Genetic Analysis Of Grain Traits And Gene Mapping Of GL-2 In Rice

Rice grain characters are one of the most important factors influenced the rice appearance quality. The grain shape are not only affect severely the rice yield but also to the rice appearance quality. In this research, a NIL (near isogenic line) is constructed through the crosses, backcrosses between Bobai.B ,with a small grain ,as recurrent parent and two varieties WFC and RW11, with large grain, as the donor parent. The inheritance of the grain length, grain width and grain shape are studied here. Mapping of the gene controlling the small grain character of Bobai.B was performed in BC3F2 population, Using SSR markers, bulked-segregant analysis (BSA) and recessive-class analysis (RCA). The main results are summarized as below:The size of length, width and the ratio of length to width in F₁ grain were lay between the two parents and tended to WFC , RW11, indicated that the genes controlling grain length, grain width and grain shape are incompletely dominant. There are differences for the size of length, width and ratio of length to width in F₁ grain between positive and negative cross derived from Bobai.B and RW11, the grain length in F₁ while small parent as the female parent is much smaller than the value while large parent as the female parent, which indicated the existence of cytogene effects. The F₁ grain length of Bobai.B and WFC tended to WFC, which means the grain length gene is incompletely dominant.In the BC3F2 population, both grain length and width displayed two distinct phenotypic groups ,respectively,The ratio of the both two groups fit well to the expected ratio (3:1) of single locus Mendelian segregation , which indicated that both the grain length and width in BC3F2 population were mainly controlled by a large-grain dominant gene and a wide-narrow dominant gene, respectively. The heritance of grain length, grain width and the ratio of length to width of grain in BC₁F₁( the Bobai.B//RW11/ Bobai.B) population were more complicated.The polymorphism analyzed results of detecting the differences of Bobai.B ,WFC and RW11 genome using 396 SSR primers uniformly distributed on 12 chromosome ,out of 396 SSRs , 86 and 84 polymorphic SSRs were found between Bobai.B and WFC, between Bobai.B and RW11, respectively, the proportion are 21.7%, 21.2% respectively.A linkage analysis using molecular markers was performed in BC3F2 mapping population through bulked-segregant analysis (BSA) in combination with recessive-class analysis (RCA). The result showed that the marker RM530 and RM13969 on chromosome 2 are linked with the target gene in BC3F2, the genetic distance is 8.1 cM and 11.2 cM, respectively. So far, the large-grain dominant gene has not reported .Thus this research is the first to map a large-grain dominant gene on the chromosome 2 in rice, which was temporarily designated as GL—2.