Scientists have identified genes that help rice plants keep their leaves above water during prolonged flooding. The research should help boost rice supplies in flood-prone areas.
Experts say farmers will have to double rice production by 2050 to feed the world's population, which is expected to swell to 9 billion by mid-century. Today, much of the world's rice crop is grown in low-lying areas that are prone to flooding. And more flood-prone lands are likely to be farmed to meet the growing demand for rice.
Most rice plants will drown if they're underwater for more than a few days. Some local varieties in flood-prone areas can tolerate the water, but they produce much less than high-yielding rice strains. So-called submarine rice can survive underwater for more than two weeks by limiting its growth until the water subsides. But varieties known as deepwater rice have a different strategy, says plant biologist Rens Voesenek at the University of Utrecht in the Netherlands.
Watching rice grow
"They have the capacity to suddenly switch on the growth rate of their stems in an enormous way," he says. "Deepwater rice can grow up to 25 centimeters in 24 hours. So that's a centimeter per hour. You can almost see it happening."
The plants grow until their leaves are above water. Sometimes they'll grow as much as four meters. Now, a team of Japanese scientists has isolated the genes responsible for that rapid growth and published its findings in the journal Nature. Voesenek wrote a commentary accompanying the article. He says the research shows that when a plant with these genes is submerged, levels of a gaseous hormone build up inside of it.
Voesenek says, "That tells the plant, in effect, you're under water, chap, you have a problem. Do something. And then, a cascade of reactions occur[s] to allow fast plant growth." And it grows and grows until it can breathe again. But since these deepwater varieties don't yield much rice, Voesenek says the Japanese team's findings are an important step toward boosting global rice production.
He says, "We now know how this elongation is brought about. We know which genes play a role. And that means we can introduce those genes into high-yielding rice varieties. And we can combine high yields with the capacity to escape from flood waters."
Voesenek says flood-resistant, high-yielding rice varieties will probably be available for farmers in five years or so.