@proceedings {353, title = {Phytophthora kernoviae {\textendash} of southern hemisphere origin?}, year = {2007}, month = {August, 2007}, pages = {1 page}, address = {Monterey, Calif. Coll. of Nat. Resourc., Univ. of Calif., Berkeley.}, author = {Tod D. Ramsfield and Margaret A. Dick and Ross E. Beever and Ian J. Horner} } @proceedings {605, title = {Phytophthora kernoviae in New Zealand}, volume = {General Technical Report PSW-GTR-221}, year = {2009}, pages = {47-53}, publisher = {U.S. Department of Agriculture, Forest Service Pacific Southwest Research Station}, address = {Monterey, California}, abstract = {

Phytophthora kernoviae was first recognised in New Zealand in 2005 by DNA sequencing of an isolate that had been recovered from diseased Annona cherimola (cherimoya or custard apple) in an abandoned orchard in Northland in 2002. Subsequent investigation has recovered P. kernoviae from the soil in Northland, Auckland, Bay of Plenty and Taupo regions. Similarity between P. kernoviae and descriptions of an undescribed Phytophthora sp. found previously in New Zealand indicates that the organism has been present here since at least 1953. This, along with the geographic range of P. kernoviae, and a polymorphism in the ITS sequence, suggest that the pathogen has been present in New Zealand for an even longer time. Little is known of the ecological behaviour of the pathogen in New Zealand; disease has only been recorded on A. cherimola.

}, author = {Ramsfield, T.D. and Dick, M.A. and Beever, R.E. and Horner, I.J. and McAlonan, M.J. and Hill, C.F.}, editor = {Goheen, Ellen Michaels and Susan J. Frankel} } @article {PPA:PPA2463, title = {Two novel and potentially endemic species of Phytophthora associated with episodic dieback of Kwongan vegetation in the south-west of Western Australia}, journal = {Plant Pathology}, volume = {60}, year = {2011}, pages = {1055{\textendash}1068}, publisher = {Blackwell Publishing Ltd}, abstract = {

Two novel homothallic species of Phytophthora causing dieback of Kwongan vegetation in south-west Western Australia are described here as Phytophthora arenaria sp. nov. and Phytophthora constricta sp. nov. DNA sequencing of the ITS rDNA and cox1 gene confirmed that P.\ arenaria and P.\ constricta are unique species residing in ITS clades 4 and 9, respectively. Phytophthora arenaria has been isolated from vegetation occurring on the northern sandplains which are warmer and drier than the southern sandplains from which P.\ constricta has been predominantly isolated, and both species appear morphologically and physiologically well adapted to the ecosystems in which they occur. Both species have been associated mainly with dead and dying Banksia species and the pathogenicity of both P.\ arenaria and P.\ constricta to Banksia attenuata was confirmed in this study. The combination of unique DNA sequences, including considerable variation in cox1 sequence data, thick oospore walls and physiological characteristics that appear to be adaptations favouring survival in the harsh Kwongan ecosystem suggest that these species may be endemic to Western Australia.

}, keywords = {Mediterranean climate, natural ecosystems, pathogens, phylogeny, Phytophthora arenaria, Phytophthora constricta}, issn = {1365-3059}, doi = {10.1111/j.1365-3059.2011.02463.x}, url = {http://dx.doi.org/10.1111/j.1365-3059.2011.02463.x}, author = {Rea, A. J. and Burgess, T. I. and Hardy, G. E. St J. and Stukely, M. J. C. and T. Jung} } @article {3961, title = {Phytophthora elongata sp. nov., a novel pathogen from the Eucalyptus marginata forest of Western Australia}, journal = {Australasian Plant Pathology}, volume = {39}, year = {2010}, pages = {477-491}, abstract = {

A novel homothallic species of Phytophthora producing semipapillate sporangia on sympodially branching sporangiophores, thick-walled oospores in smooth-walled oogonia, and paragynous antheridia is described here as Phytophthora elongata sp. nov. DNA sequencing of the internal transcribed spacer (ITS) DNA and coxI gene confirm P. elongata as a distinct species within ITS clade 2. It has been isolated in the northern jarrah forest of Western Australia (WA) from the roots and collars of dead and dying Eucalyptus marginata and occasionally Corymbia calophylla in rehabilitated bauxite mine pits. It has also been associated with dead and dying plants of several mid- and understorey species in the northern and southern jarrah forest{\textemdash}Banksia grandis, Leucopogon propinquus, Dryandra squarrosa and an Andersonia sp., as well as the monocotyledonous Xanthorrhoea preissii, X. gracilis and Patersonia xanthina. P. elongata has also been isolated from sandy soils and loams in Victoria in eastern Australia. The pathogenicity of P. elongata to E. marginata and Banksia spp. has been shown in this and earlier studies. Due to the uniformity of the ITS DNA and cox 1 sequence data in WA, P. elongata may be the result of a recent clonal introduction. More pathogenicity tests on a wider range of native plant species are needed to assess the host range of P. elongata and its invasive potential in WA.

}, keywords = {biosecurity, natural ecosystems, phylogenetics}, issn = {0815-3191}, doi = {10.1071/AP10014}, url = {http://dx.doi.org/10.1071/AP10014}, author = {Rea, Alexander J. and Thomas Jung and Burgess, Treena I. and Stukely, Michael J. C. and Hardy, Giles E. St J.} } @article {4475, title = {First Report of Phytophthora pseudosyringae Causing Basal Cankers on Horse Chestnut in Sweden}, journal = {Plant Disease}, volume = {100}, year = {2016}, month = {Jan-05-2016}, pages = {1024}, abstract = {

Phytophthora pseudosyringae causes stem necrosis, and root and collar rot of several woody tree species (Fagus sylvatica, Alnus glutinosa, Castanea sativa, Nothofagus spp., and Quercus spp.) across Europe (Jung et al. 2003; Pintos Varela et al. 2007; Scanu and Webber 2015) and severe dieback of heathland plants such as bilberry (Vaccinium myrtillus) in the UK (Beales et al. 2010). In June 2014, a symptomatic horse chestnut tree (Aesculus hippocastanum) was detected in Sankt J{\"o}rgens Park in Gothenburg, southern Sweden (57{\textdegree}45'1.5" N; 11{\textdegree}57'8.1" E; elevation 22 m). The tree displayed 30\% crown dieback and several tongue -shaped necrosis at the base of the stem. The outer bark over the bleeding patches was removed and small pieces of infected phloem from the margin of the necrosis were directly plated onto CMA-PARPBH selective medium (17 g/liter corn meal agar (CMA), 0.125 g/liter sodium ampicillin, 0.02 g/liter benomyl, 0.07 g/liter hymexazol, 0.1 g/liter PCNB, 0.01 g/liter primaricin, and 0.01 g/liter rifamycin) and incubated at 20{\textdegree}C. Growing hyphae were later transferred to V8 agar and incubated at 20{\textdegree}C in darkness. After 7 days, the colony reached 5.4 cm in diameter and displayed a stellate growth pattern with faint aerial mycelium. Sporangia were sympodial, semipapillate, mostly ovoid, less commonly limoniform to ellipsoid, with a length/breadth average ratio of 1.44 μm (SE = 0.03). Oogonia were 28.1 μm (SE = 0.46) in diameter, smoothly walled, spherical, and with paraginous antheridia, although some amphiginous antheridia were observed. Morphological features and growth pattern on V8 agar corresponded to those of P. pseudosyringae. DNA was extracted from mycelia and the ITS region was amplified and sequenced using the ITS4 and ITS6f primers (Cooke et al. 2000) and deposited in GenBank (Accession No. KU257470). BLAST search showed 99 to 100\% identity with reference sequences of P. pseudosyringae deposited in GenBank. Under-bark inoculation with mycelium plugs was performed on 10 one-year-old excised shoots obtained from three different horse chestnut trees. Inoculated shoots were placed over autoclaved and moistened filter paper inside sterile Petri dishes and incubated at 23{\textdegree}C in darkness. After 14 days, the length of the lesion on inoculated shoots was significantly higher than on control shoots (8.53 mm, SE = 0.74 vs. 0.91 mm, SE = 0.93; P \< 0.0001). The pathogen was reisolated from all infected shoots fulfilling Koch postulates. To our knowledge, this is the first report of P. pseudosyringae in Sweden and the first report of P. pseudosyringae causing basal cankers and dieback on horse chestnut worldwide. The number of recent reports of damage caused by P. pseudosyringae raises concerns about the potential impact of this pathogen on horse chestnut trees, widely planted as ornamentals in Sweden, as well as to natural beech and oak forests across the country.

