Rice, like most plants, needs water. In fact, it needs more water than most: the shoots of this marsh plant are typically partially submerged. But rice, like most crops, still does not stand up to total submersion. Despite being the staple of flood-prone regions, most strains of rice die if submerged for more than four days and even short-term inundation can stunt growth and impact harvests. Now researchers have identified a gene that confers the ability to survive extended submersion in some rice cultivars and successfully introduced it into those that lack this critical protection.

Pamela Ronald of the University of California, Davis and her colleagues first identified a stretch of DNA--dubbed Submersion 1--linked to immersion survival. Narrowing their focus to one gene in this stretch that proved highly variable in various rice strains--Sub1A-1--the researchers found that it conferred the ability to withstand high waters for up to two weeks and then renew growth once the waters subsided. "Each year millions of small farmers in the poorest areas of the world lose their entire crops to flooding," Ronald says. "These newly developed rice varieties will help ensure a more dependable food supply."

Current annual rice crop losses exceed $1 billion, particularly because the highest yielding varieties do not withstand flooding at all. But by introducing the gene into strains that previously lacked it, the researchers improved tolerance for submersion without diminishing yield levels and grain quality. Already, submergence-tolerant rice is being developed for Bangladesh, Laos and India--all subjects of recent, devastating floods. The research appears in today's Nature.

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