Abstract
Drought is likely the main abiotic stress that affects wheat yield. The identification of drought-tolerant genotypes represents an effective way of dealing with the continuous decrease in water resources as well as the increase in world population. The aim of this study was to identify single nucleotide polymorphisms (SNP) associated with drought tolerance indices in wheat by using a genome-wide association study (GWAS) under fully irrigated and rain-fed conditions. The drought tolerance indices (i.e., Stress Susceptibility Index, Stress Tolerance Index, Tolerance Index and Yield Stability Index) were calculated based on grain yield, 1,000-kernel weight and kernels per spike. The association panel was genotyped using genotyping-by-sequencing (GBS). A total of 175 SNPs exhibited statistical evidence of association with at least one drought tolerance index, explaining up to 6 % of the phenotypic variation. Forty-five SNPs were associated with more than one tolerance index (up to 4 agronomic traits). Most associations were located on chromosome 4A, supporting the hypothesis that this chromosome has a key role in drought tolerance which should be exploited for wheat improvement. In addition, statistical analysis detected SNPs associated with tolerance indices in both growing seasons, providing information about genetic regions with stable effects under different environmental conditions. This GWAS experiment serves as one of the few studies on association mapping for drought tolerance indices in wheat, which could increase the efficiency of rain-fed and irrigated crop production.
Highlights
Wheat (Triticum aestivum) is one of the most important crops in the maintaining of the security of the food supply and is the second most consumed cereal worldwide (Galetto et al, 2017; Franco et al, 2018; Oliveira and Pinto-Maglio, 2017)
Wheat culture is strongly affected by drought; the generation of drought tolerant cultivars is one of the main challenges to genetics and breeders
single nucleotide polymorphisms (SNP) markers linked to the QTL of drought tolerance indices were identified in a diverse genotype collection, and the phenotypic variation explained by SNP markers was within an expected range according to other studies
Summary
Wheat (Triticum aestivum) is one of the most important crops in the maintaining of the security of the food supply and is the second most consumed cereal worldwide (Galetto et al, 2017; Franco et al, 2018; Oliveira and Pinto-Maglio, 2017). The negative effects of drought could be overcome by the identification and use of drought-tolerant varieties (Van Oosten et al, 2016). Given this solution, the dissection of molecular mechanisms that underlie adaptive traits represents one approach to understanding stress tolerance in plants (Budak et al, 2015; Liu et al, 2017; Arriagada et al, 2017). Edae et al (2014) found chromosome regions (on 4A) that were associated with drought tolerance related traits such as the drought susceptibility index, leaf senescence, green leaf area and flag leaf traits. The aim of this study was to identify SNP associated with drought tolerance as measured by different stress tolerance indices of key agronomic traits in wheat
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