Allozyme variation and population genetic structure of common wild rice Oryza rufipogon Griff. in China

In order to determine the genetic diversity and genetic structure of popula tions in common wild rice Oryza rufipogon, an endangered species, allozyme diversity was analyzed using 22 loci in 607 individuals of 21 natural popul ations from the Guangxi, Guangdong, Hainan, Yunnan, Hunan, Jiangxi and Fuji an provinces in China. The populations studied showed a moderate allozyme v ariability (A=1.33, P=22.7%, Ho=0.033 and He=0.068), which was relatively h igh for the genus Oryza The levels of genetic diversity for Guangxi and Gua ngdong were significantly higher than those for the other regions, and thus South China appeared to be the center of genetic diversity of O. rufipogon in China. A moderate genetic differentiation (F-ST=0.310, I=0.964) was fou nd among the populations studied. Interestingly the pattern of population d ifferentiation does not correspond to geographic distance. An estimate of t he outcrossing rate (t=0.324) suggests that the species has a typical mixed -mating system. The deficit of heterozygotes (F=0.511) indicates that some inbreeding may have taken place in outcrossing asexual populations because of intra-clone outcrossing events and "isolation by distance" as a result o f human disturbance. In order to predict the long-term genetic survival of fragmented populations, further studies on gene flow among the remaining po pulations and the genetic effects of fragmentation are proposed. Finally, s ome implications for the conservation of endangered species are suggested.