Was Asian Rice (Oryza sativa) Domesticated More Than Once?

Abstract

Recently, a dual or multiple origin of domesticated rice has been the prevailing opinion among rice scientists because rice is clearly differentiated into two major varietal groups, indica and japonica, and several minor groups. Molecular clock studies that suggested that divergence in the A-genome wild rice genepool occurred prior to domestication gave further weight to the opinion that rice had a dual origin. However, recent analysis of the major gene that is responsible for the difference in degree of shattering between rice and wild rice has revealed that it is the same mutation in indica and japonica rice, which is not compatible with a dual origin of domesticated rice. Here, we discuss the geographic and genetic reasons why a single origin for domesticated rice is compatible with current data regarding the evolution of rice. The apparently conflicting data regarding the origin of rice can be resolved by the role hybridisation-introgression has played during rice evolution since domestication.

Genetic structure of landraces in foxtail millet (Setaria italica(L.) P. Beauv.) revealed with transposon display and interpretation to crop evolution of foxtail millet

“…Thus, to discuss domestication origin of the foxtail millet, it is necessary to test larger number of the green foxtail millet collected from wider range of Eurasia. In addition, even a crop species with sequenced genomes such as rice, the origin is still under discussion (Vaughan et al 2008). Particular genes related to the domestication traits will allow us to further elucidate the phylogeny and evolution of the foxtail millet.…”

The Evolutionary History of Ehrhartoideae, Oryzeae, and Oryza

“…Evidence has accumulated in the literature for various evolutionary histories, summarized in tabular form by Vaughan et al (2008b).…”

Genetic Diversity of Isolated Populations of Indonesian Landraces of Rice (Oryza sativa L.) Collected in East Kalimantan on the Island of Borneo

“…In contrast, the accelerated evolution provided by intense artificial selection and seed exchanges among local farmers has led to dramatic changes in the genetics of cultivated crops in a relatively short time frame (<10,000 years). While the story of rice domestication is still being unraveled based on interpretations of geographic and phylogenetic data (Caicedo et al 2007;Londo et al 2006) and analysis of cloned domestication genes (Kovach et al 2007;), it appears that rice was domesticated from diverse gene pools and that gene flow among sub-populations and with wild ancestral populations has created a complex series of events leading to the modern day fabric of rice diversity (Sang and Ge 2007;Sweeney and McCouch 2007), although the possibility of a single domestication event is still debated (Gao and Innan 2008;Vaughan et al 2008). While the relationships between the earliest domesticates and indigenous landraces surviving in rice-growing regions today are still unclear, signatures of shared ancestry, selection, and introgression are written in the genomes of traditional varieties.…”