Analysis of Genotype × Environment Interactions for Polyphenols and Antioxidant Capacity of Rice by Association Mapping

Uncovering the genetic basis of polyphenol content and antioxidant activity traits in rice accessions is important to improve the nutritional quality of whole grain rice and to ameliorate the increasing nutrition problem of the rice-eating population. In this study, 20 diverse rice accessions were planted in Hainan province, China, for 2 years to investigate the effects of genotype, environment, and their interactions on total phenolic (TPC), flavonoid (TFC), proanthocyanidins content (TPAC), ABTS, and DPPH radical scavenging activity by association mapping. Analyses of variance (ANOVA) showed that TPC, TFC, TPAC, ABTS, and DPPH were mainly affected by genetic variance, accounting for >94% of the total variance. The interaction between genotype × environment (G × E) was also highly significant (P < 0.001). Red-pericarp rice accumulates proanthocyanidins, which had significantly higher TPC, TFC, ABTS, and DPPH than white-pericarp rice. The correlation coefficient among these parameters were highly significant (r > 0.96; P < 0.001). Twenty-three putative unique loci were identified by association mapping. Five loci were close to previously identified genes or quantitative trait loci (QTLs). Among them, qPAC7-3 identified for TPAC in 2011 was near to the brown pericarp and seed coat (Rc) gene, and the locus at the qPC4/qFC4/qPAC4/qACA4/qACD4 cluster on chromosome 4 detected in two environments was near to a transcriptional activator A (Ra) gene. Some loci were identified in only one environment, indicating that these QTLs were sensitive to environment. This study provides a primary SNP-resource for further identification of genes responsible for polyhenol contents and antioxidant activity in rice whole grains.