Molecular Markers and Candidate Genes for Thermo-Sensitive Genic Male Sterile in Rice

The discovery of thermo-sensitive genic male sterility (TGMS) has led to development of a simple and highly efficient two-line breeding system. In this study, genetic analysis was conducted using three F₂ populations derived from crosses between IR68301S, an indica TGMS rice line, and IR14632 (tropical japonica), Supanburi 91062 (indica) and IR67966-188-2-2-1 (tropical japonica), respectively. Approximately 1:3 ratio between sterile and normal pollen of F₂ plants from the three populations revealed that TGMS is controlled by a single recessive gene. Bulked segregant analysis using simple sequence repeat (SSR) and insertion-deletion (InDel) markers were used to identify markers linked to the tms gene. The linkage analysis based on the three populations indicated that the tms locus was located on chromosome 2 covering the same area. Using IR68301S × IR14632 F₂ population, the results showed that the tms locus was located between SSR marker RM12676 and InDel marker 2gAP0050058. The genetic distance from the tms gene to these two flanking markers were 1.10 and 0.82 cM, respectively. InDel marker 2gAP004045 located between these two markers showed complete co-segregation with the TGMS phenotype. In addition, InDel marker vf0206114052 showed 2.94 cM linked to the tms gene using F₂ populations of IR68301S × Supanburi 91062. These markers are useful tool for developing new TGMS lines by marker-assisted selection. There were ten genes located between the two flanking markers RM12676 and 2gAP0050058. Using quantitative real-time PCR for expression analysis, 7 of the 10 genes showed expression in panicles, and response to temperatures. These genes could be the candidate gene controlling TGMS in IR68301S.