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Rust Never Sleeps
CFANS researchers play vital role in the race to defeat a new form of wheat stem rust
By Becky Beyers
For half a century, wheat stem rust has been a low priority for the wheat community, thanks to CFANS-developed techniques for breeding rust-resistant wheat varieties.
But it turns out that stem rust—called “the shifty enemy” by pioneering University of Minnesota plant pathologist E.C. Stakman (’10–M.A., plant pathology)—is more persistent than almost anyone expected.
A new and particularly virulent strain—called UG99 because it was first noticed in Uganda in 1999—has scientists around the world and on the St. Paul campus racing to find the right combination of genes and traits that plant breeders can use to create new rust-resistant wheat varieties.
Seventy percent of the world’s wheat supply has no resistance to UG99, and the disease is spreading. If it follows the expected migration path, it soon will be into southwest Asia and could eventually migrate to North America. With wheat supplies already at historic lows, the threat to food supplies, especially in developing countries, is real.
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UG99 worries pathologists and breeders so much because it has the unique ability to break through the “pyramid” of rust-resistant genes that has been used in wheat in North America and much of the wheat in developing countries—rather than a single resistant gene—that have protected wheat crops since the 1950s. Even worse, it’s already mutating again.
An ancient enemy returns
Stem rust destroys a wheat crop by damaging stem tissues so that nutrients can’t get from the leaves to the grain, which causes the grain head to shrivel and die. The telltale rust-colored spores are produced on the stem but spread via the wind and rain, often traveling long distances.
The disease has been around for centuries; the Romans even had a god—Rubigal—devoted to wheat rust. They celebrated the festival of Robigalia each April 25 to plead for a rust-free crop. In modern times, rust epidemics periodically ravaged wheat crops worldwide,
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UG99 destorys wheat by damaging the stem so nutrients can't get to the grain.
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