scholarly journals First reports of Phytophthora ramorum clonal lineages NA1 and EU1 causing Sudden Oak Death on tanoaks in Del Norte County, California

Plant Disease ◽  
2021 ◽  
Author(s):  
Matteo Garbelotto ◽  
Francesco Dovana ◽  
Douglas Schmidt ◽  
Cameron Chee ◽  
Chris Lee ◽  
...  
Keyword(s):  
San Francisco ◽  
Perfect Match ◽  
Ornamental Plants ◽  
Forest Health ◽  
Phytophthora Ramorum ◽  
Sudden Oak Death ◽  
Clonal Lineage ◽  
Humboldt County ◽  
The North ◽  
Cox 1

A year of forest health surveys has led to the first detection of Phytophthora ramorum in Del Norte County followed by the first wildland detection of the EU1 clonal lineage (Grunwald et al. 2009) of this pathogen in California. In July 2019, leaves were sampled from two tanoaks (Notholithocarpus densiflorus) and 16 California bay laurels (Umbellularia californica) in Jedediah Smith State Park in Del Norte County, the northernmost coastal County of California. Leaves displayed lesions normally associated with Sudden Oak Death (SOD) caused by P. ramorum and were discovered during the citizen science-based survey known as SOD Blitz (Meentemeyer et al. 2015). Samples were surface sterilized using 75% Ethanol and plated on PARPH-V8 agar (Jeffers and Martin 1986). After plating, DNA was extracted and amplified using two P. ramorum-specific assays (Hayden et al. 2006, Kroon et al. 2004). Leaves from two tanoaks exhibiting twig die-back had typical SOD lesions along the midvein, gave positive PCR results and yielded cultures with colony morphology, sporangia and chlamydospores typical of the NA1 lineage of P. ramorum originally isolated in California from tanoaks and coast live oaks (Quercus agrifolia) (Rizzo et al. 2002). The ITS locus and a portion of the Cox-1 locus were sequenced from DNA extracts of each culture using primers DC6-ITS4 (Bonants et al. 2004) and COXF4N-COXR4N (Kroon et al. 2004), respectively. ITS sequences (GB MN540639-40) were typical of P. ramorum and Cox-1 sequences (GB MN540142-3) perfectly matched the Cox-1 sequence of the NA1 lineage (GB DQ832718) (Kroon et al. 2004). Microsatellite alleles were generated as described in Croucher et al. (2013) for the two Del Norte cultures and for eight P. ramorum cultures, representative of the four main multilocus genotypes (MLGs) present in California, namely c1 (Santa Cruz/Commercial Nurseries), c3 (San Francisco Bay Area), c2 (Monterey County), and c4 (Humboldt County) (Croucher et al. 2013). The two Del Norte MLGs were identical to one another and most similar to MLG c1, with a single repeat difference at a single locus. SSR results suggest the inoculum source may not be from Humboldt County, neighboring to the South, but from a yet unidentified outbreak, possibly associated with ornamental plants. Jedediah Smith State Park was surveyed for 12 months following the initial detection, however the pathogen has yet to be re-isolated in that location. In July 2020, SOD symptomatic leaves from two tanoak trees exhibiting twig cankers were collected 8 Km north of Jedediah Smith State Park, where three additional tanoak trees displayed rapidly browned dead canopies consistent with late stage SOD. Leaves were processed as above. Colonies from these samples produced chlamydospores and sporangia typical of P. ramorum on PARPH-V8 agar, but displayed a growth rate faster than that of NA1 genotypes and were characterized by aerial hyphae, overall resembling the morphology of EU1 lineage colonies (Brasier 2003). The EU1 lineage was confirmed by the perfect match of the sequence of a portion of the Cox-1 gene (GB MW349116-7) with the Cox-1 sequence of EU1 genotypes (GB EU124926). The EU1 clonal lineage has been previously isolated from tanoaks in Oregon forests, approximately 55 Km to the North (Grünwald et al. 2016), but this is the first report for California wildlands and will require containment and government regulations. It is unknown whether the EU1 strains in Del Norte County originated from Oregon forests or elsewhere.

scholarly journals First Report of the European Lineage of Phytophthora ramorum on Viburnum and Osmanthus spp. in a California Nursery

