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Evaluation of model plants for use in elucidation of Sclerotinia homoeocarpa pathogenesis.
R. RIOUX (1), J. Kerns (1). (1) University of Wisconsin, Madison, WI, U.S.A.

Dollar spot of turfgrass, caused by <i>Sclerotinia homoeocarpa</i>, occurs on many turfgrass species worldwide and is among the most important diseases with respect to pesticide expenditures. Studies of <i>S. homoeocarpa</i> pathogenesis may decrease the costs of control but are limited by the amount of genetic information available for natural hosts. Various plants with well-characterized genomes as well as the natural host <i>Agrostis stolonifera</i> were utilized to study <i>S. homoeocarpa</i> infection. Leaves of all plants were inoculated with agar plugs of 7 day-old potato dextrose agar cultures of four <i>S. homoeocarpa</i> isolates to monitor the progression of infection. Results on all plants were similar and showed an initial 72-hour biotrophic phase prior to the onset of host tissue necrosis. These findings were corroborated by microscopic analysis of inoculated tissues. Isolation attempts from necrotic host tissue on monocot models were unsuccessful unless samples were within 10cm of the inoculation site. Consequently, semi-purified culture filtrates were determined to induce symptoms similar to those observed in the infection assays. Symptom development was not correlated with oxalic acid content of culture filtrates, which is typical of other <i>Sclerotinia</i> species. This research enhances understanding of the infection process and virulence mechanisms of <i>S. homoeocarpa</i> and demonstrates the usefulness of various model plant species for further study of <i>S. homoeocarpa</i> pathogenesis. <p><p>Keywords: Fungus, Turfgrass, Cool-season

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