Zhian Kamvar
Botany & Plant Pathology
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Presentation Time: 
2015 - 2:15pm
A disease known as Sudden Oak Death was discovered in California in the mid 1990’s. It was formally described as the clonal Oomycete, Phytophthora ramorum in 2000. Known to infect a wide range of hosts including Rhododendron, Quercus, and Notholithocarpus species, P. ramorum has a large impact on forest health. It was first detected in Oregon forests in 2001 by aerial surveys, and was followed by an ongoing and aggressive eradication effort by the Oregon Department of Forestry in Curry County. Populations from symptomatic tanoaks were sampled from 2001 to 2014, genotyped using microsatellite markers, and studied to infer population genetic history. While there are three clonal lineages found in nurseries on the North American west coast, only the NA1 lineage has been discovered in OR forests. Since the initial introduction event into the Joe Hall area, the pathogen has spread North, West, and Southwest within Curry county. A discovery in the Hunter Creek area in 2011 appears to be a second introduction as it does not cluster with the early introduction or subsequent infections. Utilizing population genetic analyses appropriate for clonal organisms with data from OR forests and west coast nurseries, we give support for a most parsimonious scenario of at least two distinct introduction events from Oregon or California nurseries. Continued vigilance and eradication of nursery populations of P. ramorum are important to avoid further emergence and potential introduction of other clonal lineages.