Genome-wide Association Study of Plant Water Status under Terminal Drought Environments Using Spring Wheat Collections

Bread wheat (Triticum aestivum L.) is an important crop in the world; however, its production is being affected by more frequent drought stress worldwide. In the present study, we evaluated 262 spring wheat collections from different breeding groups in the north America (Canada, USA and Mexico, including a few from national small grains collection) for canopy spectral reflectance (CSR) under terminal drought environments, and used genome-wide association study (GWAS) to discover quantitative trait loci (QTL) related to plant water status in the grain filling stage. Normalized water index 3 (NWI3) was calculated based on the CSR and was used to represent the plant canopy water status. Significant correlation between NWI3 and grain yield was observed in all the environments. A total of 19 validated QTL were identified under terminal drought conditions. Most of these 19 QTL were also located in the same chromosome regions as previously reported drought related QTL. A few of the 19 QTL have been highly distributed in all the breeding programs, possibly due to their beneficial functions; and majority of the favorable alleles of the 19 QTL are still in low frequencies in the breeding programs. These QTL have the potential to be used in breeding programs to increase the drought tolerance of wheat.