Fine mapping of Rf2, a major locus controlling pollen fertility restoration in sorghum A1 cytoplasm, encodes a PPR gene and its validation through expression analysis

Sorghum is one of the pioneering cereal crops where cytoplasmic male sterility (CMS) was successfully exploited for mass production of F-1 hybrid seed. Mapping genes for fertility restoration (Rf) is an important aspect of understanding the molecular basis of fertility restoration in crop plants. In this study, we fine-mapped a fertility restoration locus, Rf2 of sorghum reported earlier (Jordan, Mace, Henzell, Klein, & Klein, ), involving two F-2 populations (296AxRS29 and 296AxDSV1) and newly developed SSR markers delimited Rf2 locus to 10.32-kb region on chromosome 2. The Rf2 locus was tightly linked with two new SSRs, MS-SB02-3460 (0.14cM) and MS-SB02-3466 (0.75cM) on both sides, and hosted only one gene (Sobic.002G057050) of PPR gene family. Another new SSR marker developed in the study, MS-SB02-37912, forms the part of PPR gene and could act as a perfect marker in marker-assisted breeding for fertility restoration involving Rf2 in sorghum breeding. The strong involvement of Sobic.002G057050 gene in fertility restoration was supported through RNA expression analysis.