Estimates of combining ability and genetic parameters for yield and fibre traits in upland cotton

Two commercially grown cotton varieties and four advanced strains were crossed in 6 x 6 diallel mating design, involving F1s only. Study was made on the estimates of general and specific combining ability of the parents and also genetic components of variances for seed cotton yield, lint %, staple length and uniformity ratio. The per se hybrid performance generally revealed that parents Karishma and CRIS-134 formed the best hybrids for yield, lint% and uniformity ratio. It is also assumed that parents that perform well in per se hybrids will also perform similar for specific combining ability (sca) but this prediction did not hold true without few exceptions. The discrepancy between per se hybrid and sca value is not a good indicator to predict parental performance in hybrid combinations. However, hybrids perse result generally connoted that parents Karishma and CRIS-134 form good combinations with other parents for hybrid crop production. Specific combining ability estimates further indicated that hybrids NH-26 x CRIS-78 for yield, CRIS-134 x NH-26 for lint%, NH- 26 x CRIS-122 for staple length and CRIS-134 x NH-26 for uniformity ratio are greatly preferred. Based on general combining ability (gca) estimates, parents NH-26 and CRIS-78 are preferred for yield, Karishma for lint%, CRIS-1 29 for staple length and CRIS-1 34 for uniformity ratio. These parents are expected to be improved for above characters through selection in segregating generations. The proportion of variance due to gca (based on the mean squares) is higher than sca for seed cotton yield, lint% and staple length suggested that these traits are predominantly controlled by additive genes whereas variation due to sca for only uniformity ratio is significant suggesting that this trait is entirely controlled by dominant genes. The higher proportion of dominant variance (S2D) for uniformity ratio also denoted the similar position as variation due to sca for this trait. The additive genetic variance ((S2A) for yield, lint% and staple length were quite substantial insinuating the importance of additive genes for these traits.