
4-week period. Roots in the wrapped packages lost 0.7% fresh weight, whereas
nonwrapped roots lost 4.2% fresh weight. Shrink-wrapped roots maintained a
lower rate of respiration for several days after removal from the packages. Hot
water and fungicide treatments reduced Rhizopus spp. decay and enhanced root
appearance. An additional benefi t of hot water treatment was an inhibition of
sprouting. Wrapped sweetpotatoes had lower alcohol insoluble solids and dry
weight. The concentration of fructose and glucose was higher in wrapped roots,
while sucrose concentration was lower. There was also a 20% increase in both
acid and neutral invertase activity in the wrapped roots compared to nonwrapped
roots. Hot water treatment is a viable alternative to fungicides in extending shelflife of consumer packaged sweetpotatoes.
558
Postharvest Application of Calcium to Whole M uskmelon
Fruits
Gene Lester* 1 and Michale Grusak2; 1USDA/ARS/SARC, 2301 South International
Blvd., Weslaco, TX 78596; 2USDA/ARS/CNRC, 1100 Bates Street, Houston, TX
77030
HORTSCIENCE, VOL. 33(3), JUNE 1998
Fully mature, abscised, hybrid netted- and honey dew-muskmelon fruits
submerged in amino acid-calcium (AA-Ca) chelate solutions, vs. non-calcium
treated fruits, were less senescent and had little or no surface decay following
21 days at 10 °C (honey dew) or 4C (netted) plus 3 days at 21 °C. Honey dew
fruits submerged in either AA-Ca or AA-Ca plus AA-Mg, and netted fruits in
AA-Ca plus AA-Mg, had hypodermal-mesocarp tissue [Ca2+] of 6.0 mg per g dry
mass or higher 10 days postharvest, which is statistically similar to [Ca2+] in
freshly harvested fruits. Non-calcium treated vs. calcium treated fruits, 10 days
postharvest, had signifi cantly less 6.0 mg per g dry mass [Ca2+]. Maintaining
muskmelon hypodermal-mesocarp tissue [Ca2+] at 6.0 mg per g dry mass or higher
maintained membrane integrity as evidenced by low free sterol: total phospholipid
ratio (mol:mol), low electrolyte leakage, high total and specifi c H+- ATPase activities, and low lipoxygenase activity; maintained fruit fi rmness; and extended fruit
storage life 2.4-fold (i.e., to 24 days) vs. non-calcium treated fruits. Application
of calcium to abscised, fully ripe honey dew and netted muskmelon fruits should
reduce fruit senescence rate in storage and should promote extended market-life
and a higher quality product.
Road, Clinton, NC 28328; 2Dept. of Horticultural Science, North Carolina State
Univ., Raleigh, NC 27695-7609.
Muskmelon plant populations and arrangements were evaluated at two sites
in North Carolina in 1997. Within-row plant spacings of single rows were 0.15,
0.30, 0.46, 0.61, and 0.76 m, while staggered twin row spacings were 0.30, 0.46,
and 0.61 m. The trials were conducted on black plastic with drip irrigation at both
locations using the ‘Athena’ cultivar. One trial was seeded 22 Apr., the other was
transplanted 21 May. Yield was recorded as fruit number and weight. Soluble solids
measurements were also taken. Yields were nearly two times greater when planted
on 22 Apr. than 21 May. Yields in the later planting ranged between 13,300 and
18,800 melons per hectare, while yields in the earlier planting ranged between
23,700 and 31,600 melons per hectare. Populations arranged in staggered twin
rows on the bed provided no yield advantage compared with single rows. As
in-row plant spacing increased, yields of large-sized fruit (>2.0 kg) tended to be
greater, while production of smaller size marketable fruit (1.4 to 2.0 kg) tended
to be greater as in-row plant spacing decreased. Soluble solids were not affected
by plant population.
559
Making Sense of Cooling Data
562
Drip Irrigation and Stand Establishment Affect Yield and Quality of Cantaloupe
M.D. Boyette*; Dept. of Biological and Agricultural Engineering, North Carolina
State Univ., Raleigh, NC 27695-7625
Prompt cooling to remove fi eld heat is an essential part of proper postharvest
handling for many types of fresh fruits and vegetables. Growers, consultants,
and horticultural agents are often encouraged to collect cooling data (time vs.
temperature) in order to compare cooling rates for different systems, containers,
etc. These data can be misleading and confusing and seldom yield much useful information. With proper analysis, cooling data can yield a large amount of
information. The problem is not the fault of the data, as much as the lack of simple
methods to analyze these data. This presentation will demonstrate several simple
methods to extract useful information from cooling data.
134 ORAL SESSION 34 (Abstr. 560–567)
Vegetable Crops—Culture & Management
560
Potassium Fertilization Affects Yield and Leaf Mineral Concentration of Slicing Cucumber
Carrie L. Smith* and George J. Hochmuth; Horticultural Sciences Dept., Univ. of
Florida, Gainesville, FL 32611-0690
Successful fertilization of a crop depends on knowing the crop nutrient requirement (CNR) for production of maximum economic yield and on using soil tests
that are properly calibrated and correlated with crop response. During Summer
1997, ‘Lightning’ cucumber was grown with white-on-black polyethylene mulch,
methyl bromide fumigation, and drip irrigation on beds with 1.2-m centers. Two
rows of cucumbers were planted per bed with an in-row spacing of 30.5 cm. Treatments were 0, 40, 85, 170, 340 kg• ha–1 K on a soil testing “low” in potassium
(Mehlich 1 extractable K = 24.3 mg• kg–1 soil). Treatments were applied 20%
preplant and the remainder injected through drip irrigation in fi ve equal amounts
as determined by treatment. The most recently matured leaf was sampled at fi rst
fl ower, full bloom, and fi rst harvest for determination of K concentration. Leaf
K concentration at fi rst fl ower showed a quadratic response with a maximum
of 54 g• kg–1 at 445 kg• ha–1 K. At full bloom and fi rst harvest sampling, leaf K
concentration showed a linear response over the range of 0 to 340 kg• ha–1 K.
Leaf K was defi cient for plants receiving 0 and 40 kg• ha–1 K at the full bloom
sampling. Early yields (harvests 1+2) of U.S. number 1 and total marketable fruits
increased linearly over the treatment range. Season total yield of U.S. fancy and
total marketable fruits increased quadratically with maxima of 43 MT• ha–1 and
67 MT• ha–1 at K rates of 270 kg• ha–1 and 300 kg• ha–1, respectively, while U.S.
number 1 yield increased linearly.
561
Effect of Plant Population on Muskmelon Yield and Quality
Allan C. Thornton* 1, Jonathan R. Schultheis2, and S. Alan Walters2; 1North
Carolina Cooperative Extension Service, Sampson County Center, 369 Rowan
HORTSCIENCE, VOL. 33(3), JUNE 1998
D.I. Leskovar* 1, J.C. Ward1, R.W. Sprague1, and A. Meiri 2; 1Texas Agricultural
Exp. Station, Texas A& M Univ., Uvalde, TX 78801; 2The Inst. of Soil and Water,
The Volcani Center, ARO, Israel
Water pumping restrictions of high-quality irrigation water from underground
aquifers is affecting vegetable production in Southwest Texas. There is a need
to develop effi cient defi cit-irrigation strategies to minimize irrigation inputs
and maintain crop profi tability. Our objective was to determine how growth,
yield, and quality of cantaloupe (Cucumis melo L. cv. ‘Caravelle’) are affected
by irrigation systems with varying input levels, including drip depth position
and polyethylene mulch. Stand establishment systems used were containerized
transplants and direct seeding. Field experiments were conducted on a Uvalde
silty clay loam soil. Marketable yields increased in the order of pre-irrigation
followed by: dry-land conditions, furrow/no-mulch, furrow/mulch, drip-surface
(0 cm depth)/mulch, drip-subsurface (10-cm depth)/mulch, and drip- subsurface
(30 cm depth)/mulch. Pooled across all drip depth treatments, plants on drip
had higher water use effi ciency than plants on furrow/no-mulch or furrow/mulch
systems. Transplants with drip-surface produced 75% higher total and fruit size
No. 9 yields than drip-subsurface (10- or 30-cm depth) during the fi rst harvest,
but total yields were unaffected by drip tape position. About similar trends were
measured in a subsequent study except for a signifi cant irrigation system ( stand
establishment interaction for yield. Total yields were highest for transplants on
drip-subsurface (10-cm depth) and direct seeded plants on drip-subsurface (10
and 30 cm depth) with mulch.
563
Winter Production of ‘Galia’ Muskmelons in Northern Florida
Using Protective Structures and Soilless Culture
Eric A. Waldo*, George J. Hochmuth, Daniel J. Cantliffe, and Steven A. Sargent;
Horticultural Sciences Dept., IFAS, Univ. of Florida, Gainesville, FL 32611
Vegetable production in southern Florida is being displaced northward due
to escalating land prices. In order to produce vegetable crops in northern Florida
during the cooler months when southern Florida has traditionally captured the
winter market, methods of protecting crops from the cold must be investigated.
In addition, the impending ban of methyl bromide in 2001 under the Clean Air
Act mandates research on alternative crop production methods not requiring this
soil fumigant. We grew ‘Galia’ muskmelons [ Cucumis melo var. reticulatus (L.)]
under walk-in tunnels and low-tunnels (rowcovers) during the Winter/Spring of
1997 and the Fall/Winter/Spring of 1997–1998. The walk-in tunnels were quonset
style structures, 10 by 20 m, covered with a single layer of polyethylene fi lm.
Three of the six walk-in tunnels had a passive heating system consisting of four
water tubes each 30.5 cm in diameter and 15.25 m long, which absorbed solar
energy and released it as thermal energy during cool nights. Half of all melons in
each tunnel treatment were grown hydroponically in bags of perlite; the other half
were grown in mulched, raised soil beds. In Spring 1997 experiment, early yield,
total marketable yield, soluble solids concentration, and average fruit weight were
greater with passively heated and unheated walk-in tunnels than with low-tunnels.
Total marketable yield and average fruit mass were greater for melons grown in
soil than for melons grown in perlite. Soluble solids concentrations were similar
545
for melons grown in soil and perlite.
564
Plant Population, Seedlings per Hill, Cultivar, and Plastic
Mulch Affect Watermelon Yield, Size, and Quality
D.C. Sanders*, J.D. Cure, J.R. Schultheis,and E.A. Estes; Depts. of Horticultural
Science and Agriculture and Resource Economics, North Carolina State Univ.,
Raleigh, NC 27695-7609
Plant population, seedlings per hill, cultivar and plastic mulch were evaluated
in fi ve environments for their affect on watermelon yield, size and quality. ‘Royal
Jubilee’ outyielded ‘Prince Charles’ in all environments, and the highest yields were
associated with low % culls and high fruit numbers per hectare. Highest yields of
marketable fruits (>4.5 kg/melon) were obtained using mulch and areas per plant
between 0.4–0.9/m. Unless there is a market for small fruits (<4.5 kg), optimum
area per plant was 1 m/plant. Results for one plant/hill at one in-row spacing
were similar to those for the alternative planting pattern of two plants/hill at half
the in-row spacing, thus supporting the feasibility of using the more economical
alterative planting pattern.
565
Foliar and Spatial Requirements for Watermelon
Warren Roberts*, Jim Duthie, Jonathan Edelson, and Jim Shrefl er; Wes Watkins
Agricultural Research and Extension Center, Oklahoma State Univ., Box 128,
Lane, OK 74555
Unrestricted watermelon plants will cover large areas of soil surface, and
watermelons are normally planted in rows 2 to 3 m apart to allow vine extension.
Even so, machinery used for cultivating, spraying, and harvesting may crush vines,
thereby reducing plant size and restricting the ground surface area available to the
plant. Insect or disease defoliation may limit the leaf surface area that is available
for fruit production. Some farmers intentionally limit vine length or surface area
in the belief that this will promote fruit set. Experiments with Citrullus lanatus (cv.
Sangria, Crimson Trio, and Scarlet Trio) have been conducted in southeastern
Oklahoma to determine the effect of branch number, branch length, melon number,
and root volume on fruit yield. Branch length was limited to 1.2, 2.4, 3.7, or 4.9
m, and branch number was limited to either one or two branches per plant. An
unpruned control treatment was included for comparison. Limitation of branch
length limited fruit yield. Likewise, limitation of branch number limited fruit yield.
Watermelons were also grown in a series of 10 containers that ranged in volume
from 0.1 to 1.0 m3. Root volume was directly correlated with watermelon yield,
but the effect was minimal. Marketable melons were produced in containers as
small as 0.1 m3 volume.
566
Germination Response of ‘Genesis’ Triploid Watermelon [Citrullus lantaus (Thunb.) Matsum & Nakai] to Hydrogen Peroxide
and Seed Coat Alteration
John R. Duval* and D. Scott NeSmith; Dept. of Horticulture Georgia Station,
Griffi n, GA 30223
Triploid watermelons are fast becoming a highly desirable specialty crop. Poor
germination and nonuniform emergence of the relatively expensive seed prohibits
to many potential growers. Improvement of germination and emergence of triploid
watermelons would reduce overall risk to a grower, thus increasing the crops
market prominence. Seeds of ‘Genesis’ triploid watermelon were subjected to three
treatments: 1) seed coat removal; 2) clipping the seed coat opposite the radicle
end, and 3) no seed coat alteration. Seeds from each treatment were germinated
on agar alone or in the presence of 5 ml of a 1% , 2% , 4% , or 8% solution of
H2O2. Test were conducted in a constant temperature (28 °C) growth chamber
in the dark. Seed coat removal, clipping, and all levels of H2O2 increased fi nal
germination percentages relative to the control. Germination differences as great
as 70% occurred. Hydrogen peroxide levels greater than 2% resulted in severe
injury to germinating seeds.
