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

Although tanoak (Notholithocarpus densiflorus syn. Lithocarpus densiflorus) is the species most affected by the introduced pathogen Phytophthora ramorum, 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 P. ramorum 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.

10aSudden oak death1 aHayden, Katherine, J1 aNettel, Alejandro1 aDodd, Richard, S1 aGarbelotto, Matteo uhttp://www.sciencedirect.com/science/article/B6T6X-52F7TF6-1/2/55216e9ccfc0fafe0035e3d3f20ff81b02477nas a2200217 4500008004100000022001400041245009800055210006900153260001600222300001600238490000800254520178300262653001502045653001702060653002702077100002402104700002002128700002802148700001802176856006502194 2015 eng d a0031-949X00aWinter Conditions Correlate with Phytophthora alni Subspecies Distribution in Southern Sweden0 aWinter Conditions Correlate with Phytophthora alni Subspecies Di cJan-09-2015 a1191 - 11970 v1053 a

During the last century, the number of forest pathogen invasions has increased substantially. Environmental variables can play a crucial role in determining the establishment of invasive species. The objective of the present work was to determine the correlation between winter climatic conditions and distribution of two subspecies of the invasive forest pathogen Phytophthora alni: P. alni subspp. alni and uniformis killing black alder (Alnus glutinosa) in southern Sweden. It is known from laboratory experiments that P. alni subsp. alni is more pathogenic than P. alni subsp. uniformis, and that P. alni subsp. alni is sensitive to low temperatures and long frost periods. By studying the distribution of these two subspecies at the northern limit of the host species, we could investigate whether winter conditions can affect the geographical distribution of P. alni subsp. alni spreading northward. Sixteen major river systems of southern Sweden were systematically surveyed and isolations were performed from active cankers. The distribution of the two studied subspecies was highly correlated with winter temperature and duration of periods with heavy frost. While P. alni subsp. uniformis covered the whole range of temperatures of the host, P. alni subsp. alni was recovered in areas subjected to milder winter temperatures and shorter frost periods. Our observations suggest that winter conditions can play an important role in limiting P. alni subsp. alni establishment in cold locations, thus affecting the distribution of the different subspecies of P. alni in boreal regions.

10aAlnus spp.10ainvasiveness10aPhytophthora plurivora1 aRedondo, Miguel, A.1 aBoberg, Johanna1 aOlsson, Christer, H. B.1 aOliva, Jonàs uhttp://apsjournals.apsnet.org/doi/10.1094/PHYTO-01-15-0020-R00716nas a2200193 4500008004100000245007900041210006900120260011100189300001200300490003200312100001800344700001100362700001600373700001500389700001700404700001900421700001800440856006400458 2008 eng d00aWildland management of Phytophthora ramorum in northern California forests0 aWildland management of Phytophthora ramorum in northern Californ aSanta Rosa, CaliforniabU.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station a305-3120 vGen. Tech. Rep. PSW-GTR-2141 aValachovic, Y1 aLee, C1 aMarshall, J1 aScanlon, H1 aFrankel, S J1 aKliejunas, J T1 aPalmieri, K M uhttp://www.fs.fed.us/psw/publications/documents/psw_gtr214/