Abstract
Yunnan province in China is located in the center of genetic diversity of cultivated rice, an area which in-cludes East Nepal, Bhutan, Assam in India. Myanmar, Laos and Northern Thailand (Chang, 1976; Nakagahra and Hayashi, 1977). Several studies on genetic variation and differentiation of the Yunnan rice varieties based on isozyme analyses (Hu et al., 1981; Nakagahra, 1984; Zhu et al., 1984; Xiong et al., 1987; Nagamine et al., 1992) have been conducted, indicating that allelic varia-tions at the isozyme loci increase from north to south in the province and that genetic diversity is the highest in the varieties from the southern and/or southwestern re-gions of the province. Geographically, this region is bordered by Myanmar. Laos and Vietnam and is located in the northeastern part of the center of genetic di-versity for cultivated rice. However, the sampling sites of the varieties used in previous reports were apparent-ly rather limited; the materials from the northern region of the province were particularly scarce. To reconfirm that the rice varieties from the southern or southwest-ern region in the province show the highest genetic di-versity, a larger number of indigenous varieties, collected from almost all counties in the province, were analyzed for isozyme variation at the county level.
