Evaluation of rice genotypes based on yield and yield components under complete irrigation and drought stress conditions and drought tolerance indices using biplot analysis

To evaluate rice genotypes to drought stress and determine the effective traits on grain yield, 18 rice genotypes (14 M5 mutant lines and four drought sensitive cultivars) were studied in two separately experiments under normal irrigation and drought stress conditions in reproductive stage based on randomized complete block design with three replications at Rice Research Institute of Iran (RRII), Rasht, Iran, during 2014-2015 growing season. Genotype by trait (GT) biplot analysis indicated positive correlations between grain yield and tiller number, grain productivity and width of grains in normal irrigation condition and width and length of grains, number of tillers, grain productivity and number of filled grains in drought stress condition. Stress tolerance index (STI), mean productivity (MP), geometric mean productivity (GMP) and harmonic mean (HM) indices were as suitable indices to select the high-yielding genotypes under drought stress condition. Based on drought stress tolerance indices and overall performance of traits under drought condition, Khazar, Hashemi, Tarom and Gilaneh were as the most sensitive genotypes and mutant lines G1, G2, G3, G4 (derived from Tarom) and G7 (derived from Hashemi) with 2788.33, 2163.00, 2178.33, 2194.00 and 2375.00 kg.ha-1 grain yield in drought stress condition, were the tolerant genotypes. Stress tolerance score (STS) were also introduced the above genotypes as tolerant genotypes. Therefore, it is seems that use of mutations has been able to increase drought tolerance on the progenies. The above mutant lines in addition to use as parents in crosses, could also be used in the introduction of drought tolerant cultivars.