@article {934, title = {Scientific opinion on the pest risk analysis on Phytophthora ramorum prepared by the FP6 project RAPRA}, journal = {EFSA Journal}, volume = {9(6)}, year = {2011}, month = {28 June 2011}, pages = {107 pp.}, chapter = {2186}, abstract = {

The Panel on Plant Health was asked to deliver a scientific opinion on the Pest Risk Analysis on Phytophthora ramorum prepared by the FP6 project RAPRA, taking into account comments by Member States and additional information since RAPRA. P. ramorum is the oomycete causing sudden oak death in the USA and leaf and twig blight/dieback on a range of ornamental species in North America and Europe. Currently P. ramorum is not listed as a harmful organism in Council Directive 2000/29/EC, but the Commission adopted in 2002 provisional emergency measures to prevent introduction into and spread within the EU. Recent large-scale outbreaks in Japanese larch (Larix kaempferi) plantations in the UK and Ireland have worsened the potential consequences in the risk assessment area. However, the Panel concludes that the broad narrative in the RAPRA report stands and supports its conclusion that {\textquotedblleft}There is a risk of further entry (of known or new lineages and/or mating types), establishment and [{\textellipsis}] impact{\textquotedblright}. It is advisable to avoid introductions of different lineages because of inherent phenotypic differences and the potential for sexual recombination. The Panel supports the management options proposed in the RAPRA report and adds further measures for consideration. Uncertainty remains over the extent to which the association between control measures and gradual reduction in the number of cases in nurseries is causal. The emergency measures have not prevented outbreaks occurring in the natural environment. The many other remaining uncertainties (fitness of progeny, hybridisation with other Phytophthora species, host range and epidemiological role of new hosts, early detection of new outbreaks, understanding of long-range dispersal, structure of plant trade networks, origin of the pathogen) call for further research on P. ramorum across Europe. Regulatory work should keep updated with research results on P. ramorum and further development of the Japanese larch outbreaks. {\textcopyright} European Food Safety Authority, 2011

}, keywords = {Larix kaempferi, management options, Phytophthora ramorum, ramorum blight, RAPRA, risk assessment, Sudden oak death}, doi = {10.2903/j.efsa.2011.2186}, url = {http://www.efsa.europa.eu/en/efsajournal/pub/2186.htm}, author = {EFSA Panel on Plant Health (PLH)} } @article {1293, title = {Variation among Phytophthora cinnamomi isolates from oak forest soils in the eastern United States}, journal = {Plant Disease}, volume = {96}, year = {2012}, month = {11/2012}, pages = {1608-1614}, abstract = {

Phytophthora cinnamomi isolates from geographically diverse oak forest soils in the Mid-Atlantic regions were studied to determine the extent of genotypic, phenotypic, and pathogenic variation. Four microsatellite loci were targeted for genetic analysis. Phenotypic characteristics measured included sexual and asexual spore dimensions and colony growth rate and morphology. Red oak (Quercus rubra) logs were inoculated with selected isolates to determine relative pathogenicity. Microsatellite analysis showed that the genetic variability of P. cinnamomi isolates was low, with two predominant microsatellite fingerprint groups (MFG). Isolates in MFG1 (48\% of the total isolates examined) were characterized by DNA fragment lengths of 120 and 122 bp at locus d39, 169 and 170 bp at locus e16, and 254 and 255 bp at locus g13. MFG2 isolates were characterized by marker sizes of 122 and 124 bp at locus d39, 161 and 163 bp at locus e16, and 247 and 248 bp at locus g13. Asexual and sexual spore dimensions varied greatly among isolates but were similar to previously published descriptions. Phenotypic differences were most pronounced when data were grouped by MFG; the most significant were colony morphology and growth rate. Neither characteristic was a reliable predictor of isolate genotype. Differences in growth rates of MFGs were observed, with MFG1 being less tolerant at higher incubation temperatures. No variation in pathogenicity was observed on red oak logs. The low level of phenotypic and genotypic variation of P. cinnamomi suggest that other factors such as climate might play a more important role in its northern distribution and the diseases it causes.

