Dec. 11, 2008 -- Around the world, rice sustains billions of people with a cheap source of nutrition. There's only one problem: Rice generally requires lots of water, and many people who depend on the crop live in extremely dry places. When the rain stops, rice wilts. Hunger follows.
Now, for the first time, scientists have identified a group of genes that consistently double the yield of rice in drought conditions. The discovery could help provide a reliable source of food for people in some of the poorest places.
"This was far more than we ever would have expected," said Jerome Bernier, who recently completed his Ph.D. at the University of Alberta Department of Agricultural, Food and Nutritional Science, and will begin working with Dow Agro-Sciences in Hawaii in January. If the crop proves its worth, he added, "The applications will be tremendous."
In Myanmar, Bangladesh, and other Asian countries, rice provides up to 60 percent of people's calories. But growing conditions are not always ideal.
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Scientists have been trying for a long time to breed rice that grows well in dry conditions -- with little success. In previous work, groups of researchers actually found regions of the rice genome that led to drought-resistance. But in every case, those genes only helped the rice grow in one place or in one year.
In the search for something more reliable, Bernier and colleagues first created a new strain of rice by crossing two other strains: one that farmers grows in lush lowlands and one that's commonly used in upland areas, where soils tend to be drier and far less productive. Then, they attempted to grow about 400 of the resulting lines of rice in extremely dry conditions.
Some of the new strain yielded 700 kilograms of rice per hectare -- more than double what any of the parent plants yielded in the same conditions, said Dean Spaner, a researcher at the University of Alberta, who was involved with the work.
Genetic mapping showed that these high-yield lines carried a specific set of genes on chromosome 12. The poorer-performing lines didn't carry the same gene forms.
Next, the scientists planted a sample of 21 lines from the original cross in a variety of environments in India and the Philippines. Some lines carried the high-yield genes. Some didn't. Nine of these environments ended up facing severe drought. In those places, lines containing the genes produced twice as much rice as expected.
The newly discovered genes help the plants produce deeper roots that can collect 8 percent more water from the soil, Spaner said -- enough to make a big difference in how much rice the plants produce. Results appeared in October on the Web site of the plant sciences journal Euphytica. Publication will follow.
"The effect of the [gene region] on grain yield was the highest ever identified in rice or in any other crop actually," Bernier said.
Still, while promising, the genetic discovery is preliminary, said Katherine Steele, a researcher at Bangor University in the United Kingdom.
Plenty of unanswered questions remain. For example, scientists will need to show that the genes work equally well in different strains of rice. And farmers will need to accept the new crop's taste and other features.
"Much more work is required in order to use the [genes] effectively in the development of modern varieties for subsistence farmers," Steele said. Only after more breeding work is done will farmers have the chance to grow new strains of drought-resistant rice.
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University of Alberta Department of Agricultural, Food and Nutritional Science
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