}, issn = {0191-2917}, doi = {10.1094/PDIS-09-15-1000-PDN}, url = {http://apsjournals.apsnet.org/doi/10.1094/PDIS-09-15-1000-PDN}, author = {Redondo, M. {\'A}. and Boberg, J. and Stenlid, J. and Oliva, J.} } @article {4482, title = {First Report of Phytophthora pseudosyringae Causing Stem Canker on Fagus sylvatica in Spain}, journal = {Plant Disease}, volume = {100}, year = {2016}, month = {Jan-07-2016}, pages = {1508 - 1508}, abstract = {

Phytophthora pseudosyringae T. Jung \& Delatour was described in 2003 as a pathogen associated with root and collar rot of several tree species (Fagus sylvatica, Alnus glutinosa, Quercus spp.) (Jung et al. 2003), and as the causal agent of stem lesions on beech in Europe (Scanu and Webber 2016). In August 2015, a beech (Fagus sylvatica L.) tree displaying 25\% crown dieback and a bleeding canker at the base of the stem was observed in a forested area used for recreational purpose in Central Pyrenees (42{\textdegree}36.87' N, 0{\textdegree}46.09' E, 1,546 m above sea level). Coarse sections of wood surrounding the bleeding patches were sampled and kept moist and cold for 5 days until processed. Once in the laboratory, small phloem pieces from the margin of the lesion were plated onto corn meal agar-PARPBH medium (Jeffers and Martin 1986) and incubated at 20{\textdegree}C. Growing hyphae were transferred to V8 agar and incubated at 20{\textdegree}C in darkness. Colony growth on V8 medium averaged 3.4 cm/week and had a distinct stellate pattern. Sporangia were sympodial, semipapillate, and ovoid, with a length/breadth average ratio of 1.41 μm (SE = 0.02). Oogonia were 21.9 μm (SE = 0.49) in diameter, smoothly walled, spherical, and with paraginous antheridia, although some amphiginous antheridia were observed. Morphological features and growth appearance on V8 corresponded to those reported for P. pseudosyringae (Jung et al. 2003). DNA was extracted from mycelium, and the ITS region was amplified using the ITS4 and ITS6 primers (Cooke et al. 2000). A BLAST search of the sequenced isolate (submitted to GenBank, Accession No. KU321521) showed 100\% identity with P. pseudosyringae ITS sequence (AY230190) from Jung et al. (2003). An under-bark inoculation test with mycelia plugs were performed on 16 excised shoots of 1 cm of diameter obtained from four different F. sylvatica trees. After 4 weeks, inoculated shoots displayed longer necrotic lesions than control inoculations with agar (3.55 cm SE: 2.2 versus 0.59 cm SE: 2.8, P \< 0.0001). The P. pseudosyringae inoculated shoots exhibited lesions that were dark red underneath the bark, whereas the control lesions did not. P. pseudosyringae, which was identified morphologically, was reisolated from 40\% of the infected shoots. No reisolation of the pathogen occurred from any of the six control shoots. Although previously detected in nursery stock on sweet chestnut (Castanea sativa) (Pintos Varela et al. 2007), our report represents the first report of P. pseudosyringae naturally affecting trees in Spain, and widens the geographical distribution of this pathogen in southwestern Europe. In Spain, F. sylvatica is the third species in terms of standing volume, where it covers 400,000 ha, mainly in the Pyrenees. Our finding proves the capacity of this pathogen to establish in nature, and it raises concern over the potential impact on beech forests in Spain.

}, issn = {0191-2917}, doi = {10.1094/PDIS-12-15-1497-PDN}, url = {http://apsjournals.apsnet.org/doi/10.1094/PDIS-12-15-1497-PDN}, author = {Redondo, {\'A}. and Oliva, J.} } @article {4554, title = {First Report of Phytophthora uniformis and P. plurivora Causing Stem Cankers on Alnus glutinosa in Denmark}, journal = {Plant Disease}, year = {2016}, month = {Aug-12-2017}, pages = {PDIS-09-16-1287}, abstract = {

Phytophthora uniformis (Brasier \& S.A. Kirk) Husson, Ioos \& Aguayo, comb. nov. is an aggressive pathogen associated with root and collar rot of alder trees (Alnus spp.) in Europe (Husson et al. 2015). In summer 2016, symptomatic trees were observed in the banks of a backwater lake area of the river Gurre {\r A} (56{\textdegree}1'46.24"N, 12{\textdegree}27'15.30"E, 29 m above sea level). Several trees displayed chlorosis, reduced leaf size, defoliation, and bleeding cankers on the base of the stem. Inspections upstream near Gurre forest failed in finding other trees with similar crown symptoms, whereas a tree with a bleeding canker was observed downstream (56{\textdegree}3'10.97"N, 12{\textdegree}26'4.40"E, 23 m above sea level). Bark from six trees in the first site and from the tree in the second site was removed from the canker area. As described in Redondo et al. (2015), pieces of 1 cm {\texttimes} 0.5 cm {\texttimes} 1 mm of necrotic cambial tissue from the infection front were plated directly into CMA-PARPBH selective medium. Growing hyphae were transferred onto V8 juice agar medium and incubated at 20{\textdegree}C. Isolates from the first site grew 5 mm/day and formed cottony uniform colonies. After 1 week, spherical smooth-walled oogonia often showing two-celled amphigynous antheridia developed profusely ({\O} 39.6 μm; SE = 0.84). Sporangia were ellipsoid and nonpapillate, often with nested proliferation. Colonies from the second site grew 5.5 mm/day, and formed a stellate colony pattern with limited aerial mycelium. Abundant spherical ({\O} 29.8 μm; SE = 0.53) oogonia with paragynous antheridia formed after 1 week. Sporangia were commonly ovoid and semipapillate. DNA was extracted from all isolates and the ITS region was amplified using the ITS4 and ITS6f primers. BLAST searches showed 99\% similarity with P. uniformis sequence no. AF139367.1 for the six isolates from the first site (GenBank accession nos. KX822022 to KX822027), and 99\% similarity with P. plurivora sequence no. FJ665227.1 for the isolate from the second site (KX822028). As morphological characteristics of the first six isolates corresponded to those of the P. alni species complex, primers TRP-PAU-F/-R and RAS-PAM1-F/-R (Ioos et al. 2006) were used to classify them as P. uniformis. ITS patterns from Jung and Burgess (2009) were used to classify the P. plurivora-like isolate as P. plurivora. Pathogenicity of two P. uniformis isolates and the P. plurivora isolate was confirmed by immersing 30 alder seedlings, grown in vermiculite for 3 weeks, in a zoospore suspension of each isolate adjusted to 3 {\texttimes} 104 zoospores ml{\textendash}1 for 3 h. Seedlings were later kept in dark Eppendorf tubes in sterile water, and rewatered daily. After 10 days, mortality was 76.6 and 86.6\% among those inoculated with P. uniformis, and 60\% for those inoculated with P. plurivora. Surviving seedlings after 10 days displayed wilting symptoms, while seedlings immersed in water were symptomless. The roots of the dead seedlings were plated onto CMA-PARPBH selective medium. Growing hyphae were observed in all plated roots, and were transferred to V8 juice agar medium. The reisolated Phytophthora colonies were morphologically similar to P. uniformis and P. plurivora, fulfilling Koch{\textquoteright}s postulates. Our finding raises concern about the future health of alder trees in Denmark, a country from which P. alni has not yet been reported. However, symptoms of Phytophthora disease have been observed on alder since 1995 (Thinggaard 1996). Further monitoring should investigate the extent of the outbreak.

}, issn = {0191-2917}, doi = {10.1094/PDIS-09-16-1287-PDN}, url = {http://apsjournals.apsnet.org/doi/10.1094/PDIS-09-16-1287-PDN}, author = {Redondo, {\'A}. and Thomsen, I. M. and Oliva, J.} } @article {4321, title = {Winter Conditions Correlate with Phytophthora alni Subspecies Distribution in Southern Sweden}, journal = {Phytopathology}, volume = {105}, year = {2015}, month = {Jan-09-2015}, pages = {1191 - 1197}, abstract = {

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.

}, keywords = {Alnus spp., invasiveness, Phytophthora plurivora}, issn = {0031-949X}, doi = {10.1094/PHYTO-01-15-0020-R}, url = {http://apsjournals.apsnet.org/doi/10.1094/PHYTO-01-15-0020-R}, author = {Redondo, Miguel A. and Boberg, Johanna and Olsson, Christer H. B. and Oliva, Jon{\`a}s} } @article {4315, title = {First Report of Phytophthora occultans Causing Root and Collar Rot on Ceanothus, Boxwood, Rhododendron, and Other Hosts in Horticultural Nurseries in Oregon, USA}, journal = {Plant Disease}, volume = {99}, year = {2015}, month = {Jan-09-2015}, pages = {1282}, abstract = {

Dead and dying Ceanothus sanguineus, C. velutinus, and C. integerrimus plants grown in a native plant nursery in Oregon for landscape restoration were reported in 2011. Plants were wilted with stem lesions above necrotic roots. Using selective media (Hansen et al. 2012), twelve similar Phytophthora isolates were obtained. DNA sequences of the cox 1, β tubulin, and the rDNA ITS regions were generated (Hansen et al. 2012). All isolates had identical ITS sequences (GenBank KP742989), and were identical to Phytophthora occultans (Man in{\textquoteright}t Veld et al. 2014) (JX978155) and 99\% similar to P. himalsilva (HM752784) in a BLAST analysis. They were also identical to P. occultans in cox 1 and β tubulin (KR028484 and KR028483). Isolates were homothallic, with smooth 30-{\textmu}m-diameter oogonia, and slightly aplerotic oospores. Antheridia were mostly paragynous. Colonies were stellate on carrot agar, growing 6 to 7 mm/d at optimum temperature (25{\textdegree}C). Sporangia were ovoid to irregular and papillate. Morphology and growth were consistent with P. occultans. Collections of unidentified Phytophthora spp. from the OSU Plant Clinic and from other Oregon nurseries (J. Parke et al. 2014) revealed additional isolates with similar morphology and identical DNA sequences. P. occultans was identified from boxwood (Buxus spp.), rhododendron, Gaultheria shallon, Arctostaphylos uva-ursi, and Mahonia nervosa in addition to Ceanothus spp. Two inoculation trials were conducted: (i) Healthy 1-year-old plants of C. sanguineus and C. velutinus were stem wound inoculated with two isolates of P. occultans from Ceanothus, or with sterile agar. There were 3 to 5 replications for each host and the control. The test was repeated with addition of two isolates from boxwood. (ii) Boxwood (B. sempervirens) and rhododendron (R. catawbiense Alba) were stem wound inoculated with two isolates each of P. occultans from Ceanothus and boxwood. There were four replications of each host for each isolate. All plants were incubated at 20 to 22{\textdegree}C. In test 1, all isolates induced stem lesions and wilting on all inoculated plants of both Ceanothus species. Wilting began in 14 days and lesions, measured at 19 days, averaged about 150 mm. There were no symptoms on control plants. In test 2, lesions developed on rhododendron stems, often girdling the stem within 12 days. Most boxwood showed no foliar symptoms or only mild yellowing, although stem lesions averaging 3.5 cm in 7 weeks were present on all plants. P. occultans was reisolated from all hosts in both tests. P. occultans was recently described from Buxus nursery stock in The Netherlands (Man in{\textquoteright}t Veld et al. 2014), and isolates with identical DNA sequences were reported from Germany and Romania (Nechwatal et al. 2014). This is the first report from North America. It appears that a single clone of P. occultans recently has been spread widely in the nursery trade. P. occultans is similar to P. himalsilva (Vettraino et al. 2011) and to other members of the poorly defined P. citrophthora clade. Phylogenetic analysis may revise species definitions. Nursery plants grown for wildland restoration are at high risk to carry exotic Phytophthora species into vulnerable landscapes. Forest restoration specialists must demand healthy stock from nurseries.

