Genetics analysis, combining ability and heterosis of some yield and yield component traits in summer squash (Cucurbita pepo L.)

This study was carried out from 2020 to 2022 at Kaha Research Farm, Kaliobia Governorate under unheated plastic house to produce F1 seeds then the six parents and fifteen hybrids were evaluated in open field in the two successive seasons (2021 and 2022). Significant differences among genotypes were observed in mean performance for all studied characters. Highly significant differences for general and specific combining abilities were found for all studied characters. Line 220-2 (P3) was the best combiner for most studied characters i.e. days to female flower anthesis, average fruit weight, fruit length, fruit diameter and total yield/plant followed by the lines 202-2 (P1) and 264 (P4). The best crosses were P1×P3, P1×P6, P1×P2 and P2×P3 since they showed significant SCA effect values for number of days to anthesis of first female flower, early yield/plant and total yield/ plant. For early yield/ plant all crosses indicated desirable positive MP heterosis ranged from 23.80 (P2×P5) to 147.83 % (P3×P4) and all crosses indicated desirable positive HP heterosis ranged from 18.18 (P2×P5) to 137.50 % (P3×P4) except the cross (P1×P4) for the same character. All of the studied crosses showed over dominance for the high early yield/ plant parent except one cross i.e. P1×P4. For total yield/ plant all crosses indicated desirable positive MP and HP heterosis except three crosses i.e. P2×P5, P4×P6 and P5×P6. MP heterosis ranged from 39.28 (P1×P4) to 152.11 % (P2×P4) and HP heterosis ranged from 32.79 (P1×P4) to 127.31 % (P2×P4).