Genome-Wide Association Analysis Reveals the Gene Loci of Yield Traits under Drought Stress at the Rice Reproductive Stage

Drought is an important factor limiting the growth and development of rice and thereby seriously affects rice yield. The problem may be effectively solved by dissecting the drought-resistance mechanism of rice, creating excellent drought-resistant germplasm, and mining new drought-resistant genes. In this study, 305 accessions (189 Xian, 104 Geng, 5 Aus, and 7 Basmati) were used to identify drought-related phenotypes such as grain yield per plant (GYP), grain number per panicle (GNP), panicle number per plant (PNP), and plant height (PH) under two-year drought stress. The 2017 GYP and 2018 GNP were Xian max, 2018 GYP, 2017 GNP, 2017 and 2018 PNP, and 2018 PH were Basmati max, and only the 2017 PH was Geng max. The population genetic diversity and population structure were analyzed by combining 404,388 single nucleotide polymorphism (SNP) markers distributed on 12 chromosomes. A total of 42 QTLs with significant correlations was identified, among which 10 were adjacent to the loci reported to be associated with drought resistance. Four candidate genes, LOC_Os03g48890, LOC_Os04g35114, LOC_Os11g45924, and LOC_Os06g38950, were identified by functional annotation and haplotype analysis. The R-2 of qGYP3.1 was 11.53%, the R-2 of qGNP4.2 was 12.09%, the R-2 of qPNP11.1 was 10.01%, and the R-2 of qPH6.1 was 13.06%. The results have an important theoretical significance and practical application value for the improvement of drought resistance in rice.