Physiological-based Selection Criteria for Terminal Drought in Wheat (Triticum aestivum L.)

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Drought is the most restricting factor in agricultural production in arid and semi-arid regions. This research was conducted on 19 facultative and winter wheat genotypes grown under normal irrigation (N), early post-anthesis (S1), and late post-anthesis (S2) drought stress conditions. The experiments were conducted at Karadj, Arak, and Jolgehrokh Agricultural Research Stations in Iran, during 2008-11 cropping seasons. Stress reduced grain number per spike, thousand grain weight, grain weight per spike, harvest index, biological weight, and grain yield.Effect of environment, irrigation, and genotype on most of the traits, including grain yield, was significant. Remobilization, efficiency of remobilization, and pre-anthesis photo-assimilate contribution to grain filling increased under drought stress condition. Correlation coefficients between those traits and grain yield were significantly positive under N, S1, and S2 conditions. Based ondifferent drought tolerance indices, the improved line Alvd//Aldan/Ias58*2/3/Gaspard was identified as the most tolerant genotype under anthesis and post-anthesis drought stress conditions.It also had the highest remobilization, efficiency of remobilization, and pre-anthesis photo-assimilate contribution to grain fillingunder drought stress conditions.