Determination of Drought Tolerance Indices of some Selected Rice Genotypes under Drought Stress at Flowering Stage

Drought stress, as an important constraint to reduce crop yields in Iran. To identify rice genotypes tolerant and sensitive to drought stress during flowering 15 genotypes were studied under two environments (stressed and non–stressed conditions) in a randomized complete block design with three replications at Abbas Abad and Katalom regions during 2018 growing season. To evaluate the susceptibility or tolerance of genotypes to drought stress, traits like yield under non-stress (Yp) and drought stress (Ys) and average yield of all genotypes under stress and nonstress (Ȳs), stress tolerance indicators, arithmetic mean (MP), geometric mean (GMP), harmonic mean (HM), tolerance (TOL), stress tolerance (STI), yield index (YSI), yield index (YI) and sensitivity to stress (SSI) were evaluated. Among the genotypes under study, sixty (54.62) and Ali Kazemi (46.92) showed the highest values for HM index. Shastack based on MP and GMP, shastack (61.04) and Tarom genotype (3.15) and STI index with similar trend to shastack (1.54) and Ali Kazemi (1.08) genotypes, respectively. Stress sensitivity (SSI) and yield stability index (YSI) values were similar for both genotypes of Shirudi (0.32) and Caspian (0.76). Cluster analysis based on 10 indices under drought stress resulted in two groups. Based on the results of principal component analysis, the first two components accounted for more than 92.6% of total information. The first component explained 58.76% of the total variation. According to the drought tolerance index of Shastak, Ali Kazemi and Sang Tarom genotypes are recommended as tolerant genotypes having the highest yield in both environmental conditions and having high stress tolerance index.