@article {4282, title = {Phytophthora austrocedrae emerges as a serious threat to juniper Juniperus communis in Britain}, journal = {Plant Pathology}, volume = {64}, year = {2015}, month = {Jan-04-2015}, pages = {456 - 466}, abstract = {

From 2011 to 2013, Phytophthora austrocedrae was isolated from diseased Juniperus communis exhibiting dieback and mortality at eight geographically separate sites in Scotland and northern England. The pathogen was also confirmed present either by standard PCR of the ITS locus and sequencing or by real-time PCR on J.\ communis with symptoms at a further 11 sites in northern Britain. Out of 167 J.\ communis sampled across the 19 sites, 154 had foliage dieback over all or part of the crown as a result of basal lesions, which extended up the stem. Thirteen sampled trees had aerial branch lesions or discrete stem lesions with no apparent connection to the base of the tree. At 13 sites, dieback was concentrated in areas of poor drainage and/or alongside streams and other watercourses. In artificial inoculation experiments, P.\ austrocedrae caused rapidly extending stem and root lesions on J.\ communis and was reisolated from these lesions. Lesions also developed on Chamaecyparis lawsoniana and Chamaecyparis nootkatensis but the pathogen was not reisolated. All P.\ austrocedrae isolates obtained from J.\ communis in Britain shared 100\% identity across the ITS locus but were distinct at one sequence position from P.\ austrocedrae isolates collected in Argentina from diseased Austrocedrus chilensis. This study provides clear evidence that P.\ austrocedrae is a primary pathogen of J.\ communis and now presents a significant threat to this species in Britain. Pathways for the emergence of P. austrocedrae in Britain, and possible ways in which the pathogen may have spread within the country, are discussed.

}, doi = {10.1111/ppa.2015.64.issue-210.1111/ppa.12253}, url = {http://doi.wiley.com/10.1111/ppa.2015.64.issue-2http://doi.wiley.com/10.1111/ppa.12253}, author = {Green, S. and Elliot, M. and Armstrong, A. and Hendry, S. J.} } @article {EFP:EFP788, title = {The destructive invasive pathogen Phytophthora lateralis found on Chamaecyparis lawsoniana across the UK}, journal = {Forest Pathology}, volume = {43}, year = {2012}, month = {02/2013}, pages = {19{\textendash}28}, abstract = {

In 2010{\textendash}2011, Phytophthora lateralis was isolated from diseased Chamaecyparis lawsoniana exhibiting dieback and mortality at eight geographically separate forest, parkland and shelterbelt locations in England, Scotland and Northern Ireland. In 2011, P.\ lateralis was also isolated from young symptomatic nursery plants of C.\ lawsoniana and Thuja occidentalis recently imported into Scotland from mainland Europe. These are the first findings of P.\ lateralis in the UK. At six of the field sites, only collar and root lesions were observed. However, at two sites, large stem and branch lesions unconnected to the collar region were also observed. Phytophthora lateralis was readily isolated from both aerial and basal lesions. In artificial inoculation experiments, two Scottish isolates of the pathogen caused lesions on C.\ lawsoniana shoots and were readily reisolated from the lesions, their pathogenicity being comparable to that of P.\ lateralis isolates originating from outside the UK. Isolates from six field sites and the two nursery interceptions exhibited ITS and coxII sequences identical to published sequences of French and North American isolates. However, the isolates from two field sites shared an ITS sequence with Taiwanese isolates and differed from North American, French and Taiwanese isolates by a single-base substitution in coxII, suggesting a separate evolutionary history. It is clear that P.\ lateralis now presents a significant threat to C.\ lawsoniana in Britain. The main source of the outbreaks is likely to be imported infested nursery stock.

