حدیث مقدم

 Drought is one of the most important global threats to food production, in addition to that, climate change and the increase in the global population also widen the dimensions of this problem. One of the ways to solve this problem is to create new cultivars with greater tolerance to drought stress. Wheat has been one of the most important sources of human food all over the world and it is used in various food products and processing industries. Wheat together with rice and corn provide more than 60% of calories and protein needed for human nutrition. In areas like Iran, where most of the rain occurs in winter and early spring, wheat will face water shortage and drought stress at the end of the growing season. In crops, one of the effective methods that can minimize the effect of this phenomenon in combination with other methods of water deficit management is the use of high-yielding and drought-tolerant cultivars. Despite the numerous scientific sources published in this field, there are still many gaps in these studies, so studying the effects of drought stress is always a research priority. Ilam province, as one of the irrigated wheat production areas, suffers from the lack of cultivars that are resistant or tolerant to low irrigation conditions, so investigating the response of different wheat genotypes in low irrigation conditions as low input production systems is very important and is addressed in this study. 

In order to evaluate some bread wheat genotypes under normal and drought stress co ditions, 36 wheat genotypes were evaluated in the form of a randomized complete block design in three replicates in the crop year of 2019-2019 in Darehshahr city located in Ilam province. The examined traits include spike length, spike number per plant, spike length, peduncle length, sub-peduncle axis, flag leaf length, flag leaf width, number of stem nodes, plant height, number of spikes per plant, number of seeds per spike, number of seeds per plant. plant, number of tillers, hundred seed weight, single plant seed weight and seed yield. Based on performance under stress (Yp) and normal (Ys), drought tolerance indices such as average productivity tolerance index, harmonic mean, geometric meanproductivity (GMP), stress sensitivity index, stress tolerance index, performance stability index (YSI) and Relative Stability Index (RSI) and Performance Index (YI) were calculated. The mean comparison test was performed using Duncan's method and using R software. Simple correlation (Pearson), decomposition into components, decomposition into factors were also performed between the tested traits. SAS 9.1 statistical software was used for statistical analysis of traits. 

The results of the analysis of variance in drought and normal stress conditions showed that there was a significant difference between genotypes in all traits at the probability level of 1%. The most important significant correlation coefficient in both conditions between seed yield was related to the seed weight of a single plant and the number of seeds per plant. Considering the high and significant correlation of grain yield under stress and non-stress conditions with drought tolerance indices, higher productivity indices, geometric mean productivity (GMP), geometric mean  and stress tolerance index  as the best indicators. were chosen. It seems that in order to evaluate stress tolerance, the selection of genotypes should be based on several indicators. Factor analysis at the drougth stress condition indicated that the two first factors expalined a total of 97. 57% of the variance. The first factor was called the performance stability factor and the second factor was named theStability Factor. The biplot diagram also showed that the genotypes of no. 13 and 47 were placed in the vicinity of the ranges related to drought resistance indices (STI, MP, GMP, and HM) and were introduced as superior genotypes. 

According to the data obtained from analysis of variance in both normal and drought stress conditions, the genotypes were significant in terms of all traits. The significance of the studied traits indicates the existence of diversity between genotypes in terms of the studied traits, and some of these traits can be used to evaluate stress tolerance. The best genotypes had the best averages for peduncle length of genotype 33, for the number of seeds per plant of genotype 5, for seed weight of a single plant and seed yield of genotype 1. The heat map shows the relationship between drought tolerance based on different yield and drought stress toleranceindices. Considering the high and significant correlation of grain yield under stress and non-stress conditions with drought tolerance indices, average productivity indices, GMP, geometric mean and stress tolerance index were selected as the best indices that are able to distinguish tolerant genotypes from other Screen the genotypes. The yield index (YI) had the highest correlation coefficient with grain yield under stress conditions. Based on biplot results, genotypes No. 13 and 47 were the most tolerant genotypes under drought stress conditions more than other genotypes and were introduced as superior genotypes.