Heterosis and combining ability of seed cotton yield and its contributing traits under drought conditions [electronic resource].

Includes references.

A half diallel set of crosses involving eight cotton parental cultivars, six of them belonging to Gossypium barbadense, Giza 45, Giza 70, Giza 83, Giza 85, Pima S-7 and Sea island as well as two Upland cultivars (G.hirsutum), Tamcot and Deltapine 703, were evaluated under three irrigation intervals 15, 25 and 35 days. The results revealed that irrigation regimes mean squares were found to be highly significant for all studied traits. Highly significant differences among genotypes, parents and FJ crosses were observed for all studied traits under the three irrigation regimes and their combined analysis. The interactions of irrigation regimes with each of genotypes, parents and crosses were found to be highly significant for all studied traits. Heterobeltiosis was generally pronounced and existed for all studied characters except boll number .Both general and specific combining ability (GCA and SCA) variances were found to be highly significant for all studied traits under the three irrigation regimes and the combined data, suggesting that both additive and non-additive gene effects were operative for these traits. The GCA/SCA ratios indicated that additive and additive by additive types of gene action were of greater importance in the inheritance of all studied traits either under normal irrigation or water stress conditions. The best general combiners under normal irrigation were: Tamcot and Deltapine 703 for earliness, boll weight, seed index and seed cotton yield/plant, Giza 70 for boll number, lint percentage and seed cotton yield, Giza 45 for boll number, Gizc. 83 and Giza 85 for boll number, lint percentage and seed index and Pima S-7 and Sea island for boll number and lint percentage. On the other hand, the four exotic varieties Pima S-7, Sea island, Tamcot and Deltapine 703 were good general combiners for seed cotton yield and some of its components under the relatively water stress conditions. Some cross combinations revealed desirable SCA effects for yield under normal irrigation and water stress conditions. The best cross-combinations were Giza 45 x Giza 85, Giza 70 x Sea island, Giza 83 with both of Pima S-7 and Tamcot and Pima S-7 x Tamcot under normal irrigation condition and the two crosses Giza 45 x Giza 83 and Sea island x Deltapine 703 under drought condition. Moreover, the four cotton genotypes Giza 85, Pima S-7, Tamcot and Deltapine and three crosses Pima S-7 x Tamcot, Giza 85 x Sea island and Tamcot x Deltapine 703 showed the lowest drought susceptibility index (most drought tolerance).

Summary in Arabic.

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