RESPONSES OF WHEAT GENOTYPES TO TERMINAL DROUGHT STRESS BY USING STRESS TOLERANCE INDICES

One of the important abiotic stress factors limiting wheat production in Mediterranean basin is drought. Eight wheat genotypes were evaluated under both drought conditions in post anthesis stage (El) and non-stress (E2) field environments using a randomized complete block for each environment in 2007/08 and 2008/09 growing seasons. Five drought tolerance indices including stress susceptibility index (SSI), stress tolerance index (STI), Stress Tolerance Index (TOL), mean productivity (MP) and geometric mean productivity (GMP) were used. According to grain yield under normal and terminal drought stress conditions the indices were adjusted. Greater values of GMP, STI and MP indices were associated with higher yielding genotypes under both growing conditions. Inversion of genotypes ranking was obtained for SSI and TOL. Higher TOL and SSI values were associated with significant grain yield reduction in stressed environment suggesting higher stress responses of genotypes. Higher grain yield was recorded in DN-11 during both normal and terminal drought stress conditions whereas Bahar had considerably lower yield than other genotypes. The results of our research were that MP, GMP and STI values were appropriate parameters for selecting high yielding wheat genotypes in both normal and terminal drought stress conditions.