Sudden Oak Death Caused by <i>Phytophthora ramorum</i> in Oregon

Goheen, E. M.; Hansen, E. M.; Kanaskie, Alan; McWilliams, Michael; Osterbauer, Nancy; Sutton, Wendy

doi:10.1094/pdis.2002.86.4.441c

Cited by 81 publications

(45 citation statements)

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“…1). The disease was also recently found in Oregon (Goheen et al 2002), and is a growing concern outside the United States (Brasier 2003;Ivors et al 2004). It is caused by a newly discovered pathogen, Phytophthora ramorum, which has already caused the mortality of vast numbers of oaks (Quercus spp.)…”

Section: Introductionmentioning

confidence: 94%

Examining the strength and possible causes of the relationship between fire history and Sudden Oak Death

Moritz

Odion

2005

Oecologia

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Fire can be a dominant process in the ecology of forest vegetation and can also affect forest disease dynamics. Little is known about the relationship between fire and an emerging disease epidemic called Sudden Oak Death, which is caused by a new pathogen, Phytophthora ramorum. This disease has spread across a large, fire-prone portion of California, killing great numbers of oaks and tanoaks and infecting most associated woody plants. Suitable hosts cover a much broader geographic range, raising concern over where the disease may spread. To understand the strength and potential sensitivities of a fire-disease relationship, we examined geographic patterns of confirmed P. ramorum infections in relation to past fire history. We found these infections to be extremely rare within the perimeter of any area burned since 1950. This finding is not caused by spatial bias in sampling for the disease, and is robust to variation in host abundance scenarios and to aggregation of closely spaced sampling locations. We therefore investigated known fire-related factors that could result in significantly lower incidence of the disease in relatively recently burned landscapes. Chemical trends in post-fire environments can influence the success of pathogens like P. ramorum, either by increasing plant nutrient stress or by reducing the occurrence of chemicals antagonistic to Phytophthoras. Succession in the absence of fire leads to greater abundance of host species, which will provide increased habitat for P. ramorum; this will also increase intraspecific competition where these trees are abundant, and other density-dependent effects (e.g. shading) can reduce resource allocation to defenses. Despite these findings about a fire-disease relationship, a much deeper understanding is necessary before fire can be actively used as a tool in slowing the epidemic.

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Section: Introductionmentioning

confidence: 94%

Examining the strength and possible causes of the relationship between fire history and Sudden Oak Death

Moritz

Odion

2005

Oecologia

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“…In 2001, a new pathogen called Phytophthora ramorum Werres, de Cock & Man in't Veld, was described (60) and identified as the causal agent of SOD (12,14,20,37,45,51). This pathogen has since spread to several counties in California (14 in 2004) and was discovered in Oregon in 2001 (22,33), but is now increasing its range. It was found again in 2003 in nurseries in Oregon, Washington, and British Columbia (25), and was subsequently eradicated from infested sites.…”

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confidence: 99%

Molecular Detection of Phytophthora ramorum by Real-Time Polymerase Chain Reaction Using TaqMan, SYBR Green, and Molecular Beacons

Bilodeau¹,

Lévesque²,

Cock³

et al. 2007

Phytopathology®

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Bilodeau, G. J., Lévesque, C. A., de Cock, A. W. A. M., Duchaine, C., Brière, S., Uribe, P., Martin, F. N., and Hamelin, R. C. 2007. Molecular detection of Phytophthora ramorum by real-time polymerase chain reaction using TaqMan, SYBR Green, and molecular beacons. Phytopathology 97:632-642.Sudden oak death, caused by Phytophthora ramorum, is a severe disease that affects many species of trees and shrubs. This pathogen is spreading rapidly and quarantine measures are currently in place to prevent dissemination to areas that were previously free of the pathogen. Molecular assays that rapidly detect and identify P. ramorum frequently fail to reliably distinguish between P. ramorum and closely related species. To overcome this problem and to provide additional assays to increase confidence, internal transcribed spacer (ITS), β-tubulin, and elicitin gene regions were sequenced and searched for polymorphisms in a collection of Phytophthora spp. Three different reporter technologies were compared: molecular beacons, TaqMan, and SYBR Green. The assays differentiated P. ramorum from the 65 species of Phytophthora tested. The assays developed were also used with DNA extracts from 48 infected and uninfected plant samples. All environmental samples from which P. ramorum was isolated by PARP-V8 were detected using all three real-time PCR assays. However, 24% of the samples yielded positive real-time PCR assays but no P. ramorum cultures, but sequence analysis of the coxI and II spacer region confirmed the presence of the pathogen in most samples. The assays based on detection of the ITS and elicitin regions using TaqMan tended to have lower cycle threshold values than those using β-tubulin and seemed to be more sensitive.

