02812nas a2200217 4500008004100000245010700041210006900148260001700217300001200234490000900246520210600255653002002361653002302381653002502404653001902429653001002448653002002458653002102478100003702499856005802536 2011 eng d00aScientific opinion on the pest risk analysis on Phytophthora ramorum prepared by the FP6 project RAPRA0 aScientific opinion on the pest risk analysis on Phytophthora ram c28 June 2011 a107 pp.0 v9(6)3 a

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 “There is a risk of further entry (of known or new lineages and/or mating types), establishment and […] impact”. 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. © European Food Safety Authority, 2011

10aLarix kaempferi10amanagement options10aPhytophthora ramorum10aramorum blight10aRAPRA10arisk assessment10aSudden oak death1 aEFSA Panel on Plant Health (PLH) uhttp://www.efsa.europa.eu/en/efsajournal/pub/2186.htm02221nas a2200157 4500008004100000245010300041210006900144260001200213300001400225490000700239520172000246100001601966700001301982700001901995856004902014 2012 eng d00aVariation among Phytophthora cinnamomi isolates from oak forest soils in the eastern United States0 aVariation among Phytophthora cinnamomi isolates from oak forest  c11/2012 a1608-16140 v963 a

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.

1 aEggers, J E1 aBalci, Y1 aMacDonald, W L uhttp://dx.doi.org/10.1094/PDIS-02-12-0140-RE01935nas a2200205 4500008004100000245013700041210006900178300001400247490000800261520121700269653003501486653002201521100002801543700002501571700001801596700001901614700002001633700002901653856004701682 2010 eng d00aA statistical model to detect asymptomatic infectious individuals with an application in the Phytophthora alni-Induced alder decline0 astatistical model to detect asymptomatic infectious individuals  a1262-12690 v1003 a

In some diseases—in particular, tree root infection—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’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.

10aspatial point pattern analysis10asurvival analysis1 aElegbede, Chabi Fabrice1 aPierrat, Jean-Claude1 aAguayo, Jaime1 aHusson, Claude1 aHalkett, Fabien1 ac}ais, Beno{\^ıt Mar{\c uhttp://dx.doi.org/10.1094/PHYTO-05-10-014001448nas a2200193 4500008004100000245011800041210006900159260001800228300001400246490000700260520077400267100001501041700001701056700001901073700002001092700001301112700001601125856011301141 2015 eng d00aAn improved method for qPCR detection of three Phytophthora spp. in forest and woodland soils in northern Britain0 aimproved method for qPCR detection of three Phytophthora spp in  cDecember 2015 a537–5390 v453 a

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.

1 aElliot, M.1 aSchlenzig, A1 aHarris, C., M.1 aMeagher, T., R.1 aGreen, S1 aBelbahri, L uhttp://doi.wiley.com/10.1111/efp.12224http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fefp.1222402015nas a2200229 4500008004100000022001400041245011600055210006900171260002900240300001400269490000700283520131600290100001501606700001701621700001301638700001701651700001301668700001301681700001701694700001901711856005501730 2009 eng d a1439-032900aPCR-RFLP markers identify three lineages of the North American and European populations of Phytophthora ramorum0 aPCRRFLP markers identify three lineages of the North American an bBlackwell Publishing Ltd a266–2780 v393 a

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.

1 aElliott, M1 aSumampong, G1 aVarga, A1 aShamoun, S F1 aJames, D1 aMasri, S1 aBrière, S C1 aGrünwald, N J uhttp://dx.doi.org/10.1111/j.1439-0329.2008.00586.x01694nas a2200217 4500008004100000022001400041245007900055210006900134260002900203300001100232490000700243520106400250100001501314700001701329700001301346700001701359700001301376700001301389700001901402856005501421 2011 eng d a1439-032900aPhenotypic differences among three clonal lineages of Phytophthora ramorum0 aPhenotypic differences among three clonal lineages of Phytophtho bBlackwell Publishing Ltd a7–140 v413 a

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.

1 aElliott, M1 aSumampong, G1 aVarga, A1 aShamoun, S F1 aJames, D1 aMasri, S1 aGrünwald, N J uhttp://dx.doi.org/10.1111/j.1439-0329.2009.00627.x01958nas a2200169 4500008004100000022001400041245012300055210006900178260001200247300001600259490000700275520141000282100001901692700001501711700001201726856005001738 2013 eng d a0191-291700aDevelopment of a Nested Quantitative Real-Time PCR for Detecting Phytophthora cinnamomi in Persea americana Rootstocks0 aDevelopment of a Nested Quantitative RealTime PCR for Detecting  c08/2013 a1012 - 10170 v973 a

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.