}, issn = {0191-2917}, doi = {10.1094/PDIS-02-15-0156-PDN}, url = {http://apsjournals.apsnet.org/doi/10.1094/PDIS-02-15-0156-PDN}, author = {Reeser, P. W. and Sutton, W. and Hansen, E. M. and Goheen, E. M. and Fieland, V. J. and Gr{\"u}nwald, N. J.} } @proceedings {reeser2010phytophthora, title = {Phytophthora siskiyouensis, a new species from soil and water in southwest Oregon}, volume = {General Technical Report PSW-GTR-214}, year = {2010}, month = {03/2008}, pages = {439{\textendash}441}, publisher = {U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station, Albany, CA}, address = {Santa Rosa, CA}, keywords = {coast live oak, invasive species, Phytophthora ramorum, Sudden oak death, tanoak}, url = {http://www.fs.fed.us/psw/publications/documents/psw_gtr214/}, author = {P. Reeser and E. Hansen and Sutton, W.}, editor = {Susan J. Frankel and John T. Kliejunas and Katharine M. Palmieri} } @article {PaulW.Reeser01012011, title = {Phytophthora species in forest streams in Oregon and Alaska}, journal = {Mycologia}, volume = {103}, number = {1}, year = {2011}, pages = {22-35}, abstract = {

Eighteen Phytophthora species and one species of Halophytophthora were identified in 113 forest streams in Alaska, western Oregon and southwestern Oregon that were sampled by baiting or filtration of stream water with isolation on selective media. Species were identified by morphology and DNA characterization with single strand conformational polymorphism, COX spacer sequence and ITS sequence. ITS Clade 6 species were most abundant overall, but only four species, P. gonapodyides (37\% of all isolates), P. taxon Salixsoil, P. taxon Oaksoil and P. pseudosyringae, were found in all three regions. The species assemblages were similar in the two Oregon regions, but P. taxon Pgchlamydo was absent in Alaska and one new species present in Alaska was absent in Oregon streams. The number of Phytophthora propagules in Oregon streams varied by season and in SW Oregon, where sampling continued year round, P. taxon Salixsoil, P. nemorosa and P. siskiyouensis were recovered only in some seasons.

}, doi = {10.3852/10-013}, url = {http://www.mycologia.org/cgi/content/abstract/103/1/22}, author = {Reeser, Paul W. and Sutton, Wendy and Hansen, Everett M. and Remigi, Philippe and Adams, Gerry C.} } @proceedings {431, title = {Phytophthora species associated with stem cankers on tanoak in southwestern Oregon}, year = {2007}, address = {Santa Rosa CA}, author = {P. Reeser and Sutton, W. and Hansen, E.M.} } @article {4186, title = {Phytophthora pluvialis, a new species from mixed tanoak-Douglas-fir forests of western Oregon, U.S.A.}, journal = {North American Fungi}, volume = {8(7)}, year = {2013}, month = {May/2013}, pages = {1-8}, abstract = {

A new species, Phytophthora pluvialis is described. P. pluvialis has been recovered from streams, soil and canopy drip in the mixed tanoak-Douglas-fir forest in Curry County, Oregon, and in two additional streams in other areas of western Oregon. It has been found only rarely in association with twig and stem cankers on tanoak but not with any other plant host. The earliest isolate of P. pluvialis was from soil in 2002. P. pluvialis is classified in ITS Clade 3.

}, keywords = {canopy drip, environmental Phytophthora, oomycetes, rainwater, soil, streams}, doi = {10.2509/naf2013.008.007}, url = {http://dx.doi.org/10.2509/naf2013.008.007}, author = {Reeser, P. and Sutton, Wendy and Hansen, Everett} } @article {4659, title = {Phytophthora species in forest streams in Oregon and Alaska}, journal = {Mycologia}, volume = {103}, year = {2011}, month = {Aug-01-2012}, pages = {22 - 35}, abstract = {

Eighteen Phytophthora species and one species of Halophytophthora were identified in 113 forest streams in Alaska, western Oregon and southwestern Oregon that were sampled by baiting or filtration of stream water with isolation on selective media. Species were identified by morphology and DNA characterization with single strand conformational polymorphism, COX spacer sequence and ITS sequence. ITS Clade 6 species were most abundant overall, but only four species, P. gonapodyides (37\% of all isolates), P. taxon Salixsoil, P. taxon Oaksoil and P. pseudosyringae, were found in all three regions. The species assemblages were similar in the two Oregon regions, but P. taxon Pgchlamydo was absent in Alaska and one new species present in Alaska was absent in Oregon streams. The number of Phytophthora propagules in Oregon streams varied by season and in SW Oregon, where sampling continued year round, P. taxon Salixsoil, P. nemorosa and P. siskiyouensis were recovered only in some seasons.

}, issn = {0027-5514}, doi = {10.3852/10-013}, url = {https://www.tandfonline.com/doi/pdf/10.3852/10-013}, author = {Reeser, Paul W. and Sutton, Wendy and Hansen, Everett M. and Remigi, Philippe and Adams, Gerry C.} } @article {PaulW. Reeser09012007, title = {Phytophthora siskiyouensis, a new species from soil, water, myrtlewood (Umbellularia californica) and tanoak (Lithocarpus densiflorus) in southwestern Oregon}, journal = {Mycologia}, volume = {99}, number = {5}, year = {2007}, pages = {639-643}, abstract = {

An unknown Phytophthora species was recovered in southwestern Oregon from rhododendron and tanoak leaf baits used for monitoring streams and soils for the presence of Phytophthora ramorum, from a blighted shoot of myrtlewood and from tanoak bark cankers. Isolates of this species yielded ITS-DNA sequences that differed substantially from other Phytophthora sequences in GenBank. Morphological features also differed from available descriptions of known Phytophthora species. Based on the combination of unique morphology and unique ITS sequences a new species is proposed. The new species, Phytophthora siskiyouensis, is homothallic with globose to subglobose oogonia, which may be terminal, sessile or laterally intercalary. Antheridia are capitate and mostly paragynous but sometimes amphigynous. Oospores are mostly aplerotic. Sporangia are variable but commonly ovoid to reniform, with apical, subapical or lateral semipapillae (occasionally more than one). Sporangia are terminal, subterminal or occasionally intercalary on unbranched sporangiophores, with basal, subbasal or lateral attachment. Sporangia are weakly deciduous, with variable length pedicels. This combination of characters clearly separates Phytophthora siskiyouensis from other known Phytophthora species.

}, doi = {10.3852/mycologia.99.5.639}, url = {http://www.mycologia.org/cgi/content/abstract/99/5/639}, author = {Reeser, Paul W. and Hansen, Everett M. and Sutton, Wendy} } @article {1318, title = {Phytophthora species causing tanoak stem cankers in southwestern Oregon}, journal = {Plant Disease}, volume = {92}, year = {2008}, month = {08/2008}, pages = {1252}, abstract = {

