Abstract

Study of combining ability and gene action for drought tolerance in wheat were carried out using Genotype-by-Environment (GGE) biplot techniques. Eight-parental diallel crosses, excluding reciprocals, were grown in a randomized complete block design with three replications under two different water regimes (irrigated and rainfed) in the Agricultural Research Institute of Sararood, Kermanshah, Iran. Significant differences were found for yield potential (Y_p), stress yield (Y_s), stress tolerance index (STI), water use efficiency (WUE) and evapotranspiration efficiency (ETE). GGE biplot analysis showed that the parent A, A, A and B were the best general combiners with two additive genes (A₁ and A₂), for improvement of Y, STI, WUE and ETE under drought conditions, respectively. Parents A and C also exhibited positive GCA for all the studied traits. The crosses (A, D and H) × (C, E, F and G), (A, C and F) × (B, E, H and G), (A, C and E) × (B, G, H and F) and (A, C, G and D) × (F, B, E and H) for Y, STI, WUE and ETE were identified as heterotic groups with different dominant tolerance genes (D₁ and D₂), respectively. The polygon view of the biplot indicated that combining of A × G and A × C produced the best drought tolerance hybrids for all the traits through integrated the four tolerance genes (A₁, A₂, D₁, and D₂).

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