TY - JOUR T1 - Defining plant resistance to Phytophthora cinnamomi: a standardized approach to assessment JF - Journal of Phytopathology Y1 - 2012 A1 - Allardyce, Jane A. A1 - Rookes, James E. A1 - Cahill, David M. KW - Phytophthora cinnamomi KW - resistance KW - root pathogen KW - Zea mays KW - zoospores AB -

Phytophthora cinnamomi is a soil-borne plant pathogen that causes devastating disease in agricultural and natural systems worldwide. While a small number of species survive infection by the pathogen without producing disease symptoms, the nature of resistance, especially under controlled conditions, remains poorly understood. At present, there are no standardized criteria by which resistance or susceptibility to P. cinnamomi can be assessed, and we have used five parameters consisting of plant fresh weight, root growth, lesion length, relative chlorophyll content of leaves and pathogen colonization of roots to analyse responses to the pathogen. The parameters were tested using two plant species, Zea mays and Lupinus angustifolius, through a time course study of the interactions and resistance and susceptibility defined 7 days after inoculation. A scoring system was devised to enable differentiation of these responses. In the resistant interaction with Z. mays, there was no significant difference in fresh weight, root length and relative chlorophyll content in inoculated compared with control plants. Both lesion size and pathogen colonization of root tissues were limited to the site of inoculation. Following inoculation L. angustifolius showed a significant reduction in plant fresh weight and relative leaf chlorophyll content, cessation of root growth and increased lesion lengths and pathogen colonization. We propose that this technique provides a standardized method for plant–P. cinnamomi interactions that could be widely used to differentiate resistant from susceptible species.

PB - Blackwell Publishing Ltd VL - 160 UR - http://dx.doi.org/10.1111/j.1439-0434.2012.01895.x ER - TY - JOUR T1 - Distinct Trophic Specializations Affect How Phytophthora ramorum and Clade 6 Phytophthora spp. Colonize and Persist on Umbellularia californica Leaves in Streams JF - Phytopathology Y1 - 2018 A1 - Aram, Kamyar A1 - Rizzo, David M. AB -

Phytophthora spp. are regularly recovered from streams but their ecology in aquatic environments is not well understood. Phytophthora ramorum, invasive in California forests, persists in streams at times when sporulation in the canopy is absent, suggesting that it reproduces in the water. Streams are also inhabited by resident, clade 6 Phytophthora spp., believed to be primarily saprotrophic. We conducted experiments to determine whether differences of trophic specialization exist between these two taxa, and investigated how this may affect their survival and competition on stream leaf litter. P. ramorum effectively colonized fresh (live) rhododendron leaves but not those killed by freezing or drying, whereas clade 6 species colonized all leaf types. However, both taxa were recovered from naturally occurring California bay leaf litter in streams. In stream experiments, P. ramorum colonized bay leaves rapidly at the onset; however, colonization was quickly succeeded by clade 6 species. Nevertheless, both taxa persisted in leaves over 16 weeks. Our results confirm that clade 6 Phytophthora spp. are competent saprotrophs and, though P. ramorum could not colonize dead tissue, early colonization of suitable litter allowed it to survive at a low level in decomposing leaves.

UR - https://apsjournals.apsnet.org/doi/pdf/10.1094/PHYTO-06-17-0196-R JO - Phytopathology ER - TY - JOUR T1 - A diverse range of Phytophthora species are associated with dying urban trees JF - Urban Forestry & Urban Greening Y1 - 2013 A1 - P.A. Barber A1 - Paap, T. A1 - Burgess, T. I. A1 - Dunstan, W. A1 - G.E.St.J. Hardy AB -

Surveys of dying vegetation within remnant bushland, parks and gardens, and streetscapes throughout the urban forest of Perth and the South-west of Western Australia revealed symptoms typical of those produced by Phytophthora species. A total of nine Phytophthora species, including P. alticola, P. multivora, P. litoralis, P. inundata, P. nicotianae and P. palmivora were isolated. In addition, three previously undescribed species, Phytophthora aff. arenaria, Phytophthora aff. humicola and Phytophthora sp. ohioensis were isolated. Isolates were recovered from a wide range of native and non-native host genera, including Agonis, Allocasuarina, Brachychiton, Calothamnus, Casuarina, Corymbia, Dracaena, Eucalyptus, Ficus, Pyrus and Xanthorrhoea. Phytophthora multivora was the most commonly isolated species. Out of 230 samples collected 69 were found to be infected with Phytophthora. Of those 69, 54% were located within parks and gardens, 36% within remnant bushland, and 10% within streetscapes. These pathogens may play a key role in the premature decline in health of the urban forest throughout Perth, and should be managed according to the precautionary principle and given high priority when considering future sustainable management strategies.

UR - http://dx.doi.org/10.1016/j.ufug.2013.07.009 JO - Urban Forestry & Urban Greening ER - TY - JOUR T1 - Detection of Phytophthora ramorum in Nurseries and Forest Lands in California in 2004 to 2009 JF - Plant Disease Y1 - 2016 A1 - Blomquist, C. L. A1 - Yakabe, L. E. A1 - Rooney-Latham, S. A1 - McRoberts, N. A1 - Thomas, C. AB -

From December 2004 through May 2009, samples were collected from California nurseries and wild lands to survey for Phytophthora ramorum and comply with federal regulations of nursery stock. Samples were prescreened by an enzyme-linked immunosorbent assay (ELISA) that detects Phytophthora spp. and tested by culture, P. ramorum-specific real-time polymerase chain reaction (PCR), and nested PCR. Yearly percentages of infected samples ranged from 0.6 to 2.3%. Camellia spp., Rhododendron spp., Magnolia spp., Pieris spp., and Laurus nobilis tested positive the most frequently in the nurseries and Lithocarpus densiflorus, Umbellularia californica, and Quercus agrifolia tested positive most often from wild lands. Of the 118,410 samples isolated onto PARP media, 0.8% was identified as P. ramorum. Of 115,056 samples tested by ELISA, 5.9% tested positive for Phytophthora spp. Of the 6,520 samples tested by PCR, 12.4% tested positive for P. ramorum. The false-negative, positive, and internal control failure rates of the assays are discussed. After removing the seasonal effect of sampling strategy, isolation of the pathogen into culture was found to be seasonally dependent whereas detectability by PCR and ELISA was not. To our knowledge, this is the first evaluation of a regulatory testing program for a plant pathogen on this scale using standardized assays.

VL - 100 UR - http://apsjournals.apsnet.org/doi/10.1094/PDIS-12-14-1302-RE IS - 1 JO - Plant Disease ER - TY - Generic T1 - A disease survey of cherimoya orchards in Northland, New Zealand. T2 - 16th Biennial Australasian Plant Pathology Conference Y1 - 2007 A1 - Braithwaite, M. A1 - Bullians, M.S. A1 - Pay, J.M. A1 - Gill, G.S.C. A1 - Hill, C.F. JF - 16th Biennial Australasian Plant Pathology Conference CY - Adelaide ER - TY - JOUR T1 - Diversity and Pathogenicity of Phytophthora Species Associated with Declining Alder Trees in Italy and Description of Phytophthora alpina sp. nov JF - Forests Y1 - 2020 A1 - Bregant, Carlo A1 - Sanna, Gian Paolo A1 - Bottos, Adriano A1 - Maddau, Lucia A1 - Montecchio, Lucio A1 - Linaldeddu, Benedetto T. AB -

