SSR Analysis Of Genetic Diversity Of Oryza Rufipogon Griff. From Southeast Region Of Guangxi In China

To estimate genetic diversity of Oryza rufipogon Griff, in Southeast region of Guangxi in China, a total of 301 individuals from 8 natural populations in Hezhou City, Fangchenggang City and Chongzuo City were analyzed using 25 microsatellites loci. The results are as follows:A moderate high level of genetic diversity was obtained at population levels. The overall number of alleles (A) was 10.24. The overall effective number of alleles (Ae) was 5.02. The overall expected heterozygosity (He) and observed heterozygosity (Ho) was 0.76 and 0.48. Most populations have high level of genetic diversity except population SB and population YL. Gene flow between wild rice and cultivated rice might be the reason for the high level of genetic diversity of O.rufipogon, because found all O.rufipogon populations in this study were surrounded by cultivated rice.A moderate genetic differentiation (Fst=0.35) was found among the populations, suggesting that 35% genetic variation existed among the populations. Furthermore, microsatellite showed less deviation from Hardy-Weinberg expectation and a slight deficiency of heterozygotes within and among populations (Fis=0.27, Fit=0A8). And an estimate of the outcrossing rate (t=0.46) suggested that the species has a typical mixed-mating system.The genetic relationship among populations was studied by Nei unbiased genetic coefficient, Nei unbiased genetic distance, clustering analysis and principal coordinate analysis (PCO). Population DP and DT have the nearest genetic relationship (D=0.23, I=0.78); population YL and QT have the farthest genetic relationship (Z)=1.50, I=0.22). All the populations were divided into 5 clusters. Population SB, YL and YJ clustered together and had a close relationship; Population DP and population DT also clustered together but several individuals of these two populations mixed each other. Thereforepopulation DP and DT maybe derived from one larger population.The populations from south region of Guanxi fit the "Isolation-Distance" model well and a special pattern of distribution of the genetic diversity was found, presuming that the populations from south region of Guangxi distributed along a same water system. Meanwhile, the correlation coefficient (r=0.77 P<0.05) between the genetic diversity of O rufipogon populations and the latitude indicated that with the increasing of latitude the genetic diversity of O.rufipogon reduced.Together with the field investigation and the pattern of genetic variation of natural populations of O.rufipogon from Southeast region of Guangxi, it could be suggested that populations of QT, YJ, TJ be given priority for in-situ conservation and population SB be given for ex-situ conservation.