Abstract
Tibetan wild barley has been identified to show large genetic variation and stress tolerance. A genome-wide association (GWA) analysis was performed to detect quantitative trait loci (QTLs) for drought tolerance using 777 Diversity Array Technology (DArT) markers and morphological and physiological traits of 166 Tibetan wild barley accessions in both hydroponic and pot experiments. Large genotypic variation for these traits was found; and population structure and kinship analysis identified three subpopulations among these barley genotypes. The average LD (linkage disequilibrium) decay distance was 5.16 cM, with the minimum on 6H (0.03 cM) and the maximum on 4H (23.48 cM). A total of 91 DArT markers were identified to be associated with drought tolerance-related traits, with 33, 26, 16, 1, 3, and 12 associations for morphological traits, H+K+-ATPase activity, antioxidant enzyme activities, malondialdehyde (MDA) content, soluble protein content, and potassium concentration, respectively. Furthermore, 7 and 24 putative candidate genes were identified based on the reference Meta-QTL map and by searching the Barleymap. The present study implicated that Tibetan annual wild barley from Qinghai–Tibet Plateau is rich in genetic variation for drought stress. The QTLs detected by genome-wide association analysis could be used in marker-assisting breeding for drought-tolerant barley genotypes and provide useful information for discovery and functional analysis of key genes in the future.
Highlights
Drought is one of the major environmental stresses restricting crop productivity and occurs largely due to the effects of global climate change, the depletion of the underground water table, and erratic rainfall patterns [1,2]
We evaluated the population structure, linkage disequilibrium (LD) decay, and phenotypic variation of Tibetan wild barley accessions to determine the associations between diversity array technology (DArT) markers and phenotypes relevant to drought tolerance
Large differences were found for relative shoot dry weight (RSDW) and relative root dry weight (RRDW) among the accessions, with values ranging from 0.42 to 0.98 and 0.42 to 1.48, respectively (Figure 1a,b)
Summary
Drought is one of the major environmental stresses restricting crop productivity and occurs largely due to the effects of global climate change, the depletion of the underground water table, and erratic rainfall patterns [1,2]. The tolerance of crops to drought stress is a complex quantitative trait that involves a number of physiobiochemical processes at the cellular and organism levels during plant development [3]. We evaluated the genetic diversity of cultivated and Tibetan wild barley using 20 genomic simple sequence repeat (SSR) and 49 expressed sequence tag SSR (EST-SSR) markers and identified 213 alleles [12]. The Tibetan wild barley is likely to provide germplasm containing genes confer drought tolerance that can be introduced into cultivated barley to produce high-yielding cultivars with increasing yield stability under drought stress
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