Extensive decline and mortality events of alder trees have recently been observed in several riparian ecosystems in Italy. Since there is little information about the aetiology of this disease and given the high ecological relevance of riparian ecosystems, an in-depth study was conducted in three sites spanning from the Mediterranean to Alpine regions. From spring 2019 to spring 2020, 261 samples of bleeding cankers, rhizosphere soil and leaves used as baits along waterways were collected and used for Phytophthora isolation. Based on morphology, colony appearance and DNA sequence data, 10 species belonging to 6 clades were identified. These included P. plurivora (84 isolates), P. pseudocryptogea (50), P. hydropathica (18), P. gonapodyides (14), P. bilorbang (13), P. pseudosyringae (12), P. lacustris (11), P. acerina (7), P. cactorum (1) and one isolate of the hybrid Phytophthora ×serendipita. In addition, two new Phytophthora species, one of which is described here as Phytophthora alpina sp. nov., were isolated. The pathogenicity of P. alpina and other species obtained from samples collected in the green alder stand was assessed on 3-year-old seedlings. All species proved to be pathogenic on green alder causing symptoms congruent with field observations. Results obtained have allowed us to expand knowledge about alder decline aetiology. The diversity of pathogenicity of Phytophthora species associated with symptomatic alder trees suggested that no single agent is responsible for the disease, but that it is the result of multiple infections of different Phytophthora species, variable in assemblages among sites.

VL - 11 UR - https://www.mdpi.com/1999-4907/11/8/848/htm IS - 8 JO - Forests ER - TY - JOUR T1 - Developing a taxonomic identification system of Phytophthora species based on microsatellites JF - Revista Iberoamericana de Micologia Y1 - 2012 A1 - J. del Castillo-Múnera A1 - M. Cárdenas A1 - A. Pinzón A1 - A. Castañeda A1 - A.J. Bernal A1 - S. Restrepo AB -

Phytophthora spp. is the most important genus of the Oomycete plant pathogens. Nowadays, there are 117 described species in this genus, most of them being primary invaders of plant tissues. The different species are causal agents of diseases in a wide range of crops and plants in natural environments. In order to develop control strategies against Phytophthora spp., it is important to know the biology, ecology and evolutionary processes of these important pathogens.

VL - In press UR - http://www.sciencedirect.com/science/article/pii/S1130140612001106 ER - TY - JOUR T1 - Detection of mRNA by reverse-transcription PCR as an indicator of viability in Phytophthora ramorum JF - Forest Pathology Y1 - 2012 A1 - Chimento, A. A1 - Cacciola, S. O. A1 - Garbelotto, M. AB -

In the last few decades, the use of molecular tools has greatly improved the efficiency of plant disease diagnosis. However, one of the major setbacks of most molecular diagnostic approaches is their inability to differentiate between dead and viable pathogens. We propose a new strategy for the detection of plant pathogens, based on the use of mRNA as a viability marker, on the basis that mRNA degradation in dead cells is significantly more rapid than that of DNA. A real-time reverse-transcription PCR (RT-PCR) assay targeting the mRNA of the subunit I of the cytochrome oxidase gene was designed for Phytophthora ramorum, the causal agent of sudden oak death and ramorum blight. In controlled laboratory tests, the developed RT-PCR assay did not detect the target mRNA a week after the pathogen had been killed by rapid lyophilization, while DNA of the pathogen could still be detected 3 months after the pathogen had died. The RT-PCR assay was then compared with a traditional culturing approach using PARP selective medium and two nested real-time PCR techniques on symptomatic California bay laurel leaves. Samples were either collected in three different sites in July, or in the same site but in three different seasons. Overall, RT-PCR results showed less positive samples than DNA-based nested PCR techniques (p < 0.0001), but more than culturing (p = 0.017). Nested PCR-positive but RT-PCR-negative samples may not be viable. On the other hand, RT-PCR-positive but culture-negative samples may be viable but dormant. A comparative analysis of the results indicated that RT-PCR and culturing provide comparable results when climatic conditions are optimal for the pathogen, but RT-PCR may be the most accurate approach to determine pathogen viability when climatic conditions are less than optimal for the pathogen.

PB - Blackwell Publishing Ltd VL - 42 UR - http://dx.doi.org/10.1111/j.1439-0329.2011.00717.x ER - TY - JOUR T1 - The distribution and significance of the chestnut root rot Phytophthoras, P. cinnamomi and P. cambivora. JF - Plant Disease Reporter Y1 - 1950 A1 - Crandall, B.S. KW - Abies alba disease KW - Abies nordmanniana KW - Abies sibirica KW - Betula alba KW - Castanea crenata KW - Castanea sativa diseases KW - Cedrus atlantica KW - decay KW - Disease KW - fungal diseases KW - Ink disease KW - Juglans regia disease KW - Pseudotsuga laxifolia diseases KW - Quercus robur KW - Quercus suber disease KW - trees AB -

A review of literature, with special reference to some recent publications in Spain and Portugal [cf. For. Abstr. 11 (Nos. 1468, 2268)]. The author concludes that Phytophthora cinnamomi plays a great part in disease of Chestnut in Spain, Portugal, France and Italy, and elsewhere in southern Europe, and is probably the major cause of death in the more southerly regions. P. cinnamomi has a considerable range of hosts. It has been found to attack Castanea sativa, Juglans regia, Pseudotsuga taxifolia, Quercus robur, Q. suber, Betula alba, Cedrus atlantica, Abies nordmanniana, A. alba, A. sibirica and Castanea crenata var. tamba. A close watch on Douglas Fir in the U.S.A. seems advisable in case a strain of the fungus should encounter and attack it. In contrast P. cambivora has only been found on Castanea sativa and C. crenata var. tamba.

VL - 34 UR - http://www.cabdirect.org/abstracts/19500602345.html ER - TY - JOUR T1 - DNA-based method for rapid identification of the pine pathogen, Phytophthora pinifolia JF - FEMS Microbiology Letters Y1 - 2009 A1 - Durán, Alvaro A1 - Bernard Slippers A1 - Marieka Gryzenhout A1 - Rodrigo Ahumada A1 - Drenth, Andre A1 - Brenda D. Wingfield A1 - Michael J. Wingfield KW - Monterey pine KW - oomycetes KW - Pinus radiata KW - tree defoliation AB -

Phytophthora pinifolia causes a needle and shoot disease in Pinus radiata, referred to as ‘Daño Foliar del Pino’. This newly discovered disease requires intensive research efforts that necessitate the processing of large numbers of samples for which accurate identification, often by people not experienced in Phytophthora taxonomy, is required. The aim of this study was, therefore, to develop species-specific primers for P. pinifolia that amplify the internal transcribed spacer region of the ribosomal operon and the nuclear Ypt1 gene, respectively. The primers were tested over several Phytophthora spp., as well as fungi isolated from P. radiata. In all cases, only P. pinifolia was amplified. In addition to the species-specific primers, a PCR-restriction fragment length polymorphism protocol using available Phytophthora genus-specific primers was also used to generate a species-specific profile for P. pinifolia. This provided a characteristic profile that allows the identification of P. pinifolia, and it could also discriminate between 27 different species of Phytophthora. Both techniques reported in this study make it possible to identify large numbers of P. pinifolia cultures accurately and efficiently, which will be important for both quarantine work and biological research on this important new pathogen.