567
Influence of Cyclic Cold Temperature Stress on Watermelon
Seedling Growth, Earliness, Yield, and Quality
Ahmet Korkmaz* and Robert J. Dufault; Clemson Univ. Coastal Research &
Education Center, Charleston, SC 29414
Watermelon seedlings may be repeatedly exposed to temperatures alternat-
546
ing between almost freezing and optimal temperatures for growth during stand
establishment in coastal South Carolina. ‘Carnival’ watermelon transplants were
exposed to 2 °C for 3, 6, and 9 h, for 1, 3, 6, and 9 days in a walk-in cooler
and then to warm temperatures (24 °C) immediately prior to fi eld planting. Our
objective was to determine the long term effect of early season cold temperature
exposure on seedling growth, earliness, yield and quality by simulating the
cold/warm alternations possible in the fi eld. Cold-stressed transplants were fi eld
planted after the risk of ambient cold stress was negligible. Exposure to cycling
cold temperatures generally did not affect earliness, total productivity and quality,
although seedling growth characteristics were reduced in response to the longer
cold-stress treatment. Therefore, cold temperature stresses occurring in the fi eld
at transplanting have negligible benefi cial or detrimental effects on yield potential
of ‘Carnival’ watermelon.
139 ORAL SESSION 35 (Abstr. 568–572)
Vegetable Crops—Breeding & Genetics
568
Genetic Similarity Among Broccoli Inbreds “Essentially Derived” from Commercial Cultivars
Mark W. Farnham* 1, Jiang Lu2, and Julie M. Villand3; 1USDA–ARS–U.S. Vegetable
Laboratory, Charleston, SC 29414; 2Center for Viticultural Sciences, Florida
A& M Univ., Tallahassee, FL 32307; 3Dept. of Horticulture, Univ. of Wisconsin,
Madison, WI 53706
DNA markers can assess close genetic relationships between individuals of
a crop as when one variety is developed (i.e., “essentially derived”) from another.
An acceptable threshold, based on empirical results, should be established for a
crop to indicate what constitutes an “essentially derived” variety in the absence
of clear pedigree information. Empirical data could help settle infringements of
intellectual property rights, but appropriate data are not being generated for most
crops. Thus, our objectives were to characterize genetic relationships among
broccoli varieties “essentially derived” from known parents using random amplifi ed polymorphic DNA (RAPD) markers as a measure of genotype and to provide
an empirical basis for threshold levels in this crop. Six F1 broccoli hybrids and
three inbred lines (doubled-haploids) developed from each of the hybrids (24
entries) were evaluated by RAPD analysis. RAPD assays were conducted using 23 different oligonucleotide 10-mers. Of 179 RAPD bands scored, 94 were
polymorphic among the entries. Similarity indices were computed from RAPD
data, and a multi-dimensional scaling (MDS) plot was constructed. Similarity
indices for all pairwise comparisons ranged from 0.40 to 0.90. ‘High Sierra’ and
it’s derived lines were the most closely related group with indices from 0.81 to
0.90. With ‘High Sierra’, ‘Sultan’, and ‘Marathon’, the three derived lines were more
closely related to their respective parental hybrids than were any other entries.
The hybrids ‘Futura’, ‘Everest’, and ‘Viking’ were more genetically similar to other
entries than to their derived lines. A threshold level based on data from ‘High
Sierra’, ‘Marathon’, ‘Sultan’, and their derived lines would not identify “essentially
derived” lines developed from other hybrids.
569
Molecular Marker Linked to High Solanine/Chaconin (Nil/Low
Leptin) in Solanum chacoense, and Implications for Leptine
Biosynthesis
C.M. Ronning* , J.R. Stommel, L.L. Sanford, and S.P. Kowalski; USDA–ARS
Vegetable Lab., 10300 Baltimore Ave., BARC-West, Beltsville, MD 20705
Solanum chacoense, a wild relative of the cultivated potato, contains several
glycoalkaloids, including solanine, chaconine, and leptine. The foliar-specifi c
leptine glycoalkaloids are believed to confer resistance to the Colorado Potato
Beetle (CPB). Data from segregating F1 populations developed from crosses of
high x nil and high x high leptine producers were consistent with control of leptine
production by a single recessive gene; however, data from subsequent generations
strongly suggests the presence of additional factors affecting the inheritance and
expression of leptine glycoalkaloids in this population of S. chacoense. Using two
bulked DNA samples composed of high- and low-percent leptine individuals from
a segregating F1 population of S. chacoense, a 1500-bp RAPD product, UBC3701500, was identifi ed that is closely linked to high percent solanine+chaconine, and
HORTSCIENCE, VOL. 33(3), JUNE 1998
conversely to low percent leptine. This marker mapped to the end of the short arm
of potato chromosome 1, near the location of a previously mapped major QTL for
solanidine. The observed distribution of the UBC370-1500 marker, in conjunction
with these QTL data, suggest that hydroxylation of a common precursor to form
leptinidine occurs prior to formation of the solanidine aglycone. Implications
of these fi ndings for the development of CPB-resistant potato varieties will be
discussed.
570
Comparative Mapping of Three Bacterial, Three Fungal, and
One Virus Disease-resistance Genes in Common Bean
Geunhwa Jung* 1, James Nienhuis1, Dermot P. Coyne2, and H.M. Ariyarathne2;
Univ. of Wisconsin, Madison, WI 53706; and 2Univ. of Nebraska, Lincoln, NE
68583
Common bacterial blight (CBB), bacterial brown spot (BBS), and halo blight
(HB), incited by the bacterial pathogens Xanthomonas campestris pv. phaseoli
(Smith) Dye, Pseodomonas syringae pv. syringa, and Pseudomonas syringae
pv. phaseolicola, respectively are important diseases of common bean. In addition three fungal pathogens, web blight (WB) Thanatephorus cucumeris, rust
Uromyces appendiculatus, and white mold (WM) Sclerotinia sclerotiorum, are
also destructive diseases attacking common bean. Bean common mosaic virus is
also one of most major virus disease. Resistance genes (QTLs and major genes)
to three bacterial (CBB, BBS, and HB), three fungal (WB, rust, and WM), and one
viral pathogen (BCMV) were previously mapped in two common bean populations
(BAC 6 x HT 7719 and Belneb RR-1 x A55). The objective of this research was to
use an integrated RAPD map of the two populations to compare the positions and
effect of resistance QTL in common bean. Results indicate that two chromosomal
regions associated with QTL for CBB resistance mapped in both populations. The
same chromosomal regions associated with QTL for disease resistance to different
pathogens or same pathogens were detected in the integrated population.
1
571
Detection and Mapping of RAPD Markers Associated with QTL
Affecting Seed Size and Shape in Common Bean
Soon O. Park* 1, Dermot P. Coyne1, Geunhwa Jung2, E. Arnaud-Santana3, and
H. Ariyarathne1; 1Univ. of Nebraska, Lincoln, NE 68583; 2Univ. of Wisconsin,
Madison, WI 53706; 3Arroyo Loro Experiment Station, San Juan de la Maguana,
Dominican Republic
Seed size is an important trait in common bean. The objective was to identify
RAPD markers associated with QTL for seed weight, seed length, and seed height
in a molecular marker-based linkage map in a recombinant inbred (RI) population from the common bean cross of the larger seeded (100 seed/39 to 47 g)
PC-50 (ovate seed shape) x smaller seeded (100 seed/26 to 35 g) XAN-159 (fl at
rhomboidal seed shape). The parents and RI lines were grown in two separate
greenhouse and two fi eld (Wisconsin, Dominican Republic) experiments using
a RCBD. Continuous distributions for seed weight, seed length, and seed height
were observed for RI lines indicating quantitative inheritance. One to three QTLs
affecting seed weight explained 17% to 41% of the phenotypic variation. Two to
three QTLs for seed length explained 23% to 45% of the phenotypic variation. One
to four QTL associated with seed height explained 17% to 39% of the phenotypic
variation. A RAPD marker M5.850 in linkage group 3 was consistently associated
with seed weight, seed length, and seed height in all experiments and explained
7% to 13% of the phenotypic variation for these traits. A seedcoat pattern morphological marker (C ) in linkage group 1 was associated with seed weight and
seed height in two greenhouse experiments.
572
Mapping of Five Morphological Markers (dgs, blu, rnd, Ib, and
asp) in a Molecular Linkage Map of Common Bean
Gino Beltran* 1, Geunhwa Jung1, Mark Bassett2, and James Nienhuis1; 1Dept. of
Horticulture, 1575 Linden Dr., Univ. of Wisconsin, Madison, WI 53706; 2Horticultural Sci. Dept., 1143 Fifi eld Hall, Univ. of Florida, Gainesville, FL 32611
The classical genetic linkage map of common bean contains only a fraction of
the total genes that has been reported. These genes can be mapped in a molecular
linkage map so that genetic relationship among diferent genes can be better
understood. The objective of this study was to identify RAPD markers linked to
genes for fi ve morphological traits using bulked segregant analysis and to map
the markers to a molecular linkage map previously constructed in common bean.
HORTSCIENCE, VOL. 33(3), JUNE 1998
Five segregating populations were evaluated. Three BC2F2 populations with dgs
(dark green savoy leaf), blu (blue fl ower), and rnd (round leaf), respectively, were
developed with a Florida breeding line 7-1404 and 5-593 as the recurrent parent.
One BC3F2 population with the asp (dull seed coat) was developed from a BC2F2
5-593 line and 5-593 as the recurrent parent. Finally, an F2 segregating population
for Ib (fl at pod) was developed from ‘Hialeah’ fl at pod mutant x ‘Hialeah’. The linked
RAPD markers were mapped in a molecular linkage map previously constructed
using recombinant inbred population of the cross PC-50 x XAN-159. The results
of this study indicate that integrating morphological and molecular merkers can
result in a more complete genetic linkage map in common bean.
140 ORAL SESSION 36 (Abstr. 573–578)
Fruits/Nuts—Culture & Management
573
Effect of Canopy Angle and Row Spacing on Tree Growth,
Yield, Light Interception, and Fruit Quality of Y-trellis-trained
Apple Trees
Terence L. Robinson*; Dept. of Horticultral Sciences, Cornell Univ., New York
State Agricultural Experiment Station, Geneva, NY 14456 USA
‘Empire’/M.9/MM.106 and ‘Ace Delicious’/MM.106 apple trees were planted in
1985 at three between row spacings (3.0 m, 4.25 m and 5.5 m) and were trained
as either free standing central leaders or as Y-shaped hedgerows for 13 years. The
Y hedgerow arms had varying angles from 40° to 80° above the horizontal. Final
scaffold length, canopy volume, trunk cross-sectional area, and above-ground
canopy weight were positively correlated to the angle of the Y arms. As the angle of
the Y arms became more horizontal, the amount of growth removed during summer
pruning increased. At the fl attest angle (40° above horizontal), terminal growth of
both cultivars ceased and excessive vertical sucker growth resulted. As the angle
of the Y arms became more vertical, more terminal growth was obtained and less
shoot growth had to be removed during summer pruning. Cumulative yields of
the Y-shaped trees were generally greater than those of the central-leader-trained
trees. Exceptions were the most horizontal and the most vertical canopy angles,
which had the lowest yields. The relationship between angle of Y arms and yield
showed a broad optimum between 50° and 70° above the horizontal. There was
also a strong positive relationship between tree density and yield. ‘Empire’ fruit
size was smaller from the Y-shaped trees than from the central-leader trees. The
optimum angles for fruit size were the intermediate angles. Fruit color was poorest
on the fl attest angles and best on the most-vertical angles. The best yield effi ciency
was at intermediate angles (50° 70°). This resulted in the best balance of vegetative
growth and cropping.
574
Orchard Groundcover Systems Affect Meadow Vole Populations
and Damage to Apple Trees.
I.A. Merwin*, J.A. Ray, and P.D. Curtis; 118 Plant Science Bldg., Dept. of Fruit
and Vegetable Science, Cornell Univ., Ithaca, NY 14853.
Meadow vole (Microtus pennsylvanicus L.) populations, feeding activity, and
damage to young apple (Malus domestica Borkh.) trees were monitored by direct
observation, trap counts, and a feeding activity index in different groundcover
management systems (GMSs) for fi ve years in a New York orchard. Vole populations differed greatly among GMSs, with consistently higher populations and more
damage to tree trunks in crownvetch (Coronilla varia L.), hay-straw mulch, and red
fescue (Festuca rubra L.)sodgrass GMSs. Vole populations were highest in the
fall and lowest during the spring seasons each year. Anticoagulant rodenticides
and natural predation did not result in adequate control of voles in GMSs that
provided favorable habitat for nesting and feeding of this pest. The percent of soil
surface vegetation coverage was not, but the amount of groundcover biomass was,
a signifi cant predictor of vole populations and damage to trees, independent of
groundcover vegetation species. Trunk applications of thiram fungicide were less
effective than 40-cm-high plastic mesh trunk guards, but better than no protective
measures for controlling vole depredation in groundcover management systems
(GMSs) with high rodent populations. A combination of late fall vole trapouts,
close and consistent mowing of orchard fl oor vegetation, tree trunk protection
with mesh guards, ample surrounding habitat for natural predators of voles, and
547
suppression of tree row groundcover species with herbicides provided adequate
control of meadow voles without the use of rodenticides at this orchard.
