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Phillip A. Wadl, John A. Skinner, John R. Dunlap, Sandra M. Reed, Timothy A. Rinehart, Vincent R. Pantalone, and Robert N. Trigiano

crosses. Development of improved cultivars with desired combinations of specific traits requires controlled crosses. Often these crosses are done manually and the procedure is a time-intensive process ( Reed, 1999 ). The inflorescences of flowering and

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Richard A. Reinert and Gwen Eason

Identification of genetic control of ozone (O3) sensitivity is desirable for selection of plant cultivars which are indicators of O3 stress. A cross was made between two cultivars of snap bean (Phaseolus vulgaris L.), `Oregon 91' (P1) and `Wade Bush' (P2), an O3-sensitive and O3-insensitive cultivar, respectively. Ten genetic populations (generations), `Oregon 91' (P1), `Wade Bush' (P2), F1, F2, backcrosses to both parents, and all reciprocal crosses, were field planted in each of two summers and evaluated for injury to O3. Ozone responses for the reciprocal crosses were not significantly different for any generation, so injury ratings from the reciprocal crosses were combined for each generation to provide six populations (P1, P2, F1, F2, BC1, and BC2) for analysis. When components of genetic variation were estimated from the six generations, additive genetic variance was the most important component in the total genetic variance available, although dominance variance was also a significant component. There was an inconsistency in the magnitude and the direction of the factors contributing to the dominance effects and also a large environmental component making up the phenotypic variance. Estimates of broad-sense heritability and narrow-sense heritability were 60% and 44%, respectively. Results suggest that O3-sensitive and O3-insensitive selections could be screened and evaluated in an ambient O3 environment. Several generations will be necessary, however, to develop `Bush Blue Lake' type selections that vary only in sensitivity to O3.

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Alan T. Whittemore and Alden M. Townsend

. Table 1. Plants used as parents in crossing experiments. Controlled crosses. About a month before normal anthesis, mature branches were brought inside the greenhouse to force pollen shed. Pollen was collected on waxed paper, transferred

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Tera M. Bonney, Shawn P. Brown, Snake C. Jones, Kirk W. Pomper, and Robert L. Geneve

The pawpaw [Asimina triloba (L.) Dunal] is a native plant found mainly in the southeastern and eastern United States, and its fruit has great potential as a new high-value crop in these regions. Although there are ≈45 named pawpaw cultivars, breeding for improvement of specific traits, such as fruit size and quality, is desirable. Our long-term goal is to utilize molecular marker systems to identify markers that can be used for germplasm diversity analyses and for the construction of a molecular genetic map, where markers are correlated with desirable pawpaw traits. The objective of this study was to identify random amplified polymorphic DNA (RAPD) markers that segregate in a simple Mendelian fashion in a controlled A. triloba cross. DNA was extracted from young leaves collected from field-planted parents and 20 progeny of the cross 1-7 × 2-54. The DNA extraction method used gave acceptable yields of ≈7 μg·g-1 of leaf tissue. Additionally, sample 260/280 ratios were ≈1.4, which indicated that the DNA was of high enough purity to be subjected to the RAPD methodology. Screening of 10-base oligonucleotide RAPD primers with template DNA from the parents and progeny of the cross has begun. We have identified two markers using Operon primer B-07 at 1.1 and 0.9 kb that segregate in a simple Mendelian fashion in progeny of the 1-7 × 2-54 cross. Other primers and controlled crosses will also be screened.

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John R. Stommel and Kathleen G. Haynes

Fruit of the cultivated tomato (Lycopersicon esculentum Mill.) store predominantly glucose and fructose whereas fruit of the wild species L. hirsutum Humb. & Bonpl. characteristically accumulate sucrose. Reducing sugar and sucrose concentrations were measured in mature fruit of parental, F1, F2, and backcross (BC1) populations derived from an initial cross of L. esculentum `Floradade' × L. hirsutum PI 390514. Generational means analysis demonstrated that additive effects were equal to dominance effects for percentage of reducing sugar. It was determined that a single major gene, dominant for a high percentage of reducing sugar, regulates the percentage of reducing sugar in tomatoes. We propose that this gene be designated sucr. Only additive effects were demonstrated to be important for glucose: fructose ratios. Using L. hirsutum as a donor parent for increasing total soluble solids concentration in the cultivated tomato is discussed.

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D.M. Glenn, G. Puterka, T. van der Zwet, and R. Byers

102 POSTER SESSION 4G (Abstr. 234–247) Disease Control–Cross-commodity

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Susan L. Eggleston, Darlene M. Lawson, and Martha A. Mutschler

145 ORAL SESSION 44 (Abstr. 330–337) Weed Control & Pest Management/Cross-commodity

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Ryan N. Contreras, John M. Ruter, and David A. Knauft

reproduction exists in the genus and at least some level of outcrossing is observed. The goal of the current research was to use controlled crosses to investigate the genetics of fruit color in C. americana . Results of crosses and segregation ratios of

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Richard L. Bell

of European origin. Material and Methods Seedling populations and controls. Nine seedling populations derived from crosses among five resistant European P. communis cultivars (‘Batjarka’, ‘Erabasma’, ‘Ilinjaca’, ‘Spina Carpi’, and ‘Zelinka’), a

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Bruce L. Dunn and Jon T. Lindstrom

within Lamiaceae is reported to be common and has been seen in Salvia L., Mentha L., Monarda L., Dicerandra Benth., and Hyptis Jacq. ( Huck, 1992 ). Lewis (personal communication) attempted crosses between T . lanatum and T . parishii