AsianScientist (May 3, 2011) – Asian rice, Oryza Sativa, is one of the world’s oldest crops and was believed to be domesticated about 9000 years ago. Previous research suggested domesticated rice may have two points of origin – India as well as China.
The crop species Oryza Sativa has tens of thousands of varieties of rice throughout the world. Two major subspecies of Asian rice – indica and japonica – represent most of the world’s varieties. Sushi rice, for example, is a type of japonica, while most of the long-grain rice in risottos are indica.
Previously, there were two models to explain the origin of domesticated rice. The single origin model proposed that indica and japonica were domesticated from the wild rice Oryza rufipogon. The multiple-origin model suggested that both subspecies were domesticated separately and in different parts of Asia. The second model has been favored due to strong genetic differentiation observed between species as well as from phylogenetic studies of rice domestication.
Molina and Sikora’s team aimed to re-examine the history of domesticated rice by re-sequencing 630 gene fragments on chromosomes 8, 10, and 12 from several sets of wild and domesticated rice varieties. The team then used patterns of single nucleotide polymorphisms (SNPs) to identify 20 valid differences in the cultivated rice.
Using two methods (demographic modeling and Bayesian phylogenetic analysis) with the aid of previously published phylogenetic sequence data sets, the team analyzed the data-set and discovered strong support for the single domestication origin of rice.
In results published online in the Proceedings of the National Academy of Sciences, the team dates the origin of domestication of rice in the Yangtze Valley beginning approximately 8,000 to 9,000 years ago, while domestication of rice in the India’s Ganges region was around 4,000 years ago.
The article can be found at: Molina J et al. (2011) Molecular evidence for a single evolutionary origin of domesticated rice.
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Source: New York University; Photo: World Bank Photo Collection.
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