Combining ability as a function of inbreeding for fruit traits in Cucurbita moschata Duch. ex Poir.

Abstract

Three diallel crosses of butternut squash (Cucurbita moschata), each consisting of six parents with S0, S1, and S2 levels of inbreeding, were evaluated to estimate the effect of inbreeding on both general (GCA) and specific combining abilities (SCA) for the following traits: fruit pulp thickness, number of seeds per fruit, fruit pulp color, dry matter, 100-seed weight, diameter of placental cavity, polar diameter of fruits, and equatorial diameter of fruits. A randomized complete block experimental design was used with four replicates, arranged in split plots, with the main plot corresponding to the diallel cross (level of inbreeding) and the subplot for the evaluated genotypes (six parents and 15 F1 hybrids, in each of the diallel crosses). Additive effects (GCA) were responsible for the genetic control of most of the traits in the three diallel crosses, whereas non-additive effects (SCA) were also responsible for the genetic expression of most of the traits, but almost exclusively in crosses between S1 and S2 inbred lines. Recommended genotypes for the simultaneous genetic improvement of fruit pulp thickness and color for the fresh consumption market, which is formed by consumers who prefer whole, non-sliced fruit, were the S0 parents (P3 and P4) as well as the between S2 lines hybrid (P1×P6). On the other hand, a genotype recommended for the improvement of the same traits but intended either for agro-industrial use or for the fresh consumption market formed by consumers for whom fruit weight is not a limiting characteristic for purchase (large fruits), was the S2 parent (P2).