New wheat disease could spread faster than originally thought

EOnow.com reported the following:

CORVALLIS - A study by Oregon State University and other institutions has shown that wind-borne human and plant diseases have the potential to spread far more rapidly than previously understood.

The findings, which were published in "The American Naturalist," pose serious concerns for some diseases, including a new fungus that threatens global wheat production.

"It's now becoming clear that some types of diseases can spread more rapidly and widely than we anticipated," said Chris Mundt, a professor of plant pathology at OSU. "This makes it especially important, in some cases, to stop a spreading disease quickly if you hope to stop it at all."

The studies help to explain, for example, how West Nile Virus spread so rapidly across the United States when experts expected a slow, methodical progression. They also aid the analysis of historic diseases, such as the potato blight that led to the Irish potato famine in the mid-1840s.

Researchers used stripe rust, a wheat disease that has spores that can spread on the wind, as a model to help explain how wind-borne pathogens can move. Mundt, an international expert on pathogens of several important food crops, has studied stripe rust for years.

"If we didn't have crops that could resist wheat stem rust, we pretty much wouldn't have a wheat industry," Mundt said. "From this pathogen we've learned a lot about plant disease resistance in general, and also how pathogens can move and spread. And this new study confirms that it is crucial to get prepared for the rapid spread of a new variety of wheat stem rust that appeared in Uganda in 1999."

That new type of wheat stem rust, Mundt said, has the potential to attack 75 percent of the world's known wheat varieties, and in a bad year might cause up to 50 percent crop losses in some parts of the world. Scientists are aware of the problem and are working on developing resistant wheat varieties, Mundt added.

"We don't want to suggest that the sky is falling, but major losses could occur if the right set of conditions converges," Mundt said. "This is something that we shouldn't take a chance on. It's already spread to Iran, and the new research shows that its global spread may be about to pick up speed."

Most plant and animal diseases that are spread by contact or close proximity tend to move in a fairly predictable and constant rate of speed, researchers say. However, a significant number of pathogens can be borne by wind-carried spores or migrating birds. In those cases, even though only small amounts of an invading pathogen may show up at any one remote spot, it has the potential to get a foothold and spread rapidly at this distant location - giving the invading pathogen the ability to literally accelerate as the epidemic spreads.

In just two years from 2004-06, the avian bird flu spread across parts of three continents in Africa, Europe and Asia, carried by migrating birds. From an initial source of infection in New York City in 1999, the West Nile Virus spread across most of North America within three years, and soon thereafter to the entire Western Hemisphere.

The spread of these diseases seems to follow very definable mathematical formulas, researchers found.

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