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Scientists find key ingredients in genetic recipe for hardier rice

By / August 20, 2009

Farmers plough a rice field with a water buffalo, locally called "carabao", and a hand tractor in a village in Dinalupihan town, northwest Philippines

REUTERS/Erik de Castro

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As rice genes go, SNORKEL1 and 2, and SUBMERGENCE1a, b, and c have more evocative names than most. Not so much with pi21.

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Taken together, however, some of these genes hold the promise of helping rice farmers in developing countries -- who feed more than 2 billion people -- keep the harvests coming under increasing pressure from rising populations and extreme climate events expected from global warming.

This week, two groups of Japanese scientists are reporting progress on two important fronts: boosting disease resistance in rice; and giving rice the ability to withstand prolonged, deep-water flooding. In the case of flooding, they do this not by temporarily shutting down rice growth, as other researchers have, but by triggering a growth spurt when the rice finds itself in over its head.

The good news is that these look like they can be bred into current strains without resorting to the kind of high-tech genetic engineering that sets so many people's teeth on edge, explains Susan McCouch, a Cornell University plant geneticist who specializes in rice research.

"There's been a lot of hype around moving genes around from once species to another with genetic engineering" to develop more stress-resistant crops, Dr. McCouch said during a phone chat.  "But both of these studies are based on the utilization of natural variations" enhanced through traditional crossing-breeding.

This sidesteps the need for regulations imposed on growers who want to use crops that get their hardiness from genes introduced from other plant species, she adds.

Who cares? More than 2 billion people, who rely on rice as a staple. And the developing-country farmers that have to grow the grain under increasingly marginal conditions.

One team of Japanese scientists report in tomorrow's issue of the journal Science that they've isolated a naturally occurring, but odd form of a rice gene dubbed pi21. Pi21 is present in all rice varieties. But this version -- which, ironically, is missing some pieces compared with the "normal" gene --  increases the plant's ability to win out over rice-blast infections. Rice blast is one of the most prevalent diseases rice faces worldwide.

And the team identified the gene's location on the rice plant's chromosome. This solves a decades-old puzzle that allows the mutant gene to be bred into many rice varieties without sacrificing flavor -- a goal that has been elusive in the past.

Rice defense strategies

Most approaches to conferring disease resistance in rice involve coaxing an existing gene into overdrive to generate the compounds that will knock the fungus flat as soon as it tries to infect the plant, say the researchers, led by Shuichi Fukuoka, with the QTL Genomics Research Center in Japan's Tsukuba City.

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