Ecological-Genetic Studies on Genetic Resources of Wild and Cultivated Rice(4th Survey)

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We investigated wild and cultivated rice in Indochina area during 1991-1993.1.In 1991, we visited Laos and northeastern Thailand. In Laos, we investigated wild and cultivated rice in Luang Prabang, Vientiane and Pakse areas.(1)Luang Prabang. One population of Oryza glanurata was observed. Almost cultivators were grown in upland or rainfed fields. They were glutinous cultivars.(2)Vientiane. Populations of O.rufipogon were observed. Cultivators were mostly landraces, but recently modern ones were introduced from Vietnam and Thailand.(3)Parse. Annual-like O.rufipogon was frequently observed.2.In 1992, we observed rice in Vietnam and Cambodia. In the Mekong delta of Vietnam, perennial rufipogon having japonica-like cytoplasmic genome was predominant. Modern cultivators are taking place of landraces. Wild rice was frequently seen in Cambodia. A huge population was found in the west suburb of Punom Penh city.3.In 1993, we visited Laos again to evaluate the change of biomass of natural population of wild rice in Vientiane area, so as to learn the level of genetic erosion in this country. Two wild rice populations were found to be maintain their size and density, suggesting that genetic erosion is not so serious in Laos.4.During this project, we visited wild rice populations in Thailand, which we have visited at the first survey of this project (in 1983). We compared biomass of wild rice population in every observation-site, and found high level of genetic erosion. In particular, annual populations were seriously damaged due to destroy of the sites. It was evaluated that annual populations will be vanishing by the end of this century. An effective way for the conservation of genetic resources, such as the establishment of in situ conservation should be conducted.