Identification of common wheat (Triticum aestivum L.) genotypes for drought stress tolerance

]Introduction Today, wheat is grown on more land area than any other commercial crop and continues to be the most important food grain source for humans. Its production leads all crops, including rice, maize and potatoes. Wheat is the most widely grown crop in the world and provides 20% of the daily protein and of the food calories for 4.5 billion people. It is the second most important food crop in the developing world after rice. Drought is a major environmental stress threatening wheat productivity worldwide. Global climate models predict changed precipitation patterns with frequent episodes of drought. Although drought impedes wheat performance at all growth stages, it is more critical during the flowering and grain-filling(terminal drought) and results in substantial yield losses. So drought stress is one of the most common environmental stresses that makes production limitation in wheat. According to the FAO, 90 percent of Iran is located in dry and semi-arid areas. Iran, with an average rainfall of about 250 mm, has an average of about one-third of the world's rainfall. At present, the population of Iran is about 80 million and according to forecasts, the Iranian population will pass 120 million by 2020, based on a growth rate of 2% in 1400. Therefore, increased wheat production is inevitable. Materials and methods In order to identify drought stress tolerant wheat genotypes in greenhouse and field, 30 genotypes were studied as a sub factor in split plot experiment in a completely randomized design with randomized complete block design with three replications under normal and drought stress conditions in 2016-17. Results and discussion Analysis of variance showed a significant difference between genotypes in terms of grain yield under stress and non-stress conditions. In terms of seed yield in the field, genotypes cd-1, c-93-10 and Mihan with mean of 290.535, 282.835, 311.229 g/m2 were the most tolerant and in the greenhouse, Urom and C-93-8 genotypes with an average of 5.769 and 5.236 g in 5 plants per plant were identified as the most susceptible genotype for drought stress. Also, based on the genotypic groupings based on the stress tolerance indices in field and greenhouse experiments, genotypes were located in four clusters and genotypes of cd-7, c-94-4, cd-2, c-93-5, c-93-9, cd-10, cd-11, cd-5, c- 94-6, c-94-8, cd-9, c-94-7, cd-1, c-93-3, c-93-10, and Urom were known as the most susceptible which were suitable for crosses or introductions for farmers in the target area. Considering that the use of an index is not effective for introducing the most tolerant figure and based on this principle, the results of genotypic grouping based on all indices, showed that the genotype was considered as the most tolerant genotype under greenhouse conditions due to low TOL, SSI and YP, YS, MP, GMP, HMP, STI, YI and YSI. Also, under field conditions, genotypes cd-7, c-94-4, cd-2, c-93-5, c-93-9, cd-10, cd-11, cd-5, c-94-6, c-94-8, cd-9, c-94-7, cd-1, c-93-3 and c-93-10, according to most indices, are most susceptible under field conditions. And are applicable in breeding programs for the production of high tolerance cultivars to end-of-season stress.