Molecular Mapping Of Two Semi-dwarf Genes In Indica Rice (Oryza Sativa L.)

The success of the development of semi-dwarfism was one of the most significant achievements in rice breeding since 1960s. However, most of the semi-dwarf and dwarf genes identified show negative effects on agricultural characters, which limits their use in cross-breeding. Because the semi-dwarf and dwarf genes utilized now are only sd-1, d12 and d60, it becomes an important task for rice breeder to identify new and useful semi-dwarf and dwarf genes. At the same time, rice is the model of the grass, cloning of rice new dwarf genes will be useful to understand the molecular mechanism of plant growth and development.In this study, a cross between a semi-dwarf variety M29 and a dwarf line Yizhilashuangai was made. Plant height of the F2 population was measured and it was found that there were two kinds of plants, semi-dwarf and dwarf. The plant number of each kind was 437 and 134, respectively. It well fitted to the segregation ratio of 3:l(x2=0.6669 < x20.05=3.84) indicating the monogenic inheritance from Yizhilashuangai. It could be inferred that the plant height segregation of the F2 population was caused by the locus sd-n. 114 dwarf plants of the F2 population were used for mapping, and the semi-dwarf gene sd-n was located between two SSR markersRM289 and RM291. The genetic distances between sd-n and RM289 as well as RM291 were 1.5cM and 14.3cM, respectively. It was suggested that sd-n gene was located on the middle of the long arm of chromosome 5.Another cross between a semi-dwarf variety 02428 and a dwarf line Xinguiaishuangai was made. Plant height of the F2 population was measured and it was also found that there were two kinds of plants, semi-dwarf and dwarf. The plant number of each kind was 335 and 101, respectively. It also well fitted to the segregation ratio of 3:l(x2=0.7828 < x2o.o5=3.84) indicating the monogenic inheritance from Xinguiaishuangai. It can be inferred that the plant height segregation of the F2 population was caused by the locus sd-g. 101 dwarf plants of the ?2 population were used for mapping, and the semi-dwarf gene sd-g was first located between two SSR markers RM440 and RM163 on chromosome 5. The genetic distances between sd-g and RM440 as well as RM163 were 0.5cM and 2.5cM, respectively. In order to establish the fine location of the semi-dwarf gene sd-g, the public rice genome sequence in the region contain sd-g gene was used to search new SSR loci. Two new SSR markers SSR371 and SSR418 between RM440 and RM163 were developed. SSR418 was co-segregated with sd-g, while SSR371 was between RM163 and sd-g and was only 0.5cM to sd-g. Based on these studies, A BAC contig encompassing sd-g locus was constructed and sd-g might be on AC105319 or AC137620. The result would be the basis to clone the semi-dwarf gene sd-g.