ESTIMATING COMBINING ABILITY THROUGH LINE × TESTER ANALYSIS IN UPLAND COTTON

Combining ability of the parents was estimated via line x tester analysis so as to determine the ability of parents to combine their favourable alleles/genes during the process of hybridization and transfer those to their progenies. Two types of combining abilities were estimated, the general combining ability (GCA) which is due to additive genes whereas specific combining ability (SCA) is due to dominant and epistatic gene effects. Eight parents (Five lines and three testers) alongwith their fifteen F1 hybrids were studied in randomized complete block (RCB) Design with four replications during 2006 at Department of Plant Breeding and Genetics, Sindh Agriculture University, Tandojam, Pakistan. The traits studied were; number of bolls per plant, boll weight (g), seed cotton yield per plant (g), ginning outturn percentage and seed index (g). The GCA variances due to lines and testers and SCA due to lines x testers interaction were significant for all the characters studied. However, the magnitude of GCAs from lines (females) and testers (pollinators) were higher than the SCA indicating preponderance of additive genes in the expression of all the traits. Nonetheless, among the lines, CIM-506 whereas in testers, NB-999 by manifesting maximum GCA effects were regarded as the best general combiners for almost all the traits suggesting the presence of more additive genes in these parents, hence may serve as potential parents to be considered for hybridization and selection programmes to improve the characters studied. Among the F1 hybrids, CIM-497 x BH-147, FH-901 x NB- 999, CIM-506 x NB-999 were found as the best specific combiners for number of bolls per plant, boll weight and seed cotton yield. While CIM-497 x BH-147, NIBGE-2 x BH-147 and FH-901 x BH-147 were the best specific combiners for G.O.T% and seed index. Therefore, these hybrids may be preferred for hybrid crop development.