Combining ability of physiological traits in bread wheat under drought stress

In order to compare of inheritance، combining ability، heterosis and genes action in the genetic control of flag leaf area، leaf relative water content and grain filling rate in bread wheat cultivars under drought stress conditions، a study was conducted on eight cultivars using method 2 in fixed model of Griffing. General combining ability and specific combining ability mean of squares were highly significant for all the traits with the exception of specific combining ability mean of squares for leaf relative water content that designated importance of both additive and dominance gene effects in inheritance of traits studied in drought stress conditions. The general combining ability mean of square/specific combining ability mean of square ratio was not significant for all the traits. The results of this study showed that non-additive genetic effects were found to be more important than additive effects in genetic control of all the traits. In conclusion، genetic improvement of flag leaf area، leaf relative water content and grain filling rate in drought stress conditions at early generations will have low genetic gain. Therefore، selection for improvement of these traits is better that delayed until advanced generations and increase of its heritability.