HETEROSIS AND NATURE OF GENE ACTION FOR EARLINESS AND YIELD COMPONENTS IN SUMMER SQUASH (Cucurbita pepo L.)

摘要

One Egyptian and three exotic parental genotypes of Summer squash were self pollinated for one generation and crossed in half diallel design to study heterosis and nature of gene action for earliness, vegetative and yield components traits. Mean squares of genotypes were found to be highly significant for all studied traits, providing evidence for presence of considerable amount of genetic variation among studied genotypes. The results showed that the majority of crosses exhibited significant heterosis estimates over mid and best parents for all studied traits. The results revealed that the general combining ability (GCA) and specific combining ability (SCA) mean squares were highly significant for all studied traits. The results indicated that themagnitude of additive genetic variance (sigma~2 A) were positive and lower than those of non additive (crD) one for all of studied traits, indicating that non additive gene action played a major role in the inheritance of summer squash. The broad sense heritability estimates (H_b~2 %) were more than 85% and larger than their corresponding narrow sense heritability (H_n~2 %) for all studied traits. However, estimates of narrow sense heritability were 21.25% for earliness and ranged from 4.02% to 13.46% for sex ratio (SR) and number of branches per plant, respectively. Respecting to yield components, the estimates of narrow sense heritability ranged from 8.92 % to 18.39% for number of total fruit yield per plant and average fruit weight per plant (g), respectively. The results showed that Eskandarany (P_1) was excellent general combiners for earliness and yield components traits. The cross combination (P_2 x P_3) showed desirable SCA effects and significant heterosis values for earliness. While, the cross (P_1 x P_3) exhibited desirable SCA effects for vegetative and early yield components. However, the cross combinations (P_1 x P_3), (P_1 x P_4), (P_2 x P_3) and (P_2 x P_4) revealed significant SCA effects for total yield components. These promising crosses could be used for constitution of summer squash hybrids.