Genetic Analysis And Mapping Of Panicle Traits With Major QTLs From A Large Grain Rice Variety

The yield of rice is great importance to the countries that depend on the rice as the maple food. As an important agronomic trait, grain shape is an key component factor for the yield. The grain shape, including grain length, grain width, length/width ratio, grain thickness and grain weight, is one of important appearance qualities for rice, which may have an effect on both grain yield and milling quality. This study focus on QTLs of grain length, grain width, length/width ratio and grain weight mapping with molecular markers. The main results were as the following:(1) The female parent large grain and male parent Huahang 1 were crossed to observe and gather the phenotype grain traits data of F1 individuals and F2 population. The agronomic traits include grain length, grain width, length/width ratio, grain thickness and grain weight among F1, male and female parent. The statistical results of F2 population showed that the segregation of the phenotype grain traits was generally normal distribution. The phenotype of F2 population was not only that of female parent, but also that of male parent, that of most between male and female parent.(2) The polymorphism analysis was carried out between parents and F1 with 136 pairs of SSR markers evenly distributed in 12 chromosomes of rice. The results demonstrated that there were 60 pairs of SSR markers showing the polymorphism between parents and F1,the polymorphic percentage was 44.44%. Analysis with Mapmaker3.0/MapDraw, the aimed genes related to grain length was mapped between the marker Rm7562 and Rm 12468 on 2nd chromosome and between the marker Rm3695 and Rm 18646 on 5th chromosome. The aimed genes related to grain width was mapped between the marker Rm6167 and Rm1287 on lth chromosome and between the marker Rm5512 and Rm7355 on 2nd chromosome.(3) F2:3 population with 2988 individuals were applied to fine mapping of the aimed genes, and some new SSR markers were developed. We find the aimed genes genetic distance to the aimed gene was 28.2cM and 15.6cM.The aimed genes related to grain width was mapped between the marker Rm 10451 and Rm6138 on 1th chromosome and genetic distance to the aimed gene was 9.3cM.(4) Analysis QTLs related to grain length and grain width with QTL IciMapping V3.2. We found two QTLs on 2nd chromosome related to grain length. They account for 26.02% and 36.25% of Phenotypic variance. There is no QTL locus on 5th chromosome. Concerning the grain width on 1st chromosome, much more LOD wave crests were observed and they close to each other. But among these LOD wave crests, no one above 2.5, so no obvious QTL locus was detected. The analysis on the major genes plus polygenes mixed inheritance model and additive-dominant-polygenes indicated that further confirmation is needed.(5) In order to shorten distance, some new InDel markers were developed. Compose 846 InDel markers between Rm7562and Rm 12468. there are 8 InDel markers showing the polymorphism between parents and gene pools. The polymorphisms analysis for F23 population with InDel-6, InDel-95 and InDel-297. We find the aimed genes related to grain length was mapped between the marker InDel-95 and InDel-297 on 2nd chromosome. Genetic distance to the aimed gene was 4.9cM.