}, doi = {10.1094/PDIS-02-12-0140-RE}, url = {http://dx.doi.org/10.1094/PDIS-02-12-0140-RE}, author = {Eggers, J. E. and Balci, Y. and MacDonald, W. L.} } @article {1228, title = {A statistical model to detect asymptomatic infectious individuals with an application in the Phytophthora alni-Induced alder decline}, journal = {Phytopathology}, volume = {100}, year = {2010}, pages = {1262-1269}, abstract = {

In some diseases{\textemdash}in particular, tree root infection{\textemdash}stages of infection and inoculum production level and timing are not readily observable because of uncertainty or time lags in symptom appearance. Here, we pose a criterion, based on relative hazard of disease symptoms, to discriminate between healthy and asymptomatic infected individuals. We design a statistical procedure to estimate the criterion for a 6-year survey of alder decline along a northeastern French river. Individual tree symptom hazard was modeled with Cox{\textquoteright}s regression model, taking estimation of local infection pressure as a risk factor. From an inoculum production experiment, we thereafter assessed the inoculum production level of target trees, including symptomatic and asymptomatic trees ranked according to their symptoms hazard. Using receiver operating characteristic methods, we first evaluated the criterion performance and determined the discrimination threshold to sort out asymptomatic individuals into healthy and infected. Then, we highlighted the fact that the infected asymptomatic trees were among the major inoculum producers whereas severely declining and dead trees were found to be poor inoculum sources.

}, keywords = {spatial point pattern analysis, survival analysis}, doi = {10.1094/PHYTO-05-10-0140}, url = {http://dx.doi.org/10.1094/PHYTO-05-10-0140}, author = {Elegbede, Chabi Fabrice and Pierrat, Jean-Claude and Aguayo, Jaime and Husson, Claude and Halkett, Fabien and Beno{\^{\i}t Mar{\c c}ais} } @article {4339, title = {An improved method for qPCR detection of three Phytophthora spp. in forest and woodland soils in northern Britain}, journal = {Forest Pathology}, volume = {45}, year = {2015}, month = {December 2015}, pages = {537{\textendash}539}, abstract = {

Summary

Using TaqMan qPCR assays, DNA of P.\ ramorum, P.\ kernoviae and P.\ austrocedri was detected in 500\ g soil samples collected from twelve infected forest and woodland sites in northern Britain. Phytophthora DNA was also amplified in soil adhering to boots after walking transects along footpaths or animal trails. At two sites, Phytophthora DNA was detected in soil over a 4-year period following removal of infected hosts. This new method enabling assessment of larger quantities of soil demonstrates the contamination risk of these pathogens in soil at infected sites and improves our understanding of the mechanisms of persistence and spread.

}, doi = {10.1111/efp.12224}, url = {http://doi.wiley.com/10.1111/efp.12224http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111\%2Fefp.12224}, author = {Elliot, M. and Schlenzig, A. and Harris, C. M. and Meagher, T. R. and Green, S.}, editor = {Belbahri, L.} } @article {EFP:EFP627, title = {Phenotypic differences among three clonal lineages of Phytophthora ramorum}, journal = {Forest Pathology}, volume = {41}, number = {1}, year = {2011}, pages = {7{\textendash}14}, publisher = {Blackwell Publishing Ltd}, abstract = {

There are three major clonal lineages of Phytophthora ramorum present in North America and Europe named NA1, NA2, and EU1. Twenty-three isolates representing all three lineages were evaluated for phenotype including (i) aggressiveness on detached Rhododendron leaves and (ii) growth rate at minimum, optimum, and maximum temperatures. Closely related species P. foliorum and P. hibernalis were included in phenotypic tests since these species are encountered in nursery surveys for P. ramorum. Isolates from the NA2 and EU1 lineages were the most aggressive and isolates from the NA1 group were the least aggressive. The NA1 lineage of P. ramorum was the most variable in aggressiveness and growth rate. The variability in the NA1 lineage was due to the presence of non-wild type (nwt) isolates. There was no significant difference in growth rate among NA1 wild type (wt), NA2, and EU1 lineages at any temperature tested. The difference between wt and nwt P. ramorum isolates is discussed.

