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Gene that helps rice grow in flooded fields

New Delhi, Aug. 9: Plant biologists have discovered a gene that allows rice plants to survive complete submergence in water for up to two weeks, a finding that might lead to flood-tolerant rice.

In laboratory experiments, the scientists at the International Rice Research Institute (IRRI) in the Philippines have shown that the gene, called Sub1A, can impart flood tolerance to a rice variety especially suited for growing conditions in India. Their findings will appear in the journal Nature tomorrow.

While rice is the only cereal crop that can withstand submergence, most rice varieties will die when fully submerged for too long.

When the plant is covered with water, its oxygen and carbon dioxide supplies are reduced, and most rice varieties can survive only four or five days of complete inundation.

Crop scientists estimate that annual flooding leads to losses worth $1 billion across south and southeast Asia. “For half a century, researchers have been trying to introduce submergence tolerance into commonly grown rice varieties through conventional breeding,” said David Mackill, a plant biologist at the IRRI.

Working with researchers at the University of California, the IRRI team found that when the Sub1A gene is hyperactive in rice plants, the plants become tolerant to submergence.

The scientists inserted the gene into a rice variety suited for India and found that the genetically transformed plants survived when submerged, produced high yields and retained crop qualities.

“Rice plants that can tolerate prolonged submergence would be a potentially big contribution to agricultural biotechnology,” said Arun Lahiri Mazumder, a plant scientist at the Bose Institute in Calcutta.

“Flooding is a problem in many rice-growing areas of eastern India,” said Mazumder, who heads a Bose Institute team that discovered a gene that could be used to induce salt-tolerance in rice plants.

Five years ago, Mazumder had screened wild species of rice that grow in the Sunderbans and isolated a gene that appears to allow rice plants to thrive in conditions of high salinity.

“Imagine taking our salt-tolerance gene and the submergence gene and putting both of them into a rice plant. We could then have plants that survive in flooded saline water,” he said.

Several traditional rice varieties have shown a greater tolerance to submergence, but previous attempts to breed that tolerance into commercially viable rice have failed to generate new varieties, Mackill said.

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

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