Study of terminal drought tolerance in promising winter and facultative wheat genotypes using stress susceptibility and tolerance indices

In order to study the response of different winter and facultative wheat (T. aestivum L.) genotypes to terminal drought stress, this experiment was conducted in the Experimental Field of Cereal Research Department, Seed and Plant Improvement Institute at Karaj in 1999/2000 and 2000/2001 cropping seasons. Twenty winter and facultative wheat genotypes were evaluated in two separate experiments, one with non-stress and in the other one, stress was applied from anthesis to physiological maturity. A randomized complete block design with three replications was used. Results of combined analysis of variance of grain yield showed significant difference between genotypes. Genotype x year and genotype x irrigation interactions were significant at 5% probability level, however, genotype x irrigation x year was not significant. Stress tolerance index (STI), stress susceptibility index (SSI), geometric mean productivity (GMP), mean productivity (MP) and tolerance (Tol) were calculated based on the grain yield of the genotypes in both conditions. Among the genotypes number 8 (Pck/Vee) was outstanding. Grain yield of this genotype in non-stressed and stressed conditions was 9320 and 7079 kgha-1, respectively. MP, GMP, STI and SSI for this genotype were 8200 kgha-1, 8123 kgha-1, 0.85 and 0.98, respectively. Results showed that correlation coefficients between STI, GMP and MP indices and grain yield (under both conditions) were positive and highly significant, therefore, these indices can be used to identify high yielding and tolerant genotypes under non-stressed and stressed conditions. Finally, using cluster analysis based on indices and grain yield (in both conditions), genotypes were classified in five groups.