Tanoak (Lithocarpus densiflorus) is a principal host of Phytophthora ramorum, cause of sudden oak death (SOD), in the western United States (1). In the course of SOD surveys in southwestern Oregon, other Phytophthora species were encountered to be causing stem cankers on tanoak that were indistinguishable from those caused by P. ramorum. In Oregon, SOD is subject to quarantine and eradication. Aerial surveys are flown two or more times a year to locate symptomatic tanoaks, which are then examined from the ground to determine the cause of death. Isolations on selective media were attempted from all trees with stem cankers typical of Phytophthora. Phytophthora species were identified by morphological features and DNA sequencing of either internal transcribed spacer (ITS) or the mitochondrial COX spacer region. ITS sequences were compared with validated GenBank records, and COX spacer sequences were compared with known reference isolates in the OSU collection. From 2001 through 2006, Phytophthora spp. were isolated from 482 of 1,057 tanoak stem cankers sampled. P. ramorum was isolated from 359 cankers, P. nemorosa was isolated from 102 cankers, P. gonapodyides was isolated from six cankers, P. cambivora was isolated from four cankers (all A1 mating type), P. siskiyouensis was isolated from four cankers, P. pseudosyringae was isolated from two cankers, P. cinnamomi was isolated from one canker (mating type A2), and P. taxon {\textquotedblleft}Pgchlamydo{\textquotedblright} was isolated from one canker. Three cankers yielded isolates that were not identified but were closely related to P. pseudosyringae based on ITS sequence. No Phytophthora spp. were cultured from the remaining cankers. One isolate from each species identified (except P. ramorum and P. pseudosyringae) was tested for pathogenicity on tanoak stems (11.4 to 16.0 cm DBH) in the field. A 5-mm-diameter plug from the margin of a V8 agar culture was placed in a hole in the bark, covered with wet cheesecloth, and sealed with aluminum foil and duct tape. Each isolate was inoculated into five different stems. Each stem received three different isolates and an agar control. After 4 weeks, bark was removed to reveal lesion development. Lesions were measured (length by width), and pieces from four points on the lesion margin were plated in selective media to reisolate. P. cambivora, P. cinnamomi, P. gonapodyides, P. nemorosa, P. siskiyouensis and P. taxon {\textquotedblleft}Pgchlamydo{\textquotedblright} all caused substantial lesions in inoculated tanoak trees (average area 11.5 to 18.6 cm2). In all cases, the species used for inoculation was recovered on reisolation from lesion margins. Control inoculations caused necrotic areas averaging 0.2 cm2. Isolations from these areas were clean. Prior to the recent SOD epidemic, no species of Phytophthora were known as pathogens of tanoak. The discovery of P. ramorum as a pathogen of tanoak in California was quickly followed by the discovery that P. nemorosa and P. pseudosyringae were also associated with tanoak cankers (2). Six years of diagnostic support for survey and detection of P. ramorum in tanoak forests of southwest Oregon has revealed the occurrence, at very low frequency, of at least five additional species of Phytophthora causing stem cankers in tanoak.

}, url = {http://dx.doi.org/10.1094/PDIS-92-8-1252B}, author = {Reeser, Paul W. and Sutton, W. and Hansen, E.M.} } @proceedings {225, title = {Phytophthora species in tanoak trees, canopy drip, soil, and streams in the sudden oak death epidemic area in southwestern Oregon.}, year = {2010}, publisher = {N. Z. J. Forestry}, address = {Auckland and Rotorua, New Zealand}, author = {Reeser, Paul and Sutton, Wendy and Everett Hansen} } @article {4256, title = {Comparative study of Phytophthora faberi on coconut and cacao in the Philippine Islands}, journal = {Journal of Agricultural Research }, volume = {25}, year = {1923}, pages = {267-284}, url = {http://worldcocoafoundation.org/wp-content/files_mf/reinking1923.pdf}, author = {Reinking, OA} } @article {4695, title = {Detection and spread of Phytophthora austrocedri within infected Juniperus communis woodland and diversity of co-associated Phytophthoras as revealed by metabarcoding}, journal = {Forest Pathology}, volume = {50}, year = {2020}, month = {May-17-2020}, pages = {e12602}, abstract = {

Phytophthora austrocedri is a recently invasive soilborne pathogen which is causing widespread mortality of Juniperus communis in northern Britain. The pathways by which a single genotype of P. austrocedri has spread to infect such a geographically dispersed range of woodland sites within a relatively short timeframe are unknown. This study examined the detectability of P. austrocedri in soil and water within infected J. communis woodland using qPCR to gain a better understanding of the pathogen{\textquoteright}s key mechanisms of spread. A Phytophthora metabarcoding method was also applied to investigate the wider diversity of Phytophthora species present in water at one of the sites. qPCR analyses of P. austrocedri in soil samples at a J. communis woodland exhibiting low-to-moderate levels of disease suggested a slow natural spread of the pathogen in soil, requiring high moisture conditions. However, the ubiquity of P. austrocedri DNA in soil samples collected across a heavily infected J. communis site suggests that once established at a site the pathogen can be spread readily in soil locally, most likely vectored by animal movements and/or human activities. The hypothesis that P. austrocedri is aerially transmitted in rainwater was not adequately proven, and an alternative hypothesis for the widespread distribution of the pathogen on J. communis in northern Britain is presented. Metabarcoding identified DNA from a diverse range of Phytophthora species in river and rainwater samples although the main target pathogen, P. austrocedri, was not amplified which disagreed with some of the qPCR findings. Possible reasons for this are discussed.

}, doi = {10.1111/efp.v50.310.1111/efp.12602}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/efp.12602}, author = {Riddell, Carolyn E. and Dun, Heather F. and Elliot, Matt and Armstrong, April C. and Clark, Mhairi and Forster, Jack and Hedley, Pete E. and Green, Sarah} } @article {4203, title = {In Situ Production of Zoospores by Five Species of Phytophthora in Aqueous Environments for Use as Inocula}, journal = {Plant Disease}, volume = {98}, year = {2014}, month = {Jan-04-2014}, pages = {551 - 558}, abstract = {

The goal of this study was to develop a procedure that could be used to evaluate the potential susceptibility of aquatic plants used in constructed wetlands to species of Phytophthora commonly found in nurseries. V8 agar plugs from actively growing cultures of three or four isolates of Phytophthora cinnamomi, P. citrophthora, P. cryptogea, P. nicotianae, and P. palmivora were used to produce inocula. In a laboratory experiment, plugs were placed in plastic cups and covered with 1.5\% nonsterile soil extract solution (SES) for 29 days, and zoospore presence and activity in the solution were monitored at 2- or 3-day intervals with a rhododendron leaf disk baiting bioassay. In a greenhouse experiment, plugs of each species of Phytophthora were placed in plastic pots and covered with either SES or Milli-Q water for 13 days during both summer and winter months, and zoospore presence in the solutions were monitored at 3-day intervals with the baiting bioassay and by filtration. Zoospores were present in solutions throughout the 29-day and 13-day experimental periods but consistency of zoospore release varied by species. In the laboratory experiment, colonization of leaf baits decreased over time for some species and often varied among isolates within a species. In the greenhouse experiment, bait colonization decreased over time in both summer and winter, varied among species of Phytophthora in the winter, and was better in Milli-Q water. Zoospore densities in solutions were greater in the summer than in the winter. Decreased zoospore activities for some species of Phytophthora were associated with prolonged temperatures below 13 or above 30{\textdegree}C in the greenhouse. Zoospores from plugs were released consistently in aqueous solutions for at least 13 days. This procedure can be used to provide in situ inocula for the five species of Phytophthora used in this study so that aquatic plant species can be evaluated for potential susceptibility.

}, issn = {0191-2917}, doi = {10.1094/PDIS-06-13-0591-RE}, url = {http://apsjournals.apsnet.org/doi/abs/10.1094/PDIS-06-13-0591-RE}, author = {Ridge, G. A. and Jeffers, S. N. and Bridges, W. C. and White, S. A.} } @article {727, title = {First Report of Phytophthora ramorum infecting grand fir in California}, journal = {Plant Health Progress}, volume = {2011}, year = {2011}, month = {1 April 2011}, publisher = {Plant Management Network}, abstract = {

Phytophthora ramorum was detected on grand fir in 2003 and 2005 in a Christmas tree plantation near Los Gatos, CA, in association with infected California bay laurel. Isolates derived from stem lesions were used to inoculate grand fir seedlings in two tests. Isolations from lesions on inoculated plants were positive for P. ramorum in both tests. This work provides the completion of Koch{\textquoteright}s postulates to establish grand fir as a host of P. ramorum. The potential for grand fir to be infected within its native range is unknown.

}, doi = {10.1094/PHP-2011-0401-01-BR}, url = {http://www.plantmanagementnetwork.org/sub/php/brief/2011/grand/}, author = {Kathleen L. Riley and Chastagner, Gary A. and Cheryl Blomquist} } @article {4479, title = {Screening brassicaceous plants as biofumigants for management of Phytophthora cinnamomi oak disease}, journal = {Forest Pathology}, year = {2016}, month = {Jan-06-2016}, abstract = {

Brassicaceous plants rich in glucosinolates have been used as biofumigants for the management of soilborne pathogens. Efficacy of Brassica plant tissue has mainly been attributed to toxic isothiocyanates released upon the hydrolysis of glucosinolates. Management of Phytophthora cinnamomi, the causal agent of oak root rot in rangeland ecosystems using biofumigation, is promising, but requires further validation. The biofumigation activity of 14 brassicaceous plants was evaluated under experimental conditions. All evaluated plants rich in sinigrin suppressed (100\%) the mycelial growth of P.\ cinnamomi, while plants rich in aromatic or other aliphatic glucosinolates had little or no suppressive effect. Simulating soil amendment in field conditions, the effects on natural soil artificially infested with P.\ cinnamomi chlamydospores were examined with Brassica juncea, Eruca vesicaria and Lepidium sativum, three species with different glucosinolate profiles. Only B.\ juncea decreased the viability of chlamydospores significantly in comparison with untreated soil only 1\ day after biofumigation, whereas E. vesicaria needed 8\ days to reach significance and L.\ sativum had no effect at all. Despite the decreases in soil inoculum, biofumigation with B.\ juncea did not prevent the root infections in a highly susceptible host (Lupinus luteus). However, biofumigation with plants rich in sinigrin, such as B.\ juncea, decreased P.\ cinnamomi soil inoculum under the experimental minimum threshold for oak disease expression. Although biofumigation should be considered as an effective measure to be incorporated in integrated control of the oak disease, biofumigation by itself would not be effective enough for the substantial suppression of P.\ cinnamomi inoculum.

