For more than 80 years, the Agricultural Research Service (ARS) Cereal Disease Laboratory in St. Paul, Minn., has been a sentry for wheat, barley and oat diseases. In addition to monitoring for wheat scab, leaf rust, stripe rust and Asian soybean rust--a fairly recent arrival to this country--ARS scientists at St. Paul and elsewhere are also monitoring for a new strain of stem rust from Africa.

The new strain of the wheat stem rust, Ug99, has emerged as an international threat to wheat and barley that could affect the Green Revolution's outstanding yield increases of 50 years ago. Rusts are fungal diseases whose spores are spread by the wind. Ug99 first surfaced in Uganda in 1999. It is now in Kenya and Ethiopia.

The Green Revolution is the name for breeding successes by Nobel Peace Prize winner Norman Borlaug and CIMMYT, the International Maize and Wheat Improvement Center based in Mexico--with help from ARS. Breeding wheat resistance to stem rust was a major reason for the successes.

At Borlaug's request, ARS is leading a search for resistance to Ug99 in U.S. wheat, as part of a new Global Rust Initiative.

ARS plant pathologist Yue Jin found that 80 percent of the hard red spring wheat grown in the U.S. Northern Plains has no resistance to this new race of stem rust. However, there are sources of resistance and Jin is working with breeders to develop resistant wheat varieties.

If Ug99 does reach this country, it will likely first be spotted by the Cereal Disease Laboratory scientists who monitor fields from south to north annually. ARS geneticist Les Szabo is working on developing molecular tools to detect Ug99. This test would detect spores in rain samples. Currently, Szabo is using rain samples sent by the National Atmospheric Deposition Program network to monitor the movement of Asian soybean rust fungal spores.

ARS has a network of sentinel nurseries throughout the barley- and wheat-growing areas of the United States to detect rust diseases.

Source: June 2006 issue of Agricultural Research magazine, available online at:

http://www.ars.usda.gov/is/AR/archive/jun06/crops0606.htm

ARS is the U.S. Department of Agriculture's chief scientific research agency

The mission of the Cereal Disease Laboratory is to reduce losses in wheat, oat, and barley to major diseases including leaf rust, stem rust, and Fusarium head blight. This mission is accomplished through research on the biology of the pathogens that cause these diseases and on methods to enhance disease resistance in small grains.

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