}, issn = {1439-0329}, doi = {10.1111/j.1439-0329.2009.00627.x}, url = {http://dx.doi.org/10.1111/j.1439-0329.2009.00627.x}, author = {Elliott, M. and Sumampong, G. and Varga, A. and Shamoun, S. F. and James, D. and Masri, S. and N. J. Gr{\"u}nwald} } @article {EFP:EFP586, title = {PCR-RFLP markers identify three lineages of the North American and European populations of Phytophthora ramorum}, journal = {Forest Pathology}, volume = {39}, number = {4}, year = {2009}, pages = {266{\textendash}278}, publisher = {Blackwell Publishing Ltd}, abstract = {

Phytophthora ramorum, the cause of sudden oak death and ramorum blight, has three major clonal lineages and two mating types. Molecular tests currently available for detecting P. ramorum do not distinguish between clonal lineages and mating type is determined by cultural methods on a limited number of samples. In some molecular diagnostic tests, cross-reaction with other closely related species such as P. hibernalis, P. foliorum or P. lateralis can occur. Regions in the mitochondrial gene Cox1 are different among P. ramorum lineages and mitochondrial genotyping of the North American and European populations seems to be sufficient to differentiate between mating types, because the EU1 lineage is mostly A1 and both NA1 and NA2 lineages are A2. In our study, we were able to identify P. ramorum isolates according to lineage using polymerase chain reaction-restriction fragment-length polymorphism (PCR-RFLP) of the Cox1 gene, first by using ApoI to separate P. ramorum from other species and EU1 from North American populations, and then AvaI to distinguish between NA1 and NA2 genotypes. However, P. foliorum had the same restriction profile as P. ramorum NA1 isolates.

}, issn = {1439-0329}, doi = {10.1111/j.1439-0329.2008.00586.x}, url = {http://dx.doi.org/10.1111/j.1439-0329.2008.00586.x}, author = {Elliott, M. and Sumampong, G. and Varga, A. and Shamoun, S. F. and James, D. and Masri, S. and Bri{\`e}re, S. C. and N. J. Gr{\"u}nwald} } @article {4029, title = {Development of a Nested Quantitative Real-Time PCR for Detecting Phytophthora cinnamomi in Persea americana Rootstocks}, journal = {Plant Disease}, volume = {97}, year = {2013}, month = {08/2013}, pages = {1012 - 1017}, abstract = {

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.

}, issn = {0191-2917}, doi = {10.1094/PDIS-11-12-1007-RE}, url = {http://dx.doi.org/10.1094/PDIS-11-12-1007-RE }, author = {Engelbrecht, J. and Duong, T. A. and van den Berg, N.} } @article {183, title = {Interaction of light and sterol on sporangium and chlamydospore production by Phytophthora lateralis}, journal = {Phytopathology}, volume = {70}, year = {1980}, pages = {650-654}, abstract = {

Chlamydospore production by Phytophthora lateralis was most abundant in V8 broth with 20 μg/ml β-sitosterol, and maximum sporangium production occurred with 10 μg/ml. Growth (dry weight) was not enhanced by sterol concentrations ranging from 1 to 200 μg/ml. Cultures grown on V8 sterol agar or broth, and illuminated (680 μW cm2, combined Blacklight Blue and Cool White fluorescent lamps) either continuously or 12 hr daily, produced at least four times as many sporangia as were produced by cultures in the dark on sterol media, or in the light or dark on media not amended with sterol. Chlamydospores were produced most abundantly in the dark on V8 sterol agar or broth, with production greatly reduced by continuous or 12 hr of light daily. Chlamydospore production was suppressed by all light intensities tested (85, 170, 340, 680 μW cm2) compared with production in the dark. Few chlamydospores formed in cultures on media without sterol, whether incubated in the light or dark. Growth (dry weight or colony size) was not affected by illumination. None of numerous regimes of diurnal temperature cycles enhanced sporulation more than constant temperatures. Optimal sporangium production requires incubation on media with sterol at 14-16 C in the light; optimal chlamydospore production requires incubation at 24-25 C in the dark on media with sterol.

