The United Nations is observing World Food Day (Saturday, Oct. 16). Food prices have been climbing in recent months because of bad weather in several major agricultural regions. Experts predict there will be more extreme weather as climate changes, jeopardizing food supplies around the world. And that's in addition to the constant threats of pests, weeds, and disease. But scientists think they have a way to feed the ever growing human population.

In a greenhouse here at the University of Maryland, researchers are growing the next generation of wheat. Their goal is to help Maryland farmers deal with a disease that claimed half their wheat crop last year. Researcher Jose Costa leads the effort. "We're looking here at healthy seed, and then scabby seed," he said.

Wheat scab is a fungus that turns the grains white...and poisonous.

"It causes vomiting in humans. So, we don't really want that in our bread or cookies," said Costa.

Scab is just one disease that infects wheat worldwide.

But just like some people don't get as sick as others, Costa says some wheat varieties are less likely to get scab. "One of them is from China. Ning 7840 that has scab resistance," he said.

The challenge, Costa says, is to mate a local wheat variety that produces a lot of grain with the Chinese variety that's resistant to scab - but doesn't produce as much. "One or two plants in a thousand [will] carry the right combination of genes," he said.

Recent advances in genetics make the job easier.

Scientists are mapping the entire genetic code of wheat. They've already figured out the location of some of the key genes, including those for scab resistance and productivity. And to locate them quickly, they've found small stretches of DNA called markers, says graduate student Lydia Cardwell.

"Just like in real life you would use a landmark when you give directions, we use markers," she said.

Scientists mate the wheat plant from Maryland with the one from China by cross pollinating them.

Until recently, they relied on big test fields like this one to find that one-in-a-thousand plant that was both resistant and productive.

Now, they grow the plants in a room-sized incubator.

They extract the genetic material from a small piece of each offspring and look for the markers. That way they can identify the offspring they're looking for.

Costa says out in the field, some plants just get lucky and escape infection. "With markers, now we can tell if they do have the genes or not," he said.

Costa says with the challenges facing farmers - climate change, population growth, and the never-ending battle with pests and disease - he'll need all the help he can get. "It's the best we can do at this time. But it gives us a lot more weapons than what we had before," he said.

Costa hopes those same weapons will allow researchers around the world to ward off the looming threat of hunger.

scab: a disease of plants, especially apples and potatoes, that causes a rough surface （植物）疮痂病，斑点病

cross pollinating: （使）异花传粉；（使）异花受粉

incubator: a piece of equipment in a hospital which new babies are placed in when they are weak or born too early, in order to help them survive （体弱或早产婴儿）恒温箱

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（来源：VOA 编辑：陈丹妮）