VL - 298 UR - http://onlinelibrary.wiley.com/doi/10.1111/j.1574-6968.2009.01700.x/abstract ER - TY - JOUR T1 - Development of a Nested Quantitative Real-Time PCR for Detecting Phytophthora cinnamomi in Persea americana Rootstocks JF - Plant Disease Y1 - 2013 A1 - Engelbrecht, J. A1 - Duong, T. A. A1 - van den Berg, N. AB -

Phytophthora cinnamomi causes Phytophthora root rot (PRR) in avocado (Persea americana), an important disease that causes severe economic losses to the avocado industry globally. To date, no PRR-resistant avocado rootstock variety has been discovered, although certain rootstock varieties have been shown to be more tolerant than others. In this study, we developed an accurate, low cost assay for in planta quantification of P. cinnamomi to evaluate disease tolerance. A nested real-time polymerase chain reaction assay was developed to sensitively detect pathogen DNA in plant tissues. Root samples from a highly tolerant (Dusa) and less tolerant (R0.12) rootstock were collected at 0, 3, 7, 14, and 21 days after inoculation with P. cinnamomi and used for pathogen quantification. Nested primers developed in this study were specific and sensitive and could detect P. cinnamomi in root tissues. The amount of P. cinnamomi quantified in roots was significantly higher in the less-tolerant R0.12 plants when compared with the highly tolerant Dusa plants at all time points. This study has confirmed the known status of disease tolerance of Dusa and R0.12 avocado rootstocks in a quantitative manner and provides a reliable molecular tool to assist with industry breeding programs for the selection of PRR-resistant avocado rootstock varieties.

VL - 97 UR - http://dx.doi.org/10.1094/PDIS-11-12-1007-RE IS - 8 JO - Plant Disease ER - TY - JOUR T1 - Detection, Diversity, and Population Dynamics of Waterborne Phytophthora ramorum Populations JF - Phytopathology Y1 - 2015 A1 - Eyre, C. A. A1 - Garbelotto, M. AB -

Sudden oak death, the tree disease caused by Phytophthora ramorum, has significant environmental and economic impacts on natural forests on the U.S. west coast, plantations in the United Kingdom, and in the worldwide nursery trade. Stream baiting is vital for monitoring and early detection of the pathogen in high-risk areas and is performed routinely; however, little is known about the nature of water-borne P. ramorum populations. Two drainages in an infested California forest were monitored intensively using stream-baiting for 2 years between 2009 and 2011. Pathogen presence was determined both by isolation and polymerase chain reaction (PCR) from symptomatic bait leaves. Isolates were analyzed using simple sequence repeats to study population dynamics and genetic structure through time. Isolation was successful primarily only during spring conditions, while PCR extended the period of pathogen detection to most of the year. Water populations were extremely diverse, and changed between seasons and years. A few abundant genotypes dominated the water during conditions considered optimal for aerial populations, and matched those dominant in aerial populations. Temporal patterns of genotypic diversification and evenness were identical among aerial, soil, and water populations, indicating that all three substrates are part of the same epidemiological cycle, strongly influenced by rainfall and sporulation on leaves. However, there was structuring between substrates, likely arising due to reduced selection pressure in the water. Additionally, water populations showed wholesale mixing of genotypes without the evident spatial autocorrelation present in leaf and soil populations.

VL - 105 UR - http://apsjournals.apsnet.org/doi/abs/10.1094/PHYTO-07-13-0196-R IS - 1 JO - Phytopathology ER - TY - JOUR T1 - Detection, distribution, sporulation, and survival of Phytophthora ramorum in a California redwood-tanoak forest soil JF - Phytopathology Y1 - 2007 A1 - Fichtner, E. J. A1 - Lynch, S. C. A1 - D. M. Rizzo VL - 97 UR - http://apsjournals.apsnet.org/doi/abs/10.1094/PHYTO-97-10-1366 ER - TY - ICOMM T1 - Distribution of the Phytophthora disease of alder Y1 - 2006 A1 - Forestry_Commission_Great_Britain PB - UK Forestry Commission UR - http://www.forestry.gov.uk/fr/INFD-737J2S ER - TY - JOUR T1 - Dieback and mortality of Juniperus communis in Britain associated with Phytophthora austrocedrae JF - New Disease Reports Y1 - 2012 A1 - Green, S. A1 - Hendry, S.J. A1 - MacAskill, G.A. A1 - Laue, B.E. A1 - Steele, H. AB -

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°C) in the dark. After transfer to V8 agar, colonies were very slow growing (<0.5 mm per day at 17°C), forming dense, white mycelia (Fig. 5a) with coralloid hyphae (Fig. 5b); amphigynous antheridia measuring 10.8-19.9 µm in diameter (mean 13.2-16.2 µm); and globose oogonia with smooth hyaline to brown walls ranging in diameter between 23.5-41.2 µm (mean 34.4 µm). Semi- and non-papillate sporangia measuring 35.3-58.8 x 23.5-35.3 µm 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°C with natural lighting. Four weeks after inoculation, five of the juniper plants exhibited orange-brown phloem lesions of mean length 49 ± 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’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.

VL - 26 UR - http://www.ndrs.org.uk/contents.php?vol=26http://www.ndrs.org.uk/article.php?id=026002 JO - New Dis. Rep. ER - TY - JOUR T1 - The destructive invasive pathogen Phytophthora lateralis found on Chamaecyparis lawsoniana across the UK JF - Forest Pathology Y1 - 2012 A1 - Green, S. A1 - C.M. Brasier A1 - Schlenzig, A. A1 - McCracken, A. A1 - MacAskill, G. A. A1 - Wilson, M. A1 - Webber, JF AB -

In 2010–2011, 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.

VL - 43 UR - http://dx.doi.org/10.1111/j.1439-0329.2012.00788.x IS - 1 ER - TY - JOUR T1 - Der Buchenkeimlingspilz, Phytophthora (Peronospora fagi M). (The beech seedling fungus Phytophthora (Peronospora fagi M)) JF - Untersuchungen aus dem Forstbotanischen Institut zu München Y1 - 1880 A1 - Hartig, R. VL - 1 ER - TY - JOUR T1 - Die Buchencotyledonen-Krankheit (The cotyledon disease of beech) JF - Zeitschrift für Forst- und Jagdwissenschaft Y1 - 1876 A1 - Hartig, R. VL - 8 ER - TY - JOUR T1 - Detection and quantification of Phytophthora ramorum from California forests using a real-time polymerase chain reaction assay-0 JF - Phytopathology Y1 - 2004 A1 - Katherine J. Hayden A1 - David Rizzo A1 - Justin Tse A1 - Garbelotto, Matteo AB -

The timely and accurate detection of pathogens is a critical aid in the study of the epidemiology and biology of plant diseases. In the case of regulated organisms, the availability of a sensitive and reliable assay is essential when trying to achieve early detection of the pathogen. We developed and tested a real-time, nested polymerase chain reaction (PCR) assay for the detection of Phytophthora ramorum, causal agent of sudden oak death. This technique then was implemented as part of a widespread environmental screen throughout California. The method here described is sensitive, detecting less than 12 fg of pathogen DNA, and is specific for P. ramorum when tested across 21 Phytophthora spp. Hundreds of symptomatic samples from 33 sites in 14 California counties were assayed, resulting in the discovery of 10 new host species and 23 infested areas, including 4 new counties. With the exception of a single host, PCR-based discovery of new hosts and infested areas always was confirmed by traditional pathogen isolations and inoculation studies. Nonetheless, molecular diagnostics were key in early pathogen detection, and steered the direction of further research on this newly discovered and generalist Phytophthora species.

