Yunnan Academy of Agric. Sciences, Kunming, 650205, China
Recent studies on Asian wild rices and land races of cultivars indicate that South Asia is most likely the main center of origin of cultivated rice. Differentiation of the indica (hsien) rice would have occurrend in South Asia, and that of the japonica (keng) rice in South-eastern and Eastern Asia. The wild rices and land races from the two areas differ in their predominant isozymes and other biological traits.
In the Chinese common wild rice, well isolated populations appeared more primitive than others, as the enzymatic variations they carried were limited. In tracing the domestication and differentiation of cultivated rice, they may be taken as prototypes.
The central and lower Yangtze basin seems to be the cradle of Chinese rice cultivation as evidenced by recent archaeological excavations. Yunnan may be a secondary center, and is regarded as the northern border of South-eastern area of rice evolution.
The Indica-Japonica differentiation is more advanced among land races of Eastern Asia than among those of South Asia. It may be suggested from this that rice cultivation has made progress at earlier time in Eastern Asia than in South Asia. The evolutionary stituation of special types like small-grained, sickle-shaped, and hairless (nuda) varieties needs more investigation in the future. (This is an abstract of a full paper written in Chinese.)