A novel digenic epistatic interaction at two loci regulating spikelet fertility in rice

Abstract

The seed setting rate (spikelet fertility) is an important determinant of rice yield. In the past few decades, genes that control rice seed set have been cloned, and many quantitative trait loci (QTL) have been identified. However, the epistasis influencing rice seed set remains largely unclear. In this study, a recombinant inbred line population, which consisted of 219 lines developed by crossing the Lemont and Yangdao4 rice cultivars, was grown in five environments to identify the QTL and epistatic loci related to seed set. A total of 26 minor-effect QTL were detected by multiple interval mapping, which explained less than 12.7% of the phenotypic variation individually. A pair of new epistatic loci were detected and confirmed by two-way analysis of variance; the homozygous Yangdao4 allele at the qSS6.1 locus interacted with the homozygous Lemont allele at the qSS8.1 locus and resulted in a low seed setting rate. A linear regression analysis and a multiple comparison test suggested that eight alleles at four QTL (qSS1.3, qSS6.3, qSS7.1, and qSS8.1) control seed set simultaneously. Marker-assisted selection using these four loci guaranteed a greater than 70% average seed setting rate in all five environments.