Genetic control of internode length in winter squash (Cucurbita moschata)
Understanding the genetic control of internode length is essential to develop more compact winter squash genotypes. Our objective was to elucidate the genetic control of internode length before and after emergence of the first female flower in winter squash, Cucurbita moschata. This was done by estimating the linear and quadratic genetic components and using the maximum likelihood estimation function. The parents used were the long-vined accession BGH 7319 (P1) and the compact cultivar ‘Tronco Verde’ (P2). The F1 plants from this cross were self-fertilized to obtain the F2 generation, and then they were backcrossed with P1 and P2 to obtain generations BC1 and BC2, respectively. By examining the linear and quadratic genetic components of variations in internode length, we found evidence of dominance effects both before and after flowering, with a reversal in dominance after flowering. Using maximum likelihood, we observed that the internode length before flowering was controlled by one major gene with additive and dominance effects, while the internode length after flowering was controlled by multiple genes with additive and dominance effects, plus environmental effects. Based on these results, strategies using backcrosses for introgression of the major gene controlling this trait before flowering and recurrent selection for introgression of the polygenes involved in trait control after flowering are recommended.