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New Maps of 20 Rice Varieties Help Identify Useful Traits

Rice is an essential crop for half the world's population. Now, researchers have taken an important step toward identifying the plant genes that impart to some rice varieties drought-tolerance, disease-resistance and other important traits.

Researchers mapped the basic genetic code for rice several years ago. But mapping the genome is only the first step. Researchers still need to find the genes for the specific traits they are looking for. In a new study, researchers compared 20 different varieties of rice using a technique that identifies tiny genetic differences between individual plants.

"What it enables you to do is get a read on how one variety differs from another variety, from another variety, from another variety, in very few steps," says Jan Leach at Colorado State University, who led the group.

Once they have identified how the varieties differ, she says, researchers can go looking for what these differences mean.

"We have 20 varieties. And let's say five of them are drought-tolerant and 15 are not. Maybe we can compare across those genomes and say, OK, here is a region that correlates with drought tolerance in all the varieties that have it. It's different from the region in the varieties that don't," she says.

Leach and her colleagues from four countries on three continents found a region of DNA from highly drought-tolerant strains that turned up in newly-bred strains.

"We were able to show where pieces of DNA were introduced from those varieties into modern varieties that were not drought-tolerant," she says. "And now we can focus in on those regions and see exactly what the differences are and maybe find out the change in the DNA that is responsible for that trait."

Leach and her colleagues identified nearly 160,000 tiny genetic variations among the 20 strains of rice they surveyed. She says these variations can serve as markers for plant breeders looking to breed drought tolerance or a wide variety of other desirable crop characteristics.

"That's very powerful," she says. "If a breeder has a marker that allows them to select for a trait, then they can go after that trait with a lot more power than if they're breeding blindly."

The research was published in the Proceedings of the National Academy of Sciences.