Genetic analysis and molecular mapping of Rp, a mutant gene encoding red pericarp in rice (Oryza sativa L.)

Coloured rice has pigments deposited in the grain pericarp; red rice is the most common type of coloured rice. Red rice is rich in essential nutrients and has been grown and consumed in China for a long time. In this study, we report the genetic characterisation and preliminary molecular mapping of a mutant gene encoding red pericarp in rice (Oryza sativa L.). To analyse the genetic basis of the red pericarp mutant, a reciprocal cross between GER-3 (red pericarp, indica cv.) and 898 (white pericarp, indica cv.) was made. The genetic analysis results confirmed that there was only one dominant gene, temporarily designated Rp (Red pericarp) controlling the segregation of the red pericarp in the F2 population. For the molecular mapping of Rp, an F2 population derived from an inter-subspecific cross between Gene Engineering Rice-3 (GER-3) and C418 (japonica cv., white pericarp) was constructed. The genotype of the pericarp colour of the F2 individuals in the mapping population was validated by progeny testing of the F2:3 families. Simple sequence repeat (SSR) markers and the bulked segregation analysis (BSA) method were used; Rp was mapped to the short arm of chromosome 7 between the SSR markers RM21182 and RM21268, with a genetic distance of 3.5 and 12.0 cM, respectively. In this paper, the potential origin of the red pericarp mutant gene Rp was also discussed.