Genetic Analysis And Gene Mapping Of A Semi-dwarf Mutant In Rice

Rice height characters are one of the most important agronomic traits of rice. Over higher plant would easily result in plant lodging and output reducing. On the other hand, the dwarf varieties with proper plant height had higher lodging resistance and a greater harvest, allowed for the increased use of nitrogen fertilize.Dwarf breeding had made a great breakthought in the rice breeding.The breeding and extension of excellent dwarf varieties remarkably improved the yield potential of rice.Therefore, the plant height is still one of focuses in rice genetic research.In my study, a semi-dwarf mutant was founded.Through crossing with several tall,semi-dwarf and dwarf varieties, the semi-dwarf mutant was carried out. The main result are summarized as bellow:1. The mutant was treated with gibberellin acid(GA₃) in the seeding stage, it was sensitive to GA3 treating.The height of the mutant increased and did not recover to the normal height.The mutant's sensitivity to GA3 was less than NJ11, and stronger than NJ6.2. In this study, genetic analysis for the mutant in F₁ and F₂ population revealed the semi-dwarfism is controlled by two recessive genes.3. Bucked segregant method and co-segregation analysis in F₂ population were used to screen molecular marker linked with the dwarf gene.It was showed that the dwarf gene lay in rice chromosome 1.The result showed that the SSR marker RM259 in chromosome was linked with target gene, and the genetic distance is 8.9cM.Thus this research is the first to map a new semi-dwarf recessive gene molecular linkage map,which was temporarily designated as sd-b(t).4. With the near isogenic lines (NILs) of mutant, the effection of the semi-dwarf mutant was researched. The result redicated that this mutant gene can reduce the plant height about 20 percent.The reducation of plant height in the presence of semi-dwarf gene is expressed through the shortening on the length of all internode. At the same time, the number of the tiller increased more than 100 percent, but this phenomena is independent of the semi-dwarf gene.