Pathogenicity variation in two west coast forest Phytophthoras, Phytophthora nemorosa and P. pseudosyringae, to bay laurel

Abstract

Two recently described pathogenic oomycetes, Phytophthora nemorosa and P. pseudosyringae, have overlapping host and geographic ranges in California and Oregon forests with P. ramorum, causal agent of ?sudden oak death? disease. Preliminary genetic evidence indicates P. nemorosa and P. pseudosyringae may be introduced in this region; their sympatric distribution with P. ramorum suggests they may be an interacting factor in P. ramorum disease.

The ultimate goal of this project is to characterize the outcome of interaction during infection by P. ramorum, P. nemorosa and P. pseudosyringae in the epidemiologically important host, bay laurel (Umbellularia californica). Experiments will account for variability in host, pathogen and environment, and leaf lesion area in detached bay leaves will be used as the proxy for pathogenicity. Therefore, the proximal goals of this portion of the project are to describe pathogenicity variability and refine methods for leaf infection. Here, we describe four preliminary experiments conducted to select Phytophthora isolates for inoculation and to optimize leaf infection methods.

Parent Publication

• Proceedings of the sudden oak death third science symposium

Citation

Linzer, R.E.; Garbelotto, M. 2008. Pathogenicity variation in two west coast forest Phytophthoras, Phytophthora nemorosa and P. pseudosyringae, to bay laurel. 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. 387-388