Abstract
Understanding the genetic bases of economically important traits is fundamentally important in enhancing genetic gains in durum wheat. In this study, a durum panel of 208 lines (comprised of elite materials and exotics from the International Maize and Wheat Improvement Center gene bank) were subjected to genome wide association study (GWAS) using 6,211 DArTseq single nucleotide polymorphisms (SNPs). The panel was phenotyped under yield potential (YP), drought stress (DT), and heat stress (HT) conditions for 2 years. Mean yield of the panel was reduced by 72% (to 1.64 t/ha) under HT and by 60% (to 2.33 t/ha) under DT, compared to YP (5.79 t/ha). Whereas, the mean yield of the panel under HT was 30% less than under DT. GWAS identified the largest number of significant marker-trait associations on chromosomes 2A and 2B with p-values 10−06 to 10−03 and the markers from the whole study explained 7–25% variation in the traits. Common markers were identified for stress tolerance indices: stress susceptibility index, stress tolerance, and stress tolerance index estimated for the traits under DT (82 cM on 2B) and HT (68 and 83 cM on 3B; 25 cM on 7A). GWAS of irrigated (YP and HT combined), stressed (DT and HT combined), combined analysis of three environments (YP + DT + HT), and its comparison with trait per se and stress indices identified QTL hotspots on chromosomes 2A (54–70 cM) and 2B (75–82 cM). This study enhances our knowledge about the molecular markers associated with grain yield and its components under different stress conditions. It identifies several marker-trait associations for further exploration and validation for marker-assisted breeding.
Highlights
Durum wheat (2n = 28, AABB, Triticum turgidum L. ssp. durum) is the most commonly cultivated form of allotetraploid wheat, and is grown on 8% of the world’s wheat area (FAOStat, 2016)
The genetic position is represented by numbers
This study evaluated a durum wheat panel systematically assembled from the CIMMYT gene bank for grain yield (YLD), thousand grain weight (TGW), grain number m−2 (GNO), days to anthesis (DTA), days to maturity (DTM), plant height (PH), normalized difference vegetative index at vegetative (NDVIvg), and NDVIlg under yield potential (YP), drought stress (DT), and heat stress (HT)
Summary
Durum) is the most commonly cultivated form of allotetraploid wheat, and is grown on 8% of the world’s wheat area (FAOStat, 2016) It originated in the Mediterranean region, and is used to make pasta and semolina products (Ren et al, 2013). Dissecting the genetic bases of durum wheat responses to drought and heat stress is a prerequisite for breeding future genotypes (Graziani et al, 2014), and can be accomplished through the complementary approaches of association mapping and QTL mapping (Zhu et al, 2008). Maccaferri et al (2011) evaluated a collection of 189 elite durum wheat lines in 15 environments with varying water availability during the cropping cycle They identified 56 markers that explained 3.5–4.2% of the variation in grain yield, but the number of marker-trait associations (MTA) under drought stress were less in number compared with irrigated conditions. Several studies have focused on genetic diversity and molecular characterization of durum wheat landraces using different markers systems, but not many have used the DArTseq marker system in durum wheat (Yildirim et al, 2011; Kabbaj et al, 2017; Monostori et al, 2017)
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