Multi-Experiment and Multi-Locus Genome-Wide Association Mapping for Grain Arsenic in Rice Population

Rice is a globally important crop and is particularly efficient at assimilating arsenic (As). Identifying QTLs and genes associated with grain As is essential for breeding low-As rice cultivars. In this study, data on As accumulation in grains of Rice Diversity Panel 1 in five field environments at four diverse geographic sites were reanalyzed to compare genome-wide association (GWA) methods. Two single-locus (EMMAX for single trait and GEMMA for multi-experiments) and six multi-locus (FASTmrEMMA, ISIS EM-BLASSO, mrMLM, pKWmEB, pLARmEB, and FASTmrMLM) GWA methods were used. A total of 90 and 111 QTLs were detected using EMMAX and GEMMA, respectively. A total of 2, 11, 12, 19, 23, and 25 QTNs were identified by FASTmrEMMA, ISIS EM-BLASSO, mrMLM, pKWmEB, pLARmEB, and FASTmrMLM, respectively. Among these, 22 QTLs/QTNs were co-detected by single-locus and multi-locus GWAS methods. From these QTLs/QTNs, a total of 10 candidate genes were identified. Analysis of the haplotype variants of one candidate genes, OsABCC1, and one cluster of the plasma membrane intrinsic proteins genes revealed that a greater than 10% reduction in grain As could be achieved. The QTLs/QTNs and candidate genes identified give insight into the molecular mechanisms regulating As accumulation in rice and serve as breeding targets for developing low grain As rice cultivars.