DNA of Rice Varieties

EVERY cook knows there are two main types of rice: the sticky, short-grained stuff used in desserts, sushi and risotto, and the drier, long-grained varieties. Crop scientists call them japonica and indica rice respectively. Both were bred from a wild grass, Oryza rufipogon, some 9000 years ago, but researchers have never been sure whether they came from a single domestication or independent origins.

Now an analysis of the DNA sequences in cultivated rice has shown that japonica and indica rice are genetically more different than previously supposed, and were domesticated in different places at different times. The sticky, short-grained japonica was first bred by Chinese hunter-gatherers, probably along the banks of the Yangtze river, as the world warmed at the end of the last ice age. The long-grained indica was bred independently, from a different gene pool of wild O. rufipogon growing south of the Himalayas, in India.