Genetic studies of yield and its component traits using generation mean analysis in summer squash (Cucurbita pepo subsp. pepo)

Abstract

The present investigation involved the generation mean analysis of six generations (P1, P2, F1, F2, BC1P1 (F1 × PCK-1) and BC1P2 (F1× Lady Godiva) derived from cross of PCK- 1(hulled seed) × Lady Godiva (hull-less seed) in summer squash. The pooled analysis of variances revealed highly significant differences among the generation means of different populations for vine length (cm), leaf length (cm), days to 50% flowering, inter-nodal length (cm), peduncle length (cm), polar diameter (cm), equatorial diameter (cm), flesh thickness (cm), fruit yield per plant (kg), number of seeds per fruit and seed yield per fruit (g).The epistasis was absent for node number of 1st female flower, node number of 1st male flower, number of primary branches, leaf width (cm), days to 1st harvest, number of fruits per plant, average fruit weight (kg), fruit shape index and petiole length (cm), where leaf width, number of fruits per plant, and petiole length with highly significant additive genetic variances and partial dominance can be improved through inbreeding and selection. However, over-dominance in the inheritance of node number to first female flower, node number to first male flower, number of primary branches per vine, days to 1st harvest, average fruit weight and fruit shape index suggested use of heterosis breeding for improvement. Six parameter model unveiled the preponderance of dominance and dominant × dominant [l] gene interactions for most of the other traits with the inheritance of many dominant genes carrying small and cumulative effects. However, the opposite effects of dominance [h] and the estimates of dominant × dominant [l] interactions highlighted duplicate type of gene
interactions. Therefore, summer squash cross involving PCK-1(hulled seed) × Lady Godiva (hull-less seed) can be used as a source of dominant genes and inter-allelic gene combinations for the expression of yield and related traits that can be exploited in the form of hybrid vigour through heterosis breeding.