Comparing Phytophthora ramorum diagnostic protocols for the national Sudden Oak death stream monitoring program

Abstract

Oregon was a participant in the pilot test of the national stream monitoring protocol for SOD. We routinely and continuously monitor about 50 streams in and near the SOD quarantine area in southwest Oregon using foliage baits. For the national protocol, we added six additional streams beyond the area of known infestation, and compared results from different diagnostic tests with results from six streams within the quarantine area. Foliage baits were in streams for two weeks, then assayed by: 1) culture on selective medium; 2) PCR diagnosis using the P. lat multiplex primers; 3) nested PCR using the Garbelotto and others protocol; and 4) Real- Time PCR using the CSL protocol. Most samples at most sample times gave consistent results, regardless of diagnostic method. However, occasional positive results from the various molecular protocols were not supported by isolation in culture, and despite intensive surveys near the streams, no plants infected by P. ramorum were located. We concluded that culturing from leaf baits was the single most reliable diagnostic method. False positives arose from several sources, including laboratory error, insufficient specificity of primers, and presence of undescribed Phytophthora species in the streams.

Parent Publication

• Proceedings of the sudden oak death third science symposium

Citation

Sutton, W.; Hansen, E.M.; Reeser, P.; Kanaskie, A. 2008. Comparing Phytophthora ramorum diagnostic protocols for the national Sudden Oak death stream monitoring program. 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. 461-466