Close-up of stem rust (''Puccinia graminis'') on wheat. Photo by Yue Jin.
Though most Americans have never heard of it, Ug99 -- a type of fungus called stem rust because it produces reddish-brown flakes on plant stalks -- is the No. 1 threat to the world's most widely grown crop -- wheat.
Crop scientists fear the Ug99 fungus could wipe out more than 80% of worldwide wheat crops as it spreads from eastern Africa. It has already jumped the Red Sea and traveled as far as Iran. Experts say it is poised to enter the breadbasket of northern India and Pakistan, and the wind will inevitably carry it to Russia, China and even North America -- if it doesn't hitch a ride with people first.
To make matters worse, the fungus is becoming more virulent as it spreads. Scientists discovered a Ug99 variant in 2006 that can defeat Sr24, a resistance gene that protects Great Plains wheat.
Last year, another variant was found with immunity to Sr36, a gene that safeguards Eastern wheat.
Should those variants make their way to U.S. fields any time soon, scientists would be hard-pressed to protect American wheat crops.
"It's a time bomb," said Jim Peterson, a professor of wheat breeding and genetics at Oregon State University in Corvallis. "It moves in the air, it can move in clothing on an airplane. We know it's going to be here. It's a matter of how long it's going to take." -- LA Times
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