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The present studies were conducted during cotton season 2012 at experimental farm of Central Cotton Research Institute, Sakrand. Six non-Bt females viz. CRIS-342, BH-167, CIM-573, CRIS-134, FH-941 and Sadori and six males containing Bt gene (Cry1Ac) viz. FH-113, IR-NIBGE-1524, IR-NIBGE-3701, MG-6, AA-802 and Sitara-008 were crossed in 6 × 6 North Carolina Design II fashion, thus 36 crosses were developed for genetic analysis. The characters such as days to open 1st flower, seed cotton yield kg ha-1, bolls plant-1, sympodial branches plant-1, lint %, staple length and fibre fineness were evaluated. The male × female interaction’s significant differences clearly indicated the importance of specific combining ability (SCA) of hybrids and proposed the dominant genes involvement in the articulation of studied characters. The significant mean squares owing to both female and male parents determined the general combining ability (GCA) indicated predominant effect of the additive variances advocating the studied parameters. Higher values of σ2SCA against σ2GCA, greater ratio of σ2 SCA/σ2 GCA than one, greater degree of dominance (σ2D/σ2A)1/2 than unity clearly revealed the foremost role of dominant gene effect. These results showed the prevalence of dominant gene action suggesting the achievability of hybrid crop development. General combining ability estimates designated that non- Bt females CRIS-134, CIM-573 and FH-941 and Bt males IR-NIBGE-3701, MG-6 and AA-802 were found as promising general combiners for earliness, seed cotton yield and fibre quality characters. Specific combining ability and heterotic effects are imperative estimates for deciding appropriateness of F1 hybrid crop development. For SCA effects, thirteen hybrids out of thirty six were recognized as best specific combiners for seed cotton yield, earliness and fibre quality parameters.
Keywords: Bt and non-Bt cotton; Combining ability; Fibre traits; Yield