This discovery will not only overcome one of agriculture's oldest challenges, but also offer relief to millions of poor rice farmers around the world, said the scientists from the International Rice Research Institute and the University of California's Davis and Riverside campuses.

    The study was published in the Aug. 10 edition of the journal Nature.

    Rice is the primary food for more than 3 billion people around the world. Some one-fourth of the global rice crop is grown in rain-fed, 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.

    However, most rice varieties will die if fully covered with water for several days, as the submerged plants lack the air and sunlight they need to function, and growth is inhibited.

    During any given year, yield losses resulting from flooding in these lowland areas may range from 10 percent to total destruction. Annual crop loss has been estimated at more than 1 billion U.S. dollars, according to the researchers.

    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 gene, known as Sub1A. 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 that are key to the plant's ability to survive even when inundated with water.

    The researchers then introduced the Sub1A gene into a rice variety that is especially suited for conditions in India. Most rice plants die within days of being submerged, but the new breed can survive underwater for up to two weeks while producing high yields and retaining other beneficial qualities.

    "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," said David Mackill, a plant-breeding expert at the University of California, Davis, and co-author of the work.

    "We're confident that even more important discoveries like this are in the pipeline," he added.

    Development of submergence-tolerant varieties for commercial production in Laos, Bangladesh and India is now well under way, and the team is now trying to identify genes in other plants such as maize and soy bean to improve crops, Mackill said. Enditem