Abstract The wild barley species is considered a valuable genetic resource which enriched during natural selection and evolution in Fertile Crescent regions, especially the Middle East, under different environmental conditions. This study was conducted in three separate experiments with the ultimate objective of developing an understanding of heat tolerance in wild barley (H. vulgare ssp. spontaneum) genotypes collected from western Iran. The first experiment eva‎luated 45 spontaneum genotypes and 4 cultivated barleys for heat-tolerance at the grain filling stage under normal and delayed planting dates using lattice 7 × 7 design replicated twice within each of two growing seasons (2015-2017). The findings were that one-quarter of the wild genotypes originating from a warmer climate were the most heat tolerant which were slightly affected by heat stress compared with cultivars in terms of having the better physiological stability, lowest yield reduction and the highest tolerance indices (stress tolerance (STI), yield stability (YSI) and modified heat tolerance (HTI) indices). Cluster analysis of barley genotypes under heat stress conditions completely separated barley cultivars from wild genotypes based on Euclidean distance 10. In second experiment, 98 F3, and 79 BC1F2 families derived from hybridization of a heat-tolerant wild genotype and a sensitive cultivar ‘Mona’ were eva‎luated at two sowing dates (normal and delayed). Number of grains per spike and grain weight was the most important yield components for screening heat tolerant families in F3 and BC1F2 populations. Given that some F3 and BC1F2 families out-yielded their parents, we explore possible transgressive segregations that might address the extreme rise ingrain yield in these families. Proline and membrane stability index were correlated strongly with grain yield and STI in both F3 and BC1F2 populations under heat stress conditions. Cluster analysis divided F3 families into 4 groups based on agronomic and physiological attributes in heat stress conditions. The second group F3 families had been identified as the most tolerant families with the highest in spike length, number of grains per spike, grain yield, STI, chlorophyll content, proline and membrane stability. Likewise, BC1F2 families 25, 27, 28, 35, 44, 47, 55, 64, 64 and 65 had the highest number of grains per spike, 1000-grain weight, grain yield, proline, membrane stability, and highest STI under heat stress conditions and could be suggested as the most heat-tolerantBC1F2 families. These experiments lead us to conclude that use of tolerance index and agronomic/physiological attributes should facilitate accurate and reproducible identification of the more stable and high yielding barley genotypes. The third experiment was to study the transcriptome of wild barley genotype and ‘Mona’ cultivar grown in normal (24 ± 2 ° C) and heat stress (39 ± 2 ° C, 3 hours) conditions through RNA sequencing with Illumina Hiseq2500 platform. Transcriptome sequencing yielded the high-quality trimmed reads about 21.3 and 20 million (normal conditions) and 24.7 and 24.6 million (heat stress) for wild barley and ‘Mona’, respectively, with optimal parameters. A total of 1154 up-regulated and 1442 down-regulated transcripts were differentially expressed in wild barley in response to heat stress. Heat stress resulted in upregulation of 571 differentially expressed genes (DEGs) and downregulation of 1314 DEGs in ‘Mona’. In wild barley, 32 heat shock proteins (HSPs) genes, six heat shock factors (HSFs) and nine late embryogenesis abundant proteins (LEAs) showed up-regulation under heat stress. The significant alterations in the expression level of catalytic chaperons such as HSPs and their regulators (HSFs) in response to high-temperate support the pivotal role of these genes in wild barley thermo-tolerance.

احمد ارزاني، مهدي رحيم ملك

قدرت اله سعيدي، علي محمد مير محمدي ميبدي

آقا فخر مير لوحي، سعداله هوشمند،مجيد طالبي