Molecular mapping of a rice gene conditioning thermosensitive genic male sterility using AFLP, RFLP and SSR techniques

The discovery and application of the thermosensitive genic male sterility ( TGMS) system has great potential for revolutionizing hybrid seed production technology in rice. Use of the TGMS system in two-line breeding is simple, inexpensive, efficient, and eliminates the limitations associated with the cytoplasmic-genetic male sterility (CMS) system. An F-2 population develop ed from a cross between a TGMS indica mutant, TGMS-VN1, and a fertile indic a line, CH1, was used to identify molecular markers linked to the TGMS gene and to subsequently determine its chromosomal location on the linkage map of rice. Bulk segregant analysis was performed using the AFLP technique. Fr om the survey of 200 AFLP primer combinations, four AFLP markers (E2/M5-600 , E3/M16-400, E5/M12-600, and E5/M12-200) linked to the TGMS gene were iden tified. All the markers were linked to the gene in the coupling phase. All except E2/M5-200 were found to be low-copy sequences. However, the marker E 5/M12-600 showed polymorphism in RFLP analysis and was closely linked to th e TGMS gene at a distance of 3.3 cM. This marker was subsequently mapped on chromosome 2 using doubled-haploid mapping populations derived from the cr osses IR64xAzucena and CT9993xIR62666, available at IRRI, Philippines, and Texas Tech University, respectively. Linkage of microsatellite marker RM27 with the TGMS gene further confirmed its location on chromosome 2. The clos est marker, E5/M12-600, was sequenced so that a PCR marker can be developed for the marker-assisted transfer of this gene to different genetic backgro unds. The new TGMS gene is tentatively designated as tms4(t).