Drought tolerance evaluation of bread wheat cultivars and promising lines in warm and dry climate of the south

To determine drought tolerance of bread wheat genotypes, nineteen commercial varieties along with nine promising lines were studied in research field of Darab Agricultural and Natural Resources Research Center, Fars province, Iran, for two cropping seasons (2015 –2017). The experiments were conducted in a randomized complete block design (RCBD) with two replications under water stress at flowering stage and non-stress (normal irrigation) conditions. Thirteen  selection indices including stress susceptibility index (SSI), stress tolerance index (STI), tolerance index (TOL), yield index (YI), yield stability index (YSI), mean productivity (MP), geometric mean productivity (GMP), abiotic-stress tolerance index (ATI), stress susceptibility percentage index (SSPI),stress non-stress production index (SNPI), relative drought index (RDI), harmonic mean (HM) and percentage of yield decrease (R%) were evaluated based on grain yield under drought-stressed and irrigated conditions. Also, selection index of ideal genotype (SIIG) based on all tolerance indices was defined and calculated. The results of grouping these indices based on the principal component analysis (PCA) classified them into three groups and the second group indices (HM, GMP and STI) showed the highest positive correlation with grain yield in both non-stress and drought stress conditions. Based on the results of SIIG index, the S-92-13 and Baharan genotypes with the highest SIIG (0.709 and 0.701, respectively) were the most ideal genotypes and Narin with the lowest SIIG (0.324) was the most susceptible genotype to drought stress. Three dimensional diagram of principal component analysis showed that the genotypes G5 (Sirvan), G22 (S-91-15) and G27 (M-92-20) with the higher grain yield than total average and high SIIG were most tolerant genotypes to drought stress. The results of this research showed that SIIG index could be used as a suitable method for identifying drought tolerant genotypes with the help of other drought tolerance indices.