Genetic Analysis of Anthocyanin Pigmentation in Sterile Lemma and Apiculus in Rice

Genetic analysis of genes that regulate the color pigmentation of sterile lemma and apiculus has been conducted. “Josaengjado” has small and round grains with purple leaf, sterile lemma and apiculus. In the F2 population from a cross between Josaengjado and Daeribbyeo 1, 246 and 182 plants exhibited purple and straw-white sterile lemma, respectively. It fitted a 9:7 segregation ratio indicating that two complementary genes control the pigmentation in sterile lemma and apiculus. Genetic analysis was performed using the F2:3 and KASP (Kompetitive Allele-Specific PCR) markers. Genes for the coloration of leaf sheath, ligule, sterile lemma, and apiculus were detected on chromosomes 1 and 6. Sequence comparison showed a single nucleotide substitution C (Josaengjado) to A (Daeribbyeo 1) in the second exon of the Rd gene on chromosome 1 leading to a premature stop in Daeribbyeo 1. In C1, a 3-bp deletion in the second exon was detected in Daeribbyeo 1. Haplotype analysis was performed in the Rd and C1 genes of the 78 rice accessions. 78 accessions were divided into 14 groups. A total of 11 and 1 mutation sites were detected in OsC1 and Rd, respectively. The haplotype analysis also confirmed that two complementary genes, Rd and OsC1 are necessary to express anthocyanin pigmentation in sterile lemma and apiculus. To our knowledge, this is the first report to identify genes for the coloration of sterile lemma in rice.