Experiments were conducted to estimate the relative importance of additive and dominance genetic variances and non-allelic interactions in the inheritance of resistance to Colletotrichum spp. in strawberry (Fragaria × ananassa Duch.). Progeny of 40 parents crossed in a Comstock and Robinson Design II Mating scheme were inoculated with three isolates of C. fragariae and one isolate of C. acutatum. Disease development on each plant was rated visually. Variance components were estimated and converted to genetic variances. Estimates of were six to 10 times higher than those for Within-family variance not accounted for by equaled 35% and 38% of the total genetic variance in females and males, respectively, indicating probable epistatic effects. The frequency distribution of disease severity ratings was bimodal in both experiments, suggesting major gene action. Narrow-sense heritability estimates were 0.37 and 0.26, and broad-sense heritability estimates were 0.87 and 0.85 for females and males, respectively. Narrow-sense heritability estimates are probably sufficient to produce gains from recurrent selection. Gains from selection of clonal value should be possible because of the high broad sense heritability estimates. It appears feasible to establish a broad genetic-based population resistant to Colletotrichum spp. from which selections could be evaluated per se and/or recombined to produce improved populations.

To determine the effects of pollen source on blueberry production, we made a partial diallel set of crosses involving seven rabbiteye (Vaccinium ashei Reade) and seven southern highbush (SH; V. corymbosum L.) parents. Pollination of rabbiteye blueberry flowers with SH pollen reduced fruit set, seeds per berry, and berry weight and increased fruit development period (FDP) compared to pollination with rabbiteye pollen. Pollination of SH flowers with rabbiteye pollen resulted in about the same fruit set and FDP but fewer seeds per berry and slightly lower berry weight compared to intraspecific pollination. Self-pollination significantly decreased the number of seeds per berry and berry weight and increased FDP in SH. Pollination of rabbiteye and SH flowers with mixed pollen produced the same results as intraspecific pollination. Using `Tifblue' and `Baldwin' (rabbiteye) as the pollen parent significantly increased FDP in rabbiteye blueberry. Using `Georgiagem' and `Cape Fear' as pollen parents produced the longest FDP, and using `O'Neal' and `Gulfcoast' produced the shortest FDP in SH blueberry. The heaviest berries were produced by using `Blue Ridge', `O'Neal', and `Gulfcoast' (SH) as pollen parents on SH females. These results suggest that xenia possibly could be used to increase yield and reduce FDP in blueberry.

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Fruit set in the muscadine grape (Vitis rotundifolia Michx.) depended on insect cross-pollination, although flowers were well adapted for selfing. Pollinizer cultivars produced about half of their optimal fruit set when selfed, but cross-pollination was needed to reach an optimal fruit set of 33.7%. Eighty-one percent of the overall fruit set in pistillate vines was attributed to insect cross-pollination; wind played only a small role. Diminished fruit set and fewer seeds per berry occurred in cultivars receiving no effective cross-pollination. Components of fruit quality were not profoundly affected by the pollination treatments, although seed set and berry weight in pistillate cultivars was lower in the absence of cross-pollination. Parthenocarpy was rare, except in `Fry Seedless'. Muscadine production throughout the southeastern United States depends on cross-pollination by indigenous insects, particularly bees. To ensure consistently high yields, bees must have safe access to flowers and their nesting sites must be preserved.

Nine populations were derived in the selection phase of experiments designed to evaluate a recurrent selection scheme in hurley tobacco (Nicotiana tabacum L.). We produced an unselected population of heterozygotes (Co), three populations by recurrent selection for increased weight of green leaves, and five populations by recurrent selection for decreased percent total alkaloids (% TA) of green leaves. Evaluations of the experimental material were made at three locations. The objectives wre to determine the effects of phenotypic recurrent selection on green tobacco and to ascertain the correlated effects of such selection on the yield and alkaloid content of cured tobacco.In response to selection, green leaf weight increased somewhat consistently from C0 to C3 and % TA declined linearly from Co, to C3 The correlated response of cured leaf weight to selection on a green weight basis was a linear increase, averaging 8.1 g per plant per cycle. Percent total alkaloids of cured leaf also declined linearly with successive cycles of selection on a green leaf basis. Five cycles of selection resulted in nearly 23% reduction in percent TA.The genetic correlation coefficient between green leaf weight and percent TA was −0.50 and −0.62 at two locations. This negative relationship may be a limiting factor in practical usage of phenotypic recurrent selection to increase yields without the aid of a selection index.

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