02228nas a2200181   4500008004100000022001400041245011000055210006900165300001600234490000800250520157600258653002101834100002501855700002201880700002101902700002301923856010001946       2011                        eng d  a0378-112700aWill all the trees fall? Variable resistance to an introduced forest disease in a highly susceptible host0 aWill all the trees fall Variable resistance to an introduced for  a1781 - 17910 v2613 a<p>Although tanoak (<em>Notholithocarpus densiflorus syn. Lithocarpus densiflorus</em>) is the species most affected by the introduced pathogen <em>Phytophthora ramorum</em>, with demonstrable risk of extirpation, little is known about the origin, range or structuring of the tree’s susceptibility. We examined variation in resistance to <em>P. ramorum</em> using a wound inoculation assay of detached leaves from trees at five geographically separated sites, and a non-wound inoculation assay on twigs from trees at two sites. The structure of variation in resistance was compared to the structure at nine nuclear microsatellite markers. Resistance varied quantitatively, with 23% and 12% of the variation among individuals and populations, respectively. There was a significant correlation between resistance in detached leaves and lesion size in non-wounding twig inoculations. Among-population genetic diversity at nine microsatellite loci was weakly structured but significantly non-zero, with 9.5% of variation among populations. Within-population neutral genetic diversity was a poor predictor of resistance, and estimates of phenotypic distances for resistance were no greater than neutral genetic distances. The limited phenotypic and genetic structure we found indicates that tanoaks at all study sites are susceptible, and there is no evidence of prior selection for disease resistance. We conclude that tanoak populations across the species’ range are at risk, but local disease dynamics will depend on both host genetics and environmental conditions.</p>10aSudden oak death1 aHayden, Katherine, J1 aNettel, Alejandro1 aDodd, Richard, S1 aGarbelotto, Matteo  uhttp://www.sciencedirect.com/science/article/B6T6X-52F7TF6-1/2/55216e9ccfc0fafe0035e3d3f20ff81b01860nas a2200157   4500008004100000245013300041210006900174300001400243490000700257520128500264100002501549700001701574700001601591700002301607856007201630       2004                        eng d00aDetection and quantification of Phytophthora ramorum from California forests using a real-time polymerase chain reaction assay-00 aDetection and quantification of Phytophthora ramorum from Califo  a1075-10830 v943 a<p>The timely and accurate detection of pathogens is a critical aid in the study of the epidemiology and biology of plant diseases. In the case of regulated organisms, the availability of a sensitive and reliable assay is essential when trying to achieve early detection of the pathogen. We developed and tested a real-time, nested polymerase chain reaction (PCR) assay for the detection of <em>Phytophthora ramorum</em>, causal agent of sudden oak death. This technique then was implemented as part of a widespread environmental screen throughout California. The method here described is sensitive, detecting less than 12 fg of pathogen DNA, and is specific for <em>P. ramorum</em> when tested across 21 <em>Phytophthora spp</em>. Hundreds of symptomatic samples from 33 sites in 14 California counties were assayed, resulting in the discovery of 10 new host species and 23 infested areas, including 4 new counties. With the exception of a single host, PCR-based discovery of new hosts and infested areas always was confirmed by traditional pathogen isolations and inoculation studies. Nonetheless, molecular diagnostics were key in early pathogen detection, and steered the direction of further research on this newly discovered and generalist <em>Phytophthora</em> species.</p>1 aHayden, Katherine, J1 aRizzo, David1 aTse, Justin1 aGarbelotto, Matteo  uhttp://apsjournals.apsnet.org/doi/abs/10.1094/PHYTO.2004.94.10.1075