A target region amplified polymorphism marker for fertility restorer gene rf1 and chromosomal localization of rf1 and rf2 in cotton
Cytoplasmic male sterility (CMS), a maternally inherited trait characterized as an inability to produce functional pollen, is an important biological system for economically producing hybrid seed to enhance crop yield and studying cytoplasmic and nuclear gene interactions. In cultivated tetraploid cotton (Gossypium hirsutum L.), male fertility in two systems CMS-D2 and CMS-D8 is restored by two restorer genes Rf1 and Rf2, respectively. The objectives of the present study were to identify additional molecular markers for the two restorer genes and to determine their chromosomal location in the cotton genome. Two backcross (BC1F1) populations were developed with D2 and D8 restorers containing their respective cytoplasms as female in crosses with the same Upland cotton maintainer as male and recurrent parent. One pentatricopeptide repeat (PPR)–based target region amplified polymorphism (TRAP) marker was developed to be tightly linked to the Rf1 gene with a genetic distance of 0.8 cM, while three more simple sequence repeat (SSR) markers (NAU2232-550/650, NAU2232-750/850, and NAU 2801-250) were identified to be closely linked to Rf2. Using two common SSR markers, a consensus linkage group was constructed to include both Rf1 and Rf2 loci that were anchored in a 14.0-cM region by the two PPR gene-based markers. Based on four chromosome-anchored SSR markers, Rf1 and Rf2 were localized on chromosome D5 within a genetic distance of 1.4 cM, providing an incentive for further investigations of this Rf1/Rf2–containing region.