Quantitative Trait Loci For Grain Shape And Identification Of Candidate Genes For Seed Dormancy In Rice

Rice is one of the most important food crop. Increasing grain yield is a key project for rice researcher. Grain shape is an important appearance quality, which is closely associated with thousand-grain weight, an important component of grain yield. Grain shape is determined by its three dimentions, length, width and thickness, which are controlled by multiple quantitative trait loci.Dissection of the genetic basis of grain shape will help to improve grain production.The occurrence of pre-harvest sprouting frequently in China and Southeast Asia leads to great loss in rice production and reduce grain quality. For hybrid rice yield, pre-harvest sprouting rate can reach up to about5%, and even to20%-30%in severe cases. Seed dormancy is an important trait, which can repress pre-harvest sprouting. Seed dormancy is not only astrategy for flowering plants to survive in adverse natural environment, but it is a certain extent of dormancy can effectively resist the occurrence of field sprouting on yield.In this study, a RIL populaiton was used to identify the QTLs for grain shape and three candidate genes for seed dormancy were tested by transformation. In addition, I identified three candidate genes for seed dormancy on the basis of previous work of our research team. The main results of this study were as follows:1. Grain shape and thousand-grain weight were investigated for a population (generations of F7and F8) of153RILs derived from XZ2and ZS97in two years. A RICE6K SNP array was used to genotype the F7population. A genome-wide linkage BIN map with3350SNP markers was constructed.22QTLs were detected for grain shape. Of them,11QTLs were commonly detected in both years.Compared with the previous research,6QTLs are novel. At11loci, ZS97alleles increased grain length/width, and at the other11loci, XZ2alleles increased trait values. Among them, there were six QTLs with pleiotropic effects on two or three traits, which well explained the correlation between different traits.2. No significant difference in grain shape was detected between the parents XZ2and ZS97. However, transgressive segregation was observed in the recombinant inbred lines. Positive alleles at the detected loci were distributed in two parents, which gave the chance that more positive or negative alleles in the RILs were pyramided than parents. that is why transgressive segregation in the population was occurred. 3. For each detected QTL,1-6heterozygous inbred lines were found in the recombinant inbred lines to create near-isogenic lines. Based on these HIFs, these novel QTLs will be quickly confirmed and fine positioned.4. Our group has detected three QTL from recombinant inbred lines derived from a Zhenshan97and Minghui63. Each interval contains a homologous gene to the Arabidopsis dormancy gene DOG1. In this study, I isolated these three candidate genes from the wild rice, and transformed the framents to Nipponbare for functional verification. about50transgenic seedlings were obtained for each gene. But unfortunately no genes exhibited the characterization of seed domancy by germination tests. Probably, the wild rice carried different alleles from the one Minghui63carried.