Changes in the Biochemical Traits and the Grain Yield of Barley Genotypes and their Relation with Drought Tolerance

In order to evaluate the reaction of foreign genotypes and the indigenous cultivars of barley against drought and study their biochemical traits, eight genotypes with two barley cultivars were surveyed in a randomized complete block design with three replications in two states of sufficient irrigation and non-sufficient irrigation regimes (drought) at the Faculty of Agriculture, Shiraz University, Shiraz, Iran in the cropping year 2013-2014. The main factor included drought stress and complete irrigation treatments; the sub-factors included genotypes and barley cultivars. The results showed that drought reduced the content of chlorophyll a, chlorophyll b, and carotenoids in all genotypes, causing 18.9, 26.2 and 12.6% reduction in these traits, respectively. The chlorophyll a/b ratio in this study was increased under drought stress conditions. The least reduction in the concentration of pigments was related to Youssef genotype and genotypes 79 and 120, which were considered tolerant. The activity of superoxide dismutase, catalase and peroxidase enzymes was also increased significantly under drought stress. The results also showed that the catalase enzyme had a low activity among the enzymes examined in the study; therefore, it played a role in the plant protection against drought stress, while the peroxidase enzyme was recognized as the best biochemical criterion for drought tolerance. The highest activity of this enzyme in the drought stress conditions was obtained in Yousef (74.44%) and the genotype 120 (72.61%); on the other hand, the lowest activity in the stressed plants was found to be in Basil (50.78%). In general, the genotypes 95 and 120, with the mean grain yield of 8809.7 and 8925 kg ha-1, were recognized as the best genotypes in both non-stress and drought stress conditions. Therefore, drought could have a different effect on the biochemical traits of barley genotypes, and this difference was probably related to their stress tolerance.