Comparison of the genetic diversity of common wild rice (Oryza rufipogon Griff.) and cultivated rice (O. sativa L.) using RFLP markers

Forty fourth single-copy RFLP markers were used to evaluate the genetic div ersity of 122 accessions of common wild rice (CWR, Oryza rufipogon Griff.) and 75 entries of cultivated rice (Oryza sativa L.) from more than ten Asia n countries. A comparison of the parameters showing genetic diversity, incl uding the percentage of polymorphic loci (P), the average number of alleles per locus (A), the number of genotypes (Ng), the average heterozygosity (H o) and the average genetic multiplicity (Hs) of CWR and indica and japonica subspecies of cultivated rice from different countries and regions, indica ted that CWR from China possesses the highest genetic diversity, followed b y CWR from South Asia and Southeast Asia. The genetic diversity of CWR from India is the second highest. Although the average gene diversity (Ns)of th e South Asian CWR is higher than that of the Southeast Asian CWR, its perce ntage of polymorphic loci (P), number of alleles (Na) and number of genotyp es (Ns) are all smaller. It was also found that the genetic diversity of cu ltivated rice is obviously lower than that of CWR. At the 44 loci investiga ted, the number of polymorphic loci of cultivated rice is only 3/4 that of CWR, while the number of alleles, 60%, and the number of genotypes is about 1/2 that of CWR. Of the two subspecies studied, the genetic diversity of i ndica is higher than that of japonica. The average heterozygosity of the Ch inese CWR is the highest among all the entries studied. The average heteroz ygosity of CWR is about two-times that of cultivated rice. It is suggested that during the course of evolution from wild rice to cultivated rice, many alleles were lost through natural and human selection, leading to the lowe r heterozygosity and genetic diversity of the cultivated rice.