Abstract The aim of this study was to eva‎luate drought stress tolerance of some barley genotypes by using stress tolerance and sensitivity indices (SSI, TOL, MP, GMP, STI, YSI, HMI), grain yield, yield components and some morphological and physiological traits. The experiment was conducted at the research farm of Isfahan University of Technology in which 21 barley genotypes were eva‎luated in a randomized complete block design with two replications in each of two soil moisture regimes (normal conditions and drought stress). In general, the results of this study showed that drought stress significantly affected on all agro-morphological traits, particularly grain yield and its components. In addition, the physiological, traits including proline content, fluorescence chlorophyll, hydrogen peroxide, malondialdehyde chlorophyll a, chlorophyll b, total chlorophyll, the ratio of chlorophyll a/b and the RWC were significantly affected by drought stress. Significant differences was observed among the genotypes in terms of all agro-morphological and physiological traits, except for the ratio of chlorophyll a/b. These findings indicates the exist of high genetic variation for these traits among the genotypes in both irrigation regimes. The interaction effect of genotype by irrigation regimes was significant for all physiological traits, except for of the ratio of chlorophyll a/b ratio and RWC. The presence of high and significant genetic variation among the studied genotypes for drought tolerance and sensitivity indices indicates that these genotypes have a high genetic potential for drought tolerance to be used in breeding programs. The PCA results showed that Khatam, Mehr, Es9598-9 and Es-96-6 genotypes were the superior genotypes in terms of grain yield under normal conditions and Yusuf, p98-29 and p-97-19 were recognized as superior genotypes under drought stress conditions. The PCA results also showed that genotypes of Mehtab, Gohran, Armaghan, 15-Es9597, 10-Es97 and 14-p9698 had lower grain yield with more sensitivity to drought stress. The STI index had a positive and significant correlation with grain yield per plant and biological yield. Also, this index showed a significant and negative correlation with the physiological traits of hydrogen peroxide and malondialdehyde. Therefore, these traits can be considered as selection indices of selection for drought tolerance. It was found that under normal moisture conditions, genotypes with higher grain and biological yield had lower amounts of hydrogen peroxide and malondialdehyde. In this regard, genotypes 43-p98, Mehr, Es-96-6, Es-96-13, 34-p9697 and p-97-19 had higher grain yield per plant and biological yield. Under drought stress conditions, genotypes of Khatam, 9-Es9598, 29-p98 had higher grain yield with more drought tolerance. Also, genotypes of 14-p9698, Es-96-8 and Es97-9, had higher hydrogen peroxide and malondialdehyde, and lower grain yield per plant and drought tolerance.

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احمد ارزاني

اقافخر ميرلوحي فلاورجاني , مهدي قيصري