VL - 94 UR - http://apsjournals.apsnet.org/doi/abs/10.1094/PHYTO.2004.94.10.1075 ER - TY - JOUR T1 - Decline in vitality of propagules of Phytophthora pluvialis and Phytophthora kernoviae and their inability to contaminate or colonise bark and sapwood in Pinus radiata export log simulation studies JF - New Zealand Journal of Forestry Science Y1 - 2014 A1 - Hood, Ian A A1 - Williams, Nari M A1 - Dick, Margaret A A1 - Arhipova, Natalija A1 - Kimberley, Mark O A1 - Scott, Peter M A1 - Gardner, Judy F AB -

Background: Phytophthora pluvialis Reeser, W.L. Sutton & E.M. Hansen is the cause of a newly described disease, red needle cast, in certain stands of Pinus radiata D. Don in New Zealand that experience periodic foliage browning, while Phytophthora kernoviae Brasier, Beales & Kirk is also infrequently isolated from symptomatic needles.

Methods: Studies were undertaken to test the possibility that these species may be transported on pine logs either as superficial contaminants or as colonists of bark or wood.

Results: Pine-needle baiting found no evidence of Phytophthora species in bark samples or aqueous bark washes from stems of 603 symptomatic trees in 17 affected stands implying that survival after natural deposition of sporangia or zoospores is low or absent. The persistence of zoospores or oospores was evaluated at intervals after applying them at artificially high surface densities to the bark on log segments and incubating at five temperatures between 15°C and 35°C in the laboratory. The ability to re-isolate Phytophthora kernoviae decreased with time and increasing temperature, but this species was s till obtained at low frequencies after 4 weeks at 15°C and 20°C following treatment with oospores of Phytophthora kernoviae. Phytophthora pluvialis could not be isolated under any conditions of time or temperature tested. Percentage vitality of oospores of both species as determined using tetrazolium bromide vital staining also decreased with time, although some oospores of both species remained alive after 4 weeks at all temperatures tested. In a further study to test potential log colonisation, Phytophthora spp. were not isolated from bark or xylem at or near points where zoospores, oospores or mycelium of either species were applied to the bark or sapwood of pine segments and incubated for 6 weeks under ambient or humid conditions at 17°C.

Conclusion: The results of these studies suggest that occurrence of Phytophthora kernoviae or Phytophthora pluvialis on export logs from affected stands is negligible. In addition, although some remained alive, the substantial decline in vitality among artificially applied oospores implies that the survival of any few that may be naturally present on logs is likely to be slight. Based on the evidence from this work there appears to be little risk of transporting these Phytophthora species on New Zealand radiata pine logs.

VL - 44 UR - http://www.nzjforestryscience.com/content/44/1/7 IS - 7 JO - N.Z. j. of For. Sci. ER - TY - JOUR T1 - Development of a real-time PCR assay for detection of Phytophthora kernoviae and comparison of this method with a conventional culturing technique JF - European Journal of Plant Pathology Y1 - 2011 A1 - Hughes, KelvinJ.D. A1 - Tomlinson, JennyA. A1 - Giltrap, PatriciaM. A1 - Barton, Victoria A1 - Hobden, Ellie A1 - Boonham, Neil A1 - Lane, CharlesR. KW - Diagnostic sensitivity KW - Diagnostic specificity KW - plant health KW - Rhododendron AB -

Phytophthora kernoviae is a recently described pathogen causing leaf blight, aerial dieback and bleeding cankers on trees and shrubs in parts of Great Britain and Ireland and recently reported in New Zealand. This paper describes the development of a TaqMan real-time PCR assay based on internal transcribed spacer (ITS) sequence to aid diagnosis of this pathogen in culture and in plant material. The assay showed no cross reaction with 29 other Phytophthora species, including the closely related species P. boehmeriae, and detected at least 1.2 pg of P. kernoviae DNA per reaction. A rapid and simple method can be used to extract DNA prior to testing by real-time PCR, and a plant internal control assay can be used to aid interpretation of negative results. A comparison of real-time PCR and plating for 526 plant samples collected in the UK indicated that this assay is suitable for use in routine screening for P. kernoviae.

PB - Springer Netherlands VL - 131 UR - http://dx.doi.org/10.1007/s10658-011-9843-x ER - TY - JOUR T1 - Distribution and expression of elicitin genes in the interspecific hybrid oomycete Phytophthora alni JF - Appl. Environ. Microbiol. Y1 - 2007 A1 - Renaud Ioos A1 - Panabières, Franck A1 - Industri, Beno{\^ıt A1 - Axelle Andrieux A1 - Pascal Frey AB -

Phytophthora alni subsp. alni, P. alni subsp. multiformis, and P. alni subsp. uniformis are responsible for alder disease in Europe. Class I and II elicitin gene patterns of P. alni subsp. alni, P. alni subsp. multiformis, P. alni subsp. uniformis, and the phylogenetically close species P. cambivora and P. fragariae were studied through mRNA sequencing and 3' untranslated region (3'UTR)-specific PCRs and sequencing. The occurrence of multiple 3'UTR sequences in association with identical elicitin-encoding sequences in P. alni subsp. alni indicated duplication/recombination events. The mRNA pattern displayed by P. alni subsp. alni demonstrated that elicitin genes from all the parental genomes are actually expressed in this allopolyploid taxon. The complementary elicitin patterns resolved confirmed the possible involvement of P. alni subsp. multiformis and P. alni subsp. uniformis in the genesis of the hybrid species P. alni subsp. alni. The occurrence of multiple and common elicitin gene sequences throughout P. cambivora, P. fragariae, and P. alni sensu lato, not observed in other Phytophthora species, suggests that duplication of these genes occurred before the radiation of these species.

VL - 73 UR - http://aem.asm.org/content/73/17/5587.abstract ER - TY - JOUR T1 - Development of a lab-on-a-chip device for diagnosis of plant pathogens JF - Biosensors and Bioelectronics Y1 - 2011 A1 - Sandra Julich A1 - Marko Riedel A1 - Mark Kielpinski A1 - Matthias Urban A1 - Robert Kretschmer A1 - Stefan Wagner A1 - Wolfgang Fritzsche A1 - Thomas Henkel A1 - Robert Möller A1 - Werres, Sabine KW - detection AB -

A lab-on-a-chip system for rapid nucleic acid-based analysis was developed that can be applied for diagnosis of selected Phytophthora species as a first example for use in plant pathology. All necessary polymerase chain reaction process (PCR) and hybridization steps can be performed consecutively within a single chip consisting of two components, an inflexible and a flexible one, with integrated microchannels and microchambers. Data from the microarray is collected from a simple electrical measurement that is based on elementary silver deposition by enzymatical catalyzation. Temperatures in the PCR and in the hybridization zone are managed by two independent Peltier elements. The chip will be integrated in a compact portable system with a pump and power supply for use on site. The specificity of the lab-on-a-chip system could be demonstrated for the tested five Phytophthora species. The two Pythium species gave signals below the threshold. The results of the electrical detection of the microarray correspond to the values obtained with the control method (optical grey scale analysis).

