AFLP Analysis of Phytophthora nemorosa and P. pseudosyringae Genetic Structure in North America

Rachel Linzer, & Matteo Garbelotto, Department of Environmental Science, Policy and Management, 151 Hilgard Hall, University of California, Berkeley, CA 94720; (510) 643-4282; rwarner@nature.berkeley.edu; David Rizzo, Department of Plant Pathology, University of California, Davis, CA 95616.

In California and Oregon, Phytophthora ramorum has an overlapping host and geographic range with two newly described Phytophthora, P. nemorosa and P. pseudosyringae. P. nemorosa alone causes symptoms similar to those of P. ramorum, including lethal tanoak cankers, and P. pseudosyringae is associated with oak decline in Europe. However, epidemiological observations, namely broader geographic distribution and reduced virulence, suggest the other two are endemic in this region, while P. ramorum is hypothesized to have been introduced. Though molecular evidence suggests that P. nemorosa and P. pseudosyringae are each other’s closest known relatives, both are rather distantly related to P. ramorum. In order to study patterns of genetic variability within P. nemorosa and P. pseudosyringae and to shed light on the hypothesis of endemism, we use amplified fragment length polymorphism (AFLP) analysis to generate DNA fingerprints for isolates of the two species. 41 isolates of P. nemorosa and 30 isolates of P. pseudosyringae are analyzed, and isolates were chosen from throughout the known geographic and host ranges of the two taxa in North America. From AFLP fingerprint data, we calculate a distance cladogram with P. ilicis, the closest known phylogenetic relative to P. nemorosa and P. pseudosyringae as an outgroup. The degree of genetic variability and structure within each species will be shown and implications for the history of these taxa in North America will be discussed.

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