Abstract
Six divergent genotypes of sesame (Sesamum indicum L.) were crossed using a half diallel excluding reciprocal crosses, to estimate heterosis, combining ability and nature of gene action for studied traits under two irrigation regimes. The two irrigation regimes were normal irrigation conditions with amount of applied water 5952.38 m3/ha and water stress conditions with amount of applied water 2976.19 m3/ha at Etay-El-Baroud Agricultural Research Station, Behaira governorate, Agricultural Research Center, Egypt during 2019 summer season. A randomized complete block design with three replications was used for each irrigation regimes. The variation of genotypes and their components from parents, crosses and parents versus crosses were highly significant for all studied traits under both irrigation regimes and their interactions with irrigation. Variation attributable to general and specific combining ability was highly significant for seed yield and yield components under both irrigation regimes. The parents L92 and L110 were the best combiners for seed weight per plant and most of its components under both irrigation regimes. The best F1 cross combination was L92 × L110 in specific combining ability and heterotic effects over mid- and better-parents under both irrigation regimes for seed weight per plant and most of its attributes. The preponderance of additive gene action in the inheritance of most studied traits was observed, that further confirmed by its significance and the value of average degree of dominance exceeding the unity. Narrow-sense heritability varied from 0.19 for number of branches per plant to 0.47 for 1000 seed weight under normal irrigation, whereas, under water stress conditions, it ranged from 0.14 for number of branches per plant to 0.42 for fruiting zone length. Parents L95 and L93 under normal irrigation and L93 and L110 under water stress conditions carried mostly genes with dominant effects for seed weight per plant, in contrary, L92 and L110 under normal irrigation and L92 and L12 under water stress conditions carried mostly recessive alleles for seed weight per plant. Hence, the results will be used to develop a sesame breeding scheme at Etay-El-Baroud Agricultural Research Station.
Highlights
Sesame is one of the important oil crops in Egypt
(1965) was performed for partitioning of dominance genetic effects (b) into three effects as b1 which refers to test of mean deviation of F1 from their mid-parental values, b2 which refers to test of whether mean dominance deviation of the F1 from their mid- parental values within each array differs over arrays, and b3 which refers to test of dominance deviation that is unique to each F1, for each irrigation regimes
The differences due to parents and their F1 crosses were highly significant for seed yield and yield components under both irrigation regimes and their interactions with irrigation
Summary
Sesame is one of the important oil crops in Egypt. It plays a vital and effective role in covering the requirements of oilseeds. Combining ability analysis is a common biometrical tool in half diallel analysis to identify the best general combiners and the desirable specific cross combinations Another method of half diallel analysis as Hayman (1954a, 1954b, and 1960) and Jinks (1954) provides the breeder with the detailed information on nature gene action and the genetic control in the studied traits. This information helps breeder in selection of preferred parents for future crosses at breeding programs to improve the sesame yield and related traits For achieving this objective, the efforts in this study aimed to estimate: heterotic effects, combining ability effects, nature of gene action controlling genetic expression of the studied traits under both normal irrigation and water stress conditions
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