Heterosis and Combining Ability for Development of Squash Hybrids (Cucurbita pepo L.)

Abstract

The aim of this study is to evaluate a set of inbred lines and their hybrids and to determinate the phenotypic and genotypic parameters. In addition, identify the heterosis and combining ability for the studied traits in order to determine the best combinations and the ideal improvement strategy for hybrid production in squash. The experimental study was conducted at El-Baramoon Research Station, Horticulture Research Institute during the two summer season of 2016 and 2017. Six inbred lines selected from Eskandrani cultivar and fifteen F1 hybrids were evaluated for different traits. Significant differences were observed among the hybrids and their parents for all studied traits. Based on mid-parent heterosis, the hybrid (P5 x P6) gave the highest value for early yield per plant (98.51 %) followed by the hybrid (P1 x P4) (90.24%) for the same trait. While heterosis over better parent, the hybrid (P1 x P6) gave the highest value for early yield per plant (78.95 %) followed by the hybrid (P5 x P6) (73.91 %) for the same trait. Furthermore, the highest mid-parent hertrosis for total yield per plant was obtained by the hybrid P4 x P6 (75.0%) followed by P5 x P6 (60.38%) and P4 x P5 (59.65%). Otherwise, the largest heterosis over better parent for total yield per plant were expressed by P4 x P6(61.77%) followed by P4 x P5 (46.77%) and P5 x P6 (37.10%), respectively. General combining ability (GCA) was significant or highly significant for all traits except for early yield per plant and shape index, specific combining ability was highly significant for all traits except for number of node female flower and early yield per plant. The estimated GCA/SCA mean squares revealed that the additive gene effects were the major effect in the inheritance of all studied traits, except for early yield per plant and vitamin C. Also, GCA estimates were larger than their corresponding estimates of SCA for most of the studied traits. The result illustrated that both additive and non-additive gene actions were positive for all studied traits. Heritability in broad sense ranged from 72.95 to 99.46 % for number of node female flower and total soluble solids, respectively. Also, heritability in narrow sense ranged from 28.49 to 81.94 % for number of leaves per plant and fruit shape index. The parent P1, P2 and P3 could be recommended as good combiners for average fruit weight, vitamin C, number of fruits per plant and total yield per plant whereas the P5 and P6 as promising parents for plant height, leaf area, number of leaves per plant , days to anthesis of female flowers, number of node of female flower and total soluble solids.