}, doi = {10.1111/efp.12287}, url = {http://doi.wiley.com/10.1111/efp.12287http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111\%2Fefp.12287}, author = {R{\'\i}os, P. and Obreg{\'o}n, S. and Gonz{\'a}lez, M. and de Haro, A. and Sanchez, M. E.}, editor = {Woodward, S.} } @article {4478, title = {Effect of Brassica Biofumigant Amendments on Different Stages of the Life Cycle of Phytophthora cinnamomi}, journal = {Journal of Phytopathology}, year = {2016}, month = {Jan-05-2016}, abstract = {

The oomycete plant pathogen Phytophthora cinnamomi causes a highly destructive root rot that affects numerous hosts. Integrated management strategies are needed to control P.\ cinnamomi in seminatural oak rangelands. We tested how biofumigation affects crucial stages of the pathogen{\textquoteright}s life cycle in\ vitro, in infested soils under laboratory conditions and in planta. Different genotypes of three potential biofumigant plant species (Brassica carinata, Brassica juncea, Brassica napus) were collected at different phenological stages, analysed for their glucosinolate contents, and subsequently tested. The most effective genotypes against mycelial growth and sporangial production were further tested on the viability of chlamydospores in artificially infested natural soils and in planta on Lupinus luteus, a host highly susceptible to P.cinnamomi. Brassica carinata and B.\ juncea genotypes inhibited mycelial growth, decreased sporangial production, and effectively inhibited the viability of chlamydospores in soil, but only B.\ carinata decreased disease symptoms in plants. Effective genotypes of Brassica had high levels of the glucosinolate sinigrin. Biofumigation with Brassica plants rich in sinigrin has potential to be a suitable tool for control of oak root disease caused by P.\ cinnamomi in Spanish oak rangeland ecosystems.

}, doi = {10.1111/jph.12482}, url = {http://doi.wiley.com/10.1111/jph.12482http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111\%2Fjph.12482}, author = {R{\'\i}os, Pedro and Oberg{\'o}n, Sara and de Haro, Antonio and Fern{\'a}ndez-Rebollo, Pilar and Serrano, Mar{\'\i}a-Socorro and S{\'a}nchez, Mar{\'\i}a-Esperanza} } @article {1218, title = {A Lucid key to the common species of Phytophthora}, journal = {Plant Disease}, volume = {96}, year = {2012}, month = {06/2012}, pages = {897-903}, abstract = {

The Key to the Common Phytophthora species (Lucid v 3.4) is a matrix-based computerized identification key and includes important morphological and molecular characters that are useful for identification of 55 common species of Phytophthora. A set of 20 features are used to make a correct species identification. Once a culture is obtained, the user enters responses to known character state options into Lucid Player and the correct species is identified. Illustrations of each character state for a feature are included in the key. The main morphological features included in the key are: asexual structures, sexual structures, and chlamydospore, hyphae and cultural characteristics. The user can read an illustrated {\textquotedblleft}Fact Sheet{\textquotedblright} on each species that includes pictures of morphological characters, disease symptoms, host range and relevant references. A cross-linked glossary of terminology is included in each fact sheet. In addition, a DNA Search function that contains a simple search of ITS and Barcode of Life (BOL, 5{\textquoteright} end of the cox1 gene) sequences for each species can be queried. The key was created to provide teachers, diagnosticians and regulatory personnel with easily accessible tools to distinguish common species in the genus Phytophthora based on a number of important morphological and molecular characteristics. The key is available for purchase from APS Press and should provide another useful tool for the identification of members of this destructive group of Oomycete plant pathogens.

}, issn = {0191-2917}, doi = {10.1094/PDIS-08-11-0636}, url = {http://dx.doi.org/10.1094/PDIS-08-11-0636}, author = {Ristaino, Jean Beagle} } @article {doi:10.1094/PDIS.2002.86.3.205, title = {Phytophthora ramorum as the cause of extensive mortality of Quercus spp. and Lithocarpus densiflorus in California}, journal = {Plant Disease}, volume = {86}, number = {3}, year = {2002}, pages = {205-214}, abstract = {

A new canker disease, commonly known as sudden oak death, of Lithocarpus densiflorus, Quercus agrifolia, Q. kelloggii, and Q. parvula var. shrevei in California is shown to be caused by Phytophthora ramorum. The pathogen is a recently described species that previously was known only from Germany and the Netherlands on Rhododendron spp. and a Viburnum sp. This disease has reached epidemic proportions in forests along approximately 300 km of the central coast of California. The most consistent and diagnostic symptoms on trees are cankers that develop before foliage symptoms become evident. Cankers have brown or black discolored outer bark and seep dark red sap. Cankers occur on the trunk at the root crown up to 20 m above the ground, but do not enlarge below the soil line into the roots. Individual cankers are delimited by thin black lines in the inner bark and can be over 2 m in length. In L. densiflorus saplings, P. ramorum was isolated from branches as small as 5 mm in diameter. L. densiflorus and Q. agrifolia were inoculated with P. ramorum in the field and greenhouse, and symptoms similar to those of naturally infected trees developed. The pathogen was reisolated from the inoculated plants, which confirmed pathogenicity.

}, doi = {10.1094/PDIS.2002.86.3.205}, url = {http://apsjournals.apsnet.org/doi/abs/10.1094/PDIS.2002.86.3.205}, author = {D. M. Rizzo and Garbelotto, M. and J. M. Davidson and Slaughter, G. W. and Koike, S. T.} } @article {rizzo2005phytophthora, title = {Phytophthora ramorum: integrative research and management of an emerging pathogen in California and Oregon forests}, journal = {Annual Review of Phytopathology}, volume = {43}, number = {1}, year = {2005}, pages = {309}, abstract = {

Phytophthora ramorum, causal agent of sudden oak death, is an emerging plant pathogen first observed in North America associated with mortality of tanoak (Lithocarpus densiflorus) and coast live oak (Quercus agrifolia) in coastal forests of California during the mid-1990s. The pathogen is now known to occur in North America and Europe and have a host range of over 40 plant genera. Sudden oak death has become an example of unintended linkages between the horticultural industry and potential impacts on forest ecosystems. This paper examines the biology and ecology of P. ramorum in California and Oregon forests as well discussing research on the pathogen in a broader management context.

}, doi = {10.1146/annurev.phyto.42.040803.140418}, url = {http://www.annualreviews.org/toc/phyto/43/1}, author = {D. M. Rizzo and Garbelotto, M. and Hansen, E.M.} } @article {MEN:MEN3041, title = {DNA barcoding of oomycetes with cytochrome c oxidase subunit I and internal transcribed spacer}, journal = {Molecular Ecology Resources}, volume = {11}, number = {6}, year = {2011}, pages = {1002{\textendash}1011}, publisher = {Blackwell Publishing Ltd}, abstract = {

Oomycete species occupy many different environments and many ecological niches. The genera Phytophthora and Pythium for example, contain many plant pathogens which cause enormous damage to a wide range of plant species. Proper identification to the species level is a critical first step in any investigation of oomycetes, whether it is research driven or compelled by the need for rapid and accurate diagnostics during a pathogen outbreak. The use of DNA for oomycete species identification is well established, but DNA barcoding with cytochrome c oxidase subunit I (COI) is a relatively new approach that has yet to be assessed over a significant sample of oomycete genera. In this study we have sequenced COI, from 1205 isolates representing 23 genera. A comparison to internal transcribed spacer (ITS) sequences from the same isolates showed that COI identification is a practical option; complementary because it uses the mitochondrial genome instead of nuclear DNA. In some cases COI was more discriminative than ITS at the species level. This is in contrast to the large ribosomal subunit, which showed poor species resolution when sequenced from a subset of the isolates used in this study. The results described in this paper indicate that COI sequencing and the dataset generated are a valuable addition to the currently available oomycete taxonomy resources, and that both COI, the default DNA barcode supported by GenBank, and ITS, the de facto barcode accepted by the oomycete and mycology community, are acceptable and complementary DNA barcodes to be used for identification of oomycetes.

}, keywords = {cytochrome c oxidase subunit I, DNA barcoding, internal transcribed spacer, oomycete, species identification}, issn = {1755-0998}, doi = {10.1111/j.1755-0998.2011.03041.x}, url = {http://dx.doi.org/10.1111/j.1755-0998.2011.03041.x}, author = {Robideau, Gregg P. and De Cock, Arthur W. a. M. and Michael D. Coffey and Voglmayr, Hermann and Brouwer, Henk and Bala, Kanak and Chitty, David W. and D{\'e}saulniers, Nicole and Eggertson,Quinn A. and Gachon, Claire M. M. and Hu, Chia-Hui and K{\"u}pper, Frithjof C. and Rintoul, Tara L. and Sarhan, Ehab and Verstappen, Els C. P. and Zhang, Yonghong and Peter J.M. Bonants and Ristaino, Jean B. and Andr{\'e} L{\'e}vesque, C.} } @article {198, title = {Root and aerial infections of Chamaecyparis lawsoniana by Phytophthora lateralis: a new threat for European countries}, journal = {Forest Pathology}, volume = {41}, year = {2010}, month = {10/2011}, pages = {417{\textendash}424}, doi = {10.1111/j.1439-0329.2010.00688.x}, url = {http://dx.doi.org/10.1111/j.1439-0329.2010.00688.x}, author = {Robin, C. and Piou, D. and Feau, N. and Douzon, G. and Schenck, N. and Hansen, E.M.} } @article {4238, title = {Pathogenicity of Phytophthora lateralis lineages on resistant and susceptible selections of Chamaecyparis lawsoniana}, journal = {Plant Disease}, year = {2014}, month = {Oct-10-2015}, abstract = {

Phytophthora lateralis, the cause of Chamaecyparis lawsoniana root disease, was introduced in North America about 1950, and has since killed trees along roads and streams throughout the tree{\textquoteright}s range. Recent results suggest an Asian origin for this Oomycete and four genetic lineages were identified. This raised questions for the genetic exapted resistance demonstrated in 1989 within the wild population of C. lawsoniana but with only one P. lateralis lineage. The main goal of the present research was to test the durability of the demonstrated resistance and to compare the pathogenicity of isolates representing the four lineages. No breakdown of resistance was observed in five separate tests using different inoculation techniques, resistant and susceptible C. lawsoniana trees, and seedling families. Differences in mortality and lesion length were observed between the lineages. The higher aggressiveness of isolates of the TWJ and PNW lineages and the lower aggressiveness of the TWK lineage are discussed in view of the hypotheses on the history of spread and evolutionary history of the P. lateralis lineages.

