Genetic Studies Of Rice Multi-tillers Dwarfing Mutant Sdc And Sdc Gene's Mapping

Rice is one of the most important food crops. It has a small genome showing a high colinearity with genomes of other cereal species. Rice genome has been used as the mode of monocotyledon genomics. The plant height of rice is one of the important factors affecting grain yields, and is also a key trait for plant development studies. In the sixties of last century, the introduction of dwarfing mutants greatly enhanced grain yields of rice and wheat, resulting in the first" green revolution " in the world (Peng et al. ,1999). Dwarfing crops can resist lodging and assign assimilation products to seeds much effectively, and therefore, dwarfing trait is one of the important agronomic characters (Francesco et al., 2003). For agricultural production, breeding rice varieties with ideal plant architecture is a powerful way to increase rice grain yields. The dwarfing rice germplasm and mutants have been focused extensively by experts in plant genetics and breeding.Combined using various research tools in cytogenetics, molecular marker and gene mapping, genomics and bioinformatics, this study was conducted for understanding genetics of rice multi-tillers dwarfing mutant Sdc and fine mapping sdc gene. Transpositional points between chromosome 6 and 12 were anchored in 1 and 3 BAC clone's pool respectively by fluorescence in situ hybridization technology of pachytene chromosomes. A F₂ segregation population was constructed with a cross between the rice multi-tillers dwarfing mutant of (v3037) and japonica rice variety (wu yun jing N0.8). Primary mapping of gene sdc was performed using 400 double recessive mutation individuals of the F₂ population and 10 pairs of primers (STS, CAPS). The sdc gene was found to be linkage with 2 CAPS markers, which identified 1 recombinant from 400 mutation individuals of the F₂ population respectively. The sdc gene was mapped at the genetic region between CAPS-7 and CAPS-8 on chromosome 12. The physical distance between these two markers is 150kb.Based on the data generated by cytological analysis and the primary mapping, a fine mapping of sdc gene was carried out using a bigger mapping population consisting of 6000 F2 individuals so as to isolate this target gene by positional cloning approach. Twenty eight pairs of primers were selected for this mapping. Of them, 2 CAPS markers (CAPS-2 and CAPS-24) identified 6 and 1 recombinants respectively by screening 6000 mutation individuals of F₂ population. The sdc gene was found to be linkage with these two markers whose physical distance is 10 kb. Therefore, the sdc gene was mapped at the region between CAPS-2 and CAPS-24 on the long arm of chromosome 12.The present studies developed the foundational data for the map-based cloning of the sdc gene controlling the multi-tiller dwarfing of rice. The information described here would be further used for basic theory studies such as dwarfing mechanism of the rice, morphogenesis and signal transduction in plants. These data also show great values in genetic improvements of cereal crops.