00588nas a2200169 4500008004100000245009600041210006900137300001200206490000800218100001900226700001600245700002600261700001900287700001900306700002600325856006700351 2011 eng d00aPhytophthora ramorum in Canada: evidence for migration within North America and from Europe0 aPhytophthora ramorum in Canada evidence for migration within Nor a166-1710 v1011 aGoss, Erica, M1 aLarsen, Meg1 aVercauteren, Annelies1 aWerres, Sabine1 aHeungens, Kurt1 aGrünwald, Niklaus, J uhttp://apsjournals.apsnet.org/doi/abs/10.1094/PHYTO-05-10-013301952nas a2200205 4500008004100000022001400041245009600055210006900151260001600220300001400236490000800250520129900258100001901557700001601576700002601592700001901618700001901637700002601656856006401682 2011 eng d a0031-949X00aPhytophthora ramorum in Canada: Evidence for Migration Within North America and from Europe0 aPhytophthora ramorum in Canada Evidence for Migration Within Nor cJan-01-2011 a166 - 1710 v1013 a

Phytophthora ramorum, the cause of sudden oak death on oak and ramorum blight on woody ornamentals, has been reported in ornamental nurseries on the West Coast of North America from British Columbia to California. Long-distance migration of P. ramorum has occurred via the nursery trade, and shipments of host plants are known to have crossed the U.S.-Canadian border. We investigated the genotypic diversity of P. ramorum in Canadian nurseries and compared the Canadian population with U.S. and European nursery isolates for evidence of migration among populations. All three of the P. ramorum clonal lineages were found in Canada but, unexpectedly, the most common was the NA2 lineage. The NA1 clonal lineage, which has been the most common lineage in U.S. nurseries, was found relatively infrequently in Canada, and these isolates may have been the result of migration from the United States to Canada. The EU1 lineage was observed almost every year and shared multilocus genotypes with isolates from Europe and the United States. Estimation of migration rates between Europe and North America indicated that migration was higher from Europe to North America than vice versa, and that unidirectional migration from Europe to North America was more likely than bidirectional migration.

1 aGoss, Erica, M1 aLarsen, Meg1 aVercauteren, Annelies1 aWerres, Sabine1 aHeungens, Kurt1 aGrünwald, Niklaus, J uhttps://apsjournals.apsnet.org/doi/10.1094/PHYTO-05-10-013301842nas 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