VL - 26 UR - http://www.sciencedirect.com/science/article/pii/S0956566311001916 ER - TY - JOUR T1 - Diversity of Phytophthora species in Valdivian rainforests and association with severe dieback symptoms JF - Forest Pathology Y1 - 2018 A1 - Jung, Thomas A1 - Durán, Alvaro A1 - Sanfuentes von Stowasser, Eugenio A1 - Schena, Leonardo A1 - Mosca, Saveria A1 - Fajardo, Sebastian A1 - González, Mariela A1 - Navarro Ortega, Angella D. A1 - Bakonyi, Jozsef A1 - Seress, Diana A1 - Tomšovský, Michal A1 - Cravador, Alfredo A1 - Maia, Cristiana A1 - Horta Jung, Marilia ED - Woodward, S. AB -

The Valdivian rainforest, one of the global hotspots of biodiversity, is a temperate rainforest originating as a Tertiary relic from the supercontinent Gondwana. In November 2014, a survey of Phytophthora diversity was performed in 13 natural forest stands and 20 forest streams and rivers in two protected areas near Valdivia and in a temperate montane forest in the Concepción area. One planted stand each of the introduced tree species Castanea sativa and Fagus sylvatica were also included. Using baiting assays, eight described species and four previously unknown taxa of Phytophthora were isolated from 86% of the 50 rhizosphere soil samples from seven of the eight tree species sampled in 12 forest stands, and from 20 streams: P. chlamydospora, P. cinnamomi, P. kernoviae, P. lacustris, P. plurivora, P. pseudosyringae, P. ×cambivora, P×stagnum, P. valdiviana nom. prov. from Clade 2b, P. madida nom. prov. from Clade 8a, and P. chilensis nom. prov. and P. pseudokernoviae nom. prov. The latter two species are the closest relatives of P. kernoviae from Clade 10. Phytophthora pseudokernoviae nom. prov. was also isolated from necrotic leaves of Drimys winteri. From the Valdivia river, a swarm of three Clade 6 hybrids was recovered. Each hybrid isolate resulted from multiple reticulation events with P. thermophila as maternal and both P. amnicola and P. chlamydospora as paternal parents. In addition, three previously unknown and recently described Nothophytophthora species, N. caduca, N. chlamydospora and N. valdiviana, were isolated from several forest streams. Phytophthora cinnamomi, the most common and widespread species in soils of native forests, was associated with severe dieback of Valdivian rainforest trees, in particular D. winteri, Luma apiculata, Nothofagus dombeyi and the endangered Saxegothaea conspicua. A first pathogenicity test demonstrated high aggressiveness of P. cinnamomi to several native tree species, including N. dombeyi, Blepharocalyx cruckshanksii and Gevuina avellana.

UR - https://onlinelibrary.wiley.com/doi/abs/10.1111/efp.12443 JO - For. Path. ER - TY - JOUR T1 - Diversity of Phytophthora species in natural ecosystems of Taiwan and association with disease symptoms JF - Plant Pathology Y1 - 2017 A1 - Jung, T. A1 - Chang, T. T. A1 - Bakonyi, J. A1 - Seress, D. A1 - Pérez-Sierra, A. A1 - Yang, X. A1 - Hong, C. A1 - Scanu, B. A1 - Fu, C. H. A1 - Hsueh, K. L. A1 - Maia, C. A1 - Abad-Campos, P. A1 - León, M. A1 - Horta Jung, M. AB -

In 2013 a survey of Phytophthora diversity was performed in 25 natural and seminatural forest stands and 25 rivers in temperate montane and subtropical lowland regions of Taiwan. Using baiting assays, 10 described species and 17 previously unknown taxa of Phytophthora were isolated from 71.5% of the 144 rhizosphere soil samples from 33 of 40 tree species sampled in 24 forest stands, and from 19 rivers: P. capensis, P. citrophthora, P. plurivora, P. tropicalis, P. citricola VII, P. sp. × botryosa-like, P. sp. × meadii-like and P. sp. occultans-like from Clade 2; P. palmivora from Clade 4; P. castaneae and P. heveae from Clade 5; P. chlamydospora and P. sp. forestsoil-like from Clade 6; P. cinnamomi (Pc), P. parvispora, P. attenuata nom. prov., P. flexuosa nom. prov., P. formosa nom. prov., P. intricata nom. prov., P. × incrassata nom. prov. and P. × heterohybrida nom. prov. from Clade 7; P. sp. palustris and five new hybrid species from Clade 9. The A1 mating type of Pc was widespread in both montane and lowland forests and rarely associated with disease, whereas the A2 mating type was limited to lowland forests and in some cases causing severe dieback. Most other Phytophthora species were not associated with obvious disease symptoms. It is concluded that (i) Taiwan is within the centre of origin of most Phytophthora taxa found, (ii) Pc A2 is an introduced invasive pathogen, and (iii) interspecific hybridizations play a major role in speciation and species radiations in diverse natural ecosystems.

VL - 66 UR - http://doi.wiley.com/10.1111/ppa.12564http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fppa.12564 JO - Plant Pathol ER - TY - Generic T1 - Detection and eradication of Phytophthora ramorum from Oregon forests, 2001–2008 T2 - Sudden oak death fourth science symposium Y1 - 2010 A1 - Kanaskie, A. A1 - Hansen, E.M. A1 - Goheen, E. M. A1 - Osterbauer, N. A1 - McWilliams, M. A1 - J. Laine A1 - M. Thompson A1 - S. Savona A1 - H. Timeus A1 - B. Woosley A1 - Sutton, W. A1 - P. Reeser A1 - R. Schultz A1 - D. Hilburn ED - Frankel, S.J. ED - T. Kliejunas ED - K. M. Palmieri JF - Sudden oak death fourth science symposium PB - U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station CY - Santa Cruz, California VL - Gen. Tech. Rep. PSW-GTR-229 UR - http://www.fs.fed.us/psw/publications/documents/psw_gtr229/ ER - TY - JOUR T1 - The decline of Austrocedrus chilensis forests in Patagonia, Argentina: soil features as predisposing factors JF - Forest Ecology and Management Y1 - 2004 A1 - La Manna, Ludmila A1 - Rajchenberg, Mario KW - Topography VL - 190 UR - http://www.sciencedirect.com/science/article/B6T6X-4BD5PHG-4/2/6181ecf7a2cf4ba397d9afef97ee478d ER - TY - THES T1 - Developing techniques for evaluating the susceptibility of root-disease resistant Port-Orford-Cedar to foliar and stem canker diseases. Y1 - 2008 A1 - Danielle Martin ER - TY - JOUR T1 - Diplanetism and microcyclic sporulation in Phytophthora ramorum JF - Forest Pathology Y1 - 2011 A1 - Moralejo, E. A1 - Descals, E. AB -

The zoosporic phase of the pathogen Phytophthora ramorum plays a crucial role in the process of plant infection, yet little is known about the fate of zoospores failing to target their hosts. Here, we describe new stages in the life cycle of P. ramorum concerning the in vitro development of monomorphic diplanetism and microcyclic sporulation in free water. Papillate cysts were formed after zoospore suspensions of isolates of the EU1 and NA1 clonal lineages were vortexed. Cysts usually germinated directly forming an emerging tube, or indirectly by releasing a secondary zoospore, which leaves behind an empty cyst with a short evacuation tube. Germinate cysts frequently developed either an appressorium or a microsporangium both terminally. We also observed microcyclic sporulation, i.e. sporangia indirectly germinated by forming a microsporangium, as in microcyclic conidiation of true fungi. Temporal progress of encysted zoospores in solution showed that percentage of germination varied significantly among and within isolates as well as between experiments, suggesting that germination is partly ruled by internal mechanisms. Diplanetism and microcyclic sporulation in P. ramorum may provide a second opportunity for host infection and may increase the chance of long dispersal in moving water.

