A gene that enables rice to survive for up to two weeks underwater could overcome one of agriculture's oldest challenges and offer relief to millions of poor rice farmers around the world.

A team of researchers at the International Rice Research Institute (IRRI) in the Philippines and at the University of California's Davis and Riverside campuses made the discovery. Their findings were published in the August 10, 2006, issue of Nature magazine.

Although rice thrives in standing water, like all crops it will die if completely submerged for more than a few days. The development and cultivation of the new varieties are expected to increase food security for 70 million of the world's poorest people. It also promises to reduce yield losses from weeds in areas such as the United States, where rice is seeded in flooded fields.

Approximately one-fourth of the global rice crop is grown in rainfed lowland plots that are prone to seasonal flooding. These seasonal flash floods are extremely unpredictable and may occur at any growth stage of the rice crop.

During any given year, yield losses resulting from flooding in these lowland areas may range from 10 percent to total destruction, depending on the water depth, age of the plant, how long the plants are submerged, water temperature, rate of nitrogen fertilizer use, and other environmental factors. Annual crop loss has been estimated at more than $1 billion.

"For half a century, researchers have been trying to introduce submergence tolerance into the commonly grown rice varieties through conventional breeding," said rice geneticist and study co-author David Mackill, who heads IRRI's Division of Plant Breeding, Genetics, and Biotechnology.

"Several traditional rice varieties have exhibited a greater tolerance of submergence, but attempts to breed that tolerance into commercially viable rice failed to generate successful varieties," he said.

"We're especially pleased that we have been able to use the latest advances in molecular biology to help improve the lives of the world's poor," Mackill added. "We're confident that even more important discoveries like this are in the pipeline."