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“…Phytophthora ramorum is the causal agent of extensive oak mortality (commonly known as sudden oak death) in coastal forests in California (27) and southern Oregon (12,25). This pathogen also causes ramorum leaf blight and dieback on a range of other plant species (9) and can have a profound and devastating effect on forest ecosystems.…”

mentioning

confidence: 99%

On-Site DNA Extraction and Real-Time PCR for Detection of Phytophthora ramorum in the Field

Tomlinson¹,

Boonham²,

Hughes³

et al. 2005

Appl Environ Microbiol

119

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Phytophthora ramorum is a recently described pathogen causing oak mortality (sudden oak death) in forests in coastal areas of California and southern Oregon and dieback and leaf blight in a range of tree, shrub, and herbaceous species in the United States and Europe. Due to the threat posed by this organism, stringent quarantine regulations are in place, which restrict the movement of a number of hosts. Fast and accurate diagnostic tests are required in order to characterize the distribution of P. ramorum, prevent its introduction into pathogen-free areas, and minimize its spread within affected areas. However, sending samples to a laboratory for testing can cause a substantial delay between sampling and diagnosis. A rapid and simple DNA extraction method was developed for use at the point of sampling and used to extract DNAs from symptomatic foliage and stems in the field. A sensitive and specific single-round real-time PCR (TaqMan) assay for P. ramorum was performed using a portable real-time PCR platform (Cepheid SmartCycler II), and a costeffective method for stabilizing PCR reagents was developed to allow their storage and transportation at room temperature. To our knowledge, this is the first description of a method for DNA extraction and molecular testing for a plant pathogen carried out entirely in the field, independent of any laboratory facilities.Phytophthora ramorum is the causal agent of extensive oak mortality (commonly known as sudden oak death) in coastal forests in California (27) and southern Oregon (12,25). This pathogen also causes ramorum leaf blight and dieback on a range of other plant species (9) and can have a profound and devastating effect on forest ecosystems. A distinct population of the same pathogen (6, 35) is found in a number of European countries (10,20,23,37), mostly causing dieback and leaf blight on a range of ornamental plants in nurseries and landscaped areas (2). There have also recently been a number of incidences of lethal bark cankers caused by P. ramorum in native and nonnative trees in Europe (7). P. ramorum has a broad and expanding host range (3,4,10,11,19,20,28,31), and as a result of the threat posed to forest ecosystems, the movement of a variety of its host species is subject to restrictions in Europe and the United States. Emergency European Community phytosanitary measures for P. ramorum were introduced in 2002 (1), and in the United States quarantine restrictions at both the federal and state levels control the movement of a variety of plant species from infested areas in California and Oregon (31). The availability of rapid and accurate detection methods for P. ramorum is critical to allow its prevalence to be monitored and to expedite management or eradication steps to prevent its introduction and minimize its spread.The identification of P. ramorum is not possible based on host symptoms alone due to the considerable variation in their expression and because a range of other causes can produce similar symptoms. These include infections by several other Phyt...

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Sudden Oak Death Caused by Phytophthora ramorum in Oregon

Cited by 81 publications

References 0 publications

Examining the strength and possible causes of the relationship between fire history and Sudden Oak Death

Examining the strength and possible causes of the relationship between fire history and Sudden Oak Death

Molecular Detection of Phytophthora ramorum by Real-Time Polymerase Chain Reaction Using TaqMan, SYBR Green, and Molecular Beacons

On-Site DNA Extraction and Real-Time PCR for Detection of Phytophthora ramorum in the Field

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