Genome-wide association study of field grain drying rate after physiological maturity based on a resequencing approach in elite maize germplasm

Field grain drying rate (FDR) after physiological maturity in maize ( Zea mays L.) is an essential determinant of grain moisture at harvest. Investigating the genetic structure of FDR is of great significance to breeding maize hybrids with low grain moisture at harvest that are suitable for mechanical harvesting. In this study, 80 elite maize inbred lines from Jilin Province (China) were selected as an association population, and their FDR after physiological maturity was determined by the oven-drying method in 2014 and 2015. At the same time, whole-genome resequencing was performed for the association population, and 1,490,007 high-quality single nucleotide polymorphisms (SNPs) were obtained for a subsequent genome-wide association study. The results showed high genetic variation for FDR in different maize inbred lines, with a broad-sense heritability of 0.76, indicating that the trait is mainly controlled by genetic factors. Thirteen independent genomic positions, which contain 19 SNP markers significantly associated with FDR in maize ( P < 0.000001), were detected by a genome-wide association study in 2014 and 2015. Seven genomic positions were located within the quantitative trait loci previously mapped for FDR, whereas one position was detected in both years by association analysis. Six candidate genes located in chromosome bins 4.05, 5.04 and 7.02 were identified within the 13 genomic positions. These genes were predicted to encode vegetative cell wall gp1-like glycoprotein, phosphopyruvate hydratase, mitochondrial inner membrane protease subunit 1-like protein, Cucumber mosaic virus 1a interacting protein 1 and two hypothetical proteins, which may be closely associated with FDR. The results lay a foundation for molecular marker-assisted selection of maize materials with rapid grain drying and for the cloning of relevant functional genes.