Genetic Analysis And Molecular Mapping Of A New Semidwarf Gene Sdn(t) Of Rice(Oryza Sativa L.)

The introduction of semi-dwarf rice (Oryza sativa L.) led to record yield increases throughout Asia in the 1960s. The major semi-dwarfing allele, sd-1, is still extensively used in modern rice cultivars. As the same dwarf gene used widely, it caused a risk of genetic singleness. So it is highly important to find and identify new dwarf gene.A type of mutant possessing semi-dwarf (sd) was identified from M2 population of Nantehao (NTH) treated with y -ray, named Nante' ai-2 (NTA-2). The studies on NTA-2 agriculture characters showed that it closes glume, videlicet it doesn' t blossom. Compared with Aijiaonante (ANT) which is a natural mutant from NTH, NTA-2' s culm length increase and kilo grain weight lighten. The increased culm length of NTA-2 is mainly due to the elongation of every internodes. A shorten spike, lessened kernel and decreased spikelet produce ratio cause the dimensions of kilo grain weight. Response of seedling height to gebberellin acids (GA3) treatment in several semi-dwarf varieties showed the sensitivity of NTA-2 is much lower than ANT. The studies on NTA-2 hybridization progency showed that a recessive gene governed the character of semi-dwarf of NTA-2, designated the sd gene of NTA-2 as sdn(t). The allelic test among NTA-2 and some other sd varieties reported by now, such as 1813B, Xingui' ai, Yizhila showed that the semi-dwarf gene of NTA-2 is non-allellic to that of sd1, sd-g, sdt(t).A F2 population was developed from the cross of NTA-2 and DMS616 to identify molecular markers linked with sdn(t) gene. With the aid of SSR (Simple Sequence Repeats) marker analyses, two SSR markers RM53, RM263 were screened. Using the software of MAPMAKER/EXP3. 0 showed two markers RM53, RM263 genetic distance to sdn(t) gene were 28.8cM , 3.8cM respectively, and they were also at the same side of sdn(t) gene. In order to find another side markers, using DNAman searched several BAC near RM263, and designed 5 primers RMY1, RMY2, RMY3, RMY4, RMY5. Then another side marker RMY5 with genetic distance to sdn(t) gene 6. OcM was screened. The local linkage map of sdn(t) gene was constructed with SSR markers. It showed that sdn(t) gene was located between RM263 with 3. 8cM and RMY5 with 6. OcM. Searching other located semi-dwarf genes, we found that sdn(t) gene is different from them , and could conclud that sdn(t) gene is a new semi-dwarf gene.The identification of markers RM263 and RMY5 flanking the gene sdn(t) at 3. 8cM and 6. OcM, respectively, will facilitate the selection of this character in breeding programs and provide the foundation for map-based cloning of this gene.