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Stephen L. Love, Bruce K. Werner, Horia I. Groza and Asunta Thompson-Johns

Nine commercially available true potato seed (TPS) hybrids were compared to four standard clonal cultivars with respect to mean and uniformity of foliar characteristics and tuber traits important to the North American potato industry. The TPS hybrids were planted using second vegetative generation tubers derived originally from botanical seed. Ten plants from each plot were individually evaluated for plant height, vine maturity, early blight symptoms, and verticillium wilt symptoms. Following harvest, yield was determined and the tubers were rated or measured for appearance, shape, specific gravity, and french fry color. The TPS hybrids had mean values for all tuber and foliar traits, except plant height, that were not significantly different from those of one or more of the cultivars; generally, values for the hybrids fell amid those of the cultivars. Two of the hybrids were taller on average than any of the four cultivars. In contrast to the means, trait uniformity of the TPS hybrids was consistently less than for the cultivars. For all foliar traits, except plant height, the TPS hybrids were substantially less uniform than the standard cultivars. For specific gravity and french fry color, two important processing quality traits, the hybrids tended to be less uniform than the cultivars; however, the difference was much less pronounced than for the foliar traits. Four of the hybrids were not significantly less uniform than one or more of the cultivars for french fry color and seven were not less uniform for specific gravity. For many market uses, the TPS hybrids appeared to have the tuber yield and quality characteristics needed to compete with standard clonally propagated cultivars.

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Phillip Griffiths*

Cucumber mosaic virus (CMV) is an aphid-transmitted virus that infects snap bean growing regions in New York State and Wisconsin. The core collection of common bean accessions (Phaseolus vulgaris), the complete collection of scarlet runner bean accessions (Phaseolus coccineus) and snap/dry bean cultivars were screened for resistance to CMV. Although variation in foliar symptom expression was observed, no resistance was observed in 93 snap bean and16 dry bean cultivars tested, and only one of the 406 accessions from the core collection (PI 309881) was symptomless. PI 309881 did not have common bean characteristics, and was later identified as a tepary bean (Phaseolus acutifolius) accession based on morphology and PCR-RFLP of chloroplast DNA. Screening of 260 P. coccineus accessions was inaccurate when a visual rating of foliar symptoms was used. It was necessary to determine infection using ELISA and test plant screening with grey zuccini. Using this approach it was determined that 80 P. coccineus accessions were susceptible to CMV; however, the remaining accessions provided possible sources for transfer of CMV resistance to snap bean. Crosses of P. coccineus accessions were made to breeding line 5-593 and backcrossed to 5-593 and snap bean cultivar `Hystyle'. PI 309881 was crossed with ICA Pijao in order to develop interspecific hybrids. Populations were developed from the interspecific crosses/backcrosses and evaluated for CMV resistance using ELISA and visual ratings of foliar symptoms.

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Stephen A. Carver, Michael Knee and Harry K. Tayama

Dendranthema grandiflora `Spirit' and `Iridon' were grown in a 2-factor experimental design consisting of 3 nitrogen rate/source treatments (100 mg/liter N (25% NH4 +}, 400 mg/liter N (25% NH4 +}, and 400 mg/liter N {5% NH4 +}), and 2 fertilizer termination treatments (bud-color and harvest) Evaluation of various production characteristics including plant and flower size, days to flower, leaf number and size, and leaf, shoot, flower and root fresh/dry weight, revealed few significant differences among treatments. High foliar N content in all treatments (ranging from 6.1 to 8.5%) may provide an explanation for the apparent lack of differential treatment production response. However, there were significant treatment differences in floral and foliar postharvest keeping quality. High NH4 + grown plants declined 1-2 weeks sooner than other treatments, and plants fertilized to harvest declined 0.5-1 week sooner than those fertilized to bud color. Root fresh and dry weights measured 2 weeks into postproduction disclosed significant differences between treatments that mirrored foliar and floral longevity. Results of a satellite study in which root and stem hydraulic conductivity, root total soluble carbohydrates, starch, and protein content, and water loss rate during postharvest will be presented.