}, issn = {0191-2917}, doi = {10.1094/PDIS-07-14-0720-RE}, url = {http://apsjournals.apsnet.org/doi/abs/10.1094/PDIS-07-14-0720-RE}, author = {Robin, C{\'e}cile and Brasier, Clive and Reeser, Paul W and Sutton, Wendy and Vannini, Andrea and Vettraino, Anna Maria and Hansen, Everett} } @article {doi:10.1139/x92-047, title = {Spatial and temporal enlargement of trunk cankers of Phytophthora cinnamomi in red oak}, journal = {Canadian Journal of Forest Research}, volume = {22}, number = {3}, year = {1992}, pages = {362-366}, abstract = {

Phytophthora cinnamomi Rands is the agent of ink disease on northern red oak (Quercus rubra L.). Cortical cankers on the trunk are the visible symptoms. The fungus causes necrosis of the cambium and phloem, and the tree reacts by forming xylem callus curls. These features can be dated aposteriori on cross sections. The aim of this study was to describe the spatial and temporal development of cankers on cross-sectioned infected oaks. For each lesion, dates of cambium necrosis and formation of callus were recorded at different heights. The following parameters were measured for each lesion: age, height, rate of development, and length and duration of necrosis and canker. Two hundred sixty-three lesions, on 14 trees, were studied. Trees did not exhibit cankers before 9 years of age. All visible trunk cankers could be related to a collar lesion. Phytophthora cinnamomi spreads upwards and can persist for several years, being active seasonally. In this study cambium necrosis occurred preferentially during the first flush. Twenty-nine percent of the lesions were healed over at the collar after 1 year. The collar was less susceptible than the trunk. The other lesions spread rapidly in the cambium of the trunk, which was very vulnerable. They then progressively healed. Therefore, the canker progress curve was bell shaped.

}, doi = {10.1139/x92-047}, url = {http://www.nrcresearchpress.com/doi/abs/10.1139/x92-047}, author = {Robin, C{\'e}cile and Desprez-Loustau, Marie-Laure and Delatour, Claude} } @article {doi:10.1139/x92-048, title = {Factors influencing the enlargement of trunk cankers of Phytophthora cinnamomi in red oak}, journal = {Canadian Journal of Forest Research}, volume = {22}, number = {3}, year = {1992}, pages = {367-374}, abstract = {

Development of cankers on red oak (Quercus rubra L.) caused by Phytophthora cinnamomi Rands was studied with dendrochronological techniques. Factors of variation among lesions were investigated. Lesion parameters proved to vary with the particular tree to which the lesion belonged. A discriminant factorial analysis and principal component analysis showed that this tree susceptibility was made up of two components. The first accounted for root infection and wound healing. The second concerned susceptibility to vertical spread of the pathogen in bark tissues. Relationships between (i) tree susceptibility and (ii) tree age and vigor were studied. From the occurrence of the first lesion at the collar, number and severity of lesions increased with time, following an exponential and logistic curve, respectively. A comparison of ring widths in infected and healthy trees showed that the disease had no detrimental effect on tree growth. However, annual necrosis length was positively correlated with the annual radial tree growth. The observed differences among trees could not be explained by the effects of time and vigor only. Temperature and drought were analyzed to determine their effect on lesion development. No direct effect of drought on this disease could be shown. The low cold hardiness of P. cinnamomi in the trunk was determined.

}, doi = {10.1139/x92-048}, url = {http://www.nrcresearchpress.com/doi/abs/10.1139/x92-048}, author = {Robin, C{\'e}cile and Desprez-Loustau, Marie-Laure and Delatour, Claude} } @article {EFP:EFP423, title = {Seasonal and spatial mortality patterns of holm oak seedlings in a reforested soil infected with Phytophthora cinnamomi}, journal = {Forest Pathology}, volume = {35}, number = {6}, year = {2005}, pages = {411{\textendash}422}, publisher = {Blackwell Verlag GmbH}, abstract = {

Summary The viability of 1-year-old holm oak (Quercus ilex) seedlings in a soil naturally infected with Phytophthora cinnamomi was studied during 2 consecutive years in a plot located in south-western Spain. In both years, total mortality during autumn and winter was not noticeable (\<2.1\%). In spring, mortality levels were higher (8.3{\textendash}4.6\%), especially the first year. A steep increase in total mortality occurred in summer, both in the first (11.4\%) and second (24.2\%) year, but mortality attributable to P. cinnamomi was 1.9 and 7.6\%, respectively. Thus, 2 years after planting, total cumulative mortality was 43.4\%, and that attributable to P. cinnamomi 9.6\% (i.e. 22.1\% of total mortality). Fungus-derived mortality followed a spatially aggregated pattern in the reforestation plot, suggesting a clustered distribution of the inoculum in the soil. Furthermore, mortality by P. cinnamomi was also associated with nearness of infected adult trees in the plot. Results obtained are discussed in the framework of seasonal water deficit, P. cinnamomi damage, weed competition and sanitation techniques to be used in declined holm oak stands in Spain.

}, issn = {1439-0329}, doi = {10.1111/j.1439-0329.2005.00423.x}, url = {http://dx.doi.org/10.1111/j.1439-0329.2005.00423.x}, author = {Rodr{\'\i}guez-Molina, M. C. and Blanco-Santos, A. and Palo-N{\'u}{\~n}ez, E. J. and Torres-Vila, L. M. and Torres-{\'A}lvarez, E. and Su{\'a}rez-de-la-C{\'a}mara, M. A.} } @article {4231, title = {The use of adjuvants to improve uptake of phosphorous acid applied to Pinus radiata needles for control of foliar Phytophthora diseases}, journal = {New Zealand Journal of Forestry Science}, volume = {44}, year = {2014}, month = {Jan-01-2014}, pages = {8}, abstract = {

Background

Phosphorous acid is being investigated as a fungicide for the management of a needle disease caused by Phytophthora pluvialis in Pinus radiata in New Zealand. However, little is known about the penetration characteristics of this fungicide into Pinus radiata foliage. This study was undertaken to determine: i) the penetration characteristics of a commercial phosphorous acid formulation, applied at 3\ kg\ ha-1 and 12\ kg\ ha-1 in 100\ L water, into Pinus radiata foliage and, ii) the effect of four commercially available adjuvants on phosphorous acid uptake into Pinus radiata foliage. Efficacy of the best treatment was tested in vitro with two Phytophthora species, Phytophthora kernoviae and P. pluvialis.

Methods

Foliar uptake of orthophosphoric acid radio-labelled with [32P] was used to determine penetration characteristics of phosphorous acid as affected by the adjuvants tested. Needles collected from potted Pinus radiata plants sprayed with the best performing treatment were used in a detached needle assay, where treated needles were exposed to the zoospores of the Phytophthora species being tested.

Results

Uptake of the phosphorous acid formulation into Pinus radiata needles applied without adjuvants was low (3.9-6.6\%) at both concentrations tested. An alcohol ethoxylate adjuvant (applied at 0.2\%) and two organosilicone adjuvants (applied at 0.2\%) were found to significantly increase uptake of the fungicide over that applied alone or in combination with pinolene (applied at 0.35\%). Highest uptake of phosphorous acid into Pinus radiata foliage (51.6\%) occurred over a period of 72\ hours when the phosphorous acid was applied at the equivalent of 12\ kg\ ha-1 with an organosilicone blend adjuvant at 0.2\%. A significant reduction in lesion length on infected needles was found relative to the control when the two phosphorous acid treatments were applied with 0.2\% organosilicone blend adjuvant. However, there were no significant differences in lesion length between the two treatments.

Conclusions

These results show that an organosilicone adjuvant significantly enhances uptake of phosphorous acid into Pinus radiata needles and may increase its efficacy against Phytophthora species.