}, issn = {0031949X}, doi = {DOI: 10.1094/Phyto-70-650.}, author = {Englander, L. and L.F. Roth} } @article {LarryEnglander05012006, title = {Growth and sporulation of Phytophthora ramorum in vitro in response to temperature and light}, journal = {Mycologia}, volume = {98}, number = {3}, year = {2006}, pages = {365-373}, abstract = {

Phytophthora ramorum, recently found in the US, is causing concern for hardwood forests and the nursery industry. In an effort to identify some of the environmental limitations to growth and sporulation we undertook a laboratory study of four US and three European (EU) isolates. On V8 media, isolates grew when incubated at 2-28 C and produced chlamydospores at 8-28 C. Sporangia were produced at all temperatures tested: 10-30 C for US isolates and 6-26 C for EU isolates. Optimal temperatures were 16-26 C for growth, 14-26 C for chlamydospore production and 16-22 C for sporangia production. US isolates grew less and produced fewer spores when exposed to increasing doses of near-UV radiation (50-300 {micro}W/cm2) and visible radiation (250-1500 {micro}W/cm2). EU isolates were exposed to 300 {micro}W/cm2 near-UV only, which significantly reduced growth of one of three isolates and had no significant effect on spore production. In our studies P. ramorum tolerated a broad range of temperature and light conditions, which suggests that it is capable of establishment in a wide geographic area.

}, doi = {10.3852/mycologia.98.3.365}, url = {http://www.mycologia.org/cgi/content/abstract/98/3/365}, author = {Englander, Larry and Browning, Marsha and Tooley, Paul W.} } @article {springerlink:10.1007/s10658-008-9296-z, title = {Species hybrids in the genus Phytophthora with emphasis on the alder pathogen Phytophthora alni: a review}, journal = {European Journal of Plant Pathology}, volume = {122}, year = {2008}, note = {10.1007/s10658-008-9296-z}, pages = {31-39}, publisher = {Springer Netherlands}, abstract = {

This review provides a summary of recent examples of interspecific hybridisation within the oomycetous genus Phytophthora. Species hybrids either created in the laboratory or evolved in natural environments are discussed in association with evolutionary issues and possible threats they may pose to agriculture, horticulture and forestry. It is suggested that sustainable control of such hybrids will depend on the better understanding of temporal and spatial aspects of genetic mechanisms and environmental factors that lead to the hybridisation process and thus the genetic diversity in Phytophthora populations.

}, issn = {0929-1873}, doi = {10.1007/s10658-008-9296-z}, url = {http://dx.doi.org/10.1007/s10658-008-9296-z}, author = {{\'E}rsek, Tibor and Nagy, Zolt{\'a}n} } @book {117, title = {Phytophthora diseases worldwide.}, year = {1996}, pages = {562 pp}, publisher = {APS Press, American Phytopathological Society}, organization = {APS Press, American Phytopathological Society}, address = {St. Paul, MN}, author = {Erwin, D.C and Ribeiro, O.K.} } @article {PPA:PPA2471, title = {Phosphite primed defence responses and enhanced expression of defence genes in Arabidopsis thaliana infected with Phytophthora cinnamomi}, journal = {Plant Pathology}, volume = {60}, number = {6}, year = {2011}, pages = {1086{\textendash}1095}, publisher = {Blackwell Publishing Ltd}, abstract = {

