Last month, a study in The Proceedings of the National Academy of Sciences claimed to end a longstanding dispute about the two major subspecies of rice, indica and japonica. Researchers studied select gene regions of the species and suggested that both had a single point of origin, in the Yangtze Valley of China.
But now, a new study in the journal PLoS Genetics suggests that the truth is murkier.
Researchers studied the full genome of the two rice types and determined that though the species are identical in certain gene regions, they have two distinct genetic histories.
Farmers independently bred each species, said an author of the study, Chung-I Wu, an evolutionary geneticist at the Beijing Institute of Genomics in China and the University of Chicago.
Still, the similarities indicate that the two species borrowed desirable traits from each other through cross-breeding.
"Somebody might have given a neighboring village the rice, and then it went to the next village," Dr. Wu said. "Over 100 years, traits may have traveled 1,000 or 2,000 kilometers."
The researchers sequenced 66 varieties of rice -- 22 each of wild rice, indica and japonica. Though there are exceptions, japonica generally grows in temperate zones of Asia while indica grows in either subtropic or tropic regions.
The story of rice is really a story of how human civilization has progressed through borrowing, Dr. Wu said, adding:
"Intellectual property infringement has occurred since the beginning of civilization. That's why we have this rice to eat today."
First Published: June 14, 2011, 4:00 a.m.