Evolution of the African Rice: A Historical and Biological Perspective

摘要

The usual assumption is that African rice (Oryza glaberrima Steud.) originated about 3500 yr ago from the annual wild rice, Oryza barthii A. Chev., and Asian rice (Oryza sativa L.) was introduced into West Africa in the late 15th century CE) by the Europeans. Evidences from several social science and biological science disciplines have been collated and/or reinterpreted to draw the following inferences: (i) There are several accounts of rice culture in northern and western Africa from early centuries of the Common Era; (ii) The Senegambian monoliths, linked to the time of origin of African rice as 3500 yr ago, have been carbon dated to the 7th century CE; (iii) Neolithic culture had hardly reached tropical West Africa 3500 yr ago; (iv) The characteristics of O. barthii vis-a-vis the two cultivated rices-bigger grains, higher yields, easy crossability with both intermediate features, and weediness-may suggest its hybrid nature; and (v) The rarity of O. glaberrima beginning with the time of its initial identification, acceptance of local farmers to having both rices growing together, repeated discovery of O. glaberrima-like forms in non-African rice regions, and prevalence of close colinearity between the two cultivated rices at molecular and chromosomal levels suggest their close relationships. These factors indicate that African rice might have evolved from Asian rice, and that the wild rice, O. barthii, might be a hybrid derivative of the two cultivated rices.