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Sophia Kamenidou and Todd Cavins

Silicon (Si) is a beneficial element to many agricultural crops. We found improved horticultural traits in our preliminary Si supplementation research on floricultural greenhouse crops produced in soilless substrates. The objective of this study was to establish optimum Si rates based on previous results and investigate the relationship of Si tissue and substrate content. Potassium silicate (KSiO3) weekly drenches (0, 50, 100, 150 mg·L-1 SiO2), media-incorporated KSiO3 flakes (0, 280, 400, 520 g·m-3 SiO2), and ashed rice hulls (0, 200, 270, 360 g·m-3 SiO2) were provided to Helianthusannuus`Ring of Fire'. Leaf, stem, and flower tissues as well as soilless substrate samples were collected for Si analysis. Several Si treatments resulted in plants with increased flower and stem diameter compared to untreated controls (P ≤ 0.05). Weekly drenches with KSiO3 (150 mg·L-1 SiO2), KSiO3 flakes (280 g·m-3 SiO2), and ashed rice hulls (360 g·m-3 SiO2) were the most efficient treatments based on the increased quality characteristics. Leaf tissue had the highest Si content, followed by flower, then stem tissue. Correlation analysis indicated that leaf and flower Si content was positively correlated with saturated media extract substrate samples (correlation coefficients r= 0.75 and 0.63, respectively).

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Pablo Cavagnaro, Douglas Senalik, Claudio Galmarini, and Philipp Simon

Allium plants possess organosulfur compounds and carbohydrates that provide unique flavor and health-enhancing properties. In previous studies of onion F3 families, significant phenotypic and genetic correlations have been reported between pungency, in vitro antiplatelet activity (IVAA), and soluble solids content (SSC); although in other studies SSC and pungency have not always been correlated. In this study we analyzed SSC, pungency, garlic-induced in vitro antiplatelet activity and the content of three predominant thiosulfinates in bulbs from two garlic families obtained from unrelated self-pollinated plants. A strong positive correlation was observed between pungency and IVAA for both sample sets, indicating that it will be difficult to develop garlic populations with low pungency and high IVAA. Allicin was the most abundant thiosulfinate and its content was positively correlated with pungency and IVAA (r= 0.70 and 0.74, respectively). The thiosulfinates AllS(O)SPropenyl and AllS(O)SMe were also positively correlated with pungency and IVAA. When compared with IVAA, AllS(O)SMe had higher r values than AllS(O)SPropenyl (0.88 and 0.50, respectively). These differences could reflect differential platelet anti-aggregatory properties of different thiosulfinates. SSC was not correlated with IVAA, pungency, or thiosulfinates content, suggesting that soluble solids in garlic can be independently selected.

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Jiang Lu, Elvis Clarke, and Zhong-bo Ren

Although some of the American native Vitis species and their hybrids, particularly those originated from the southeastern United States, have been known for resistance to Pierce's disease (PD), their resistant status against the glassy-winged sharp shooter [GWSS, Homalodisca coagulata (Say)], the vector transmitting PD pathogen (Xylellafastidiosa Well), has not been reported. To determine GWSS feeding preferences on different grape species/cultivars and correlations of feeding to Pierce's disease development, a survey was conducted at Florida A&M University, Tallahassee. The feeding preference of GWSS on different species/cultivars was evaluated in two different ways: 1) count the number of GWSS on different grapevines in the field; and 2) determine the feeding preference by measuring the excretion of the GWSS feeding on difference grape species/cultivars, including highly susceptible V. vinifera cultivars, native American grape species and hybrids, and muscadine grapes. Results from this study indicated that the frequency of GWSS visits on different grapevines varied among the species/cultivars investigated. For example, PD-resistant grape V. rotundifolia (muscadine grape) had significantly fewer GWSS visits than did the PD-susceptible V. vinifera grape. The frequency of GWSS visits to V. labrusca, the native American grape susceptible to PD, was intermediate between those found on V. rotundifolia and V. vinifera. Similarly, the GWSS sucked more xylem sap when they fed on PD-susceptible grapevines than on PD-resistant ones. Overall, there is a positive correlation between the GWSS visits/feeding and the status of grapevine resistance/susceptibility to Pierce's disease.

