Three foci of rice domestication

There were three independent domestications of rice in different parts of Asia, according to a new study led by Terence Brown of the University of Manchester, United Kingdom, leading to the four main varieties of domesticated rice —indica, japonica, aus, and aromatic— that are consumed today.

According to archeological evidence, the first domestication began between 82,00 and 13,500 years ago. Earlier, there were only two schools of thought about the origins of domesticated cultivation. One which claimed that it began with the japonica variety in Southern China from where it expanded to other regions of Asia. And all other varieties are it said hybrid products of this over centuries. This school believes that the other variety that has also a long history of cultivation, namely indica, was the result of crosses between japonica and the wild varieties of Asia. The second school of thought argues for the existence of two independent foci for japonica (in South China) and indica, whose domesticated cultivation originated in a region between the Brahmaputra valley in India and western Indochina.

Now, with this study we have a new third school of thought, which argues that the variety aus is genetically distinct from the others and proposes the existence of a new locale for its origin. According to the researchers, the separate and independent origin lay somewhere between Central India and Bangladesh. The aromatic variety, like the Indian basmati and the Thai jasmine, they say, arose out of hybrids between japonica and aus rice. This study has been published in the latest issue of the journal Nature Plants.

Interestingly, the new study uses the same genetic data as the 2012 paper in Nature, whose lead author was Bin Han, a geneticist at the Chinese Academy of Sciences, which proposed the single origin for domestic rice. The data used consists of genetic sequences from 446 samples of wild rice and over 1000 cultivated varieties. Han has expressed reservations about the study and says that its data analysis is wrong. The new study says that its findings are in accordance with the archaeological evidence that suggests widespread origins of rice cultivation.

R. Ramachandran