Molecular mapping of the reverse thermo-sensitive genic male-sterile gene (rtms1) in rice

TGMS (thermo-sensitive genic male-sterile) rice is widely used in hybrid ri ce production. Because of a specific temperature requirement, it can be use d only in a narrow rice-growing zone in Asia. A newly discovered reverse th ermo-sensitive genic male-sterile line, J207S, has an opposite phynotype co mpared to the normal TGMS lines. J207S is completely sterile when the tempe rature is lower than 31 degreesC. Thus, it can be widely used in a larger a rea. Genetic analysis indicated that the sterility of J207S was controlled by a single recessive gene which was first named as rtms1. An F-2 populatio n from the cross between J207S and E921 was developed and used for molecula r mapping of the rtms1 gene. The AFLP (amplified fragment length polymorphi sm) technique, combined with BSA (bulked segregant analysis), was used to s creen markers linked to the target gene, and eight polymorphic AFLP loci we re identified. Co-segregating analysis using the F2 population showed that two of them, Rev1 and Rev7, were closely linked to the target gene with a r ecombinant rate of 3.8% and 7.7%, respectively. Both Rev I and Rev7 were fo und to be single-copy sequences through Southern analysis. Rev1 was subsequ ently mapped on chromosome 10 with a doubled-haploid mapping populations de rived from the cross CT9993 x IR62266 available at Texas Tech University. R M222 and RG257 were linked to Rev1 at a distance of 11.8 cM and 4.6 cM, res pectively. Additional SSR markers from the rice map of Cornell University, RFLP markers from the map of RGP in Japan and the map of Texas Tech Univers ity were selected from the region surrounding Rev1 on chromosome 10 to cond uct the fine-mapping of the rtms1 gene. Presently, rtms1 was mapped between RM239 and RG257 with genetic distance of 3.6 cM and 4.0 cM, respectively. The most-closely linked AFLP marker, Rev1, 4.2 cM from the rtms1 gene, was sequenced and converted into a SCAR (sequence characterized amplified regio n) marker which could facilitate marker-assisted selection of the rtms1 gen e.