Analysis Of Genetic Structure Of Oryza Sativa L. In China

China is one of the centers of genetic diversity of Oryza sativa L. in the world, and it is also abundant of rice germplasm resources with the natural selection and artificial domestication. In this study, Cheng's index and 84 SSR locus distributed throughout the rice genomes were used to analyse the genetic structure and genetic diversity of Oryza sativa L. in China for clarifying the genetic differentiation and distribution. The primary results were summarized as following:1. A total of 100 introduced cultivated rice accessions (Oryza sativa L.) grouped by Glaszmann's allozyme method were selected to compare the classification of Oryza sativa based on Cheng's index and 84 SSR locus. The results show that the subpopulation features of allozyme groupⅠ(Indica) and allozyme groupⅥ-A (Temperate japonica) were obvious both classified by Cheng's index and SSR data, with goodness of fit ranged from 73.3% to 100%. Mantel test revealed that the Euclidean distance of Cheng's index was significantly correlated with Nei unbiased genetic distance of 84 SSR loci (r=0.466, P≤0.01). According to both model-based structure and neighor-joining cluster analysises, the results for classifying Oryza sativa at subspecies level based on Cheng's index coincided with that of SSR data. Within subspecies, the subpopulations classified by Cheng's 6 phenotypic characters showed lower goodness of fit than SSR marker.2. Based on Model and Nei unbiased genetic distance, 100 introduced accessions were classified into 6 different groups, which are Indica, Aus, Aromatic, Temperate japonica and Tropical japonica. According to the genetic structure, the cluster analysis of 852 chinese cultivars based on Nei unbiased genetic distance indicated that Indica and Tropical japonica, Temperate japonica groups were main type in China while Aus and Aromatic groups only existed in some special places. Otherwise, there is no Rayada group in our study. Analysis of molecular variance (AMOVA) indicated that 23% of the variation was from divergence between groups. Using locus-by-locus AMOVA procedure, there were 84 SSR locus with significant differentiation.3. A set of 84 SSR locus were used to assess the genetic diversity in 852 cultivars in China. There were 1186 alleles at 84 SSR locus. The number of alleles per locus (Na) varied widely from 2 to 34, with an average value of 14.1, and the number of rare alleles (Nr) was 792, The Nei genetic diversity index (He) ranged from 0.464 to 0.950, with a mean value of 0.751. The polymorphism information content (PIC) changed from 0.359 to 0.948, with an average value of 0.716. Compared with 100 introdced accessions, the number of specific alleles (Ns) in Chinese cultivars was 202. Based on the information of the number of allele (Na), Nei genetic diversity index (He), polymorphism information content (PIC), the number of rare alleles (Nr) and the number of special alleles (Ns) in each chromosome, we found the 9^th chromosome has the highest value for each one, which indicates that the differentiation of Oryza sativa L. in China was related with the chromosomes.