General Combining ability of parents, specific combining ability of hybrids and heterosis over better parent were studied in a cross involving ten cotton genotypes ( 6 lines × 4 testers ) for yield and quality traits. The six lines were Egyptian cotton genotypes Giza 70, Menofi, Giza 86, Giza 89, Ashmoni and Dandara, While the four testers were involved two foreign cotton genotypes ( BBB and Suvin ) and two Egyptian cotton genotypes ( Giza 92 and Giza 88 ). Ten parents and 24 F₁ hybrids were laid out in completely randomized block design with three replications at Sakha Agriculture Research Station in 2011 season. Analysis of variance revealed highly significant differences among genotypes, parents and crosses indicating the presence of considerable amount of genetic variability. Parents VS crosses was also significant, except for most fiber characters, indicating the presence of heterotic response for these characters. The magnitude of SCA variance was greater than GCA variance for all characters indicating the importance of SCA. The maximum contribution to the total variance was made by line × tester interaction for most characters. While the contribution of testers were higher than lines.
The results reported that the best general combiner; for earliness were Dandara and Giza 86, for yield were Suvin amd Giza 92 and for fiber quality was Giza 70. On the basis of specific combining ability SCA effect for yield and its components characters in relation to significant positive heterosis over better parent, the crosses Giza 86 × Suvin, Dandra × Suvin and Giza 86 × BBB exhibited highest magnitude of positive significant SCA with desirable heterosis for yield characters. Therefore, these hybrids may be preferred to improve several yield characters simultaneously by selection or may be used for hybrid cotton crop development.