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Poster Presentations


Poster Presentations


Phakopsora pachyrhizi spores in rain

Presenter: Charles W. Barnes(1),(2)

Other authors and affiliations: Les J. Szabo(1, 2), Van C. Bowersox(3), Christopher Lehmann(3). (1)Cereal Disease Laboratory, USDA-ARS, St. Paul, MN 55108, U.S.A.; (2)University of Minnesota, Plant Pathology, St. Paul, MN 55108, U.S.A.; (3)National Atmospheric Deposition Program, Illinois State Water Survey, Champaign, IL 61820, U.S.A.

Rain has been assayed for Phakopsora pachyrhizi in the eastern half of the United States for the past 3 years using precipitation collectors in the National Atmospheric Deposition Program, National Trends Network. A nested real-time PCR assay was used to detect P. pachyrhizi DNA in the filtered residue. The percentage of rain collections testing positive for P. pachyrhizi has fluctuated over this time, with 5.2% of rain samples testing positive in 2005, 15.2% in 2006, and 8.5% in 2007. This year, P. pachyrhizi spores were detected in rain north of disease reports in Texas and Oklahoma, with higher numbers of spores detected as the number of counties reporting disease increased. This trend contrasts somewhat to that seen in 2006, in which disease reports were more uniform across the Gulf Coast states and spores were detected more frequently further east than in 2007. In both 2006 and 2007, P. pachyrhizi spores were detected in rain 34 weeks prior to first disease reports in a state. Estimates of the number of spores in rain samples were made using models generated by assaying a known numbers of P. pachyrhizi spores. Estimates ranged from a single spore per square meter to more than 500 spores per square meter.

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