Association mapping of morpho-physiological traits in bread wheat under drought-stressed and non-stressed conditions

Drought is one of the main abiotic stresses limiting wheat growth and productivity worldwide. The main objective of this work was to determine population structure and marker-trait association (MTA) of 13 morpho-physiological traits of bread wheat for drought-tolerance breeding. To this end, twenty-five diverse wheat cultivars and promising lines were genotyped using AFLP. The phenotype evaluation steps of studding wheat genotypes were performed under normal and drought-stress conditions during 3 years. Low heritability estimates were obtained for spike length, heading date (DTH), and shoot biomass (24.87-28.8%) while, a high heritability was observed for the number of kernels per spike (KPS) (89.21-90.55%). The results exhibited high polymorphic level ranged from 84.62 to 100%, proving that AFLP method can be an effective tool in assessing genetic variability in any wheat breeding programs. Population structure analysis showed five subpopulations with at least 65% membership ancestry to their allocated sub-clusters, which was highly consistent with the results of cluster analysis. Mixed linear method association analysis identified 66 significant MTAs with p-values 10−06 to 10−04, justifying 7.8 to 38.7% of the phenotypic variation, observed under both environmental conditions. There were two pleiotropic markers for grain yield (GY) and KPS under normal and one pleiotropic marker for GY, thousand kernel weight (TKW) and KPS under stress conditions. The common MTAs were detected for DTH, plant height, peduncle length, and TKW under both environmental conditions. The identified linked markers with GY and its components in this study could be desirable candidate genes for future studies and marker assisted selection to develop drought-tolerant genotypes in wheat breeding programs.