GCA

Eight S 3 baby corn lines of KH101 were evaluated following line (8) × tester (3) method by determining general combining ability (GCA) and specific combining ability (SCA). Highly significant genotypic differences were observed indicated wide range of variability present among the genotypes. Variance due to SCA was larger than GCA variance for all the characters indicating the preponderance of non-additive gene action in the expression of various traits. Among the parents none were found as good general combiners for baby corn yield. None of 24 cross combinations showed significant SCA effects for yield per plant. Considering cob length, cob diameter, cob per plant, total fodder weight and yield per plant the crosses KH-101/S 3-44×VS/S 3-24 and KH-101/S 3-44×VS/S 3-25 were selected as promising baby corn hybrids.

A study was conducted on heterosis, combining ability and genetic parameters of yield and yield components in rice. Five lines were crossed with two testers in line × tester manner to produce ten F 1 hybrids. Results show that general combining ability (GCA) effect was only significant for total number of kernels per panicle, number of filled kernels and grain yield per plant, and specific combining ability (SCA) effect was significant for yield and all of its studied components (except for 100-kernel weight). Lines IR42 and Pouya showed a significant GCA for grain yield in opposite direction (20.9 and-13.7 g/plant, respectively). The two lines also showed highest significant GCA for number of filled kernels (22.7 and 23.3, respectively). In the total number of kernels, lines IR8 and IR42 and tester Usen showed the highest significant GCA (34.79, 27.97 and 12.56). In tiller number, only line IR36 and tester IR68897 had the highest significant GCA (3.51 and 0.84). Combination of IR68897×IR8 showed highest significant SCA for grain yield (9.7 g/plant), while in the case of number of filled kernels and tiller number, combinations IR68897×IR8 and Usen/IR36 showed a significant positive SCA (18.9 and 2.1, respectively), indicating that hybridization can be a choice for improving hybrids with better quantity of these traits. The highest general heritability (2 b h) was obtained for tiller number (96.1%), indicating slight effects of the environment on the trait, while for other traits, a mild general heritability (~70%) was obtained, indicating considerable effect of environment on phenotypic expression of most yield traits. A low specific heritability (2 n h) was obtained for all traits (18.2 to 26.3%), indicating that non-additive effects play an important role in genetic control of yield traits. Therefore, it seems that hybridization must be a choice for utilizing the putative heterosis in special crosses, and such a condition was observed for tiller number and grain yield in combinations of IR42×IR68897 and IR42×Usen.