Study On The Genetic Diversity Of Wild Rice (Oryza Rufipogon Griff.) In China And The Origin Of Cultivated Rice

It has been proved that wild rice (Oryza rufipogon) is the ancestor of cultivated rice (Oryza sativa). To confirm where is the genetic diversity center of Oryza rufipogon in China and how cultivated rice originated, genetic diversity of 628 individuals from 20 Oryza rufipogon populations in 6 provinces based on 28 SSR molecular markers from cultivated rice were detected. The results indicated that:1. Total 406 alleles were detected with 28 SSR primiers, among which RM253, RM336, RM333 and RM229 detected more polyporphisms. They could be more efficient to be used in genetic mapping or QTL analysis. From the relationship between latitude and genetic diversity indices such as Shannon-Weaver index (I), average expected heterozygosity (He), average observed heterozygosity (Ho), it can be seen that the populations from the north part of Hainan and the south parts of Guangdong and Guangxi between 19.5° N -23.5° N, except for several special populations, possessed relatively higher genetic diversity. It can be deduced that this area is the center of genetic diversity of O. rufipogon in China and might be the original center of O. sativa.2. From the UPGMA dendrograms and PCO, 20 populations fell into 4 groups which are related to different regions: (1) Group I includes the populations from the south part of Hainan, they have close genetic relationship, but the gene flow is small;(2) Group II covers the populations from the north part of Hainan and the south parts of Guangdong and Guangxi, this area may be the center of genetic diversity in South China;(3) Group III consists of the populations from Hunan and Jiangxi, they were called the northmost populations;(4) The populations of Group IV are from the middle and north region of Guangdong and Guangxi. This area is the interim area where genetic diversity declined gradually.3. For the populations from different provinces, the genetic diversities in Guangxi, Guangdong and Hainan were higher than those in Hunan, Jiangxi and Fujian. Analysis of UPGMA also indicated that Guangxi, Guangdong and Hainan have close each other, so do Hunan and Jiangxi. However, the population from Fujian was different from others.4. Because most Oryza rufipogon samples had more than 2 bands amplified with Primer RM20A, this primer seemed to be non-specific in Oryza genome. To confirm the conclusion, DNA samples from 50 accessions of cultivated rice were amplified and analysed. The results showed that more than one loci also existed in cultivated rice but its genetic variation was lower than wild rice.