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James Nienhuis, Steve Schroeder, and Gretchen King

An accession of the wild species of tomato, L. pennellii (Cor.) D'Arcy, LA 1077 is much more water-use efficient (WUE) than the cultivated tomato. The F1 hybrid between L. esculentum cultivar UC82 and LA 1077 was backcrossed to UC8 2 and selfed. S1 families (BC1S1) were evaluated for fruit quality characteristics at the Heinz Research Farm, Stockton, CA. Broad sense heritabilities were estimated as follows: Fruit weight, 0.52 ± .28; Soluble solids 0.56 ± .27; viscosity 0.63 ± .27; pH 0.43 ±.29 Color L 0.59 ± .27 and Color A/B ratio 0.50 ± .28. The following phenotypic correlations were observed in the BC1S1 generation between expression of soluble solids and fruit quality characteristics: Fruit weight (g), 0.15; viscosity, -0.65; pH -0.52; Color L, -0.53 and Color A/B ratio 0.02.

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John E. Preece, Carl A. Huetteman, W. Clark Ashby, Paul L. Roth, and Richard G. Adams

Sixty clones (four clones from each of 15 provenances) were micropropagated and planted in replicated plots in lowland and upland sites in Carbondale, IL in 1991. Data were collected on tree growth, including basal caliper, height, branching, crown volume, dates of bud break, bud set, and leaf fall. There were significant and strong positive genotypic and phenotypic correlations between tree height and basal caliper throughout the three years of growth. During 1993, bud break was not significantly correlated with any growth parameters. After three years in the field, tree height was significantly negatively correlated with the amount of callus that had formed after one month during the in vitro micropropagation phase. However, all shoots that formed in vitro were of axillary origin.

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E.W. Stover and C.S. Walsh

A factorial planting of three scion varieties (`Gala', `Fuji', and `Braeburn') on each of four rootstocks (Mark, M.26, M.7a, and MM.1 11) was established at two locations in MD in 1990. In 1993, trees were scored for trunk circumference (TC), extension growth, leaf color, burrknots (BK) and gall-like swellings (GLS) both above and below ground, and presence of pests on the shanks. Mark was the only rootstock with GLS; 75% of the trees examined had these tissue proliferations, Mark grafted with `Fuji' had 2-3X higher %TC composed of GLS below ground than was observed with other scion varieties. Across rootstocks, %TC composed of BK below ground was significantly affected by location. ln each rootstock, regressions between growth parameters and % of TC with BK or GLS were almost all negative and many bad significant correlations. ln Mark, % of TC with GLS below ground (but not above) was significantly correlated with reduced TC at 25 cm. The occurrence of GLS was much greater below ground than above. Orchard surveys of trees on Mark were also conducted at several commercial sites in MD and NY. The percentage of trees showing GLS ranged from 0 to 90%. There was a significant reduction in TC at 25 cm correlated with increasing levels of GLS. The percentage of trees with GLS and mean % of TC with GLS significantly correlated with percentage of trees having visible woolly apple aphids or their distinctive galls.

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Marcos R. Sachet, Idemir Citadin, Silvia Scariotto, Idalmir dos Santos, Pedro H. Zydek, and Maria do Carmo B. Raseira

be possible to incorporate it into new peach selections ( Topp et al., 1993 ). The aim of the present research was to classify peach genotypes based on their susceptibility to BLS and to examine the correlation between bacterial reaction and

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Eladio Arnaud-Santana, D.P. Coyne, K.M. Eskridge, and A.K. Vidaver