575
Hydrophobic Particle Films Improve Tree Fruit Productivity
D.M. Glenn*, G. Puterka, T. Baugher, T. Unruh, and S. Drake; USDA, ARS, Appalachian Fruit Res. Station, 45 Wiltshire Rd., Kearneysville, WV 25430
Hydrophobic particle fi lm technology (HPF) is a developing pest control system
for tree fruit production systems. Studies were established in Chile, and Washington, Pennsylvania, and West Virginia in the United States, to evaluate the effect of
HPF technology on tree fruit yield and quality. Studies in Chile, Washington, and
West Virginia demonstrated increased photosynthetic rate at the leaf level. Yield
was increased in peaches (Chile) and apples (West Virginia), and fruit size was
increased in apples (Washington and Pennsylvania). Increased red color in apple
was demonstrated at all sites with reduced russetting and ‘Stayman’ cracking in
Pennsylvania. HPF technology appears to be an effective tool in reducing water
and heat stress in tree fruit resulting in increased fruit quality.
576
Long-term Performance of Asian Pear Trees in Maryland
C.S. Walsh* A.J. Barton, M. Newell, and G.R. Welsh; Dept. of Natural Resource
Sciences and Landscape Architecture, Univ. of Maryland, College Park, MD
20742-4452 USA
Three Asian pear plantings were set during the past decade. Plantings
included an initial cultivar planting on OH x F rootstock, the SE Zonal planting,
and a rootstock by cultivar factorial. Fireblight susceptibility and survival were
assessed in the fi rst two plantings following a summer hailstorm. Trees were
compared to Magness, a blight-tolerant buttery pear. Shin Li, Daisu Li, Shinsui,
and Olympic were more resistant than Magness, while Chojuro and Niitaka were
nearly as tolerant. Eleven other cultivars showed greater fi eld-susceptibility. The
most-susceptible cultivars were Ya Li and Ts’e Li. The third planting, which was
managed “organically,” was set at a different University farm. Trees there were
precocious and productive. A high percentage of marketable fruit was picked
from that planting over a 4-year period. Fireblight damage in this planting was
low, despite its “organic” production. Limited damage was attributed to early
bloom date, ground cover management, and a lack of insect vectors to transmit
the bacteria. Hosui, Seuri and Ts’e Li produced large-sized fruit. Shinko, 20th
Century, Ya Li and Shinseiki fruit were too small to be marketable without heavy
hand-thinning. Asian pears are an interesting alternative crop which are suited to
direct-market enterprises or to specialty growers interested in producing organic
fruit in the mid-Atlantic region.
577
Effect of Hedging Interval on Yield of ‘Chandler’ Walnuts
Kathy Kelley* 1, Warren Micke2, David E. Ramos2, and Jim Yeager2; 1Univ. of
California Cooperative Extension, Stanislaus Country, Modesto, CA 65355; 2Dept.
of Pomology, Univ. of California, Davis, CA 95616
In many California orchards, expected yields of hedgerow plantings of ‘Chandler’ (Juglans regia) walnuts have fallen below grower expectations. This study
compared crop yields following 2-, 3-, and 4-year hedging intervals. Results
indicate an incremental yield increase when ‘Chandler’ trees are hedged on a
3-year rather than the standard alternate-year hedging rotation. Extending the
hedging interval beyond 3 years shows little advantage and possible long-term
negative consequences as a result of prolonged shading and loss of spurs in the
interior canopy.
578
Canopy Manipulation to Enhance Early Season Cropping of
‘Arkin’ Carambola in South Florida
Roberto Núñez-Elisea and Jonathan H. Crane*; Univ. of Florida, Tropical Research
and Education Center, 18905 SW 280th St., Homestead, FL 33031
Carambola (Averrhoa carambola L.) is a fruit tree that exhibits nearly year-round
fl owering and fruiting in its natural, tropical habitat. The carambola industry of
subtropical south Florida is based almost exclusively on the local cultivar Arkin.
‘Arkin’ is susceptible to harsh winter conditions, which debilitate canopy growth
and limit the harvest season to about 7 months (July to February). Crop value
increases up to eight-fold during times of scarce production. Less than 10% of
total crop volume is produced when fruit value is highest. Strategies to enhance
548
early season cropping of ‘Arkin’ carambola were evaluated during a 3-year period. Under favorable growth conditions, carambola trees readily initiate fl owers
throughout most of the canopy. Pruning 3- to 4-year-old branches to their main
axes (branch length was reduced to about one-half of original size) during early
spring caused abundant and synchronous fl ower initiation on pruned branches,
and produced a crop in late June-early July. Fruit from pruned branches had
excellent appearance due to lack of wind damage. Fruit from intact portions of
the canopy began to be harvested 3 to 4 weeks later. In 9-year-old trees, the fall
crop was manually shaken off the tree in November-December, when most fruits
were about 50% of their fi nal size. Crop removal resulted in abundant fl owering
(more than three-fold compared to trees which retained their fruit until harvest)
throughout the canopy during early spring and also produced an early crop (( 48
kg/tree) in early July. Carambola growers in south Florida have begun to adopt
selective pruning and fall crop sacrifi ce to increase economic returns of their
groves.
141 ORAL SESSION 37 (Abstr. 579–587)
Fruits/Nuts—Nutrition/Water Management/Temperature Stress
579
Monitoring Nitrates in Ground Water of an Apple Orchard
Moreno Toselli 1* and Ronald L. Perry2; 1Dipartimento di Colture Arboree, Università di Bologna, Bologna, Italy; 2Dept.of Horticulture , Michigan State Univ.,
East Lansing, MI 48824
Nitrate (NO3– ) pollution is of high interest in modern agriculture. Although the
amount of nitrogen (N) usually supplied to an apple orchard is lower than other
crops, it could become a factor of pollution because of the lower tree root density
and of the low nitrogen use effi ciency. In this study we monitored the concentration
of nitrate in soil water solution in a 3-year old apple orchard located near Grand
Rapids (Mich.) during 1996 and 1997. The orchard had no history of fertilization,
but alfalfa crop was previously planted for several years. Eight lysimeters, 1.8
m tall and 1.8 m of diameter, were installed in 1995 in the orchard site without
changing the soil profi le. One tree was planted in each lysimeter in spring 1996.
Leached soil solution was collected bi-weekly in a connected 143-L storage
container. Additionally, three soil suction tubes (SST) were placed inside and
outside the lysimeters at a depth of 0.6, 1.05 and 1.55 m , in order to collect water
solution to evaluate the level of nitrate at different soil layers. Daily water (L/ha)
and nitrate (kg/ha) fl ow rate were linearly correlated with an R2 of 0.9. Nitrate fl ow
rates were highest and during the wet spring and winter periods. The variation
of NO3– fl ow rate during the year is a result of root and bacteria activity. All year
long, the nitrate concentration in the SST inside the lysimeters was higher than
those outside. These results show that the application rate for N could be different
from orchard to orchard and it must be necessary to know the soil N background,
cropping history and N-NO3– availability, in order to maximize productivity and
avoid environmental risks.
580
Effects of Nitrogen Cut-off Date in Combination with Urea or
Abscisic Acid (ABA) on Terminal Bud Set, Defoliation, Cold Acclimation, and Reserve Nitrogen in ‘Gala’ Apple Nursery Stock
Sunghee Guak*, Lailiang Cheng, and Leslie H. Fuchigami; Dept. of Horticulture,
Oregon State Univ., ALS 4007, Corvallis, OR 97331
Bench-grafted ‘Gala’/M26 apple trees were grown in pots and fertigated weekly
with 150 ppm N starting from 10 May. N supply was terminated on 21 Aug., 18
Sept., and 9 Oct. for the early, mid, and late N cut-off treatment, respectively. Half
of the trees in the early N cut-off treatment were sprayed twice with 3% urea at
6-day intervals in early October. Half of the trees in the mid and late N cut-off
treatment were sprayed twice with 1000 ppm ABA at 5-day intervals in early and
mid-October, respectively. Early N cut-off signifi cantly enhanced terminal bud set,
defoliation, and induction of cold acclimation compared to the late N cut-off. Foliar
urea increased the reserve N level in all tissues of the early N cut-off trees, almost
to the level of late N cut-off trees. Soluble protein concentrations were increased
by foliar urea, which accounted for about 23% , 10% , and 17% of the increase in
HORTSCIENCE, VOL. 33(3), JUNE 1998
the total N concentration in bark, wood, and roots, respectively. ABA treatment
enhanced leaf senescence and N mobilization in the mid and late N cut-off trees,
but did not affect terminal bud set and cold hardiness.
581
Foliar Urea Can Supplement Soil-applied Fertilizer in an Early
Maturing Peach
R.S. Johnson*, R.C. Rosecrance, and H.L. Andris; Dept of Pomology, Univ. of
California, Davis, CA 95616
Despite early studies that suggested foliar urea was ineffective in supplying
nitrogen to peach trees, recent studies have shown rapid uptake of low biuret urea
by peach leaves and subsequent mobilization to perennial tree parts. Labeled
nitrogen experiments have demonstrated the distribution of N among organs to
be very similar whether the N is supplied from foliar urea or from soil-applied
fertilizer. However, questions still remain concerning the long-term productivity
of trees treated repeatedly with foliar urea. Our fi rst experiment was conducted
on an early ripening peach, which generally requires about 100 kg N/ha applied
to the soil. The treatment to replace all soil applied N with two or three foliar applications of urea in the fall resulted in similar N distribution throughout the tree
and equal vegetative growth. However, fruit size was consistently smaller than the
soil-fertilized control over a 3-year period. Our second experiment, conducted on
the same variety, imposed a treatment to supplement about half the soil applied
fertilizer with fall foliar urea applications. This treatment was able to maintain fruit
size and yield over a 2-year period. Furthermore, vegetative growth was reduced
compared to the soil-fertilized control, suggesting foliar urea may be a useful tool
to help manipulate the distribution of growth between reproductive and vegetative
processes.
582
Influence of Nitrogen Fertilization on Pecan Nut Quality and
Yield
Laurence Sistrunk* and J. Benton Storey; Dept.of Horticultural Science, Texas
A& M Univ., College Station, TX 77843-2133
The infl uence of various nitrogen fertilization rates on the marketable yield
and nut quality of 12-year-old grafted ‘Desirable’, ‘Pawnee’, and ‘Stuart’ pecans
in east Texas was investigated. Pecans are alternate-bearing, and this test was
conducted during a high-yielding season. Terminal shoot growth and change
in trunk diameter was measured to determine tree response to nitrogen rates. A
standard rate of 44 kg N/ha was applied in March, April, and May to the control
trees as NH4NO3. A second treatment used 112 kg N/ha in March and the standard
rates the next two applications. A third treatment used 112 kg N/ha in March and
April and the standard rate in May. The fourth treatment used 112 kg N/ha in all
three applications. The treatments were arranged in a randomized block design.
Nut yields were generally higher with the increase in nitrogen for all cultivars with
the exception of ‘Stuart’, which showed the least change. Highest yield, terminal
and trunk diameter growth, and nut quality was obtained with the 336 kg N/ha rate.
Some differences in percent kernel, marketable yield and nut size were measured
with the three cultivars. Our data indicates that during a high-yielding crop load
on young trees, nitrogen fertilization can make a signifi cant difference in yield.
583
Effect of Fall/Winter Application of Foliar Urea on Flowering
and Yield of ‘Nour’ Clementine Mandarine
M. El-Otmani *1, A. Ait-Oubahou1, A. Tadili 1, M. El-Hila1, and C.J. Lovatt2; 1Dept.
d’Horticulture, Institut Agronomique et Vétérinaire Hassan II, Complexe Horticole
d’Agadir, B.P. 121, 80150, Aït-Melloul, Morocco; 2Dept. of Botany and Plant Sciences, Univ. of California, Riverside, CA 92521 USA
Experiments were established using clementine (Citrus reticulata Blanco)
groves to evaluate effect of urea application (at 0% , 0.8% , and 1.6% ) during
the period from October to February on fl owering and yield. Urea signifi cantly
promoted fl owering when applied during the period from the end of December
to early February. October treatment had no effect, but November treatments
somewhat increased infl orescence numbers. “Off year” trees (i.e., trees that have
a small fruit load resulting from the previous spring fl owering) produced more
infl orescence than “on year” trees (i.e., trees with heavy fruit load from fl owering
of the previous spring), and urea enhanced fl owering on both tree types. Flower
number per infl orescence increased signifi cantly more on “on year” trees irrespective of the type of infl orescence. Fruit set was signifi cantly increased for trees
HORTSCIENCE, VOL. 33(3), JUNE 1998
receiving urea treatments from November on, with the greatest increase observed
for the December/January treatments. Fruit size was increased signifi cantly more
by the January treatment than for the December application, whereas the October
and November treatment had no effect on these parameters. Consequently, both
earliness and export yield were improved with urea.
