Evaluation of grain yield of wheat genotypes using stress tolerance indices

Drought hasunfavorable impacts on the success of agriculture in many parts of the world.Providing future populations with enough food would obviously require the evaluation of crop yield, higher potentials, and the provision of yield stability in drought-affected regions. In this research, the drought-tolerance of wheat genotypes was studied in a randomized complete block design and in a three-replication experiment under normal and drought stress conditions. In two consecutive growing seasons, the measurements wereaimed at evaluating the stress susceptibility index (SSI), drought tolerance index (TOL), mean productivity (MP, stress tolerance index (STI, harmonic mean (HARM), yield index (YI, and genomic mean productivity (GMP). These parameters described the yieldsof different genotypes for two years and under both normal and stress conditions. The combined analysis of variance showed that the environment significantly affected grain yield. The mean values of parameters by the drought stress condition were less than those of the non-stress condition.Stress intensity (SI) was 46% and 43% in the first and second year, respectively.In both years, MP, GMP, STI and HARM indices correlated significantly with grain yield under stress and normal conditions. Based on a three-dimensional diagram of these indices, the pishgam and ws-82-9 genotypes were considered as most superior in the first year (both conditions).. Furthermore, the pishgam, alvand, and ohadi genotypes were considered as superior in the second year. According to the bi-plot diagram and based on the first two major components, these genotypes were more tolerant to drought stress. In general, it is suggested that the pishgam shows a higher level of yield sustainability. It was found to be the genotype with the highest yield under both normal and stress conditions. Its grain yield and resistance indices have increased during 80 years of breeding and selection.