1 aEngelbrecht, J1 aDuong, T A1 aBerg, N uhttp://dx.doi.org/10.1094/PDIS-11-12-1007-RE 01957nas a2200145 4500008004100000022001300041245010500054210006900159300001200228490000700240520140400247100001701651700001401668856012901682 1980 eng d a0031949X00aInteraction of light and sterol on sporangium and chlamydospore production by Phytophthora lateralis0 aInteraction of light and sterol on sporangium and chlamydospore  a650-6540 v703 a

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.

1 aEnglander, L1 aRoth, L F uhttps://forestphytophthoras.org/references/interaction-light-and-sterol-sporangium-and-chlamydospore-production-phytophthora01624nas a2200145 4500008004100000245009700041210006900138300001200207490000700219520113100226100002101357700002101378700002001399856005901419 2006 eng d00aGrowth and sporulation of Phytophthora ramorum in vitro in response to temperature and light0 aGrowth and sporulation of Phytophthora ramorum in vitro in respo a365-3730 v983 a

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.

1 aEnglander, Larry1 aBrowning, Marsha1 aTooley, Paul, W uhttp://www.mycologia.org/cgi/content/abstract/98/3/36501163nas a2200157 4500008004100000022001400041245011000055210006900165260002500234300001000259490000800269520064400277100001800921700001800939856004800957 2008 eng d a0929-187300aSpecies hybrids in the genus Phytophthora with emphasis on the alder pathogen Phytophthora alni: a review0 aSpecies hybrids in the genus Phytophthora with emphasis on the a bSpringer Netherlands a31-390 v1223 a

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.

1 aÉrsek, Tibor1 aNagy, Zoltán uhttp://dx.doi.org/10.1007/s10658-008-9296-z00422nam a2200121 4500008004100000245003700041210003600078260006400114300001100178100001500189700001700204856007900221 1996 eng d00aPhytophthora diseases worldwide.0 aPhytophthora diseases worldwide aSt. Paul, MNbAPS Press, American Phytopathological Society a562 pp1 aErwin, D C1 aRibeiro, O K uhttps://forestphytophthoras.org/references/phytophthora-diseases-worldwide02504nas a2200277 4500008004100000022001400041245014100055210006900196260002900265300001600294490000700310520159700317653002301914653002101937653002201958653003801980653003402018100001602052700001602068700001802084700001502102700001402117700002102131700001902152856005502171 2011 eng d a1365-305900aPhosphite primed defence responses and enhanced expression of defence genes in Arabidopsis thaliana infected with Phytophthora cinnamomi0 aPhosphite primed defence responses and enhanced expression of de bBlackwell Publishing Ltd a1086–10950 v603 a

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 < 0·001) 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.

10acallose deposition10adefence response10ahydrogen peroxide10apotassium phosphonate (phosphite)10areactive oxygen species (ROS)1 aEshraghi, L1 aAnderson, J1 aAryamanesh, N1 aShearer, B1 aMcComb, J1 aHardy, StJ., G E1 aO’Brien, P A uhttp://dx.doi.org/10.1111/j.1365-3059.2011.02471.x02247nas a2200157 4500008004100000022001400041245009700055210006900152260001600221300001200237490000800249520172800257100001701985700001802002856006902020 2015 eng d a0031-949X00aDetection, Diversity, and Population Dynamics of Waterborne Phytophthora ramorum Populations0 aDetection Diversity and Population Dynamics of Waterborne Phytop cJan-01-2015 a57 - 680 v1053 a

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.

1 aEyre, C., A.1 aGarbelotto, M uhttp://apsjournals.apsnet.org/doi/abs/10.1094/PHYTO-07-13-0196-R01788nas a2200193 4500008004100000022001400041245011400055210006900169260001200238300001600250490000700266520115800273100001701431700001901448700001801467700002201485700001801507856006901525 2014 eng d a0191-291700aLineage, Temperature, and Host Species have Interacting Effects on Lesion Development in Phytophthora ramorum0 aLineage Temperature and Host Species have Interacting Effects on c12/2014 a1717 - 17270 v983 a

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.

1 aEyre, C., A.1 aHayden, K., J.1 aKozanitas, M.1 aGrünwald, N., J.1 aGarbelotto, M uhttp://apsjournals.apsnet.org/doi/abs/10.1094/PDIS-02-14-0151-RE