584
Fertigations and Foliar Sprays with Potassium Increase Fruit
Size of Grapefruit
Dariusz Swietlik*, Texas A& M Univ.–Kingsville, Citrus Center, P.O.Box 1150,
Weslaco, TX 78599
A study was conducted in a mature ‘Ray Ruby’ grapefruit (Citrus paradisi, Macf.)
orchard to elucidate the effect of fertigations and foliar sprays with KNO3 on fruit
size, leaf and fruit K level, and tree growth. The treatments include: 1) Control–no
K applied; fertigations applied in 2) December–April (F1); 3) February–May
(F2); 4) May–August (F3); 3 times foliar sprays applied at monthly intervals in
5) January–March (S1); 6) April–June (S2); or 7) June–August (S3). Potassium
was injected into microsprayer irrigation lines at the annual rate of 440 g K/tree
and foliar sprays were applied at 5% concentration. Compared to the control, the
S2 and F2 treatments increased the yield of large fruit, i.e., in commercial sizes
48 and larger, by 59% and 41% , respectively. Fruits this large are marketed fresh
and thus provide much higher returns to growers than those realizable from sales
of smaller fruit destined for processing. Potassium applications in April and May
were most effective in increasing fruit growth. The observed increases in yield of
large fruit were caused by a shift in the number of fruit from small to large fruit
size categories. This conclusion was supported by the observation that a total
fruit number and yield per tree were not affected by the treatments. There was a
positive relationship between fruit but not leaf K concentrations measured in May
and fruit size. No preference was established between expressing leaf and fruit K
concentrations on a dry- vs. fresh-weight basis.
585
Effects of Drought and Elevated Soil Temperature on Apple
Root Lifespan
D.M. Eissenstat*, Liqin Wang, and D.E. Flores-Alva; 103 Tyson Bldg., The Pennsylvania State Univ., University Park, PA 16802
Root lifespan has important consequences for plant growth and productivity,
plant competition, and nutrient cycling. However, compared to aboveground parts,
much less is know about root systems. Root dynamics of ‘Red Chief’ Delicious on
M26 rootstock trained on a trellis were examined near State College, Pa., using
minirhizotrons. Soil was heated 5 °C above ambient at a depth of 5 cm by circulating hot water over a stainless steel grid on the soil surface. Soil temperature (by
thermocouples) and soil moisture (by TDR) were monitored to a depth of 1 m.
Root birth rate peaked between late May and mid-June, during a period of rapid
shoot elongation and fruit expansion. Death rate was highest in July. There was
no evidence of alternate growth between roots and shoots. Drought and elevated
soil temperature increased root mortality. Median lifespan of fi ne roots near the
soil surface (<20 cm) was least in the heated-drought treatment (30 d) and longest
in the unheated-irrigated treatment (56 d). Heating caused substantial increases
in root birth rate, thus, causing higher populations in the heated than unheated
treatments despite the increased root death rate in the heated soil.
586
Evapotranspiration Measurement and Irrigation Scheduling for
Several Tropical Fruit Crops Using the EnviroScan System
Mongi Zekri* , Bruce Schaffer, Stephen K. O’Hair, Roberto Nunez-Elisea, and
Jonathan H. Crane; Univ. of Florida, Tropical Research and Education Center,
18905 SW 280 Street, Homestead, FL 33031
In southern Florida, most tropical fruit crops between Biscayne and Everglades
National Parks are irrigated at rates and frequencies based on experience and
observations of tree growth and fruit yield rather than on reliable quantitative
information of actual water use. This approach suggests that irrigation rates
may be excessive and could lead to leaching of agricultural chemicals into the
groundwater in this environmentally sensitive area. Therefore, a study is being
conducted to increase water use effi ciency and optimize irrigation by accurately
scheduling irrigation using a very effective management tool (EnviroScan, Sentek
Environmental Innovations, Pty., Kent, Australia) that continuously monitors soil
water content with highly accurate capacitance multi-sensor probes installed at
549
several depths within the soil profi le. The system measures crop water use by
monitoring soil water depletion rates and allows the maintenance of soil water
content within the optimum range (below fi eld capacity and well above the onset
of plant water stress). The study is being conducted in growers’ orchards with
three tropical fruit crops (avocado, carambola, and ‘Tahiti’ lime) to facilitate rapid
adoption and utilization of research results.
587
Effect of pH and NH4 NO3 as a Spray Additive on Penetration of
NAA Through Isolated Tomato Fruit Cuticle
Royal G. Fader* and Martin J. Bukovac; Dept. of Horticulture, Michigan State
Univ., East Lansing, MI 48824
We have reported that NH4NO3 (AN, 8 mM, pH 4.2), applied as simulated
spray droplets, enhanced penetration of 14C-NAA through isolated leaf and fruit
cuticles. One explanation for this response is that AN depresses NAA ( pKa= 4.2)
dissociation, increasing the nondissociated moiety, which penetrates more readily
than the anion (NAA’). Direct measurement of AN (concn. 0-800 mM) effect on NAA
(215 µM) dissociation as indexed by change in solution pH revealed no signifi cant
effect, with a pH change from 4.19 to 4.05. This change is not suffi cient to account
for the observed enhancement. When 14C-NAA, buffered (20 mM sodium citrate)
at pH 3.2, 4.2, 5.2, 6.2, was partitioned against chloroform, there was a marked
increase in NAA partitioning into chloroform as pH was decreased. AN (8 mM)
did not alter this partition behavior, also indicating no effect on NAA dissociation.
However, in cuticle penetration studies, using a fi nite dose system with 14C-NAA
buffered at pH 3.2, 4.2, 5.2, 6.2, and in the presence and absence of 8 mM AN,
there was no marked or consistent pH or AN (-70 to + 232 % of no AN control)
effect on penetration as indexed by initial slope (4-12 h) or penetration after 120 h
. The possible effects of AN and buffer on penetration of 14C-NAA from the droplet
deposit will be discussed.
142 ORAL SESSION 38 (Abstr. 588–594)
Vegetable Crops—Culture & Management
588
Coconut Coir Medium for Tomato Transplant Production
Mireia Arenas* and C.S. Vavrina; Dept. of Horticulture, 1143 Fifi eld Hall, Univ.
of Florida, Gainesville, FL 32611
Peat [70% peat + 30% vermiculite (v/v/)] has long been the primary growing medium in standard vegetable transplant production. However, interest has
increased in the use of coir (coconut pith) as an alternative vegetable transplant
medium because of favorable physico-chemical properties such us high water
holding capacity, low bulk density and high potassium content. Sixteen different
transplant media formulations (v/v) were tested in a mixture component experiment with tomato, using coir and peat as organic components and vermiculite
and perlite as inorganic components. Transplant growth was evaluated after 4,
5, and 6 weeks by growth analysis and at 6 weeks transplant quality parameters
(e.g. shoot/root dry weight, leaf area, stem diameter, height, etc.) were collected.
Coir grown tomato plants showed a delay in leaf production exhibiting lower leaf
area values over the total transplant growth period. Shoot and root growth was
maximized in media containing peat as the major organic component. However,
plants grown in a 50% peat/50% vermiculite medium were too tall for commercial
acceptance. Plants grown in all sixteen-transplant media pulled easily. However,
medium loss when transplants were pulled was unacceptable in medium high
in perlite content (50% by total volume). Coir-medium compared well with the
standard peat/vermiculite medium based on the transplant quality parameters of
stem diameter, root growth and height when used in the following mixtures: 50%
peat/25% coir/25% vermiculite and 50% peat/25% coir /25% perlite.
589
Effect of Red Polyethylene Mulch on Yield of Fresh-market
Tomatoes
Stephen M. Olson*; Univ. of Florida, IFAS, North Florida Research and Education
Center, Rt 3 Box 4370, Quincy, FL 32351
Trials were conducted during the spring production seasons of 1995 and
1996 comparing tomato (Lycoperisicon esculentum Mill.) Production on red
550
polyethylene mulch with black (standard) polyethylene mulch. ‘Colonial’ was
used in 1995 and ‘Mountain Spring’ in 1996. In 1995, fruit was harvested as a
mixture of color and mature greens while in 1996 fruit were harvested as pinks
only. In 1995, mulch color did not affect early, late, or seasonal yields of medium,
large, extra-large, or combined grades of fruit. Mulch color also did not affect fruit
size or percentage of fruit that were marketable. In 1996, six harvests were made
and there were no differences in yield (medium, large, extra-large, or combined
grades), fruit weight of percent marketable fruit at each harvest date or for total
season. From the results of these studies there was no benefi t from using the red
mulch, especially since the cost is higher.
590
Picking Regimes Affect Yield, Grade Distribution and Retail
Value of Colored Bell Pepper
Eric H. Simonne* and John T. Owen, Dept. of Horticulture, 101 Funchess Hall,
Auburn University, AL 36849-5408
The retail value of yellow and red bell peppers is usually three to fi ve times
higher than that of the green ones. However, colored bell pepper production in
Alabama is presently limited because most growers do not wait the additional 3
to 6 days needed for marketable green pepper to develop color. Hence, drip-irrigated yellow ‘Admiral’ and ‘Goldcoast’ and red ‘Bell Star’ and ‘Capsitrano’ bell
peppers were grown in single row and bare-ground, and harvested as needed
between July and October 1997 at the 0/3 (green), 1/3 or 2/3 colored stages. The
interaction variety x picking method was not signfi cant (P > 0.50). Early (9,136
kg/ha) and total (32,363 kg/ha) yields of green (0/3) peppers were signifi cantly
(P < 0.05) higher than those of the 1/3 and 2/3 colored ones (5,166 and 27,235
kg/ha, respectively). Higher green yields were mainly due to increased numbers
of marketable fruits rather than increased fruit size. The longer the pods stayed
on the plants,the more likely was sunscald to occur. Retail values (/ha) for the
early fancy grade were $10,800 and $20,500 for the green and colored peppers,
respectively (using $2 and $6/kg, respectively). These results suggest that the
present higher retail value of the colored bell peppers off-sets the lower expected
yields.
591
Uniformity of Photosynthetic Photon Flux and Growth of ‘Poinsett’ Cucumber Plants under Metal Halide and Microwavepowered Solar-1000 Lamps
Donald T. Krizek*, Roman M. Mirecki , and William A. Bailey; Climate Stress Lab.,
NRI, ARS, U.S. Dept. of Agriculture, Beltsville, MD 20705-2350
The uniformity of photosynthetic photon fl ux (PPF) and vegetative growth of
Cucumis sativa L. (‘Poinsett’ cucumber) were examined using growth chambers
equipped with either six 400W metal halide (MH) lamps or with a single 1000W
microwave-powered (MP) Solar-1000 lamp. PPF levels in the center of each growth
chamber were set initially at 500 mmol • m–2• s–1. Plants were grown in 7.6-cmdiameter white plastic pots fi lled with a peat-vermiculite mix and fertilized 1–2X
daily with complete nutrient solution. Pots were placed at equal distances from
one another in 10 columns of six rows each (n = 60). Growth measurements were
only taken on the center six columns of plants (n = 36) with border plants on each
side. The uniformity of PPF was greater in the MP than in the MH chamber for both
the 36-pot (495.9 ± 3.7 vs. 459.4 ± 11.5 µmol • m–2• s–1, respectively) and for the
60-pot arrangement (489.3 ± 3.3 vs. 496.6 ± 9.6 mmol • m–2• s–1, respectively).
However, growth measurements showed greater uniformity in the MH than in the
MP chamber, e.g., 492.2 ± 8.9 vs. 629.9 ± 12.7 mg dry weight of tops. Plants
grown for 14 days under MP lamps had signifi cantly greater leaf number, stem
and petiole elongation, leaf expansion, and biomass of leaves, petioles, stems,
and roots than those grown under MH lamps. These fi ndings demonstrate the
effi cacy of using MP lamps for increasing seedling production and combined
with spectroradiometric measurements, suggest that additional levels of UV- A
(320–400 nm) radiation and/or reduced red and far-red radiation may be needed
to provide the most compact seedlings when using these lamps. These results
should be of interest to growers and researchers involved in protected cultivation.
These new MP lamps should also afford a useful tool for photobiologists interested
in studying the photocontrol of stem and petiole elongation.
592
Effect of Photoselective Plastic Films on the Growth of Bell
Pepper Transplants
HORTSCIENCE, VOL. 33(3), JUNE 1998
Shumin Li* 1, Nihal C. Rajapakse1, Roy E. Young2, and Ryu Oi 3; 1Dept. of Horticulture, 2Dept. of Agricultural and Biological Engineering, Clemson Univ., Clemson,
SC 29634, USA.; 3Organic Performance Materials Laboratory, Mitsui Chemicals,
Inc., 1190, Kasama-cho, Sakae-ku, Yokohama 247, Japan.
Removing far-red (FR) light from the greenhouse environment with liquid copper
sulfate fi lters is an effective alternative to application of chemical growth regulators
for height control of greenhouse crops. However, liquid fi lters have limited value in
commercial operations because of handling diffi culties. In this study, we report the
effectiveness of photoselective plastic fi lms that contain a FR intercepting dyestuff in
controlling height of ‘Capistrano’ bell pepper seedlings. Four types of treatment fi lms,
BCE-L (control), YCE-1 #80L, YCE-1 #75L and YCE-1 #65L, with R:FR ratios of 1.2,
1.7, 2.3 and 3.7, respectively, and one 4% liquid copper sulfate (CuSO4• 5H2O) fi lter
with R:FR of 3.5 were used as the covering materials of experimental chambers.
Heights of plants grown under YCE-1 #75 or #65 fi lms were ≈30% lower than
the control plants. YCE-1 #80 fi lm reduced plant height by ≈15% . Plant height
reductions were apparent within 1 to 2 weeks after initiation of the treatments.
Plants grown in YCE-1 #75, YCE-1 #65 and CuSO4 chambers had signifi cantly
lower total leaf area, leaf size, and leaf and stem dry weights than those grown
in the control chamber. No differences were observed between YCE-1 #80 and
control plants. No difference was found in the total chlorophyll concentration and
the ratio of chlorophyll a to b between the treatment and control plants. Results
imply that in peppers, a dyestuff concentration that yields a R:FR over 2 was effective in achieving over 30% height control. Although the fi lters with R:FR ratios
higher than 2 were more effective in controlling height and producing compact
pepper plants, the reduction in light intensity, or photosynthetic photon fl ux (PPF)
by increasing dyestuff can reduce dry matter accumulation.
