Genome-Wide Association Studies Predicted Drought Stress Occuring at Anthesis and Post-Anthesis Stages in Novel Diverse Germplasm of Bread Wheat (Triticum aestivum)

Abstract

This study employed genome-wide association studies (GWAS) to identify the crucial marker–trait associations (MTAs) for agro-nomic and physiological traits in bread wheat grown under full irrigation and 40% reduced irrigation. One hundred twenty-fourgenotypes derived from three-way crosses of landraces and synthetic bread wheat were evaluated for 2 years in the field condi-tions of CIMMYT Obregon, Mexico. Irrigation was not provided at anthesis and post-anthesis stage for the drought treatment,and data of 12 traits were recorded. Most of the traits were reduced significantly under drought conditions except for vigour,wax and spike length (SL); genotypes were significantly different for the eight traits except for days to heading (DTH), numberof grains spike−1 (NGS), normalized difference in vegetation index (NDVI) and canopy temperature depression (CTD); and dif-ferences were also significant for five traits between the years. Moreover, GY was significantly and negatively correlated withwax and CTD. Our GWAS results indicated 117 significant (p ≤ 0.001) MTAs distributed on all the wheat chromosomes exceptchromosomes 4B and 4D explaining 10%–21.5% of the phenotypic variation of the corresponding traits. Moreover, 22 MTAs wererecorded for grain yield and explaining the phenotypic variations up to 14.7% with one common association under both irrigatedand drought conditions. Additionally, we also identified the associations for NDVI, CTD and SL at chromosome 1B, suggestingthat genotypes are sustaining superior grain yield through better values of traits like NDVI, CTD, and SL under the challengingconditions of anthesis and post-anthesis drought stress.