Genetic Diversity and Classification of Korean Weedy Rice based on RAPD Markers

In the preliminary screening using 92 primers, twenty-four which produced reproducible and polymorphic bands were selected and analyzed for a total of 210 rice accessions and 109 polymorphic bands were generated. The genetic similarity among the accessions were used to classify 148 accessions including 111 Korean weedy rice strains and the 37 typical ecotype reference accessions. Weedy rice accessions were classified into three types: japonica, indica, and intermediate, whereas the typical ecotype reference accessions were clearly grouped into three distinctive types: temperate japonica, tropical japonica, and indica. Comparisons of the genetic similarity were made within and between the six groups identified from the cluster analysis. Comparisons of the similarity were also made between the six groups and the four reference groups of Korean elite rice cultivars, landraces, Shareibyeo strains, and weedy strains from China. The japonica and indica type weedy accessions showed about 50% genetic similarity (GS). The japonica type weedy accessions had the highest GS coefficient of 0.725 with the Shareibyeo accessions. In contrast, indica type weedy accessions had the highest GS (0.619) with the Anhui weedy strains. The intermediate type, on the other hand, showed a very low GS coefficient with all the reference groups evaluated. Weedy rices collected from the same district showed very high GS and the 109 polymorphic bands failed to discriminate among several accessions collected from the same region. These results might suggest that weedy rice evolved in the area spontaneously and did not experience much changes. The present study also indicated that weedy rice occurred in the Korean peninsula where no wild rice is present.