593
Brushing and Temperature Control Transplant Growth of Floatirrigated Bell and Jalapeno Pepper
Bethany Galloway*, Jonathan R. Schultheis, and David W. Monks; Dept. of Horticultural Science, North Carolina State Univ., Raleigh, NC 27695-7609
Experiments were conducted at the North Carolina State Univ. Phytotron facility
in late Summer and Fall 1996. Bell and jalapeno pepper were grown in polystyrene
fl ats using continuous fl oat irrigation. Using DIF (the difference between day and
night temperatures), three temperature treatments consisting of positive (+DIF),
zero (0DIF), and negative (–DIF) DIF were assigned to three growth chambers. DIF
treatments were imposed in each chamber for only the fi rst 2 hr after lights were
turned on. Half of the plants in each chamber were brushed twice a day. Height was
affected by cultivar, brush treatment, DIF treatment, and all combinations of the
three treatments at all sampling dates. Jalapeno pepper experienced greater height
reductions due to DIF or brushing treatment than bell pepper. Shoot fresh weight
was reduced by brushing at all sampling dates, but DIF was less effective. Length
of fi rst internode was infl uenced by brush and DIF treatments, while leaf area was
only affected by brush treatment which caused reductions of 13% and 25 % in bell
and jalapeno pepper, respectively, at 6 weeks after planting. Brushing increased
pepper stem diameter. DIF had little effect on stem diameter but in combination
with brushing effectively increased stem diameter over both cultivars.
594
Enhancing Early M aturity in Processing Tomatoes with the
Use of Ethephon
Mike Murray*, Univ. of California Cooperative Extension, Colusa County, Colusa,
CA 95932
Ethephon is a tool that has been widely used to advance maturity in processing
tomatoes. However, it’s use has largely been restricted to mid- or late-season applications, due to concerns about the chemical’s stability and resultant phytotoxicity
if hot ambient air temperatures occur during or immediately following applications.
Four years of tests evaluating decreased rates of ethephon have been conducted
in commercial processing tomato fi elds. Each test included 10–15 early season
cultivars. Fruit quality, maturity and yield were evaluated. In all cases, ethephon
rates of 1–1.5 pints of product per acre resulted in maturity enhancements of
8–15 days, compared to paired untreated control plots. There were no adverse
effects on fruit soluble solids, color or yield. Industry adoption of this technology
has provided a tool to increase acreage by spreading production over a longer
period of time and maintain harvest schedules that are adversely impacted by cool
weather or replanting.
HORTSCIENCE, VOL. 33(3), JUNE 1998
76
COLLOQUIUM 3 (Abstr. 595–598)
Human Pathogens and Fresh Produce:
Prevention and Damage Control
595
Case Studies in Food-borne Illnesses from Fresh Produce
Roberta Hammond*; Bureau of Environmental Epidemiology, Tallahassee, Fla.
Since 1984, the State of Florida has placed additional emphasis on surveillance
and investigation of food-borne illnesses.With the enhanced emphasis, several
outbreaks associated with emerging pathogens and unusual vehicles have occurred.Among them are three outbreaks involving fresh produce: fresh-squeezed
orange juice, fresh raspberries, and mesclun lettuce (also known as baby greens,
spring greens).Florida continues to be alert to the ever-increasing possibility of
outbreaks from these and other fresh produce sources.There are specifi c steps that
occur when an outbreak of food-borne illness is identifi ed.These involve traceback methods, statistical comparisons, team efforts by county, state, and federal
agencies, and even international agencies.This talk will cover the investigations
of Salmonella in orange juice and cyclosporiasis in raspberries.
596
Damage Control: Handling CDC and the M edia When Your
Product is Attacked
David Riggs*; California Strawberry Commission, Watsonville, CA 95077
The California strawberry industry has unfairly suffered through two food
safety events in the past 2 years. In June 1996, an outbreak of a parasitic disease,
Cyclospora, involved consumers in several cities in the United States and Canada.
Initial reports linked the disease to consumption of strawberries from California;
however, it was later determined that the likely source of the outbreak was raspberries imported from Guatemala. The impact of the initial reports implicating
California strawberries was severe and resulted in industry losses of $20 to $40
million. In Mar. 1997, children in Michigan became ill from the consumption
of frozen strawberries grown in Mexico and processed by a California fi rm. The
incident clearly did not involve fresh strawberries nor California fi elds. Again,
initial reports were not specifi c and the industry suffered losses estimated at $15
million. Comments will focus on the California Strawberry Commission’s crisis
preparedness plan, how the industry responded to these food scares, what the
strawberry industry has learned, and the resulting and continuing government
response to these events.
597
A Case Study of Salmonellosis Linked to the Consumption
of Fresh-market Tomatoes and the Development of a HACCP
Program
James W. Rushing*; Clemson Univ., Coastal Research and Education Center,
2865 Savannah Highway, Charleston, SC 29414
Outbreaks of salmonellosis in the United States in 1991 and 1993 were epidemiologically linked to the consumption of raw tomatoes that originated from
the same fresh-market tomato packinghouse in both years.This is a case study of
the response of public agencies and an industry association to a food safety crisis
and the ensuring development, implementation, monitoring, and verifi cation of a
HACCP program that was proposed to serve as a model for the fresh-market tomato
industry.Challenges faced by regulatory agencies in monitoring the operations of
fresh-market fruit and vegetable handling facilities are discussed. Activities of an
interagency food safety committee that was formed to deal with crisis management
are described.The status of current research by private industry on safety related
issues is briefl y reviewed.
598
HACCP Principals and Product Operations: What is the Future?
Luke Howard*; Inst. of Food Science, Univ. of Arkansas, Fayetteville, AR 72704
Food safety has become a major issue for producers and processors of fresh
fruit and vegetable products. Although the safety of fresh and pre-cut fruit and
vegetables is outstanding, several recent food-borne outbreaks have increased
551
the public’s awareness of microbiological hazards associated with these products.
Hazard Analysis Critical Control Point (HACCP) programs are well-established
for many food systems. HACCP is a systematic approach to the identifi cation,
assessment, and control of hazards associated with the environment in which
foods are produced and handled. Fresh and pre-cut produce are ready-to-eat
products that do not receive a preservation (heating) treatment like traditional
canning or freezing methods. Since there is no microbiological kill step associated with these products, hazards cannot be eliminated. Therefore, it is critical
that efforts be focused on minimizing the incidence of food-borne pathogens on
fruits and vegetables through the use of good agricultural practices during growing, postharvest handling, storage, and minimal processing. Several sanitation
hurdles can be combined in a synergistic effort to control food-borne pathogens.
In addition to chlorination, researchers have investigated alternative treatments
for sanitation such as ozone, hydrogen peroxide, trisodium phosphate, edible
coatings containing antimicrobial agents, irradiation, pulsed light and bacteriocins. Selection of proper oxygen permeable packaging material is also important
to prevent anaerobic conditions that may result in growth and toxin production
by Clostridium botulinum . However, caution is advised when evaluating new
sanitation and packaging materials for fresh produce, because the elimination
of spoilage microorganisms may result in conditions that favor the growth of
surviving pathogens.
28
WORKSHOP 1 (Abstr. 599–605)
The Use of Computer and Internet in
Horticultural Research and Teaching
599
The Development of Horticulture Software on Landscape
Plants
Gary J. Kling*; Univ. of Illinois, 1201 S. Dorner Dr., Urbana, IL 61801
This presentation will cover some of the major decisions that were made in
the development and modifi cation of software to provide horticultural resources
for college students and members of the industry. Technological changes have
moved the production from video-disc technology to server-based digital formats,
CD-ROM, and the World Wide Web. Each of these changes results in a different
product suited to different audiences. The current stage of product development
will be presented.
600
Yield Mapping and GIS for Root Crops
Bernard Panneton*; Horticultural R& D Centre, Agriculture and Agri-Food Canada,
430 boul. Gouin, St-Jean-sur-Richelieu, Quebec, J3B 3E6 Canada
I will show how yield mapping data, aerial photography data, and other
agronomic data (fertility, soil parameters) can be integrated into a Geographical
Information System (GIS) and give a “feel” of the value of these tools to look at
crop production as a whole. The capability of GIS in handling and displaying
several layers of georeferenced data leads naturally to a decisionmaking process
quite similar to the one used in traditional photo interpretation of aerial imagery.
This approach can be very valuable for farm managers and consultants in crop
production.
601
Use of CD-ROMs for Teaching Systemic Botany and Horticultural Production Courses
Katrine Stewart*; McGill Univ., Faculty of Agricultural and Environmental Sciences,
12,111 Lakeshore Rd., Ste Anne de Bellevue, Quebec, H9X 3V9 Canada
Systemic botany often requires the students to visually examine plant materials
at different stages of growth and development to determine family characteristics.
Fresh plant materials used in these demonstrations are often unavailable to allow
the student to review for laboratory examinations. The timing of production courses
means that students do not have the chance to see fi eld operations for various
crops. CD-ROMs have been developed as a adjunct to lectures to allow students
to review and examine material at their own pace in order to better prepare them
for examinations.
552
602
The Use of Websites in Horticultural Classroom Instruction
Laurence Sistrunk*; Dept. of Horticultural Science, Texas A& M Univ., College
Station, TX 77843-2133
The use of WWW for college curricula has proliferated at an exponential rate
over the past 3 years. This sudden deluge of information of all types has provided valuable resources for college instruction. The working website has many
advantages for students. By dissecting the components, we can, as instructors,
increase our effectiveness and ability to provide our students with useful tools
for the near future.
603
The Development of ASHS HortBase— A Global Information
System
James L. Green*; Dept. of Horticulture, Oregon State Univ., Corvallis, OR 973317304 USA
In 1997, the ASHS Board of Directors established ASHS HortBase as a Standing
Committee of the Society. The ASHS HortBase Committee, a six-member Standing
Committee and Chair, is charged to implement and maintain ASHS HortBase. The
members of the ASHS HortBase Committee will be chair and chair-elect of the
three HortBase Task Forces: 1) Finance and Marketing; 2) Standards— authoring,
reviewing, and publishing; and 3) Technology. ASHS HortBase is a dispersed,
dynamic horticultural information system (network) on the WWW comprised of
peer— reviewed, concise, interlinked information modules to meet the information
needs of instructors and students, gardeners and growers. A strong advantage and
distinguishing characteristic of ASHS HortBase is our dynamic pool of potential
authors, reviewers, and users (ASHS Extension, Industry, and Teaching membership) to continually evolve and update the peer-reviewed information in HortBase.
We have the scholastic international standing to provide peer review and validation
of the information and to recognition to the authors, coupled with the marketing to
stimulate wide use of their information modules. ASHS HortBase is a dispersed
system (dispersed development and server costs). The “dispersed cost” for information fi le development and updating and delivery on the respective authors’
dispersed servers disperses the major costs of the HortBase information system.
Additional information on ASHS HortBase and the papers presented at the 4-h
Colloquium on HortBase at ASHS-97 can be found at http://hortbase@ashs.org
or contact me (greenjl@bcc.orst.edu, phone 541.737.5452, fax 541.737.3479).
604
The Internet— Changing the Way Horticulturists Communicate
Tim Rhodus*; Dept. of Horticulture and Crop Science, The Ohio State Univ., 2001
Fyffe Ct., Columbus, OH 43210
Four key elements in the discipline of horticulture provide a strong incentive
to use the Internet for communicating programatic information. First, a strong
visual component characterizes horticultural knowledge and study. Second, the
technical and practical element contained in the undergraduate curriculum, which,
similar to plant identifi cation, requires that students are presented highly visual
information. Third, use of the Internet increases the effi ciency and effectiveness
of communicating program information and research results. Finally, the issue
of content format for some applications precludes the use of any other media.
Taken together, the Internet is signifi cantly changing the environment in which
horticulturists communicate.
605
Pedigree and Pedigree Import Wizard
Shahrokh Khandizadeh*; Agriculture and Agri-Food Canada and McGill Univ.,
430 boul. Gouin, St-Jean-sur-Richelieu, Quebec J3B 3E6 Canada
Pedigree for Windows is a user-friendly program that allows the user to trace
agronomic characteristics, draw pedigrees, and view images of several fruit crops,
including more than 1400 apple, 800 strawberry, 800 almond, 100 blackberry,
80 blueberry, 790 pear, 200 raspberry examples. Pedigree Import Wizard® © for
Windows is an add-on software for users who are interested in importing their
research or breeding data records of fruit, fl ower, and plant characteristics and any
related images into Pedigree for Windows. Pedigree for Windows and Pedigree
Import Wizard have been designed so that a user familiar with the Windows operating environment should have little need to refer to the documentation provided
with the program. Pedigree Import Wizard uses a comma-separated value (csv)
HORTSCIENCE, VOL. 33(3), JUNE 1998
fi le format under the MS Excel environment. This option allows the user to add
or import additional data to the existing database that are already stored in other
software such as Lotus, Excel, Access, QuattroPro, WordPerfect, and MS Word
tables, etc., as long as they work under the Windows environment. A free demo
version of Pedigree and Pedigree Import Wizard for Windows is available from
http://www.pgris.com.
