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Water-saving grain

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10:57am, September 26, 2007
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Rice is the staple food for more than half the world's population, including many people in developing countries. But the rice plant consumes more than twice as much water as other grain crops do, leaving some countries especially vulnerable to drought.

Now, an international team of scientists has identified a gene that, when added to rice's DNA, reduces the plant's water consumption and boosts its growth.

The gene, called HARDY, comes from thale cress, a weedlike plant that's commonly used in genetic research. Andy Pereira of the Virginia Polytechnic Institute and State University in Blacksburg, and his colleagues found a variant of this gene in thale cress plants that had unusually small, thick leaves and extensive roots.

When Pereira and his colleagues engineered thale cress to have an overactive version of this variant, the plants were able to survive 12 days without water. Unmodified plants lasted no more than 9 days.

Inserting the overactive form of HARDY into the rice genome increased the plants' water efficiency by 50 to 100 percent. When water was plentiful, the plants grew up to 80 percent more leaves and shoots than other plants did, the researchers report in the Sept. 25 Proceedings of the National Academy of Sciences. When water was scarce, most of the extra growth occurred in the roots, which helped the plants survive.

"I think it's a very important experimental step," comments Susan R. McCouch, a specialist in plant breeding and genetics at Cornell University. However, the research doesn't address whether the increase in leafy growth comes at the expense of grain yield, she notes.

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