Researchers in Japan have identified two genes that make rice plants grow longer stems and survive floods, and hope this will enable farmers to grow high-yielding rice species in flood-prone areas.

The long-stemmed deepwater rice varieties grown at present in areas of frequent flooding have very low yields.

"In southeast Asia, there are floods in the rainy season and deepwater rice is planted in these regions. But they have yields that are only one third or one quarter that of high-yielding rice. This is a big problem," said Motoyuki Ashikari at Nagoya University's Bioscience and Biotechnology Centre.

"If we combine the deepwater genes with high-yielding rice, we can have the best combination," he said.

In their experiment, Dr Ashikari's team analysed the genes of a deepwater rice variety and found two genes that were unique to the plant.

"The genes Snorkel 1 and Snorkel 2 are only in the deepwater variety but not in the non-deepwater variety," he said.

They discovered that rice plants begin producing a lot of the plant hormone ethylene when grown in deep water.

"As water levels rise, accumulation of the plant hormone ethylene triggers expression of the Snorkel genes, which in turn switches on rapid stem growth," they wrote.

They later tested their findings by inserting the two genes into a non-deepwater variety of rice and found that it grew longer stems, enabling it to survive in deep water.

"It's hoped that the findings will help researchers to breed rice that can be grown in lowland areas that are frequently flooded during the rainy season," they wrote in a statement.