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Salt stress is one of the most important environmental stresses that negatively affects the plant growth and productivity worldwide. To delineate physio-biochemical and molecular differences among barley genotypes, antioxidant enzyme and transcriptomic profiles along with several physiological traits were compared among a set of elite genotypes of barley subjected to salinity stress. The experiment was conducted at the early growth stage under two control (0 mM NaCl) and salinity (200 mM NaCl) conditions. Salt treatment significantly increased root and shoot Na+ contents, the activity of APX and GPX antioxidant enzymes, and the relative expression of HvHKT2, HvHKT3, HvSOS1, HvSOS3, HvNHX1, HvNHX3, APX, and GPX genes. In contrast, other root and shoot fresh weights, root and shoot dry weights, root and leaf K+ contents, and root and leaf K+:Na+ ratios were significantly decreased due to salinity stress. A principal component analysis showed the relationships among measured traits and relative expression of salt-responsive genes. Remarkably, our results indicated a positive and significant association between the relative expression of HvNHX1 and HvSOS3 genes with root Na+ content and leaf K+:Na+ ratio. Furthermore, associations among relative expression of HvHKT2, HvNXH3, HvSOS1, APX, and GPX genes were positive and significant. Taken together, this study revealed that genotypes G6 responded better to salinity stress than other genotypes. Hence it could be selected as the most salt-tolerant genotype for further complementary experiments with the aim of releasing as a commercial variety. Moreover, this genotype could be used as an ideal parent for transferring favorable physiological and biochemical activities in barley breeding programs. [ABSTRACT FROM AUTHOR]

In this work, we evaluated genetic diversity and population structure in eighty-eight Aegilops accessions using several physio-chemical traits such as shoot fresh and dry biomasses (SFW and SDW), photosynthetic pigments and activity of several antioxidant enzymes such as catalase, guaiacol peroxidase, peroxidase, and ascorbate peroxidase (APX), as well as 24 simple sequence repeat markers (SSR) under two control and water deficit stress conditions. The results indicated that water deficit stress dramatically affected SFW, SDW and photosynthetic pigments, while activity of all antioxidant enzymes were increased by water deficit stress compared to the control conditions. Statistical analysis of the phenotypic data showed a significant level of variation among the 88 investigated accessions. The results of correlation analysis showed that under both conditions photosynthetic pigments had a significant correlation with each other. The correlation between SDW and the activity of APX was positive and significant. The results of AMOVA using 24 SSR markers revealed that the genetic diversity observed among populations is more than within populations. Multivariate analyses grouped all investigated accessions in the clear groups based on their genomic constitutions. Based on results, 17 and 16 markers showed significant association with the measured traits under control and water deficit stress conditions, respectively. Our findings showed eight MTAs showed sufficiently stable expression across both control and stress conditions. Furthermore, several markers, especially Xgwm-455 associated with multiple traits across both conditions. In conclusion, these results could contribute to completing knowledge of the genetics and breeding for key physio-chemical properties. [ABSTRACT FROM AUTHOR]