Rice is a dietary staple of about half the world's population. But some of the more favored varieties are threatened by seasonal flooding, which puts at risk both an affordable food source and the livelihoods of countless numbers of people. But with a little genetic manipulation, researchers have found a way to save prized rice from the ravages of flooding.
There are more than 120,000 varieties of rice in the world. Some were bred to to achieve high yield and to increase nutritional value, others to survive harsh conditions like drought and disease. But, until now, nothing could be done to save rice damaged by flooding, which is a particular problem in many parts of Asia, where monsoons frequently inundate rice crops. Experts say submerged rice plants survive at most for one week, before they wither and die.
David MacKill of the International Rice Institute in Manila says the cost of flooding is significant. "It seems that there's probably 10- to 20-million hectares of rice lands that are affected regularly by submergence stress. And, I think, it's conservatively estimated to cost about $1 billion in rice loss per year."
In an effort to prolong the survivability of flooded rice, MacKill and colleagues studied rice strains that are best able to tolerate being submerged. They discovered that a single genetic region is responsible for rice's ability to withstand flooding. "It turns out there's only a handful of rice (strains) that have a really high level tolerance to submergence (flooding). So, we picked one of these varieties, and we did a genetic analysis of this variety, and we found that about 70 percent of the tolerance level is conferred by this single genetic region. And, so, we were able to map that on the rice chromosome, on rice chromosome-9," he said.
The investigators transferred the tolerance gene, called Sub-1A, from the stronger rice to its weaker rice cousin, transferring flooding tolerance to the more vulnerable strain.
That gives the rice plants an extra two or so weeks of survival under water, and thus, increases their chance of surviving until flood water recedes.
In an interview with the editors of Nature magazine, MacKill says the genetic manipulation does not affect any of the prized rice's desirable qualities. "With this new discovery, we will be able to accelerate the development of rice with the characteristics that farmers would like, with the tolerance to submergence," he said.
David MacKill and colleagues describe their work on flood resistant rice in the journal.