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Rapid Test for Global Fungal Threat

By Don Comis
June 16, 2004

Rusts are fungal disease agents that threaten just about every plant or crop in the world. The science of detecting rusts became a bit more precise this year, thanks to Agricultural Research Service scientists who developed a wheat rust species detection kit that relies on a form of rapid DNA testing.

Geneticist Les Szabo, plant pathologist Charles Barnes and lab technician Kim Nguyen developed the polymerase chain reaction (PCR) test to identify the species that do the most damage to wheat: stem rust, stripe rust and two species of leaf rust. The test identifies species by detecting specific DNA sequences in fungal genes. The scientists work at the ARS Cereal Disease Laboratory in St. Paul, Minn.

Extra funding from the U.S. Department of Defense--along with many years of previous research on rust taxonomy, including creation of an extensive database of DNA sequences--enabled Szabo to develop the test in just one year.

Diagnostic labs will likely use the test to analyze rust samples from around the world.

Plans for future tests include all the important rusts affecting other major cereal grain crops, including barley, rye and oats.

Once the scientists develop kits to more accurately identify individual rust species, they will devise additional tests to identify subspecies and genetic lineages. This will allow labs to track the movement of rusts worldwide and to immediately recognize types of these rust fungi that might be new to this country.

Knowing the subspecies and lineages will also alert scientists to which crops and varieties are at risk. This information will be useful to farmers, and it will give scientists an early start on breeding resistant varieties and developing new controls.

The work is expected to lead to the discovery of new species of rust fungi, adding to the 7,000 known rust species in the world.

More information about ARS rust detection research can be found in the current issue of Agricultural Research magazine.

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