This paper describes the effect of phosphite (Phi), a systemic chemical, on the induction of defence responses in Phytophthora cinnamomi-infected Arabidopsis thaliana accessions Ler and Col-0. Application of Phi to non-inoculated A. thaliana seedlings of accession Ler elevated transcription of defence genes in the salicylic acid (PR1 and PR5) and jasmonic acid/ethylene (THI2.1 and PDF1.2) pathways. Furthermore, a systemic increase in the expression of the PR1 gene was demonstrated in Phi-treated seedlings using the transgenic line PR1::GUS in the presence/absence of the pathogen by 72 h after inoculation. The cells of Phi-treated A. thaliana Ler leaves responded to P. cinnamomi zoospore inoculation with a rapid increase in callose deposition and hydrogen peroxide (H2O2) production. Phi treatment resulted in the production of callose papillae 6 h earlier than in non-Phi-treated inoculated seedlings and enhanced the production of H2O2 in the leaves of A. thaliana at the site of hyphal penetration and in cells away from the inoculation point. By 24 h after infection, clear differences in the amount of H2O2 production were observed between the Phi-treated and non-Phi-treated plants. These rapid host responses did not occur in non-Phi-treated inoculated seedlings. There was also a significant (P \< 0{\textperiodcentered}001) decrease in lesion size in Phi-treated plants. These results indicate that Phi primes the plant for a rapid and intense response to infection involving heightened activation of a range of defence responses.

}, keywords = {callose deposition, defence response, hydrogen peroxide, potassium phosphonate (phosphite), reactive oxygen species (ROS)}, issn = {1365-3059}, doi = {10.1111/j.1365-3059.2011.02471.x}, url = {http://dx.doi.org/10.1111/j.1365-3059.2011.02471.x}, author = {Eshraghi, L. and Anderson, J. and Aryamanesh, N. and Shearer, B. and McComb, J. and Hardy, G. E. StJ. and O{\textquoteright}Brien, P. A.} } @article {4267, title = {Detection, Diversity, and Population Dynamics of Waterborne Phytophthora ramorum Populations}, journal = {Phytopathology}, volume = {105}, year = {2015}, month = {Jan-01-2015}, pages = {57 - 68}, abstract = {

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.

}, issn = {0031-949X}, doi = {10.1094/PHYTO-07-13-0196-R}, url = {http://apsjournals.apsnet.org/doi/abs/10.1094/PHYTO-07-13-0196-R}, author = {Eyre, C. A. and Garbelotto, M.} } @article {4247, title = {Lineage, Temperature, and Host Species have Interacting Effects on Lesion Development in Phytophthora ramorum}, journal = {Plant Disease}, volume = {98}, year = {2014}, month = {12/2014}, pages = {1717 - 1727}, abstract = {

There are four recognized clonal lineages of the pathogen Phytophthora ramorum. The two major lineages present in North America are NA1 and NA2. With a few exceptions, NA1 is found in natural forest ecosystems and nurseries, and NA2 is generally restricted to nurseries. Isolates from the NA1 and NA2 lineages were used to infect rhododendron, camellia, and California bay laurel in detached leaf assays to study the effects of lineage, temperature, and host on pathogenicity and host susceptibility. Isolates within both lineages were highly variable in their ability to form lesions on each host. There was also a tendency toward reduced lesion size in successive trials, suggesting degeneration of isolates over time. Temperature had a significant effect on lesion size, with a response that varied depending on the host and isolate. Phenotypic differences between lineages appear to be heavily influenced by the representation of isolates used, host, and temperature. The importance of temperature, host, and lineage are discussed with respect to disease management, as well as future range expansions and migrations of the pathogen.

}, issn = {0191-2917}, doi = {10.1094/PDIS-02-14-0151-RE}, url = {http://apsjournals.apsnet.org/doi/abs/10.1094/PDIS-02-14-0151-RE}, author = {Eyre, C. A. and Hayden, K. J. and Kozanitas, M. and Gr{\"u}nwald, N. J. and Garbelotto, M.} }