30
WORKSHOP 3 (Abstr. 606–610)
Current Status of Thinning of Pome and
Stone Fruit Crops
606
Physiology of Fruit Set and Abscission
Frank G. Dennis, Jr.*; Dept. of Horticulture, Michigan State Univ., E. Lansing,
MI 48824-1325 USA
Thinning, whether mechanical or chemical, prevents the development of some
fruits, allowing the remainder to become larger and more marketable. Chemicals
used for thinning either prevent fruit set or increase the proportion of fruits that
fall in the “June drop”; some, however, are effective even after this drop. The
mechanisms involved in blossom thinning are straightforward. Either pollination
is prevented, or some of the fl owers are injured, causing their abscission. The
mechanisms involved in fruit thinning are more complex; physiologists continue
to debate the effects of thinning agents on phloem transport, endogenous hormone
content/production, seed development, and other physiological processes. The
effects of ethephon in thinning have led to the suggestion that the response to
applied hormones is mediated by their effects in stimulating ethylene biosynthesis.
Hypotheses as the mechanisms of action of thinning agents will be reviewed,
emphasizing those most often invoked today.
607
Blossom Thinning in Pome and Stone Fruit
Esmaeil Fallahi *, Univ. of Idaho, 29603 U of I Lane, Parma, ID83660
Early thinning of apples is important because of its impact on fruit size and
next season’s fl ower bud initiation.In the past, apple cultivars were often sprayed
with the blossom thinner sodium dinitro-ortho-cresol(Elgetol) during full bloom,
followed by a post-bloom application of a fruit thinner such as carbaryl with or without naphthalene acetic acid (NAA).Elgetol was removed from the market in 1989
because of the high cost of re-registration.Full-bloom sprays of sulfcarbamide
(Wilthin), pelargonic acid (Thinex), and endothalic acid (Endothal), ammonium
thiosulfate (ATS) or petal fall spray of carbaryl (Sevin XLR Plus) were developed
as replacements for Elgetol. Hydrogen cyanamide (HC) and other chemicals have
been used to eliminate or to reduce chilling requirements of peaches grown under
the warm desert conditions.HC applied at “pink bloom” stage was observed to
reduce the number of open blooms in ‘Florda Prince’ peach; therefore, it was fi rst
used for blossom thinning in this cultivar in Arizona. Later, HC was also found to
be an effective blossom thinner for plums in Idaho.HC has recently been found
to effectively thin apple and peach blossoms.Armothin has also been an effective
blossom thinner for peach in California.
608
Chemicals, Timing, and Environmental Factors Involved in
Thinner Efficacy
Duane W. Greene*; Dept. of Plant and Soil Sciences, Univ. of Massachusetts,
Amherst, MA 01003
Chemical thinning of apples may be done over a 3- to 4-week period, starting
at bloom and extending through the time fruit are 20 mm or larger in diameter.
Potentially useful thinners at bloom include ammonium thiosulfate, Wilthin,
endothall, and pelargonic acid. These thinners reduce set by preventing pollination, inhibiting pollen germination, or slowing pollen tube growth. Ethephon can
be an effective thinner at bloom, but it is erratic. Petal fall application of thinners
has become widely adopted by the industry, primarily because it reduces risks
associated with one time thinner application, routinely done in the past. Carbaryl
is often the thinner of choice at this time, but where more aggressive thinning is
desired, NAA is used either alone or in combinations with carbaryl. Naphthale-
HORTSCIENCE, VOL. 33(3), JUNE 1998
neacetamide is effective when used at bloom but it less frequently used. Apple
fruitlets are very vulnerable to the stress imposed by chemical thinners at the
8- to 12-mm stage of fruit development. NAA and Accel are particularly effective
at this time, but carbaryl is frequently used because of its mild thinning action and
its ability to reduce clustered spurs to one fruit. Unless weather conditions after
bloom have been cool, effective thinning after the 18-mm stage of fruit development is less effective. Although erratic, ethephon is the most effective thinner
on large fruit. Warm temperature during and following thinner application favor
thinner uptake and response. Longer spray drying times favor thinner uptake into
the plant. Environmental infl uences and interactions infl uencing thinning will be
discussed.
609
Spray Volume, Canopy Density, and Other Factors Involved in
Thinner Efficacy
C.R. Unrath*; Dept. of Horticultural Science, North Carolina State Univ., Mountain
Horticultural Crops Research and Extension Center, Fletcher, NC 28732
Historically, most airblast chemical applications to apple orchards used a
single “average” water volume, resulting in variability of coverage with tree size
and also the greatest variable in chemical thinning. This coverage variability can
be eliminated by properly quantifying the tree canopy, as tree row volume (TRV),
and relating that volume to airblast water rate for adequate coverge. Maximum
typical tree height, cross-row limb spread, and between-row spacing are used to
quantify the TRV. Further refi nement is achieved by adjusting the water volume for
tree canopy density. The North Carolina TRV model allows a density adjustment
from 0.7 gal/1000 ft3 of TRV for young, very open tree canopies to 1.0 gal/1000
ft3 of TRV for large, thick tree canopies to deliver a full dilute application for
maximum water application (to the point of run-off). Most dilute pesticide applications use 70% of full dilute to approach the point of drip (pesticide dilute)
to not waste chemicals and reduce non-target environmental exposure. From the
“chemical load” (i.e., lb/acre) calculated for the pesticide dilute application, the
proper chemical load for lower (concentrate) water volumes can be accurately
determined. Another signifi cant source of variability is thinner application response
is spray distribution to various areas of the tree. This variability is related to tree
confi guration, light, levels, fruit set, and natural thinning vs. the need for chemical thinning. Required water delivery patterns are a function of tree size, form,
spacing, and density, as well as sprayer design (no. of nozzles and fan size). The
TRV model, density adjustments, and nozzle patterns to effectively hit the target
for uniform crop load will be addressed.
610
Experience with Thinning: What Factors Contribute to Contradicting Results?
Richard Marini *; Dept. of Horticulture, Virginia Tech, Blacksburg, VA 24061
Results from chemical thinning trials often vary with location/researcher and
from year to year within a location. Factors infl uencing both sources of variation
will be discussed. For help explain seasonal variation, the effects of fruit size
and temperature will be discussed. A multiple regression model was developed
indicating that the degree of fruit thinning is infl uenced by the interaction of
temperature two days after treatment and fruit diameter at the time of treatment.
Factors contributing to contradicting results between experiments/researcher
include application techniques, types of data collected, differences in experimental
designs and sampling techniques, statistical analyses, and potential differences
in the tree condition at the time of thinning applications.
38
WORKSHOP 4 (Abstr. 141)
Techniques of Soil Water Measurement
611
Soil Water M easurement as Basis to Optimize Irrigation
Scheduling: A Review
A.K. Alva* and A. Fares; Univ. of Florida, Citrus Research and Education Center,
Lake Alfred, FL 33850
Supplemental irrigation is often necessary for high economic returns for
most cropping conditions even in humid areas. As irrigation costs continue to
553
increase more efforts should be exerted to minimize these costs. Real time estimation and/or measurement of available soil water content in the crop root zone
is one of the several methods used to help growers in making the right decision
regarding timing and quantity of irrigation. The gravimetric method of soil water
content determination is laborious and doesn’t suite for frequent sampling from the
same location because it requires destructive soil sampling. Tensiometers, which
measure soil water potential that can be converted into soil water content using
soil moisture release curves, have been used for irrigation scheduling. However,
in extreme sandy soils the working interval of tensiometer is reduced, hence it may
be diffi cult to detect small changes in soil moisture content. Capacitance probes
which operate on the principle of apparent dielectric constant of the soil-water-air
mixture are extremely sensitive to small changes in the soil water content at short
time intervals. These probes can be placed at various depths within and below
the effective rooting depth for a real time monitoring of the water content. Based
on this continuous monitoring of the soil water content, irrigation is scheduled to
replenish the water defi cit within the rooting depth while leaching below the root
zone is minimized. These are important management practices aimed to increase
irrigation effi ciency, and nutrient uptake effi ciency for optimal crop production,
while minimizing the impact of agricultural non-point source pollutants on the
groundwater quality.
51
WORKSHOP 8 (Abstr. 612–614)
Exploring Research Methodologies in
Human Issues in Horticulture
612
Conducting Quality Survey Research in Horticulture
Jim Flowers*; Dept. of Agricultural and Extension Education, Box 7607, North
Carolina State Univ., Raleigh, NC 27685-7607
Survey research is an important methodology for many horticultural science
professionals. The need to describe, validate, or determine perceptions of various
aspects of the fi eld is necessary in order to look at the “big picture” associated
with the horticultural profession. When survey research is conducted, several
potential errors may occur that become threats to the external validity of the
research. This presentation will address the common sources of error in survey
research that should be addressed by the researcher and methods used to control
each source of error. While quantitative survey methodology will be emphasized
in the presentation, qualitative research methodology will also be addressed.
613
The Use and Adaptation of Existing M easurement Tools in
People-Plant Research.
Carol S. Dawson* and J.M. Zajicek; Dept. of Horticultural Sciences, Texas A& M
Univ., College Station, TX 77843-2133
Measurement of variables in physical science research is usually accomplished
through the use of mechanical instruments, e.g., rulers, thermometers. The
study of the effects of various horticultural activities on people often requires the
measurement of mental constructs such as attitudes, opinions, and psychological
characteristics. However, the measurement of these variables is not straight-forward. Fortunately, many measurement instruments have already been developed
and tested by psychologists and educators which measure variables of interest
to researchers studying human issues in horticulture. This workshop will review
the types of instruments available and will focus on measures of environmental
attitude, and psychological profi les. Criteria for selecting instruments appropriate to specifi c populations will be discussed. Finally, suggestions for integrating
the results of these measures into a human issues in horticulture study will be
given.
614
Designing and Evaluating Survey Instruments for Research in
Human Issues in Horticulture
Sonja M. Skelly * and Jennifer Campbell Bradley; Dept. of Environmental Horticulture, Univ. of Florida, Gainesville, FL 32611
Survey research has a long precedence of use in the social sciences. With
554
a growing interest in the area of social science research in horticulture, survey
methodology needs to be explored. In order to conduct proper and accurate
survey research, a valid and reliable instrument must be used. In many cases,
however, an existing measurement tool that is designed for specifi c research
variables is unavailable thus, an understanding of how to design and evaluate a
survey instrument is necessary. Currently, there are no guidelines in horticulture
research for developing survey instruments for use with human subjects. This
presents a problem when attempting to compare and reference similar research.
This workshop will explore the methodology involved in preparing a survey instrument; topics covered will include defi ning objectives for the survey, constructing
questions, pilot testing the survey, and obtaining reliability and validity information.
In addition to these topics some examples will be provided which will illustrate
how to complete these steps. At the conclusion of this session a discussion will
be initiated for others to share information and experiences dealing with creating
survey instruments.
53
WORKSHOP 9 (Abstr. 615)
Application of Photoperiodism in Floriculture Crop Production
615
Application of Photoperiodic Manipulation in Vegetative Specialty Floral Crop Propagation and Flowering
Millie S. Williams and Terri Woods Starman*; Dept. of Ornamental Horticulture
and Landscape Design, Inst. of Agriculture, Univ. of Tennessee, Knoxville, TN
37901-1071
Photoperiod requirements are important for optimum fl ower development,
decreasing production time, year-round fl owering, and/or for increasing vegetative growth necessary in stock plant production. The photoperiodic responses
were determined for 24 vegetatively propagated specialty fl oral crops. Each plant
species was grown at 8-, 10-, 12-, 14-, and 16-h photoperiods. Photoperiods
were provided by 8 h of sunlight, then pulling black cloth and providing daylength
extension with incandescent bulbs. Data collected included time to fl ower, fl ower
number, and vegetative characteristics. Evolvulus nuttallianus ‘Blue Daze’, Heliotropium arborescens ‘Fragrant Delight’, and Orthosiphon stamineus ‘Lavender’ were
facultative short-day plants with respect to fl owering. Time to fl ower increased as
photoperiod increased. Duranta repens ‘Blue’, Verbena hybrid ‘Tapien Lavender’,
and Verbena peruviana ‘Trailing Katie’ were facultative long day plants with respect
to fl owering. Days to visible bud and fi rst open fl ower decreased as photoperiod
increased. Argeranthemum frutescens ‘Sugar Baby’, Scaevola aemula ‘Fancy Fan
Falls’, and Portulaca hybrid ‘Apricot’ had increased fl ower number as photoperiod
increased from 8- to 16- h, although time to fi rst fl ower initiation was not affected.
Abutilon hybrid ‘Apricot’, Duranta repens ‘Blue’, Evolvulus nuttallianus ‘Blue Daze’,
Lotus berthelotii ‘Parrot’s Beak’, Lysimachia nummularia ‘Aurea Creeping Golden’,
Rhodanthe anthemoides ‘Milkyway’, and Scaevola aemula ‘Fancy Fan Falls’ had
increased vegetative growth as photoperiod increased. All other species studied
were day-neutral with regard to fl owering and vegetative parameters.
