イネの発祥中心地はどこか : これからの研究に向けて

Abstract

Asian cultivated rice (Oryza sativa L.) is believed to have been born in the hills of sub-tropical Asia, in an area stretching from Bhutan to southwest China called the "Oriental fertile crescent." This hypothesis was originally proposed by workers in such fields as agronomy, ecology, ethnology and ethnobotany. It is supported by a number of genetic studies showing the center of genetic diversity to lie in this area. This hypothesis assumes that cultivated rice has monophyletic origin : the two subspecies of cultivated rice, indica and japonica, evolved simultaneously a common ancestor in the Oriental fertile crescent. A diphyletic theory has also been proposed by several researchers since 1940s. Zhou claimed that japonica was born in China. Recent molecular genetic studies have shown that indica and japonica might have derived from different ancestors. Archaeological data also contradict the monophyletic hypothesis. Wang showed that the oldest rice cultivation was established in the Taifu area in the lower basin of the Yangtze river, not in the southwest area. From these data, it can be assumed that cultivated rice probably evolved from different ancestors at plural sites, and that some varieties of japonica were born in east China. It is necessary to accumulate more evidence to discuss origin and dissemination of cultivated rice precisely. Bio-archaeological approaches are now being applied to plant remains excavated from archaeological sites.