Scientists find key ingredients in genetic recipe for hardier rice
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Two problems make this a less-than-ideal approach, they argue. The rice blast fungus evolves resistance to the plant's intense burst of fungus-fighting agents. And each variety of rice has its own unique variation on the genetic blueprint for the agents, making it difficult to come up with a more-universal weapon.Skip to next paragraph
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Breeders had noticed that some varieties of rice have defense mechanisms that allow the fungus to gain a foothold. But then the rice plant builds its counterattack over time. The Japanese team identified the oddities in the mutant pi21 gene that made this possible.
Breeders had noticed this slo-mo defense. So they tried to breed the trait in different rice varieties. But the rice ended up with other traits that breeders -- and customers -- didn't like, such as bad-tasting rice.
By identifying a gene near Pi21 associated with the yuck factor, the team has made it easier to use precision breeding techniques to get disease-resistance without triggering upturned noses.
We like water, but not that much water
A second group has tackled another problem -- ensuring rice can survive prolonged flooding. Rice germinates in flooded fields. But not all rice can endure prolonged flooding.
Three years ago, scientists reported that by throwing a naturally occurring rice gene into overdrive, they could induce a rice plant to in effect suspend its growth for far longer than usual. The gene in question was one of three variations of the plant' native "submergence" gene. The variety in question typically could endure up to a couple of weeks under water, but not much longer.
Once the new rice variety resumed its normal growth, the rice yields and quality matched those of rice unaffected by excessive flooding.
This time around, a team of Japanese scientists identified genes from so-called deep-water varieties that allow them to survive prolonged inundation. Then they bred these with non-deep-water varieties in ways that passed along the water wings. Their results appear in this week's issue of the journal Nature.
The genes involved in this work (cleverly named SNORKEL1 and SNORKEL2) in effect accelerate growth when the rice plant becomes inundated, allowing it to rise above the surface of the water. Plants could survive this way in up to 4 meters (a shade more than 13 feet) of water.
The yin and yang of rice survival
These discoveries represent a kind of yin and yang for conferring greater stress tolerance to rice as climate changes, McCouch suggests.
With global warming come projections of increases in severe weather, including an increased frequency of drought, and more frequent flooding -- either in brief, flash-flood form, or as larger floods, depending on location ans season.
The ability to ward off rice blast is important when rice is stressed by drought and high temperatures. And you've gotta love SUBMERGENCE and SNORKEL when the water runs high for a long period of time.