PB - Blackwell Publishing Ltd VL - 41 UR - http://dx.doi.org/10.1111/j.1439-0329.2010.00674.x ER - TY - JOUR T1 - Development of a quantitative real-time PCR assay for the detection of Phytophthora austrocedrae, an emerging pathogen in Britain JF - Forest Pathology Y1 - 2013 A1 - Mulholland, V. A1 - Schlenzig, A. A1 - MacAskill, G. A. A1 - Green, S. AB -

A TaqMan real-time PCR assay was developed for Phytophthora austrocedrae, an emerging pathogen causing severe damage to juniper in Britain. The primers amplified DNA of the target pathogen down to 1 pg of extracted DNA, in both the presence and absence of host DNA, but did not amplify any of the non-target Phytophthora and fungal species tested. The assay provides a useful tool for screening juniper populations for the disease.

UR - http://onlinelibrary.wiley.com/doi/10.1111/efp.12058/abstract JO - For. Path. ER - TY - JOUR T1 - Diversity of Phytophthora megakarya in Central and West Africa revealed by isozyme and RAPD markers JF - Mycological Research Y1 - 1999 A1 - NyassÉ, S. A1 - Grivet, L. A1 - Risterucci, A.M. A1 - Blaha, G. A1 - Berry, D. A1 - Lanaud, C. A1 - DesprÉAux, D. AB -

Phytophthora megakarya is an important pathogen of cocoa in Africa. We used isozyme and RAPD markers to estimate the genetic diversity and structuring among 161 isolates, from the known distribution area of the fungus which corresponds to the cocoa belt in Ghana, Togo, Nigeria, Cameroon, Gabon and Sao Tome. Thirty six and 44 multilocus patterns were identified with isozymes and RAPDs, respectively. Patterns were separated into two highly differentiated genetic groups with both types of markers, one located in Central Africa and the other in West Africa. This distribution coincides with two major biogeographical domains which may reflect an ancient evolution of P. megakarya in this part of Africa. The genotypic diversity was lower in West Africa as compared to Central Africa. Inside Central Africa, isolates from Gabon and Sao Tome were highly differentiated based on RAPDs. Four intermediate marker patterns corresponding to isolates sampled near the border between Nigeria and Cameroon were putatively derived from genetic exchanges between the two major groups. The mating type determination permitted to confirm the high prevalence of A1 over A2. Although clonal multiplication seems to be the rule, indices of other reproduction means have been detected.

VL - 103 UR - http://www.sciencedirect.com/science/article/pii/S0953756208606711 IS - 10 JO - Mycological Research ER - TY - JOUR T1 - Detection of Phytophthora lateralis in soil organic matter and factors that affect its survival. JF - Phytopathology Y1 - 1977 A1 - W.D. Ostrofsky A1 - L.F. Roth A1 - R.G. Pratt KW - Chamaecyparis lawsoniana VL - 67 ER - TY - JOUR T1 - Detection and spread of Phytophthora austrocedri within infected Juniperus communis woodland and diversity of co-associated Phytophthoras as revealed by metabarcoding JF - Forest Pathology Y1 - 2020 A1 - Riddell, Carolyn E. A1 - Dun, Heather F. A1 - Elliot, Matt A1 - Armstrong, April C. A1 - Clark, Mhairi A1 - Forster, Jack A1 - Hedley, Pete E. A1 - Green, Sarah AB -

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'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.

VL - 50 UR - https://onlinelibrary.wiley.com/doi/abs/10.1111/efp.12602 IS - 3 JO - For. Path. ER - TY - JOUR T1 - DNA barcoding of oomycetes with cytochrome c oxidase subunit I and internal transcribed spacer JF - Molecular Ecology Resources Y1 - 2011 A1 - Robideau, Gregg P. A1 - De Cock, Arthur W. a. M. A1 - Michael D. Coffey A1 - Voglmayr, Hermann A1 - Brouwer, Henk A1 - Bala, Kanak A1 - Chitty, David W. A1 - Désaulniers, Nicole A1 - Eggertson,Quinn A. A1 - Gachon, Claire M. M. A1 - Hu, Chia-Hui A1 - Küpper, Frithjof C. A1 - Rintoul, Tara L. A1 - Sarhan, Ehab A1 - Verstappen, Els C. P. A1 - Zhang, Yonghong A1 - Peter J.M. Bonants A1 - Ristaino, Jean B. A1 - André Lévesque, C. KW - cytochrome c oxidase subunit I KW - DNA barcoding KW - internal transcribed spacer KW - oomycete KW - species identification AB -

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.

PB - Blackwell Publishing Ltd VL - 11 UR - http://dx.doi.org/10.1111/j.1755-0998.2011.03041.x IS - 6 ER - TY - JOUR T1 - Dieback and mortality of Nothofagus in Britain: ecology, pathogenicity and sporulation potential of the causal agent Phytophthora pseudosyringae JF - Plant Pathology Y1 - 2016 A1 - Scanu, B. A1 - Webber, J. F. AB -

Since 2009 extensive dieback and mortality of Nothofagus obliqua, associated with bleeding cankers on stems and branches, has been observed in the UK. The causal agent was identified as Phytophthora pseudosyringae, based on morphological and analysis of the internal transcribed spacer (ITS) sequences. Between 2011 and 2013, a survey assessed the frequency and nature of these P. pseudosyringae infections. Mature trees of Nothofagus with stem lesions caused by P. pseudosyringae were found across England, Scotland and Wales. Additional symptoms such as twig blight and leaf necrosis indicated that aerial infection was occurring. Besides N. obliqua, other hosts regularly encountered included Nothofagus alpina, Fagus sylvatica and Vaccinium myrtillus. In pathogenicity tests involving inoculation of logs, P. pseudosyringae was shown to be an aggressive bark pathogen of N. obliqua and F. sylvatica, but significantly less aggressive on N. alpina. Foliage susceptibility and sporulation tests showed marked differences between the six host species tested. Leaves of N. obliqua and V. myrtillus were highly susceptible. Leaves of N. alpina were moderately susceptible, those of Rhododendron ponticum slightly susceptible and those of F. sylvatica not susceptible at all. High levels of sporulation were observed only on inoculated N. obliqua and V. myrtillus leaves. This suggests that P. pseudosyringae may sporulate heavily on N. obliqua foliage in the field and that this inoculum initiates the aerial lesions observed on the shoots, branches and stems. The results also suggest that P. pseudosyringae has the potential to pose a serious threat to N. obliqua and other Nothofagus species in their Southern Hemisphere native ranges.

VL - 65 UR - http://doi.wiley.com/10.1111/ppa.12399http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fppa.12399 IS - 1 JO - Plant Pathol ER - TY - JOUR T1 - Detecting asymptomatic ink-diseased chestnut trees by the composition of the ectomycorrhizal community JF - Forest Pathology Y1 - 2012 A1 - Scattolin, L. A1 - Dal Maso, E. A1 - Mutto Accordi, S. A1 - Sella, L. A1 - Montecchio, L. AB - The research was performed in a new and isolated ink disease outbreak. Nine sweet chestnuts of comparable age, growing under same environmental and site conditions, and belonging to three phytosanitary classes (healthy, infected but asymptomatic and symptomatic) were randomly selected. Their ectomycorrhizal community was monitored during two periods, with regard to species abundance, to verify whether the community composition can be useful as an ink disease bioindicator. From the 216 samples, 29 ectomycorrhizal species were recorded, with abundances that changed with the health status of the tree. The results demonstrated that the mycorrhizal community composition was highly related to the ink disease level, allowing the consideration of the use of this parameter as a tool for the quick detection and control of the early stages of the disease. UR - http://dx.doi.org/10.1111/j.1439-0329.2012.00784.x ER - TY - JOUR T1 - A duplex PCR method for the simultaneous identification of Phytophthora ramorum and Phytophthora kernoviae JF - EPPO Bulletin Y1 - 2011 A1 - Schlenzig, A. AB -

Phytophthora ramorum and Phytophthora kernoviae are two fungus-like organisms affecting a wide range of hardy ornamental plants and trees. Emergency measures are implemented in the European Union for P. ramorum and aim to eradicate, or at least prevent the further spread of this harmful pathogen. Phytophthora kernoviae has so far been found only in New Zealand, the UK and Ireland, and is regulated on a UK level using the same measures as for P. ramorum. Both Phytophthora species have a similar host range and can be diagnosed using similar methods. Therefore a duplex PCR detection, based on the internal transcribed spacer (ITS) regions of the ribosomal DNA, was developed to enable simultaneous testing to reduce diagnostic times. The method was tested for its specificity and sensitivity, and on plant samples, and was shown to be reliable for identification of the two organisms.

