Genome Wide Association Study Uncovers the QTLome for Osmotic Adjustment and Related Drought Adaptive Traits in Durum Wheat.

Ebrahim Babaeian,Todd Mockler,Eder Licieri Groli,Rick Ward,Giuseppe Emanuele Condorelli,Nadia Shakoor,Marco Maccaferri,Maria Newcomb,Markus Tuller,Cristian Forestan,Roberto Tuberosa,Jeffrey Westcott White

doi:10.3390/genes13020293

Abstract

Osmotic adjustment (OA) is a major component of drought resistance in crops. The genetic basis of OA in wheat and other crops remains largely unknown. In this study, 248 field-grown durum wheat elite accessions grown under well-watered conditions, underwent a progressively severe drought treatment started at heading. Leaf samples were collected at heading and 17 days later. The following traits were considered: flowering time (FT), leaf relative water content (RWC), osmotic potential (ψs), OA, chlorophyll content (SPAD), and leaf rolling (LR). The high variability (3.89-fold) in OA among drought-stressed accessions resulted in high repeatability of the trait (h2 = 72.3%). Notably, a high positive correlation (r = 0.78) between OA and RWC was found under severe drought conditions. A genome-wide association study (GWAS) revealed 15 significant QTLs (Quantitative Trait Loci) for OA (global R2 = 63.6%), as well as eight major QTL hotspots/clusters on chromosome arms 1BL, 2BL, 4AL, 5AL, 6AL, 6BL, and 7BS, where a higher OA capacity was positively associated with RWC and/or SPAD, and negatively with LR, indicating a beneficial effect of OA on the water status of the plant. The comparative analysis with the results of 15 previous field trials conducted under varying water regimes showed concurrent effects of five OA QTL cluster hotspots on normalized difference vegetation index (NDVI), thousand-kernel weight (TKW), and/or grain yield (GY). Gene content analysis of the cluster regions revealed the presence of several candidate genes, including bidirectional sugar transporter SWEET, rhomboid-like protein, and S-adenosyl-L-methionine-dependent methyltransferases superfamily protein, as well as DREB1. Our results support OA as a valuable proxy for marker-assisted selection (MAS) aimed at enhancing drought resistance in wheat.

Highlights

IntroductionDrought is the major abiotic stress curtailing yield and lowering quality [14,15] in durum wheat
By combining the physical confidence interval position of the QTL hotspots, functional prediction of annotated genes, and biological data mining, we investigated candidate genes from selected QTLs involved in osmotic adjustment (OA) and/or drought resistance
The genetic variants within the Durum Panel evaluated allowed for the detection of significant loci for OA, ψs, relative water content (RWC), leaf rolling (LR), and Soil-Plant Analysis Development (SPAD), with eight multiple concurrent QTL hotspots, all unrelated to phenology, being more valuable from a breeding standpoint

Summary

Introduction

Drought is the major abiotic stress curtailing yield and lowering quality [14,15] in durum wheat Among the strategies adopted by plants to withstand water scarcity [18,19], osmotic adjustment (OA) plays a major role in enhancing drought resistance through an active accumulation of solutes in response to a water potential reduction, thereby preserving cellular turgor [18,20,21,22,23,24,25,26,27]. Active OA maintains relative water content at low leaf water potential in order to sustain plant growth without impairing normal cellular functions [28]

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Discussion

Conclusion