01842nas a2200181 4500008004100000245009800041210006900139260003400208300001300242490000600255520123900261100001901500700001601519700002401535700002201559700002601581856005301607 2009 eng d00aPopulation genetic analysis infers migration pathways of Phytophthora ramorum in US nurseries0 aPopulation genetic analysis infers migration pathways of Phytoph bPublic Library of Sciencec09 ae10005830 v53 a

Author Summary

Sudden oak death, caused by the fungus-like pathogen Phytophthora ramorum, has caused devastating levels of mortality of live oak and tanoak trees in coastal California forests and in urban and suburban landscapes in the San Francisco Bay Area. This pathogen also causes non-lethal disease on popular ornamental plants, including rhododendrons, viburnums, and camellias. P. ramorum was discovered in California in the late 1990s and is exotic to the United States. Recently, presence of the disease in wholesale nurseries in California, Oregon, and Washington has led to shipments of diseased plants across the US, thus risking the introduction of the pathogen to other vulnerable forests. We examined the genetic diversity of this pathogen in US nurseries in order to better understand its evolution in nurseries and movement between states. We found that California populations were genetically different enough from Oregon and Washington populations that infestations of the pathogen found in nurseries in other states could be distinguished as having originated from California or the Northwest. Our inferences were consistent with trace forward investigations by regulatory agencies.

1 aGoss, Erica, M1 aLarsen, Meg1 aChastagner, Gary, A1 aGivens, Donald, R1 aGrünwald, Niklaus, J uhttp://dx.doi.org/10.1371%2Fjournal.ppat.1000583