Heterosis and Gene Action among Single and Double-Cross Hybrids Performances in Cotton

The objective of present study was to estimate the magnitude of heterosis and gene action in different types of intra-specific crosses of Gossypium barbadense L. viz. single (A x B) and double (A x B) x (C x D) crosses. Significant or highly significant difference in most studied traits appeared due to different all genotypes (parents, single and double-cross hybrids). Mean performance of some single crosses was higher than the double-cross hybrids for most studied traits. The single-cross hybrid (Pima S x Australian) and the 6 double-cross hybrid (Pima S x Australian) x (Karashanky x Giza 88) were the best mean performances for most 6 studied traits. Some single and double-cross hybrids exhibited negative or positive and significant heterosis for most studied traits. However, the single-cross hybrid (Pima S x Australian) and (Giza 85 x Giza 88) were 6 showed desirable heterosis versus better-parent for most traits. The double-cross hybrids (Pima S x Australian) 6 x (Karashanky x Giza 88) and (Pima S x Giza 88) x (Karashanky x Giza 85) were recorded positive heterosis versus 6 better-parent and better-F hybrid for most important studied traits, respectively. The heterosis over better- 1 parents in all diallel crosses exhibited insignificant positive and desirable for all studied traits. While, the heterosis over mid-parents, Mid-F hybrids, better-parent, better-F hybrids and mid- parents and F hybrids 11 1 were desirable for some studied traits in all double-cross hybrids. In diallel crosses, both the additive and dominance genetic variances were presented in seed cotton yield/plant, lint cotton yield/plant and seed index traits, but additive genetic variance was lower in magnitude than dominance genetic variances for all studied traits. As for double-cross hybrids, additive x additive and additive x dominance genetic variances were observed and highest than the other types of epistatic genetic variances for all studied traits. Broad-sense heritability was high, but narrow-sense heritability was low for all the traits studied in single and double-cross hybrids. High and significant or highly significant correlation between mean performances and heterosis was observed for most studied traits in both single and double-cross hybrids.