Genome-wide association study of the resistant starch content in rice grains

The consumption of resistant starch (RS), which can increase satiety and reduce calorie intake, may help ameliorate lifestyle-related diseases such as diabetes, hypertension, and obesity. The identification of genes or quantitative trait loci (QTLs) may facilitate improvement in the amounts and properties of RS in cereals such as rice. A genome-wide association mapping of the RS content in milled rice grain was carried out to identify QTLs in a rice germplasm collection. The RS contents among 105 rice accessions ranged from 0.3 to 2.42%, and the apparent amylose content (AAC) was positively correlated with the RS content (R-2 = 0.75). Four QTLs were detected, and each explained a total phenotypic variation of 10-13%. Two of these, on chromosome 6, were identified at the Waxy gene locus encoding granule-bound starch synthase I and starch synthase IIa. The other two QTLs, on chromosomes 8 and 9, were close to candidate genes encoding the starch debranching enzyme isoamylase I and ADP-glucose pyrophosphorylase small subunit 1, respectively. The results of this study should improve our understanding of the genetic basis of RS in milled rice and may assist plant breeders attempting to develop new rice varieties and food processors working to develop functional foods.