July 30, 2009

Hill farmers help preserve rice diversity

The practices of Thailand's hill farmers have helped preserve the genetic diversity of rice, researchers in the United States and Thailand found.

Research by Barbara A. Schaal of Washington University in St. Louis and colleagues at Chiang Mai University in Thailand showed how natural genetic drift and agricultural practices of traditional farmers influenced the genetic diversity of a given landrace, or traditional varieties, of rice, Washington University said Thursday in a news release.

Researchers said they studied a landrace of rice grown by the Karen people in Thailand, comparing genetic variation among the same variety of rice grown in different fields and villages, noting the further apart fields are, the more genetically distinct they are.

In the lowlands of Thailand, farmers grow modern high-yield rice, while in the hills the Karen people practice traditional agriculture, growing ancestral varieties of rice with traditional practices, the university said. Expert farmers maintain their crops' genetic diversity by exchanging and choosing seeds to plant the following year.

Most modern varieties of crops, like corn in the Midwest or high-yield rice in the lowlands of Thailand, are artificial constructs developed by plant breeders, Schaal said. They are extraordinarily important in feeding the world. But they are static and not evolving in farmer's fields.

The rice grown by the Karen people is genetically dynamic, because of natural drift and a farmer's seed selection, researchers said, resulting in crops constantly evolving in response to local conditions.