Experimental studies on the origin of cultivated rice.
1) Contributions to the origin of cultivated rice made by the author and his colleagues were briefly reviewed under several headlines.-2) Two parallel series of evolution of cultivated species, the Asian form of Oryza perennis to O. sativa and O. breviligulata to O. glaberrima, were pointed out compared.-3) In both the two series, a continuous array of intergrades between wild and cultivated species is found in a particular region. The pattern of character variations among those intermediate plants was considered as indicating the evolutionary path, and the monophyletic origin of the Indica and Japonica types of O. sativa was discussed.-4) The conditions of establishment of a weedy form of O. perennis found in India were discussed. It was noticed that cultivation by man in itself works as a selective agent for cultivated types.
Oka
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National Institute of Genetics, Misima, 411 Japan.