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New Mexico State University

New Mexico State University

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NMSU Karnal Bunt Lab Results Reliable

LAS CRUCES--New Mexico wheat growers concerned about recent reports that an Arizona laboratory made an error in testing grain samples for Karnal bunt, don't have to worry. New Mexico State University's Karnal Bunt Laboratory results are reliable, said a plant pathologist.


"Some samples that Arizona tested were actually positive for the fungus but were mistakenly declared free of spores," said Natalie Goldberg with NMSU's Cooperative Extension Service. "There was concern about the possible contamination of fields with the Karnal bunt fungus, which can lower the quality of wheat."

In retesting samples, the Arizona lab detected three positive samples that account for 232 tons of seed harvested in 1998, Goldberg said. According to the U.S. Department of Agriculture-Animal and Plant Health Inspection Service PLant Protection and Quarantine office in Las Cruces, none of the newly discovered contaminated grain was planted in New Mexico.

The process of screening for the Karnal bunt fungus includes a wet sieving technique, a bunted kernel search, or both, Goldberg said. In the case of the Arizona lab incident, either the sieves were labeled incorrectly or used incorrectly, and spores from positive samples were not detected.

"I can reassure New Mexico wheat growers that the testing done at the NMSU Karnal bunt lab produces accurate and reliable results," Goldberg said. "We have checked our sieves. They are labeled correctly, and they were used correctly."

Safety checks are used each year to assure correct results, she said. First, all the sieves are checked for holes, tears or other defects that would make them unusable. Damaged sieves are removed from use.

Second, samples with the disease are periodically slipped into the screening process to assure that the sieves are working and that lab workers are processing samples and reading slides correctly. Spores in these blind control tests have always been detected in the NMSU lab, Goldberg said.

"We have found spores on grain that was grown in Arizona and bunted wheat that was damaged from Texas," she said. "But we haven't found any contaminated grain in New Mexico.