}, issn = {1179-5395}, doi = {10.1186/s40490-014-0008-5}, url = {http://www.nzjforestryscience.com/content/44/1/8}, author = {Rolando, Carol and Gaskin, Robyn and Horgan, David and Williams, Nari and Bader, Martin} } @article {4477, title = {Comparison of Five Detection and Quantification Methods for Phytophthora ramorum in Stream and Irrigation Water}, journal = {Plant Disease}, volume = {100}, year = {2016}, month = {Jan-06-2016}, pages = {1202 - 1211}, abstract = {

Propagules of Phytophthora ramorum, the causal agent of sudden oak death (SOD) and ramorum blight, can be recovered from infested stream and nursery irrigation runoff using baiting and filtration methods. Five detection methods, including pear and rhododendron leaf baits, Bottle O{\textquoteright} Bait, filtration, and quantitative polymerase chain reaction (qPCR) performed on zoospores trapped on a filter were compared simultaneously in laboratory assays using lab or creek water spiked with known quantities of P. ramorum zoospores. The detection threshold for each method was determined and methods that could be used to quantify zoospore inoculum were identified. Filtration and qPCR were the most sensitive at detecting low levels of zoospores, followed by wounded rhododendron leaves, rhododendron leaf disks, and pear baits. Filtration, qPCR, and leaf disks were able to quantify P. ramorum zoospores ranging from 2 to 451 direct-plate CFU/liter while wounded leaves and pear baits appeared to be better at detection rather than quantification. The ability to detect and quantify P. ramorum inoculum in water will assist scientists, regulatory agencies, and nursery personnel in assessing the risk of spreading P. ramorum in nurseries and landscape sites where untreated infested water is used for irrigation.

}, issn = {0191-2917}, doi = {10.1094/PDIS-11-15-1380-RE}, url = {http://apsjournals.apsnet.org/doi/10.1094/PDIS-11-15-1380-RE}, author = {Rollins, Lucy and Coats, Katie and Elliott, Marianne and Chastagner, Gary} } @article {4492, title = {Potential risk of occurrence of Phytophthora alni in forests of the Czech Republic}, journal = {Journal of Maps}, year = {2016}, month = {Jun-06-2018}, pages = {1 - 5}, abstract = {

Phytophthora alni is an invasive organism that causes root and collar rot in alders, which significantly damages the forest and riparian vegetation of alder trees in Central and Western Europe. In the Czech Republic, this pathogen was first confirmed in 2001, and since then it has been gradually spreading from the west to the east. Here, we applied a model of potential distribution that estimates the level and spatial variability of the pathogen occurrence and spread risk for Czech Republic forests to target the early detection and control the further invasion of P. alni in this region. Our predictions are based on a rigorous statistical analysis of data obtained from field survey as well as available geodatabases. We used two sets of predictor variables describing (i) the forest stands and (ii) neighbourhood of the stands, and generalized linear modelling with forward stepwise selection of predictors. The results of statistical analysis showed the significant effect of the area of the forest stand, forest vegetation zone, presence of watercourse and area of alder stands in the neighbourhood on the probability of occurrence of P. alni in the study region. The map derived based on the final model shows the potential risk of occurrence and impact of P. alni in forests of the Czech Republic as classified on a five-point scale ranging from very low risk for alder stands with a low level of likely invasion to very sensitive alder stands with high probability of pathogen occurrence and high levels of damage. This is a unique output not only for the Czech Republic but also throughout Europe.

}, doi = {10.1080/17445647.2016.1198996}, url = {http://www.tandfonline.com/doi/full/10.1080/17445647.2016.1198996}, author = {Romportl, Du{\v s}an and Chumanov{\'a}, Eva and Havrdov{\'a}, Ludmila and Pe{\v s}kov{\'a}, V{\'\i}t{\v e}zslava and {\v C}ern{\'y}, Karel} } @article {4337, title = {First detection in the US: new plant pathogen, Phytophthora tentaculata, in native plant nurseries and restoration sites in California}, journal = {Native Plants Journal}, volume = {16}, year = {2015}, month = {Jan-03-2015}, pages = {23 - 27}, abstract = {

Phytophthora tentaculata Kr{\"o}ber \& Marwitz (Pythiaceae) has been detected in several native plant nurseries in 4 California counties and in restoration sites on orange sticky monkey flower (Diplacus aurantiacus (W. Curtis) Jeps. subsp. aurantiacus [Scrophulariaceae]), toyon (Heteromeles arbutifolia (Lindl.) M. Roem. [Rosaceae]), coffeeberry (Frangula californica (Eschsch.) A. Gray [Rhamnaceae]), and sage (Salvia spp. L. [Lamiaceae]). These findings are the first detections of P. tentaculata in the US and the first ever on these host plants. Phytophthora species are a known problem in horticultural nurseries, but little attention has been placed on native plant or restoration nurseries. The potential for plant pathogens to be outplanted along with native plant nursery stock is very high, posing a threat to neighboring forests.

}, issn = {1522-8339}, doi = {10.3368/npj.16.1.23}, url = {http://npj.uwpress.org/cgi/doi/10.3368/npj.16.1.23}, author = {Rooney-Latham, S. and Blomquist, C. L. and Swiecki, T. and Bernhardt, E. and Frankel, S. J.} } @article {4336, title = {First Report of Root and Stem Rot Caused by Phytophthora tentaculata on Mimulus aurantiacus in North America}, journal = {Plant Disease}, volume = {98}, year = {2014}, month = {Jan-07-2014}, pages = {996 - 996}, abstract = {

Sticky monkey flower plant, Mimulus aurantiacus (Phrymaceae), is a small, perennial shrub that is widely distributed throughout California, especially in coastal and disturbed habitats. It is also found in native plantings in parks and landscapes. In October 2012, nearly all the M. aurantiacus plants grown in a Monterey County, CA nursery for a restoration project were stunted and had dull, yellowish leaves. Roots and stem collars had necrotic, sunken lesions with few feeder roots. Thirty percent of the plants had died. Samples of diseased plants were sent to the CDFA-PPDC Lab and tested positive for Phytophthora sp. using the Agdia ELISA Phytophthora kit (Agdia, Elkhart, IN). A Phytophthora sp. was consistently isolated from the tissue on corn meal agar-PARP (CMA-PARP) (2). Sporangia were spherical to ovoid, papillate to bipapillate and 17 to 42.5 (avg. 27.5) {\texttimes} 12 to 35 (avg. 22.9) μm, with a length/breadth ratio of 1.2:1. Chlamydospores, which were spherical, terminal to intercalary, thin walled and 27.5 to 40 μm, and hyphal swellings formed on CMA-PARP. Spherical oospores, 25 to 36 μm, with primarily paragynous antheridia formed readily on V8 juice agar. rDNA sequences of the internal transcribed spacer (ITS) region of the isolates (GenBank KF667505), amplified using primers ITS1 and ITS4, were 100\% identical to Phytophthora tentaculata (CBS 552.96, GenBank AF266775) by a BLAST query (1,3). To assess pathogenicity, exposed root crowns of three 3.78-liter potted M. aurantiacus plants were inoculated with 20 ml of zoospore suspension (2 {\texttimes} 104 ml-1). Plants were maintained in a 23{\textdegree}C growth chamber with a 12-h photoperiod and watered daily. Sterile water was applied to the exposed crowns of three control plants. At 2 weeks, all inoculated plants were wilted with chlorotic foliage. After 3 weeks, the cortical tissue of the crowns and roots was discolored and sloughing and P. tentaculata was recovered on CMA-PARP. P. tentaculata did not grow from the asymptomatic control plants. Inoculations were repeated with similar results. P. tentaculata is a homothallic species in Phytophthora clade 1 that causes crown, root, and stalk rot of nursery plants in Europe and China (1,4). A USDA PERAL analysis lists it as one of the top 5 Phytophthora species of concern to the United States (4). Genera infected with P. tentaculata include Apium, Aucklandia, Chicorium, Chrysanthemum, Delphinium, Gerbera, Lavandula, Santolina, Origanum, and Verbena (4). To our knowledge, this is the first report of P. tentaculata in North America. The source of inoculum of P. tentaculata in California remains unknown. The nursery used seed and cuttings of M. aurantiacus from nearby native areas for propagation, and P. tentaculata was not found in neighboring plant hosts or by baiting soil and water at the nursery. All infected M. aurantiacus material was destroyed. The presence of P. tentaculata in California nurseries could have serious economic impacts on the nursery industry and environmental impacts on susceptible native hosts, if spread into the wildlands.

}, issn = {0191-2917}, doi = {10.1094/PDIS-09-13-1002-PDN}, url = {http://apsjournals.apsnet.org/doi/abs/10.1094/PDIS-09-13-1002-PDN}, author = {Rooney-Latham, S. and Blomquist, C. L.} } @article {213, title = {Collar rot on Italian alder trees in California caused by Phytophthora siskiyouensis}, journal = {Plant Health Progress}, year = {2009}, publisher = {Plant Management Network}, abstract = {

In November 2006, trees of Italian alder (Alnus cordata) were observed declining in association with bleeding trunk cankers in a commercial landscape in Foster City, CA. A species of Phytophthora was isolated on PARP selective medium from the leading edge of the cankers. The Phytophthora species was homothallic with primarily paragynous antheridia and had oospores that were mostly globose and aplerotic. Sporangia were produced from mycelia on plugs of carrot piece agar in soil extraction solution and were semi-papillate and ovoid to ellipsoid in shape. The intergenic transcribed spacer region of rDNA from an alder isolate matched with 100\% identity to isolates in GenBank of Phytophthora siskiyouensis, a recently described species associated with tanoak and found in the soil and waterways of coastal Oregon. Pathogenicity was tested on young alder trees growing in pots. Pathogenicity was confirmed on Italian alder trees and potential pathogenicity was demonstrated on red and white alder trees.