}, issn = {1439-0329}, doi = {10.1111/j.1439-0329.2012.00788.x}, url = {http://dx.doi.org/10.1111/j.1439-0329.2012.00788.x}, author = {Green, S. and C.M. Brasier and Schlenzig, A. and McCracken, A. and MacAskill, G. A. and Wilson, M. and Webber, JF} } @article {4285, title = {Dieback and mortality of Juniperus communis in Britain associated with Phytophthora austrocedrae}, journal = {New Disease Reports}, volume = {26}, year = {2012}, month = {Jul-12-2014}, pages = {2}, abstract = {

In late 2010 reports were received of serious decline of native juniper (Juniperus communis) at the Upper Teesdale National Nature Reserve in northern England comprising more than 200 ha of juniper. Dead and dying juniper trees were scattered throughout an area of approximately 14 ha, mainly concentrated on wet, flat ground but also extending outwards across drier slopes. Affected trees had foliage reddening and browning over all or most of the crown (Figs. 1, 2). Examination of ten trees showing these symptoms revealed orange-brown lesions in the phloem at the stem collar and upper roots (Fig. 3). Scattered dieback of shoots or individual branches (Fig. 4a) was also observed, and three trees examined with these symptoms had discrete girdling orange-brown phloem lesions with no apparent connection to the base of the tree (Fig. 4b). Phloem samples from lesion margins were plated on to SMA + MRP Phytophthora selective medium (Brasier et al., 2005) and incubated at room temperature (15-24{\textdegree}C) in the dark. After transfer to V8 agar, colonies were very slow growing (\<0.5 mm per day at 17{\textdegree}C), forming dense, white mycelia (Fig. 5a) with coralloid hyphae (Fig. 5b); amphigynous antheridia measuring 10.8-19.9 {\textmu}m in diameter (mean 13.2-16.2 {\textmu}m); and globose oogonia with smooth hyaline to brown walls ranging in diameter between 23.5-41.2 {\textmu}m (mean 34.4 {\textmu}m). Semi- and non-papillate sporangia measuring 35.3-58.8 x 23.5-35.3 {\textmu}m were also observed on V8 agar. Based on the above morphological characteristics and sequencing of the ITS and coxII regions (GenBank Accession Nos. JQ346527 and JQ346528), the isolates were identified as Phytophthora austrocedrae Gresl. \& E.M. Hansen, associated with mortality of Austrocedrus chilensis in Argentina (Greslebin et al., 2007; Greslebin \& Hansen, 2010). Direct PCR and sequencing of diseased phloem from basal and branch lesions on juniper trees from which no Phytophthora was obtained yielded the same result.

Pathogenicity of the isolate was tested using the method of Greslebin \& Hansen (2010) in which the stem bases of six healthy, 30-40 cm high, potted junipers were inoculated with 6 mm diameter mycelial plugs from the margin of a five-week-old P. austrocedrae culture growing on V8 agar. The plants were incubated in a greenhouse at 17{\textdegree}C with natural lighting. Four weeks after inoculation, five of the juniper plants exhibited orange-brown phloem lesions of mean length 49 {\textpm} 8 mm extending both up the main stem and down into the root system. P. austrocedrae was successfully re-isolated on to SMA + MRP medium from lesion margins, thereby satisfying Koch{\textquoteright}s postulates. Control plants inoculated with sterile agar plugs remained healthy. This is the first finding of P. austrocedrae infecting a Juniperus species worldwide. Although P. austrocedrae is not currently a statutory listed organism within the European Union, biosecurity measures are being applied at the infested site to contain the pathogen. In February 2012 P. austrocedrae was confirmed infecting mature upland juniper at a second site in Britain, located in Perthshire, Scotland. Other juniper sites in Britain with similar decline symptoms are now under investigation.

}, doi = {10.5197/j.2044-0588.2012.02610.5197/j.2044-0588.2012.026.002}, url = {http://www.ndrs.org.uk/contents.php?vol=26http://www.ndrs.org.uk/article.php?id=026002}, author = {Green, S. and Hendry, S.J. and MacAskill, G.A. and Laue, B.E. and Steele, H.} }