Genetic Analysis of Yield Components in Cucumber at Low Plant Density

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Plant architecture can be manipulated in cucumber (Cucumis sativus L.) to provide an array of phenotypes. Determinate, multiple-lateral plants are unique because they afford an opportunity to increase fruit yield per plant. Estimates of genetic variances, numbers of genetic factors, and genotypic and phenotypic correlations between traits were made in a population, segregating for sex expression, leaf size, and plant habit at low plant density (≈19,000 plants/ha). Replicated evaluation of 100 F3 families derived from an initial mating between a gynoecious, determinate, moderately branched line (G421) and a monoecious, indeterminate, multiple lateral branching line (`H-19') indicated that mainstem length and multiple lateral branching exhibit mostly additive genetic variance. For sex expression, additive and dominant genetic variances were important. The minimum number of genetic factors controlling sex expression, number of lateral branches, and mainstem length were estimated at five, four, and eight, respectively. Phenotypic and genotypic correlations between traits indicated that relative leaf size may influence fruit mass while having only limited influence on the number of fruit produced per plant. The amount and type of genetic variation suggests that the development of an array of determinate, multiple-lateral branching plant types with varying sex expression and plant stature is possible.