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B.R. Bondada, J.P. Syvertsen and L.G. Albrigo

Foliar-applied urea nitrogen (N) has potential to become an important component in fertilizer programs for citrus in Florida and other citrus growing areas as it can reduce nitrate leaching into ground water. We evaluated seasonal absorption characteristics of three urea formulations, Triazone-urea, liquid urea, and spray grade urea by citrus leaves that were from 2 weeks to 6 months old. The effect of leaf age on 15N absorption by N-deficient and N-sufficient leaves, together with urea absorption over an eight-week period were studied using greenhouse-grown and field-grown plants. All foliar N applications were based on a recommended rate of 34 kg N/ha in 469 L of water. In the field studies, leaf N was increased similarly by the three urea formulations one week after three weekly applications. Young leaves (0.25 month and 1 month old) absorbed a greater percentage of N than the older leaves (3 month and 6 month old). Epicuticular wax concentration increased and 15N absorption declined with leaf age. Nitrogen deficient leaves (1.80% N) had greater wax concentration and lower N absorption than N sufficient leaves (2.60% N). Four to 8 weeks after urea applications, Triazone-urea sprayed leaves had significantly greater leaf N concentration than leaves sprayed with liquid urea or nonsprayed control leaves. The greenhouse studies revealed that the 15N absorption was greater through abaxial leaf surfaces than through adaxial surfaces regardless of leaf N level and application time. Applying foliar 15N-urea during night (2000 hr to 2200 hr) resulted in greater absorption of 15N than in the morning (0800 hr to 1000 hr) or afternoon (1200 hr to 1400 hr). It is clear that maximum N absorption from foliar urea sprays occurred at night through the abaxial surfaces of young leaves with sufficient N. Triazone-urea acted as a slow-release N source that could be exploited in supplying N over an extended period of time.

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J.M. Smagula, W. Litten and S. Dunham

Lowbush blueberries (Vaccinium angustifolium Ait.) in two commercial fields were treated with a preemergent soil application of ZnSO4 at 0.34 g Zn/m2 or a prune-year or crop-year foliar application of Zintrac (1.76 g Zn/L) in a RCB design with five treatments and nine blocks, using 1.5 x 15-m treatment plots. Prune-year foliar Zintrac treatments were applied 20 June and 30 June at 53.8 mL·m-2 or 20 June at 107.6 mL·m-2. A crop-year application of Zintrac at 53.8 mL·m-2 was made on 26 June at only one location. Composite leaf tissue samples taken 14 July of the prune year indicated that two applications of Zintrac at 53.8 mL·m-2 raised Zn concentrations at both locations more than a single application at twice the rate. Soil application of ZnSO4 did not raise leaf Zn concentrations compared to the control at either location. Crop-year leaf samples taken 6 July at the site that received the crop-year foliar treatment indicated no carryover effect of prune-year Zn treatments on leaf Zn concentration, but crop-year foliar application of Zn from Zintrac did raise leaf Zn concentrations compared to the controls. The characteristics of stems sampled in the fall of the prune year at each location (stem density, stem length, flower bud formation) were not meaningfully affected by any of the prune-year treatments. Blueberry yield was not affected by any of the treatments at either location. These data suggest that control plot leaf Zn concentrations of about 15 ppm in both fields were adequate. Raising the leaf Zn concentrations to about 80 ppm with two applications of Zintrac at 53.8 mL·m -2 had no effect on growth or yield.

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Youzhi Chen and John M. Smagula

Foliar sprays of B (400 ppm), Ca (4000 ppm), B (400 ppm) + Ca (4000 ppm), or water (control) were applied in Sept. 1993 to treatment plots of 12 lowbush blueberry (Vaccinium angustifolium) clones having low leaf B concentrations (<20 ppm). Boron concentration was raised in stem and bud tissue 3 months after application, but Ca concentration was unaffected. Twenty randomly selected stems with four flower buds were tagged in each treatment plot in Apr. 1994 to determine treatment effects on fruit set and fruit characteristics. Blossoms on tagged stems were counted in late May and a count of initial fruit was taken in early July. Initial fruit set was reduced slightly by the Ca treatment, which also resulted in a lower number of flowers per bud. Tagged stems were cut before plot harvest and stored at –15C for final fruit set and fruit characteristic measurements (fruit number, diameter, weight, and firmness, and seed number and size). Treated plots were harvested and weighed in August. Boron and Ca treatments did not increase yields averaged across all clones, but some clones showed a positive response. Yield of Ca-treated plots was significantly lower than the plots without Ca treatment. Effect of treatments on final fruit set and fruit characteristics will be presented.

