Evaluation of Drought Tolerance in Rainfed Winter Bread Wheat (Triticum aestivum L.) Genotypes

To study drought tolerant in rainfed winter bread wheat genotypes, 48 genotypes (lines and cultivars) were evaluated under two rainfed and supplementary irrigation conditions at Maragheh research field station, Maragheh, Iran, in2018-19 and 2019-20 cropping cycles. The results of combined analysis of variance showed that effects of years, genotypes and year × genotype interaction on day to heading, day to physiological maturity, grain filling duration, plant height, 1000-grainweight, biological yield, grain yield and harvest index were significant. The average grain yield of genotypes under rainfed conditions was 1707 kg ha-1. The highest grain yield under rainfed conditions related to genotypes no. 4, 23, 20 and 26, respectively, with 2080, 2066, 2035 and 1999 kgha-1.under supplementary irrigation conditions genotypes No. 13, 7, 11 and 25 with 3044, 3014, respectively, with 2943 and 2914 kgha-1 had the highest grain yield. Supplementary irrigation increased mean grain yield by 738 kg ha-1, mean plant height by eightcm, mean 1000 grain weight by three grams and mean harvest index by four percent. Drought stress reduced grain yield of all genotypes. No significant correlation was observed between grain yield of genotypes under rainfed and supplementary irrigation conditions. Positive and significant correlations were observed between MP, GMP, HM, STI and YI with grain yield (Ys) under rainfed and supplementary irrigation (Yp) conditions which indicated the suitability of these indices for selection of genotypes with reasonable grain yield under either conditions. Based on the results of principal component analysis and three-dimensional diagram, genotypes 20, 23 and 26 were identified as drought tolerant genotypes with reasonable yield in both rainfed and supplementary irrigation conditions. Genotypes 13, 7, 11, 25 and 32 were also identified suitable for supplementary irrigation conditions.