Diphyletic origin of cultivated rice based on genetic analysis and archaeology

摘要

We formulated a hypothesis on the origin of cultivated rice based on the results of DNA analysis of excavated rice grains and recent available archaeological and biological data. We concluded that a major varietal group--japonica--had differentiated from its ancestral species of wild rice in the middle and lower basins of the Yangtze River about 11,000 to 14,000 years ago. Some japonica strains were brought into the southwestern provinces of China several thousand years ago and then transmitted to the tropics. Another varietal group--indica--could have originated in the flooded plains of the tropics by incidental natural hybridization(s) between indigenous wild relatives and japonica cultivars.