}, doi = {10.1094/PHP-2009-0413-01-RS}, url = {http://www.plantmanagementnetwork.org/sub/php/research/2009/alder/}, author = {Suzanne Rooney-Latham and Cheryl L. Blomquist and Tomas Pastalka and Laurence Costello} } @proceedings {370, title = {First report of Phytophthora siskiyouensis causing disease on Italian alder in Foster City, California}, volume = {Phytopathology 97: S101.}, year = {2007}, month = {July 28{\textendash}August}, publisher = {APS Press, American Phytopathological Society}, address = {San Diego, California}, abstract = {

Phytophthora species cause cankers on the stems of many forest and landscape trees. In November of 2006, Italian alder trees, Alnus cordata, were reported to be dying with symptoms of bleeding cankers located at the base of the stem. The trees were located in a business development outside of a library in Foster City, California. Several of the trees had already been removed as hazardous. Successful isolations were made at the leading edge of the canker from the wood cambium interface onto PARP selective medium. A homothallic Phytophthora with primarily paragynous antheridia grew out in the media. The sporangia, produced easily on carrot agar plugs in soil water were ovoid to ellipsoid in shape. Oospores were mostly globose and aplerotic. The intergenic transcribed spacer region of rDNA of the oomycete matched with 100\% identity to Phytophthora siskiyouensis, a pathogen associated with tan oak and also found in the soil and water in coastal Oregon. Pathogenicity experiments were conducted on Italian, red and white alder. This Phytophthora may be endemic to California. Foster City shares a marine- influenced climate with coastal Oregon.

}, url = {http://apsjournals.apsnet.org/doi/pdf/10.1094/PHYTO.2007.97.7.S1}, author = {Rooney-Latham, S and C. L. Blomquist and T. Pastalka and L. R. Costello} } @article {4217, title = {Studies of the genus Phytophthora}, journal = {Journal of Agricultural Research }, volume = {8}, year = {1917}, pages = {233-276}, author = {Rosenbaum, J.} } @article {4705, title = {Sporulation potential of Phytophthora ramorum differs among common California plant species in the Big Sur region}, journal = {Plant Disease}, year = {2020}, month = {Nov-17-2020}, abstract = {

Sudden oak death (SOD), caused by the generalist pathogen Phytophthora ramorum, has profoundly impacted California coastal ecosystems. SOD has largely been treated as a two-host system, with Umbellularia californica as the most transmissive host, Notholithocarpus densiflorus less so, and remaining species as epidemiologically unimportant. However, this understanding of transmission potential primarily stems from observational field studies rather than direct measurements on the diverse assemblage of plant species. Here, we formally quantify the sporulation potential of common plant species inhabiting SOD-endemic ecosystems on the California coast in the Big Sur region. This study allows us to better understand the pathogen{\textquoteright}s basic biology, trajectory of SOD in a changing environment, and how the entire host community contributes to disease risk. Leaves were inoculated in a controlled laboratory environment and assessed for production of sporangia and chlamydospores, the infectious and resistant propagules, respectively. P. ramorum was capable of infecting every species in our study and almost all species produced spores to some extent. Sporangia production was greatest in N. densiflorus and U. californica and the difference was insignificant. Even though other species produced much less, quantities were non-zero. Thus, additional species may play a previously unrecognized role in local transmission. Chlamydospore production was highest in Acer macrophyllum and Ceanothus oliganthus, raising questions about the role they play in pathogen persistence. Lesion size did not consistently correlate with the production of either sporangia or chlamydospores. Overall, we achieved an empirical foundation to better understand how community composition affects transmission of P. ramorum.

}, issn = {0191-2917}, doi = {10.1094/PDIS-03-20-0485-RE}, url = {https://apsjournals.apsnet.org/doi/10.1094/PDIS-03-20-0485-RE}, author = {Rosenthal, Lisa Micaela and Fajardo, Sebastian N. and Rizzo, David} } @article {415, title = {Spatial pattern of Austrocedrus chilensis wilting and the scope of autocorrelation analysis in natural forests}, journal = {Forest Ecology and Management}, volume = {67}, year = {1994}, month = {AUG 1994}, pages = {273-279}, issn = {0378-1127}, url = {http://dx.doi.org.proxy.library.oregonstate.edu/10.1016/0378-1127(94)90022-1}, author = {Rosso, P. H. and Baccal{\'a}, N and Havrylenko, M and Fontenla, S} } @article {Roth:1 June 1966:0015-749X:147, title = {Phytophthora cinnamomi, an unlikely threat to Douglas-fir forestry}, journal = {Forest Science}, volume = {12}, year = {1966}, pages = {147-159(13)}, abstract = {

Phytophthora cinnamomi has damaged forests around the world in regions with mild climates. Its pathogenesis on Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) in southern Europe and southeastern United States suggested a potential threat to Douglas-fir forests of the Pacific Coast. Concern increased in 1950 with discovery of P. cinnamomi in nurseries growing ornamentals and in landscape plantings in western Oregon and Washington and research was undertaken to evaluate the threat. A temperature of 60{\textdegree} F was found necessary for infection. While summer soil temperatures on south exposures are above 60{\textdegree} F most of the time from June to October soil moisture is continuously below field capacity and too dry for infection. On north exposures summer soil moisture is adequate but temperatures are too low; 60{\textdegree} F is reached for only a few hours near the first of August. Forest soils of western Oregon are generally too dry for infection during the summer. The fall rains provide necessary moisture but concurrently depress temperatures below the critical 60{\textdegree} F. Adverse soil temperature and moisture influence disease by impeding infection rather than reducing survival of P. cinnamomi. The disease in ornamentals is sustained by summer irrigation of warm locations such as the south side of buildings. The data show that P. cinnamomi is unlikely to become a problem in forests of the Pacific Northwest.

}, url = {http://www.ingentaconnect.com/content/saf/fs/1966/00000012/00000002/art00005}, author = {Roth, Lewis F. and Kuhlman, E. George} } @article {241, title = {Port-Orford-cedar disease}, year = {1987}, publisher = {U.S. Department of Agriculture, Forest Service, Pacific Northwest Region}, issn = {Forest Pest Management Report No. R6 FPM PR 010 91}, url = {http://www.fs.fed.us/r6/nr/fid/fidls/poc.htm}, author = {L.F. Roth and Harvey,R.D. and J.T. Kliejunas} } @article {4515, title = {Survey and virulence of fungi occurring on diseased Acacia mearnsii in South Africa}, journal = {Forest Ecology and Management}, volume = {99}, year = {1997}, month = {Jan-12-1997}, pages = {327 - 336}, abstract = {

Various disease symptoms occur on Acacia mearnsii in South Africa, of which black butt, on older trees, is the most common. Other less commonly reported symptoms include gummosis, cracks, discoloured lesions and die-back. These diseases are of unknown aetiology. During a 2-year period, a survey of diseases on A. mearnsii was conducted in two major commercial wattle-growing areas of South Africa. Samples were collected from all symptomatic tissue on randomly selected trees in each area. A wide range of fungi were isolated, including species of Phytophthora, Seiridium, Sphaeropsis, Fusarium, Diplodia, Ceratocystis and Botryosphaeria. Of these, Phytophthora spp. were isolated only from basal lesions and soil, whereas the Diplodia and Fusarium spp. were the most frequently isolated from diseased tissue on aboveground parts of trees. Phytophthora parasitica and Ceratocystis albofundus, which are well-known pathogens of A. mearnsii, were excluded from the pathogenicity tests. All other fungi isolated, and particularly those belonging to genera that are known plant pathogens, were used in pathogenicity tests to determine their possible role in diseases. For each isolate, 20 saplings were inoculated in the field, and the resultant lesion lengths were measured. Only the Phytophthora spp., Botryosphaeria sp. and Sphaeropsis sp. produced noticeable lesions. From the surveys and pathogenicity tests, it is clear that many fungi are associated with diseases of A. mearnsii, and that these deserve further study.

}, issn = {03781127}, doi = {10.1016/S0378-1127(97)00110-2}, url = {https://doi.org/10.1016/s0378-1127(97)00110-2 }, author = {Roux, Jolanda and Wingfield, Michael J.} } @article {4085, title = {Irrigation water and Phytophthora cactorum in a forest nursery}, journal = {Scandinavian Journal of Forest Research}, volume = {23}, year = {2008}, month = {10/2008}, pages = {404 - 411}, abstract = {

Phytophthora cactorum (Lebert and Cohn) J. Schr{\"o}t is known to cause stem lesions on Betula pendula Roth in Finnish nurseries. It has been suggested that irrigation water may be one source of infection. Therefore, P. cactorum was baited from pond water used for irrigation and direct isolations were made from necrotic stem lesions in a forest nursery during the years 2004{\textendash}2006. Morphological characteristics, as well as sequencing of the β-tubulin gene and ITS1 region, confirmed the isolates as P. cactorum. The pathogen was present in the pond every year, but no diseased seedlings were found in 2005. The cultural and morphological characteristics showed high variation among the isolates, but it was not possible to identify the origins of the isolates according to them. In random amplified microsatellite (RAMS) analysis and DNA sequencing, the isolates from the pond and from the stem lesions were genetically similar, and the tested isolates were pathogenic. The results indicate that irrigation water is one source of stem lesion disease, and the microbe can overwinter in the pond. Two separate forms of the β-tubulin gene were detected in all the studied isolates, suggesting that the P. cactorum here carries two β-tubulin gene loci in its genome.

}, issn = {0282-7581}, doi = {10.1080/02827580802419034}, url = {http://www.tandfonline.com/doi/abs/10.1080/02827580802419034$\#$.UqfxDo25Ibg}, author = {Rytk{\"o}nen, Anna and Lilja, Arja and Pet{\"a}ist{\"o}, Raija-Liisa and Hantula, Jarkko} }