APS Abstracts of Presentations

Characterization of Phytophthora spp. pathogenic to asparagus in Michigan
Presenter: C. Saude, Michigan State University
Co-Author(s): M. Hausbeck, Michigan State University, East Lansing, MI 48824; O. Hurtado-Gonzales, Department of Entomology and Plant Pathology, University of Tennessee, Knoxville, TN 37996; K. Lamour, Department of Entomology and Plant Pathology, University of Tennessee, Knoxville, TN 37996
Phytopathology 95:S92

In spring 2004, symptoms of Phytophthora crown and root rot were observed on spears and roots of asparagus, Asparagus officinalis L, in several fields in Oceana and Ingham Counties, MI. Water-soaked lesions occurred on roots and near the soil line of spears. Infected spear tissue shriveled and flattened, causing the spear to curve and collapse. Root mass and vigor were reduced as infected tissue shriveled. Symptoms were not observed on crowns or stems. Crowns, roots, spears and stems of sampled plants yielded 116 Phytophthora sp. isolates. Sporangia were ovoid and nonpapillated. Sporangia and oospores were readily produced on isolation media and no chlamydospores were observed. AFLP analyses revealed genetic similarities among isolates. Sequencing of the ITS region of representative isolates with ITS6 and ITS4 primers showed Phytophthora sp. as the closest match (BLAST search, accession AF266795) with 99% sequence similarity. These results indicate that the Phytophthora sp. isolated from asparagus in Michigan is among the constituents of the Phytophthora spp. included in the P. megasperma group, whose taxa are currently under evaluation. This is the first documented report on the occurrence of Phytophthora sp. on asparagus in Michigan.

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