PB - Blackwell Publishing Ltd VL - 41 UR - http://dx.doi.org/10.1111/j.1365-2338.2010.02431.x ER - TY - JOUR T1 - Detection and quantification of Phytophthora species which are associated with root-rot diseases in European deciduous forests by species-specific polymerase chain reaction JF - Forest Pathology Y1 - 1999 A1 - Schubert, R. A1 - Bahnweg, G. A1 - Nechwatal, J. A1 - T. Jung A1 - Cooke, D. E. L. A1 - Duncan, J. M. A1 - Muller-Starck, G. A1 - Langebartels, C. A1 - Sandermann, H. Jr2 A1 - W. Osswald AB -

Oligonucleotide primers were developed for the polymerase chain reaction (PCR)-based detection of selected Phytophthora species which are known to cause root-rot diseases in European forest trees. The primer pair CITR1/CITR2, complementing both internal transcribed spacer regions of the ribosomal RNA genes, gave a 711 bp amplicon with Phytophthora citricola. The Phytophthora cambivora specific primer pair CAMB3/CAMB4, producing a 1105bp amplicon, as well as the Phytophthora quercina specific primer pair QUERC1/QUERC2, producing a 842 bp amplicon, were derived from randomly amplified polymorphic DNA (RAPD)-fragments presented in this paper. All three primer pairs revealed no undesirable cross-reaction with a diverse test collection of isolates including other Phytophthora species, Pythium, Xerocomus, Hebeloma, Russula, and Armillaria. Under the PCR conditions described the detection of a well discernable amplicon was possible down to 100 pg (P. cambivora), 4pg (P. quercina), and 2pg (P. citricola) target DNA. This diagnostic PCR system was able to detect P. citricola, P. quercina, and P. cambivora in seedlings of pendunculate oak (Quercus robur) and European beech (Fagus sylvatica) which were artificially infected under controlled conditions.

VL - 29 IS - 3 JO - Forest Pathol ER - TY - JOUR T1 - Dieback and Mortality of Pinus radiata Trees in Italy Associated with Phytophthora cryptogea JF - Plant Disease Y1 - 2014 A1 - Sechi, C. A1 - Seddaiu, S. A1 - Linaldeddu, B. T. A1 - Franceschini, A. A1 - Scanu, B. AB -

Pinus radiata D. Don is a forest tree species native to the Monterey Baja in California. Due to its rapid growth and desirable lumber and pulp qualities, between 1960 and 1980, about 12,000 ha of P. radiata were planted in Sardinia, Italy. The only disease reported on this conifer species has been Diplodia pinea, which causes tip and branch dieback (3). In January 2012, dieback and mortality of 25-year-old radiata pine trees were observed in a reforestation area of about 20 ha located in northern Sardinia (40°43′N, 9°22′E, 600 m a.s.l.). Symptoms included chlorosis, reddish-brown discoloration of the whole crown or dieback starting in the upper crown and progressing downward through the crown, and necrotic bark tissues at root collar. Approximately 25% of the trees were affected. In a first attempt, a Phytophthora species was consistently isolated from the rhizosphere of 23 symptomatic trees, which included necrotic fine roots using oak leaves as bait (4). Afterwards, it was also isolated from phloem samples taken from the margins of fresh lesions at the stem base and upper roots of affected trees using synthetic mucor agar medium (1). Isolation from soil samples of six healthy pine trees randomly selected in the site did not yield any Phytophthora isolate. On carrot agar (CA), Phytophthora colonies were stellate to slightly radiate with limited aerial mycelium. Sporangia were obpiryform, non-papillate, and non-caducous, measuring 46.9 to 51.2 × 29.1 to 32.6 μm (l:b ratio 1.9). Hyphal swellings were formed in chains or clusters; chlamydospores were not observed. These isolates had cardinal temperatures of <5°C, 25°C, and 35°C, respectively. Their morphological and cultural features were typical of Phytophthora cryptogea Pethybridge & Lafferty. They were heterothallic and produced oogonia with amphyginous antheridia when paired with an A2 mating type tester strain of P. cryptogea. This identity was corroborated by sequence analysis of the internal transcribed spacer (ITS) region of the rDNA. BLAST searches showed 99% homology with sequences of P. cryptogea available in GenBank (DQ479410 and HQ697245). The ITS sequence of a representative isolate (PH101) was submitted to GenBank (Accession Nos. KC603895). The strain PH101 was stored in the culture collection of the Department of Agriculture at the University of Sassari. Pathogenicity of isolate PH101 was verified by inoculating five freshly cut logs of radiata pine (1 m long and 15 cm diam.) with a 5-mm agar plug taken from the margin of 4-day-old culture grown on CA (4). The plug was inserted in a 5-mm hole made through the bark with a cork borer. Five control logs were inoculated with sterile CA. All logs were incubated in a growth chamber at 20°C. Phloem lesion sizes were assessed after 1 month and measured 9.7 ± 5.5 cm2 (average ± standard deviation). Control logs had no lesions. The pathogen was re-isolated from the lesions, thus fulfilling Koch's postulates. P. cryptogea has been previously reported in Australia, causing decline of radiata pine trees in wet and flooded soils (2). To our knowledge, this is the first report of P. cryptogea on P. radiata trees in Europe.

VL - 98 UR - http://dx.doi.org/10.1094/PDIS-05-13-0572-PDN IS - 1 JO - Plant Disease ER - TY - JOUR T1 - Detection and identification of Phytophthora alni. JF - Communications in agricultural and applied biological sciences Y1 - 2010 A1 - Trzewik, A. A1 - Orlikowska, T. AB -

In 2004 Brasier et al. described new species–Phytophthora alni, which was especially aeggressive to alder. Now, this Phytophthora disease of alder is widely distributed in Europe as well as in Poland. In this research note we report on identification and detection of P. alni from water and soil samples using PCR method with species-specific primers. Dilution series of P. alni zoospore were used to test the potential sensitivity of the PCR detection methods. Zoospores of P. alni were produced by flooding of 1-week-old Frozen Pea Medium (FPM) cultures in Petri dishes with 30 ml distilled water. The dishes were incubated at 20 degrees C. After 5 days, sporangial production was checked using a binocular microscope and plates were placed at 4 degrees C for 1 h to enhance zoospore release. Zoospores were counted under the microscope using Burker’s cabin. A dilution series of zoospores ranging from 5 to 5000 per 200 microl was prepared in autoclaved distilled water and in 1 g samples of autoclaved soil. DNA was extracted from artificially infected water and soil, and purified using the CleanUp Kit (A&A Biotechnology). Zoospores of P. alni in the water were detected by PCR in 5 x 10(3), 5 x 10(2), 5 x 10(1) concentrations. In case of detecting spores in the artificially infected soil it succeeded only for two highest concentrations, i.e. 5 x 10(3), 5 x 10(2) and only when the DNA was additionally purified.