62
WORKSHOP 11 (Abstr. 616–617)
The Riddle of Regular Cropping: The Case
for Hormones, Nutrition, Exogenous Bioregulators, and Environmental Factors
616
The Effects of Exogenous Bioregulators and Environment on
Regular Cropping of Apple
Kathleen M. Williams*; Washington State Univ., Tree Fruit Research and Extension
Center, Wenatchee, WA 98801
Use of exogenous bioregulators (“hormones”) to adjust crop load in apple
remains challenging to both researchers and producers. These hormones are
HORTSCIENCE, VOL. 33(3), JUNE 1998
sensitive to the rate and timing of application, to the physiological status of the
tree, the choice of orchard system, variety and rootstock, and a myriad of cultural
practices and environmental factors. All classes of plant bioregulators have been
used over the past 30 to 40 years as chemical thinning materials. Most of the
standard postbloom thinning programs involve application of a synthetic auxin,
such as naphthalene acetic acid (NAA) in combination with carbaryl, a commonly
used insecticide. The mode of action of these two compounds is not clearly
understood. Gibberellins generally have not been effective thinning materials
because of the negative impact on return bloom. Ethylene-releasing compounds
have been used successfully as postbloom thinning materials. And cytokinins,
particularly synthetic sources such as 6-BA, have been shown to effectively thin
fruit and to enhance fruit size on many commercial varieties. The rate and timing
of 6-BA applications are particularly critical to obtain the desirable thinning and
size responses. Overall, these bioregulators are sensitive to temperature. The use
of bloom thinning compounds and their effi cacy in the Pacifi c Northwest will be
discussed in the context of return bloom.
617
Effects of Nutritional Factors on Regular Cropping of Apple
Warren C. Stiles*, Dept. of Fruit & Vegetable Science, Cornell Univ., Ithaca, NY
14853
Any mineral nutrient defi ciency or toxicity that adversely infl uences the normal
biochemical and physiological processes in the tree can be expected to impact
regularity of cropping. Defi ciency of N limits growth and fl owering of young trees and
increases potential for biennial bearing in mature trees while excess N may stimulate
excessive vegetative growth that results in shading of spurs and development of
weak fl owers with reduced set potential. B, Zn, and Cu shortages infl uence regularity
of cropping through effects on fl ower development, pollination and/or fertilization.
Effects of K, Mg, Mn, Fe, or S appear to be indirect, principally as consequences of
limited carbohydrate production/availability. Crop load/vegetative growth relationships in one season can exert signifi cant infl uences on nutrient status within the tree
that may infl uence potential for cropping in the next season. Environmental stress
may limit nutrient availability of various nutrient elements at critical times during
the fl ower development and fruit setting sequence. Effects of nutritional factors on
regularity of cropping must be considered in relation to their interaction with all
other components of the fruit production system. Maintaining appropriate essential
mineral nutrient supply and availability to avoid potential defi ciencies or toxicities
is critical to regular cropping of apple trees.
79
WORKSHOP 14 (Abstr. 618–619)
Laboratory Techniques for Teaching Plant
Breeding
618
Laboratory Exercise on the Segregation of Flower Color and
Related Genes Using Salpiglossis sinuata
Chiwon W. Lee*; Dept. of Plant Sciences, North Dakota State Univ., Fargo, ND
58105
Velvet fl ower (Salpiglossis sinuata, Solanaceae) can be used as an excellent demonstration plant for horticultural crop breeding classes. Salpiglossis
produces large trumpet-like fl owers exhibiting an assortment of corolla color and
pigmentation pattern. The pistil is large (3 to 4 cm long) with a sticky stigmatal
tip and anthers can be easily emasculated prior to anthesis. The large pollen
grains are shed in tetrads, which can be separated and individually placed on the
stigma. It takes 8 to 9 weeks from seeding to blooming, with a prolifi c fl owering
cycle repeated in fl ushes. Numerous seeds (about 750/capsule) are obtained in 3
weeks after self- or cross-pollination. The infl uences of three genes that control
fl ower color and pigmentation pattern can be conveniently demonstrated with their
dominant and recessive alleles. The R gene controls fl ower color with red (RR or
Rr) being dominant over yellow (rr) fl ower color. The D gene controls the density
of pigmentation with solid (DD or Dd) color being dominant over dilute (dd)
color. Corolla color striping is controlled by the St gene with striped (stst) being
recessive to non-striped (StSt or Stst) pattern. For example, by using diploid lines
of genotypes RRDD (red, solid), RRdd (red, dilute), or rrdd (yellow, dilute) and
their crosses, students can easily learn a dominant phenotypic expression in the
HORTSCIENCE, VOL. 33(3), JUNE 1998
F1 hybrid and the digenic 9:3:3:1 segregation ratio in the F2 progeny. Another
gene (C ) that controls fl ower opening can also be used to show its infl uence on
cleistogamous (closed, self-pollinated, CC or Cc) versus normal chasmogamous
(open- pollinated, cc) corolla development. In addition, the induction and use of
polyploid (4X, 3X) plants in plant breeding can be effectively demonstrated using
this species.
619
Laboratory Techniques for Determining Ploidy Levels
Christopher S. Cramer*; Dept. of Horticulture and Agronomy, MSC 3Q, Box 30003,
New Mexico State Univ., Las Cruces, NM 88003-0003
The determination of ploidy levels is essential for breeding asexually propagated and polyploid crops that may have ploidy chimeras in their tissues or have
several polyploid series. This presentation will discuss a laboratory for teaching
students how to determine ploidy levels in different plant tissues using different techniques. The different methods for ploidy determination include root tip
squashes, pollen mother cell squashes, pollen grain size and germinal pore counts,
stomata size and density determination, and gross morphology. After completing
these laboratory experiments, students will be able 1) to initiate a study of ploidy
determination, 2) to determine the correct course of action in determining ploidy
level, and 3) to recognize the various steps required to determine ploidy level in
plants.
90
WORKSHOP 17 (Abstr. 620–621)
Pollination of Nut Crops: Practice and
Problems
620
Hazelnut Pollination
J.L. Olsen*, S.A. Mehlenbacher, and A.N. Azarenko; Oregon State Univ., Dept. of
Horticulture, 4017 Ag. & Life Sci., Corvallis, OR 97331-7304
Hazelnuts are wind- pollinated, monoecious, mostly dichogamous, and
self-incompatible of the sporophytic type. About 90% of the cultivars studied
are protandrous. Anthesis of the pistillate fl ower is temperature-dependent and
occurs from December through February, with its peak in January. Stigmatic
surfaces may remain receptive for up to 3 months. Four to 5 months separate
pollination and fertilization of the ovule, which usually occurs between mid-May
and the end of June in Oregon. A 10% pollinizer density has been the standard,
with a recommended distance of <20 m between the main cultivar and the nearest
pollinizer. Two or three different pollinizer varieties with different times of pollen
shed are recommended. The Oregon hazelnut industry is presently combating the
fungal disease, Eastern Filbert Blight, Anisogramma anomala. Part of the current
management recommendations are to reduce the susceptible pollinizer varieties
to a density of around 5% , and then gradually replace those left with immune or
more-resistant genotypes. Recent research by S.A. Mehlenbacher refi ned methods
of using fl uorescense microscopy to quickly determine genotype compatibility.
The self-incompatiblity is controlled by a single gene with multiple alleles. The
biochemical, physiological, and molecular aspects of sporophytic self-incompatiblity are being research by A.N. Azarenko.
621
Idiosyncrasies of Pecan Pollination
Bruce W. Wood*; USDA-ARS Southeastern Fruit and Tree Nut Research Lab., 21
New Dunbar Road, Byron, GA 31008
Pecan orchard productivity and yields often suffer due to pollination problems
despite copious pollen produced within or near orchards. The problem is most
acute in large block-type orchards of one or two varieties and can be due to
pollen not being present at time of stigma receptivity or due to selfi ng. Fruit-set
problems do not appear to be due to excessive pollen on stigmatic surfaces, as
is the case in walnut. Pistillate fl owers set best when pollen is received within
about 1 day after becoming receptive. While stigma receptivity appears to lasts
several days, pistillate fl owers usually fail to complete development if pollinated
after ≈2 days. Flowering dichogamy of given varieties varies with tree age and
spring temperatures, thus often leading to poor pollination and low fruit-set.
555
Orchards are therefore likely to benefi t from the presence of two complementary
pollinizers for the main crop variety. Trees in block-type orchards and are beyond
about three rows or 50 m from pollinizers are likely to exhibit pollination related
yield losses. Many orchards exhibit pollination problems because adherence to
the standard two-class Type I/II fl owering system often caused planting of noncompatible varieties. A recently developed 30-class Type I/II system allows for
greater probability of avoiding pollination problems. Removal of “off-genotype”
trees from orchards may reduce yields in block-type orchards.
91
WORKSHOP 18 (Abstr. 622)
Improvement and Production of Aromatic
and Medicinal Plants
622
Increased Yield and Quality of Herbs Using Plasticulture
Systems
P.A. Bowen*, Pacifi c Agri-Food Research Centre, Agassiz, BC V0M 1A0 Canada
In plasticulture, raised beds, plastic mulch, rowcovers, and fertigation are used
to accelerate crop growth and improve crop quality by providing heat, nutrients, and
water at near-optimum levels. Because plasticulture is intensive and input costs
are high, profi ts are maximized when high-value crops are grown. For herb crops,
plasticulture can also be used to control weeds without herbicides, to prevent soil
contamination by rain splashing, and to prevent rooting of side branches. In a
studies of Echinacea species, root yields in the fi rst year were improved by 35%
to 77% . Other crops found to be suitable for plasticulture include feverfew, lemon
balm, pineapple sage, valerian, and Chinese licorice. Implementation methods
will be described.
104 WORKSHOP 20 (Abstr. 623)
Methods of Evaluating Teaching
623
Current Practices in the Evaluation of Teaching in Horticulture
Harrison Hughes*; Dept. of Horticulture and Landscape Architecture, Colorado
State Univ., Fort Collins, CO 80523
Universities offering horticulture curriculum were surveyed for procedures for
evaluation of teaching. They were asked to indicate which of the following were
used to evaluate instructors: student surverys, peer reviews, administrator reviews,
alumni surveys, and others. They were also asked the criteria which were used
in these evaluations; i.e., instructor was well-prepared, class presentations were
clear and well-organized etc. Many programs used student surveys as the prime
means of evaluations of instructors. Some used peer evaluation as well and a few
used alumni surveys. Several indicated that they were currently reviewing their
process of instructor evaluation.
course, effective with the 1991–92 option sheets. All of our departmental teaching
faculty advise undergraduate students, and each individual professor supervises
the internship experiences of his/her advisees. Coordination is provided by a
common syllabus booklet and by leadership from a faculty Undergraduate Horticulture Teaching Coordinator and the Department Head. Outcomes are assessed
through student reports, cooperator evaluations, and a formal internship assessment seminar. The mandatory internship has added value to our degrees. Our
students graduate with documented work experience in addition to their academic
credentials. When our graduates are employed, they tend to more readily adapt to
their jobs because they already have been exposed to some of the “real-world”
aspects of their profession. This is especially true when an internship experience
results in permanent employment with the same fi rm upon graduation.
144 WORKSHOP 28 (Abstr. 625–628)
Patterns and Physiology of Nutrient Use in
Horticultural Crops: Implications for Fertilizer Efficiency
625
The Regulation of N Uptake at the Whole-plant Level in Tree
Crops
Farbod Youssefi *, Patrick H. Brown, and Steve A. Weinbaum; Dept. of Pomology,
Univ. of California, Davis, CA 95616
Coordinating fertilization practices with tree N uptake is important for reduction of
groundwater contamination with nitrate. To reach this goal, the regulation of nitrogen
uptake at the whole-plant level must be further understood. A theory that has been
proposed on this subject is that a pool of amino-N, whose size is determined by
above-ground N demand, cycles in the plant and regulates soil N uptake by exerting
an inhibitory effect at the root level. Several experiments were carried out to study
this hypothesis in fruit trees. First, foliar applications of N were made in almond
trees, which led to the observation that soil N uptake was reduced in treated trees.
In these trees, foliar-applied N was present in the roots when uptake was reduced;
further, amino-N content of leaf and bark phloem sap was increased after several
hours in the treated tree. In another experiment, amino-N content of phloem and
xylem sap of almond trees of varying N status was determined. Several trees under
each N status were given a pulse of abundant N fertilizer, so that their N uptake
would be compared. Trees of higher N status, with greater amounts of amino-N
cycling in their sap, did not take up more N than equivalent control plants, whereas
lower N status trees did. To complete this series of experiments, it was observed that
fruit-bearing shoots in walnut trees exported smaller proportions of foliar-applied
N than non-bearing shoots, indicating that above-ground N demand may regulate
the pool of N that moves down in the plant. These results and the principles that
regulate N uptake will be discussed.
626
Using Nutrient Uptake Patterns to Develop Efficient N Management Strategies for Vegetables
624
A Mandatory Internship Program at a Land-grant University:
The Case of Oklahoma State University
C.A. Sanchez*; Yuma Agricultural Center, Univ. of Arizona, Yuma, AZ 85364
Nitrogen in a soil that is not immediately taken up by a crop is subject to leaching, denitrifi cation, and other mechanisms of loss. Generally, split applications
of N throughout the growing season reduce the potential for N loss compared
to a single preplant application. Timing of N application should account for the
characteristic N uptake patterns of the crop and the lag time between application
of fertilizers and plant availability. N uptake studies allow one to identify total
amount of N accumulated by the crop and periods of peak nitrogen demand. This
information can then be used to devise management strategies aimed at supplying
N preceding anticipated N uptake. Split sidedress N application, fertigation, and
the use of controlled-release fertilizers are all viable options, depending on the
crop production scenario and available infrastructure.
