Dissection of Maize Drought Tolerance at the Flowering Stage Using Ge-Nome-Wide Association Study

Drought is one of the most critical environmental factors constraining corn production especially when it occurs during flowering, resulting in serious yield losses. In this study, anthesis to silk interval (ASI), plant height (PH), and ear biomass at the silking date (EBM) of 279 inbred lines were evaluated under water-stress (WS) and well-water (WW) field conditions for three consecutive years. Averagely, ASI was extended by 25.96%, ear biomass was decreased by 17.54%, and the PH was reduced by 12.47% under drought stress conditions. Genome wide association studies (GWAS) were carried out using phenotypic values under WS, WW and drought-tolerance index (WS-WW or WS/WW) applying mixed linear model controlling both population structure and relative kinship. Totally, 71, 159, and 21 SNPs were significantly (P < 10-5) associated with ASI, ear biomass, and PH, respectively. Candidate genes encoding ARABIDILLO 1 protein, glycoprotein, Tic22-like and Zinc finger family protein for ASI, and 26S proteasome non-ATPase regulatory subunit-9 for EBM, were identified under both WW and WS conditions. Pyridoxal phosphate transferase was associated with EBM under drought stress treatment in consecutive two years. Furthermore, most candidate genes were evidenced to be drought responsive in the association panel. Meanwhile, the favourable/drought tolerance haplotypes were identified based on haplotype analysis. These findings provide insights into the genetic basis of drought tolerance at the flowering stage especially for the female inflorescence development and will facilitate high drought tolerant maize breeding.