VL - 75 ER - TY - JOUR T1 - Discovery of a fourth evolutionary lineage of Phytophthora ramorum: EU2 JF - Fungal Biology Y1 - 2012 A1 - Van Poucke, Kris A1 - Franceschini, Selma A1 - Webber, Joan F. A1 - Vercauteren, Annelies A1 - Turner, Judith A. A1 - McCracken, Alistair R. A1 - Heungens, Kurt A1 - Brasier, Clive M. AB -

Phytophthora ramorum is a recently introduced, aggressive Phytophthora species that has caused extensive mortality of oak and tanoak trees in the western USA and Japanese larch trees in the UK. P. ramorum is also present on Rhododendron, Camellia, and Viburnum in the nursery industry, which is thought to have been the pathway for its spread into new geographic regions including forests and natural ecosystems. Three lineages of P. ramorum have been described, informally designated EU1, NA1, and NA2, and each lineage is believed to originate from an as yet unknown exotic centre of origin. Preliminary SSR and sequence analysis of isolates from a UK P. ramorum survey revealed seven isolates with profiles that did not match the previously known lineages. Detailed SSR and multilocus sequence analysis of these isolates are presented, allowing us to assign these isolates to a new P. ramorum lineage, designated EU2. Although the known geographical origin of these isolates is currently limited to Northern Ireland and western Scotland, the EU2 lineage isolates have been obtained from four different host plants, including Japanese larch. All isolates are of A1 compatibility type, which implies that this finding does not increase the risk of outcrossing with the EU1 lineage isolates already present in the UK. The oldest EU2 strain was isolated in 2007 but no SSR-based intraEU2 lineage genotypic diversity was detected. The combination of these elements points to a recent introduction, despite emergency phytosanitary measures to control introduction and spread. A PCR-RFLP method for the rapid identification of EU2 lineage isolates is presented.

VL - 116 UR - http://linkinghub.elsevier.com/retrieve/pii/S1878614612001572 IS - 11 JO - Fungal Biology ER - TY - JOUR T1 - Dieback and mortality of plantation Japanese larch (Larix kaempferi) associated with infection by Phytophthora ramorum JF - New Disease Reports Y1 - 2010 A1 - Webber, JF A1 - Mullett, M. A1 - C.M. Brasier AB -

The invasive pathogen Phytophthora ramorum is the cause of ’sudden oak death’, a dieback and mortality of more than one million live-oak and tanoak trees along 1500 km of near-coastal native forest in California and Oregon since 1995 (Rizzo et al., 2002; Frankel, 2008). P. ramorum has also spread across Europe , mainly within the ornamental nursery trade. From 2003 onwards it was found infecting rhododendron and woodland trees outside nurseries in Britain (Brasier et al., 2004) and has recently spread to native Vaccinium swards (P. Beales, personal communication). Until now, tree infections in Britain have been comparatively few (<100), mostly foliage or stems of Fagaceae (Fagus, Nothofagus, Quercus and Castanea) in the vicinity of infected Rhododendron in south west England (Webber, 2008). In August 2009 extensive dieback and mortality was observed in mature (25-30 m tall) and juvenile plantation Japanese larch, Larix kaempferi,at multiple sites in south west England (Figs. 1, 2). Symptoms included black or purple discoloured needles (Fig. 3), aborted bud flush, wilting and senescence of dwarf shoots and needle loss. Affected trees often had copious resin bleeding on the trunk, branches and side shoots plus dieback of branches and sometimes of the entire crown. Phloem lesions were often present under resinous outer bark. These usually had deep pink to maroon-red margins, older lesion areas being rusty-brown to cinnamon brown.

When symptom-bearing needles were surface-sterilised in 70% ethanol for 30 seconds or small pieces of older phloem lesion were plated onto Phytophthora selective medium (Brasier et al., 2005), P. ramorum was obtained from 25-40% of the samples. Identity was confirmed by sequencing of ITS rDNA regions (GenBank Accession No. HQ010359). P. ramorum was not obtained from the pink-maroon lesion margins. Pathogenicity of a P. ramorum isolate from L. kaempferi was tested by dipping 15 cm long L. kaempferi shoots into a zoospore suspension and damp chamber incubating for 12h light/12h dark cycle at 18°C. On half the shoots all needles were wounded by tip cutting. After seven days each needle was categorised as blackened, browned/brown bands, chlorotic or green, surface sterilised and plated onto selective medium. Both unwounded and wounded blackened needles yielded P. ramorum at high frequency (Table 1). When needles were mounted in lactic acid cotton blue and viewed 24 h later, sporangia and occasionally chlamydospores were observed on the surfaces with an exceptional 2685 sporangia counted on one unwounded needle (Fig. 4).

P. ramorum has so far been isolated from L. kaempferi at 68 currently known plantations where symptoms are present in southwest England . In May 2010 larch plantations with similar symptoms were discovered in south Wales and P. ramorum has again been isolated at multiple sites. Overall an estimated 2400 ha or c. 0.6 million mature larch have been affected to date. A large area of juvenile larch is also affected. This is the first widespread and lethal damage caused by P. ramorum to a conifer and the first to a commercial plantation tree. Adjacent to some affected larch sites in southwest England , secondary infection of Fagus sylvatica, Nothofagus obliqua, Castanea sativa, Betula pendula, Rhododendron ponticum, Tsuga heterophylla and Pseudotsuga menziesii is also occurring, apparently as result of the high levels of P. ramorum inoculum produced from larch foliage.  

VL - 22 UR - http://dx.doi.org/10.5197/j.2044-0588.2010.022.019 ER - TY - JOUR T1 - Differential behaviour in pathogenicity and enzymatic activities of Phytophthora katsurae strains from coconut trees in Côte d’Ivoire. [Article in French] JF - Journal of Applied Biosciences Y1 - 2009 A1 - Yao, NR A1 - N’Goran, B. A1 - Allou, K. A1 - Dogbo, DO A1 - Konan, KJL A1 - Kouassi, P. AB -

An experiment was conducted to study epidemiological variation of Phytophthora katsurae on coconut trees from four farming areas. Isolates of the pathogenic agent were first characterized based on morphology of sporocysts, oospore, chlamydospore and mycelium, and this enabled detection of differences between the aggressiveness of strains. Differences were also detected when measuring the mycelium growth of each strain in vitro on different culture media (V8, Malt and Carotte). A second study was conducted to confirm the observed differences based on inoculation (gentle or rough) of coconut plants cv. Equatoriale Guinea Green Dwarf (NVE), which is susceptible to P. katsurae, with each of four strains. Last, the enzymatic dosages of pectate lyase and laccase in pathogen were analysed. These enzymes degrade the pectin and lignin of the plant cell walls. Gentle inoculation enabled assessment of the level of aggressiveness of each strain. The activity of pectate lyase and laccase varied between the strains and the synthesis of these enzymes was correlated to pathogen aggressiveness on the plant. The results showed that the strains of Marc Delorme and Assinie are less aggressive than the strain of Fresco, which is less aggressive than the strain of Robert Michaux. The zoospores and the mycelia are considered as the primary inoculum of the four strains. The β-sitosterol added to V8 medium had no influence on the mycelium growth of the four strains. However, its use as ingredient added to the media favoured an increased production of sporocysts. The discovery of this intra specific variability should be of considerable help in elaborating control methods against P. katsurae of coconut trees.

PB - FACT Limited VL - 21 UR - http://www.m.elewa.org/JABS/2009/21/Abstract4-Yao.html ER -