Identification of a deletion in tms2 and development of gene-based markers for selection

Rice is one of the most important food crops. The temperature-sensitive genic male sterility (TGMS) system provides a great potential for improving food production by hybrids. The use of TGMS system is simple, inexpensive, effective, and eliminates the limitations of the conventional three-line system. A rice gene, tms2, generated by irradiation of a japonica variety has been reported to control TGMS in several rice lines. Previous studies reported genetic markers linked to this gene, and the gene was transferred to an aromatic Thai cultivar. Using information obtained from published databases, we located positions of the reported genetic markers flanking the gene in rice genomic sequences, and developed gene-based markers located inside the flanking markers for polymorphism detection. We found that inbred indica tms2 mutant plants contain about 1 Mb of japonica DNA, in which at least 70 kb was deleted. Using RT-PCR for expression analysis, four genes out of seven genes annotated as expressed proteins located inside the deletion showed expression in panicles. These genes could be responsible for TGMS phenotypes of tms2. In addition, we developed gene-based markers flanking and inside the deletion for selecting the tms2 gene in breeding populations. By genotyping 102 diverse rice lines including 38 Thai rice lines, 5 species of wild rice, and 59 exotic rice lines including TGMS lines and cultivars with desirable traits, a gene-based marker located inside the deletion and one flanking marker were shown to be highly specific for the tms2 mutant.