The heritability of leaf, pod, and seed reactions; stem color and abaxial leaf pubescence; and the association of these traits were studied in advanced dry bean recombinant inbred lines derived from the Phaseolus vulgaris crosses `PC-SO' × XAN-159, `PC-50' × BAC-6, and `Venezuela 44' × BAC-6. The reaction to Xcp was quantitatively inherited in all three plant organs. Qualitative inheritance was found for stem color and leaf pubescence. Low to intermediate heritability values were obtained for the leaf and seed reactions to Xcp. Heritability estimates were consistently low for the pod reaction to Xcp. Low nonsignificant Pearson correlations were detected between leaf and pod reactions, leaf and seed reactions, and pod and seed reactions, except for the latter two correlations, which were low and significant in lines from the cross `PC-50' × XAN-154. Genetic correlations between leaf and pod reactions and leaf and seed reactions were low and significant in lines from all crosses, except for Venezuela 44 × BAC-6 in the latter case. Genetic correlations between pod and seed reactions were low and nonsignificant, except in the cross `PC-50' × XAN-159, for which a low significant correlation was observed. No significant association was found between Xcp leaf reaction and stem color or leaf pubescence. A breeding strategy for improving resistance to Xcp in P. vulgaris is discussed.

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B.T. Scully, D.H. Wallace, and D.R. Viands

One-hundred-twelve common bean (Phaseolus vulgaris L.) lines of diverse origin were grown in three environments in 1986 and two environments in 1987. The purpose was to estimate broad-sense heritabilities of nine yield-related traits and the phenotypic, genetic, and environmental correlations among them. The traits and their heritabilities were seed yield (0.90), biomass (0.93), harvest index (0.92), days to maturity (0.96), days to flower (0.98), days of pod fill (0.94), biomass growth rate (biomass/days to maturity) (0.87), seed growth rate (seed yield/days of pod fill) (0.87), and economic growth rate (seed yield/days to maturity) (0.86). These high heritabilities were attributed to the broad genetic diversity and the comparatively small variances associated with the genotype × environment interactions. Genetic correlations of yield were: with biomass, 0.86; harvest index, 0.42; days to maturity, 0.40; days to flower, 0.33; days of pod fill, 0.24; biomass growth rate, 0.92; seed growth rate, 0.84; and the economic growth rate, 0.85. The concomitant phenotypic correlations were mostly equal to the genetic correlations for biomass and the three growth rates, but lower for the phonological traits (days to maturity, flower, and pod fill). Harvest index had the lowest correlations with yield. Correlations were also reported for the other 28 pairwise combinations among these nine traits. Indirect selection was explored with yield as the primary trait and the other eight as secondary traits. Estimates of relative selection efficiency (p) suggested that indirect selection was not a viable option for increasing common bean yields or identifying superior parents.

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Kimberly J. Walters, George L. Hosfield, Mark A. Uebersax, and James D. Kelly

Three populations of navy bean (Phaseolus vulgaris L.), consisting of recombinant inbred lines, were grown at two locations for 2 years and were used to study canning quality. The traits measured included visual appeal (VIS), texture (TXT), and washed drained mass (WDM). Genotype mean squares were significant for all three traits across populations, although location and year mean squares were higher. We found a positive correlation (r = 0.19 to 0.66) between VIS and TXT and a negative correlation (r = -0.26 to -0.66) between VIS and WDM and between TXT and WDM (r = -0.53 to -0.83) in all three populations. Heritability estimates were calculated for VIS, TXT, and WDM, and these values were moderate to high (0.48 to 0.78). Random amplified polymorphic DNA markers associated with quantitative trait loci (QTL) for the same canning quality traits were identified and studied in each population. Marker-QTL associations were established using the general linear models procedure with significance set at P=0.05. Location and population specificity was common among the marker-QTL associations identified. Coefficient of determination (R2) values for groups of markers used in multiple regression analyses ranged from 0.2 to 0.52 for VIS, 0.11 to 0.38 for TXT, and 0.25 to 0.38 for WDM. Markers were identified that were associated with multiple traits and those associations supported correlations between phenotypic traits. MAS would offer no advantage over phenotypic selection for the improvement of negatively associated traits.