The Rice Genepool and Human Migrations

Abstract

The characteristics of the rice grain, particularly its hard, tight husk and nutrient content, make it an ideal grain to accompany migrating people. This paper discusses rice diversity and movement from a historical perspective by providing contrasting examples from the homeland of Asian rice, Madagascar and West Africa. The value of modern analytical techniques to understand the origin, diversification and movement of rice is discussed. The following points emerge:

• 1. No evidence exists to support the center of origin and the center of diversity of rice being the same area, and molecular studies support multiple domestication events probably over a wide area.

• 2. Inter-subspecific hybridization and diversification after a genetic bottleneck account for much of the traditional rice diversity of Madagascar.

• 3. Introduction of Asian rice (O. sativa) to West Africa has resulted in partial replacement of indigenous African rice, O. glaberrima, introgression has occurred from Asian into African rice, and recently a new interspecific genepool has been developed by researchers with the aim of combining the best characters of both rice species.

Finally, the recent consequences of human migration from rural to urban areas and the impact on the rice ecosystem are discussed with particular reference to Malaysia. The common trend of change from transplanting to direct seeding rice and accompanying ecological changes in rice fields are discussed.