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Wol-Soo Kim* and Jin-Ho Choi

The stone cells events in the process of lignifications of plant tissues in flesh of Asian pear have been growing as a depressing factor of fruit quality. Therefore, these studies were carried out to search the effect of stone cells on fruit quality, to investigate the anatomical characteristics, such as formative period and distribution of stone cell, to seek forming causes, and to determine the effects of drought stress and calcium foliar application on the formation of stone cell. Fruit quality as contents of the stone cells, such as texture profile, reducing sugars, firmness, and fruit size, were determined. During the growing season of 2002 and 2003, samples for anatomical investigations were taken periodically in Pyrus pyriforia cv. Niitaka, Pyrus communis cv. Bartlett and Pyrus ussiriansis cv. Yari. The morphology of stone cell in the fruit flesh was observed by using optical microscope, scanning electron microscope (SEM) and transmission electron microscope (TEM).

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Fazal Sultanbawa, Sharad C. Phatak and Casimir A. Jaworski

Caphea glutinosa is a herbaceous, low-growing annual, bearing numerous attractive purple flowers and has potential as an ornamental and as a ground cover. Plants exhibit winter hardiness in USDA plant hardiness zone 8. Tissue culture techniques were developed to obtain large numbers of uniform plants. Whole leaf explants (approximately 1.0 cm2) callused profusely in MS (Murashige and Skoog, 1962) medium containing 84 mM sucrose, 1% (w/v) Difco Bacto agar and 8.8 μM N6benzyladenine. Shoot formation from calli was observed in the same medium 4 weeks after explanting. Detached shoots were rooted (100%) in half strength MS medium and rooted shoots were transferred to Promix® in the greenhouse 2 weeks after rooting. Tissue cultured plants flowered after 60 days in the greenhouse and no phenotypic differences were observed in floral or foliar characteristics.

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Ali M. El-Khoreiby, C.R. Unrath and L.J. Lehman

A single foliar spray of 250 mg paclobutrazol/liter was applied to 7-year-old `Oregon Spur Delicious' (OSD) or `Smoothee Golden Delicious' (SGD) apple trees (Malus domestica Borkh.) at 12 growth stages between tight cluster and petal fall plus 28 days. A linear increase in fruit length and length: diameter ratio and a linear decrease in percent soluble solids content were observed on OSD as sprays were applied later in the season. Russet formation on SGD was excessive if treatment was made between early bloom and petal fall. For both cultivars, best control of shoot growth and minimal change in fruit characteristics occurred when paclobutrazol was applied after bloom. Chemical name used: β -[(4-chlorophenyl)methyl]- α -(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol (paclobutrazol).

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Michael S. Stanghellini, Jonathan R. Schultheis and Gerald J. Holmes

In 1998 and 1999, a total of 27 large-fruited and 15 miniature-fruited pumpkin (Cucurbita pepo) cultivars were evaluated for adaptation to eastern North Carolina grow- ing conditions. Test categories were yield (fruit number and weight); fruit characteristics (shape, rind and stem attributes); and susceptibility to edema (wart-like growths on fruit exterior), foliar diseases, preharvest and postharvest fruit decay, and viruses. Yields of large pumpkins ranged from over 3,200 fruit/acre (7,907 fruit/ha) for `SVT 4613367', `Autumn Gold', and `Gold Standard' to less than 1,000 fruit/acre (2,471 fruit/ha) for `Gold Rush' and `Progold 200'. For miniature pumpkins, over 33,000 fruit/acre (81,542 fruit/ha) were produced by `Touch of Autumn', `Lil' Pump- ke-mon', and `HMX 5682', whereas `Mystic' and `Progold 100' produced less than 7,000 fruit/acre (17,297 fruit/ha). `Gold Rush', `Howden', and `Progold 510' (large), and `EXT 4612297', `Lil' Goblin', and `Lil' Ironsides' (miniature) appeared the most susceptible to foliar diseases. Preharvest fruit decay ranged from 0% for `Howden' and `EXT 4612297' to over 20% for `Lil' Goblin', `Jumping Jack', `Peek-A-Boo', and `Tom Fox'. Virus incidence on fruit and foliage was low on virus-resistant cultivars ('SVT 4613367' and `EXT 4612297'), and ranged from 4% to 74% for nontransgenic cultivars. Virus incidence and/or severity on foliage and fruit were not related. `Early Autumn' (large) and `Touch of Autumn' (miniature) were the most prone to edema. `Aspen' and `Magic Lantern' (large) and `Baby Pam', `Lil' Goblin', and `Spooktacular' (miniature) were the most susceptible to postharvest fruit decay. Fruit characteristics are discussed in relation to marketability and possible consumer appeal to pumpkins.