Phytophthora species associated with stem cankers on tanoak in southwestern Oregon

Abstract

In effort to eradicate Phytophthora ramorum from Oregon forests, tanoak over its entire range in southwestern Oregon is surveyed intensively for stem disease. Pieces of bark from the leading edge of tanoak stem cankers were plated on cornmeal agar amended with 10 ppm natamycin, 200 ppm a-ampicillin, and 10 ppm rifamycin SV (CARP) to favor the isolation of Phytophthora. Phytophthora ramorum was usually identified on the isolation plates based on the presence of characteristic hyphae, chlamydospores, and sporangia. Hyphae from the leading edge of other colonies resembling Phytophthora were isolated into pure culture. Isolates were grown out to obtain morphological features and DNA extracts for identification. Selected isolates were tested for pathogenicity by inoculating stems of tanoak seedlings. Phytophthora species isolated from tanoak stem cankers include the following: P. cambivora, P. cinnamomi, P. species ?Pg chlamydo,? P. gonapodyides, P. nemorosa, and the proposed new species P. siskiyouensis. An additional isolate may represent a new species of Phytophthora that has not yet been described.

Parent Publication

• Proceedings of the sudden oak death third science symposium

Citation

Reeser, Paul; Sutton, Wendy; Hansen, Everett. 2008. Phytophthora species associated with stem cankers on tanoak in southwestern Oregon. In: Frankel, Susan J.; Kliejunas, John T.; Palmieri, Katharine M., tech. coords. 2008. Proceedings of the sudden oak death third science symposium. Gen. Tech. Rep. PSW-GTR-214. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station. pp. 227-229