Abstract:

Eighty-five rice (Oryza sativa L.) varieties, including 82 rice landraces collected from 17 villages in Yunnan Province of China and three standard varieties representing typical Indica and Japonica ecotypes, were studied using simple sequence repeat (SSR) markers to estimate their genetic diversity for the purpose of strategic conservation. Nineteen selected SSR primer pairs amplified a total of 83 SSR alleles, with molecular weight ranging from 100 to 500 bp, from the 85 rice varieties. An UPGMA dendro-gram based on the cluster analysis of genetic similarity of the SSR alleles showed a significant genetic variation among the included rice varieties, with the similarity coefficients varying between 0.152 and 0.900. However, genetic diversity of the rice varieties collected from Yunnan was unevenly distributed over their geographical locations. Two distinct groups were identified from the cluster analysis of the 85 rice varieties at the similarity coefficient level of 0.152, with one group that included almost all accessions of Indica ecotype and another group that contained all accessions of Japonica ecotype. Varieties that shared the same names but collected from different villages did not always show a close genetic relationship, indicating misidentification of some varieties by local farmers. It is concluded from this study that conser-vation of genetic diversity in rice landraces is urgently necessary in Yunnan, given their high level of diversity, but an appropriate strategy needs to be followed to guarantee the effectiveness of conservation activities. Properly selected SSR primer pairs might provide an ideal method for identifying Indica and Japonica ecotypes for rice conservation and breeding programs.

Key words: Oryza sativa, rice landrace, differentiation, SSR, conservation, molecular marker