Brian A. Kahn*; Dept. of Horticulture and Landscape Architecture, Oklahoma State
Univ., Stillwater, OK 74078
Internships provide well-documented advantages to students, colleges, and
employers. The core requirements in Horticulture and in Turf Management at
Oklahoma State Univ. were expanded to include 3 h of credit in an internship
627
Properly Timed Foliar Nutrient Applications Provide an Efficient
Means to Meet Nutrient Demand to Increase Flowering, Fruit
Set, and Size of Citrus and Avocado
143 WORKSHOP 27 (Abstr. 624)
“What I Did Last Summer”
556
HORTSCIENCE, VOL. 33(3), JUNE 1998
Carol J. Lovatt* , Dept. of Botany and Plant Sciences, Univ. of California, Riverside,
CA 92521-0124
The goal of our research is to identify the role that specifi c essential nutrient elements play in the physiology of horticultural crops and then to apply the
nutrient as a fertilizer to the foliage at key times in the phenology of the tree, i.e.,
a time when the demand for the nutrient is likely to be high, in order to stimulate a
specifi c physiological process. This approach proved successful in the following
completed studies. A single winter prebloom application of nitrogen as low-biuret
urea made to the foliage of 30-year-old ‘Washington’ navel orange (Citrus sinensis
L. Osbeck) trees at the time of irreversible commitment to fl owering signifi cantly
increased yield and fruit number per tree for each of three consecutive years. In
addition, the number of commercially valuable fruit with diameters of 6.1 to 8.0
cm signifi cantly increased as yield increased (r2=0.88). Applications of boron
as sodium tetraborate to the foliage of a commercial orchard of ‘Hass’ avocado
(Persea americana Mill.) trees at the caulifl ower stage of infl orescence development (gametogenesis) increased the number of pollen tubes reaching the ovule,
ovule viability and cumulative yield (P ≤ 0.05). Additional examples from ongoing
research also will be presented.
628
Nutrient-Use Patterns in Nursery Crops
Mary Ann Rose* and Barbara Biernacka; Dept. of Horticulture and Crop Science,
The Ohio State Univ., Columbus, OH 43210
Long- standing fertilizer recommendations for field- grown nursery and
landscape ornamentals are based on maximizing growth, not nutrient effi ciency.
Further, these recommendations fall short because of failure to consider 1) the
extent of crop nutrient removal, 2) varying nutrient retention characteristics of
soils across the United States, and 3) a body of research that suggests that woody
ornamentals have a limited response to fertilization under most soil conditions.
Concern for the environmental impact of fertilization justifi es a reevaluation of current nursery fertilization practices, as well a discussion of the practical constraints
on the adoption of new approaches, e.g., nutrient demand-driven fertilization.
Research on the nutrient use patterns of woody plants will be reviewed with
emphasis on implications for increasing fertilization effi ciency. OSU research
on water availability and nutrient-use interactions also will be presented.
43
POSTER SESSION (Abstr. 629–631)
ACB Poster Competition
629
The Growth of New Guinea Impatiens with Controlled-release
Fertilizer in a Recirculating Subirrigation System
Daphne Richards* and David Wm. Reed; Dept. of Horticultural Sciences, Texas
A& M Univ., College Station, TX 77843-2133
New Guinea impatiens ‘Illusion’ were grown in a recirculating subirrigation
system using a controlled-release complete fertilizer (Osmocote 14–14–14). In a
preliminary experiment, plants were grown under varying label rates (0, 0.5x, 1x,
2x, 4x) incorporated throughout the growing medium.Excellent growth and highquality plants were produced at the 0.5x and 1x rates.Higher rates caused reduced
growth and quality. The next study was a factorial experiment of rate (0.25x, 0.5x,
0.75x, and 1x) times placement (incorporated, top dress, bottom placement, and
dibble). Slight growth increases and dramatic leaf area increases were observed
with increasing fertilizer rate, regardless of placement. Slightly higher fresh and
dry weights were observed in the incorporated treatment compared to the top dress
treatment. Both the incorporated and top dress treatments yielded better growth
than bottom placement or dibble treatments.Other parameters measured (height,
chlorophyll content) did not appear to be affected by placement. EC (dS/m) of
the growing medium was highest in the top 1/3 of the container in all placement
treatments. EC increased with increasing rate. EC was higher in the incorporated
than in the top-dress treatment, which may be due to different release rates or
may be an artifact of extraction (prill removal).No rates or placements showed
damaging EC levels.
630
Effects of Polyethylene Glycol on Development of Grape (Vitis
HORTSCIENCE, VOL. 33(3), JUNE 1998
vinifera L. ‘Thompson Seedless’) Somatic Embryos
Fred K. Westphal * and Michael E. Compton; School of Agriculture, Univ. of
Wisconsin–Platteville, Platteville, WI 53818
Torpedo-stage somatic embryos were selected from actively growing cultures
and trasferred to embryo maintenance medium [MS with (per liter) 412.5 mg
NH4NO3, 475 mg KNO3, 1 g myo-inositol, 90 g sucrose, 2 g activated charcoal,
and 7 g TC agar] supplemented with either 0% , 2.5% , 5% , 7.5% , or 10%
polyethylene glycol (PEG) for 4, 8, or 12 weeks. Embryos placed on treatment
media were transferred directly to grape somatic embryo germination medium
[MS with (per liter) 1 g myo-inositol, 30 g sucrose, 1 M benzyladenine, and 7 g
TC agar] once their PEG treatment was terminated. The number of embryos that
germinated was recorded 4 weeks after transfer to somatic embryo germination
medium. The number of germinated embryos that differentiated into plants was
recorded at 8 weeks. There was no difference in germination rates and embryo
differentiation among embryos incubated on medium with or without PEG for 4
weeks. A difference in embryo growth rate was observed after 8 weeks on medium
with PEG. Embryo grew fastest on media containing 5% or 7.5% PEG. In addition,
embryos grown on medium with 5% or 7.5% PEG were morphologically similar
to zygotic embryos.
631
Effect of C6-Volatiles on Bioluminescent Plant Pathogens
Jennifer Warr*, Fenny Dane, and Bob Ebel ; Dept. of Horticulture, Auburn Univ.,
Auburn, AL 36849
C6 volatile compounds are known to be produced by the plant upon pathogen
attack or other stress-related events. The biological activity of many of these
substances is poorly understood, but some might produce signal molecules important in host–pathogen interactions. In this research we explored the possibility
that lipid-derived C6 volatiles have a direct effect on bacterial plant pathogens.
To this purpose we used a unique tool, a bacterium genetically engineered to
bioluminesce. Light-producing genes from a fi sh-associated bacterium were
introduced into Xanthomonas campestris pv. campestris, enabling nondestructive detection of bacteria in vitro and in the plant with special computer-assisted
camera equipment. The effects of different C6 volatiles ( trans- 2 hexanal, trans-2
hexen-1-ol and cis-3 hexenol) on growth of bioluminescent Xanthomonas campestris were investigated. Different volatile concentrations were used. Treatment
with trans-2 hexanal appeared bactericidal at low concentrations (1% and 10% ),
while treatments with the other volatiles were not inhibitive to bacterial growth.
The implications of these results with respect to practical use of trans-2 hexanal
in pathogen susceptible and resistant plants will be discussed.
46
ORAL SESSION (Abstr. 632–636)
Collegiate Branch Oral Competition
632
The Effect of Thiols and Rhizopon on the Rooting of Woody
Stem Cutting of Punica granatum L.
Carol LaFaver* and Alejandro Ching; Horticulture Progam, NW Missouri State
Univ., 800 University Dr., Maryville, MO 64468
A research study was established to determine the effect of thiol compounds
glutathione (GSH) and dithiothreitol (DTT) to induce rooting and root growth of
woody stem cuttings from Punica granatum L., either alone or in combination
with rhizopon. Woody cuttings of P. granatum 10 cm long were collected from
5-year-old potted greenhouse grown plants. No leaves were left attached on the
cuttings. The proximal end of cuttings were dipped for 10 sec in 0.05 and 0.1
mM of GSH; 0.6, 1, and 2 mM of DTT followed by a 5-min rest, and immediately
dipped in a solution of 1500 ppm of Rhizopon for 10 sec. Untreated cuttings were
used as control as well as cuttings dipped only in 1500 ppm of Rhizopon for 10
sec. Rooting was continuous with bottom heating at 24 °C under greenhouse
conditions. The experimental data was analyzed statistically using a completely
randomized block design with fi ve replications. The average total number of
roots was increased when the cuttings were treated with the thiol compounds
and Rhizopon, 52 days after treatment. However, DTT at 1.0 mM increased more
signifi cantly the average total number of roots than GSH at any concentration.
The presence of DTT alone at 1.0 mM or with 1500 ppm of Rhizopon increased
557
the average number of roots to 10.04 and 10.99, respectively. No signifi cant
difference was found for the treatment of 0.05 mM GSH and 1500 ppm Rhizopon
showing average number of 12.11 roots. Signifi cant average total root length was
detected in cuttings treated with 1500 ppm Rhizopon compared to control, GSH
at 0.1 mM, and DTT at 0.6 mM and 1.0 mM.
633
Relationships of Resveratrol, Anthocyanin, and Soluble Solids
to Maturity in Vitis lambrusca
Catherine Jaubert*; Dept. of Horticulture and Landscape Architecture, Univ. of
Kentucky, Lexington, KY 40546
Resveratrol in Vitis vinifera cultivars has been shown to be important
in resistance to infection of Botrytis cinerea (gray mold). Also, resveratrol is a
constituent of wine that has been shown to confer protection against artherosclerosis, heart disease, and cancer. The relationship between grape maturity and
resveratrol concentration levels, soluble solids, and anthocyanins were examined
on V. lambrusca cultivars. ‘Concord’ and ‘Catawba’ grapes were harvested weekly
from August to maturity from a production site in Lexington, Ky. Irradiation and
non-irradiation of berries was performed in the laboratory and resveratrol concentration was analyzed. Berry skins were extracted with methanol/water (8:1 v/v)
in 10ml/g of fresh weight tissue. Resveratrol was quantifi ed using reverse-phase
HPLC. Soluble solids were measured weekly by refractometer, and anthocyanin
content was determined by spectrophotometer. Results showed a marked increase
in resveratrol concentration as grapes matured, and followed by a subsequent
decrease at fi nal harvest. Sugar content increased weekly in each cultivar, and
was maximal at fi nal harvest.
634
Optimizing Graft Union Formation between Sweetpotato (Ipomoea batatas) and Bush Morning Glory (Ipomoea carnea ssp.
fistulosa) as a Prelude to Chimera Development
Douglas W. Maxwell*; Dept. of Horticultural Sciences, Texas A& M Univ., College
Station, TX 77843-2133
Bush morning glory (Ipomoea carnea ssp. fi stulosa) and ornamental sweetpotato (Ipomoea batatas ‘Blackie’) were grafted using various procedures. Lanolin
pastes containing 3% BA, 3% NAA, and a mixture of 3% BA/3% NAA were tested
as a means of promoting adventitious shoot development at the graft union.
Excellent “take” was obtained with all graft types tested. The growth regulator
treatments resulted in marked differences in callus formation at the wounded graft
union. Lateral shoot development below the graft union also was affected by the
growth regulator treatments. The highest quantity of callus was formed using the
mixed paste, while BA enhanced lateral shoot formation below the union. Results
indicate that in-vivo grafting of these two species may not be the best procedure
for obtaining interspecifi c chimeras.
558
635
Cut Flowers Being Sold as Impulse Items: A Look at Factors
Affecting Impulse Product Merchandising
Jennifer B. Neujahr* and Karen L.B. Gast; Dept. of Horticulture, Forestry, and
Recreational Resources, Kansas State Univ., Manhattan, KS 66502-5506 USA
Consumer behavior research seems to play an big role in determining the
wants and needs of an industry. This research helps to shape the way we market
to the consumers and helps make marketing strategies more effective. In the
1950s grocery stores began to sell horticulture products in order to alleviate
the growers’ surplus. Supermarkets now have seem to found their niche in this
market due to the fact that they can infl uence their consumers to buy their fl owers
right along with their bread, and get all of their shopping done at once. This new
type of sale, commonly referred to as the impulse sale, can relate directly to how
well the store is merchandised and maintained. A study was conducted at a local
supermarket, to determine the following: good locations for impulse sales items,
special conditions affecting impulse sales items, and what types of things could
affect demand for impulse items. It was discovered that certain locations make
better sales than other locations. Locations that were front and center and allowed
easy access to seeing the mixed fl ower bouquet without having to touch it yielded
the best results. The variables used to show a change in demand showed little to
some variability and has raised some questions which may be used to conduct
future research.
636
Coordinating Sustainable Landscapes for a Low-income Community
Joshua H. Reed* and Mary T. Haque, P&A Building, Dept. of Horticulture, Clemson
Univ., Clemson, SC 29634-0375
The City of Clemson, along with the National Wildlife Federation,
Habitat for Humanity, and Clemson Univ., recently formed a strategic alliance to
incorporate ideas for the landscaping of low-income homes. Their goal was to
create an aesthetically pleasing, environmentally responsible design that catered
to the future development of the families involved. The low-income housing project
was selected as an independent study for Spring 1998. As student project manager
I coordinated and documented the project. Objectives of the project were: 1) to
promote knowledge and research on environmental issues and culturally diverse
populations; 2) to create backyard wildlife habitats and sustainable community
environments for low income families; 3) to provide students with the opportunity
to learn and mature by participating in a long-term project involving a measurable
impact. Project steps included analysis, research, design, planning, scheduling,
implementation, and refl ection on the impact made by those involved. The City of
Clemson, along with the others involved, was delighted to be the fi rst to address
the issue of enhancing open space around low-income buildings in addition to
landscaping the properties surrounding the homes.
HORTSCIENCE, VOL. 33(3), JUNE 1998