Evaluation of physiological traits in winter and facultative bread wheat genotypes under terminal drought stress conditions

Drought stress is the most limiting factor for agricultural production in arid and semi-arid regions, therefore development of drought tolerant varieties in wheat breeding programs is in top priority. This experiment was conducted to compare 19 facultative and winter wheat genotypes under normal irrigation and anthesis (S1) and post-anthesis (S2) drought stress conditions, as split plot arrangements in randomized complete blocks design with three replications at Karaj agricultural research station of Iran in 2008-11 cropping seasons. Drought stress affected grain yield, Harvest index (HI), leaf relative water content (RWC), canopy temperature depression (CTD), chlorophyll (CHL) and cell membrane stability (CMS). Results showed that genotypes with high grain yield also had higher leaf relative water content (RWC), canopy temperature depression (CTD) and cell membrane stability (CMS). Under S1 drought stress condition, grain yield had significant positive correlation with cell membrane stability (CMS) and canopy temperature depression (CTD), therefore, cell membrane stability and canopy temperature depression could be used for selection of tolerant genotypes. Among the genotypes, genotype no. 6 had higher cell membrane stability and canopy temperature depression than the others. Tolerance and susceptibility of the genotypes to drought stress were assessed using STI, SSI, TOL, MP and GMP. Considering grain yield, physiological traits and stress susceptibility indices in three conditions, genotype no. 6 (Pishtaz*2/Gaspard) was identified as the most tolerant genotype and was selected for on-farm trials