IIntegrative assessment of agronomic and enzymatic characteristics for identifying drought-tolerant genotypes of barley (Hordeum vulgare L.)

Objective: One of the most important factors limiting the yield of a crop, including barley, is water-deficit stress during critical stages of growth. Water-deficit stress reduces barley yield and associated traits, compared to optimal conditions. Previous studies have reported that drought stress significantly increases the activity of antioxidant enzymes. This study aimed to identify water-deficit-stress-tolerant barley genotypes by assessing some morphological and enzymatic traits.Methods: In this study, the tolerance of ۱۸ barley genotypes to water-deficit stress was evaluated based on some morphological and enzymatic traits. Two field experiments were conducted in a randomized complete block design with three replications: one under optimal irrigation and the other under limited irrigation, where water was withheld at the ۵۰% flowering stage (Zadok’s ۱۰.۵.۲). Subsequently, some enzymatic and agronomic characteristics were measured, including catalase (CAT) and peroxidase (POD) activity, ۱۰۰۰-grain weight, number of tillers, spike length, number of grains per spike, plant height, biomass, and grain yield. For the measured traits, genetic coefficient of variation, phenotypic coefficient of variation, and heritability were estimated. Also, cluster analysis was conducted to group genotypes under both water-deficit stress and normal conditions. In addition, the stress tolerance index (STI) was calculated to identify water-deficit-stress tolerant genotypes.Results: There were significant differences among the barley genotypes for all traits, except for POD and CAT. Also, water-deficit stress significantly affected plant height, biomass, grain yield, peroxidase, and catalase. However, the interaction between genotypes and irrigation conditions was significant only for grain yield and biomass. According to the analysis of variance, the estimates of genetic coefficients of variation, and cluster analyses, there was appreciable variation among the barley genotypes for most of the traits measured in this experiment. Genotypes ۱۲, ۱۷, and ۱۰ exhibited a higher grain yield in both normal and water-deficit stress conditions, and also the highest STI values among the genotypes. Enzyme activity analysis suggested that CAT is a more reliable indicator than POD for alleviating the adverse effects of water-deficit stress. Also, CAT exhibited a higher genetic coefficient of variation and higher heritability than POD under both conditions. The number of grains per spike showed noticeably higher heritability values than grain yield under both normal and water-deficit stress conditions. Also, a high heritability was observed for۱۰۰۰-grain weight under stress conditions. Thus, indirect selection for grain yield through the number of grains per spike and ۱۰۰۰-grain weight may be useful in segregating generations under water-deficit stress conditions, and through the number of grains per spike under normal conditions.Conclusion: Genotypes ۱۲, ۱۷, and ۱۰, with higher grain yield under normal and water-deficit stress conditions, and the highest STI values, can be recommended for future evaluation in breeding programs for drought tolerance.

کلیدواژه ها:

Catalase ، Cluster analysis ، Drought Stress ، Peroxidase ، Stress Tolerance Index (STI)