Scientists have identified a gene that allows rice plants to survive floods; a development that could help poor farmers especially in India who are having a tough time braving floods.

Most rice plants die within days of being underwater, but the team of researchers at the International Rice Research Institute in the Philippines and University of California's Davis and Riverside campuses hope the new gene will offer greater protection to the world's rice harvest.

The development and cultivation of the new varieties is expected to increase food security for 70 million of the world's poorest people, and may reduce yield losses from weeds in areas like the United States where rice is seeded in flooded fields.

"Globally, rice is the most important food for humans, and each year millions of small farmers in the poorest areas of the world lose their entire crops to flooding," said Pamela Ronald, a rice geneticist and chair of UC Davis' Plant Genomics Programme.

"Our research team anticipates that these newly developed rice varieties will help ensure a more dependable food supply for poor farmers and their families. And, in the long run, our findings may allow rice producers in the United States to reduce the amount of herbicides used to fight weeds," Ronald said.

Using genetic mapping techniques, the research team identified a cluster of three genes that appeared closely linked to the biological processes that either make rice plants vulnerable to flooding or enable them to withstand the total submergence that occurs during flooding.

The researchers then focused their attention on one of those three genes, known as the Sub1A gene. They found that when this gene is over-expressed, or hyper-activated, a rice variety that is normally intolerant of submergence becomes tolerant.

Further studies indicated that the Sub1A gene is likely successful in conferring submergence tolerance to rice because it affects the way the plants respond to hormones, such as ethylene and giberellic acid, that are key to the plant's ability to survive even when inundated with water.

Going one step further, the researchers introduced the Sub1A gene into a rice variety that is especially suited for growing conditions in India. The resulting rice plants were not only tolerant of being submerged in water, but also produced high yields and retained other beneficial crop qualities.

Development of submergence-tolerant varieties for commercial production in Laos, Bangladesh and India is now well under way.

The research team is now trying to identify all the genes that are regulated by Sub1A and to use this information to further improve tolerance to flooding and other stresses.

The study appears in the August 10 issue of the journal Nature.