Studies on combining ability and gene action for some quantitative and morphological traits in intra and interspecific hybrids of cotton

In order to study combining ability and gene action for quantitative traits in intra and interspecific hybrids, three genotypes of G.hirsutum with three genotypes of G.barbadense were intercrossed in a half-diallel pattern. Fifteen hybrids with six parents (21 genotypes) were studied in a randomized complete block design (RCBD) with three replications at Gorgan(Karkandeh) Cotton Research Station. Some quantitative and morphological traits (yield, boll weight, boll number, plant height, monopod and sympod length, monopod and sympod number) were measured and recorded in hybrids and parents. Results showed significant differences among genetypes for all traits, except for sympod number. Based on mean yield Siokra 324Tabladila (intraspecific hybrid) and Termez14Siokra324 (interspecific hybrid) were superior, in comparison to the other hybrids. Combining ability analysis showed that additive and non-additive variances were effective on cotton yield, boll number, boll weight, plant height, and sympod length, however, additive gene action may be important for the monopod number and monopod length. The siokra324 (G.hirsutum) and Termez14(G.barbadense) were identified as best parents for GCA. Siokr324Tabladila (intraspecific hybrid) and Termez14 Tabladila (interspecific hybrid) had best specific combining ability. Estimates of the genetic parameters according to Hyman and Jinks method supported the results. Average degree of dominance at each locus and graphical analysis indicated partial dominance for boll weight and monopod length, and over dominance effects for other traits. Dominant genes had positive and increasing effects on the yield, boll number, plant height and sympod length.