Plant Disease ◽  
2008 ◽  
Vol 92 (2) ◽  
pp. 314-314 ◽  
Author(s):  
N. J. Grünwald ◽  
E. M. Goss ◽  
M. M. Larsen ◽  
C. M. Press ◽  
V. T. McDonald ◽  
...  
Keyword(s):  
Sexual Reproduction ◽  
Mating Type ◽  
Genomic Dna ◽  
Phytophthora Ramorum ◽  
Sudden Oak Death ◽  
Humboldt County ◽  
The North ◽  
Nursery Stock ◽  
Genetic Analyzer

Phytophthora ramorum S. Werres & A.W.A.M. de Cock is the causal agent of sudden oak death in California and Oregon forests and ramorum blight on a broad range of host species in wildlands and nurseries. It is thought to be an introduced pathogen and only three clonal lineages are known (3). The North American lineage (lineage NA1, mating type A2) is responsible for infections in California and Oregon forests. The European lineage (lineage EU1, predominantly A1) is responsible for infections in Europe, but has also been found in nurseries in Oregon and Washington. A third lineage (NA2) has only been isolated in a few instances from nurseries in Washington and California. In June 2006, P. ramorum was isolated from diseased Viburnum tinus, Osmanthus heterophyllus, and O. fragrans cultivars from a Humboldt County retail nursery in northern California. We genotyped isolates and placed them into clonal lineages using microsatellite markers developed for P. ramorum (3,4). Genomic DNA was extracted from mycelia with the FastDNA SPIN kit (Q-Biogene, Morgan, Irvine, CA). Primers used were PrMS6, Pr9C3, PrMS39, PrMS43a, PrMS43b, and PrMS45 (3) and 18, 64, and 82 (4). We sized fluorescently labeled amplicons using capillary electrophoresis (3100 Avant Genetic Analyzer, Applied Biosystems, Foster City, CA). Isolate genotypes were compared with control isolates of known clonal lineage, including BBA9/95 (EU1), Pr102 (NA1), and WSDA3765 (NA2). Three of four isolates belonged to genotype EU1. The fourth isolate, obtained from O. fragrans, belonged to genotype NA1. We repeated genotyping on independent genomic DNA extractions and obtained identical results. Two EU1 isolates and the single NA1 isolate were tested for mating type (1) and found to be of A1, A1, and A2 mating type, respectively. The coexistence of A1 and A2 mating types in the same retail nursery suggests the potential for sexual reproduction, as is the case in P. infestans where clonal and sexual populations exist (2), although to date, sexual reproduction in nature has not been documented in P. ramorum. The California retail nursery infestation highlights the risks associated with the unintentional transport of host nursery stock infested with P. ramorum. References: (1) C. M. Brasier and S. Kirk. Mycol. Res. 108:823, 2004. (2) N. J. Grünwald and W. G. Flier. Ann. Rev. Phytopathol. 43:171, 2005. (3) K. Ivors et al. Mol. Ecol. 15:1493, 2006. (4) S. Prospero et al. Mol. Ecol. 16:2958, 2007.

scholarly journals Spatial and Temporal Analysis of Populations of the Sudden Oak Death Pathogen in Oregon Forests

2015 ◽  
Vol 105 (7) ◽  
pp. 982-989 ◽  
Author(s):  
Z. N. Kamvar ◽  
M. M. Larsen ◽  
A. M. Kanaskie ◽  
E. M. Hansen ◽  
N. J. Grünwald
Keyword(s):  
American West ◽  
Temporal Analysis ◽  
Phytophthora Ramorum ◽  
Sudden Oak Death ◽  
Clonal Lineage ◽  
Early Introduction ◽  
North American West ◽  
Genetic History ◽  
The North ◽  
Spatial And Temporal Analysis

Sudden oak death caused by the oomycete Phytophthora ramorum was first discovered in California toward the end of the 20th century and subsequently emerged on tanoak forests in Oregon before its first detection in 2001 by aerial surveys. The Oregon Department of Forestry has since monitored the epidemic and sampled symptomatic tanoak trees from 2001 to the present. Populations sampled over this period were genotyped using microsatellites and studied to infer the population genetic history. To date, only the NA1 clonal lineage is established in this region, although three lineages exist on the North American west coast. The original introduction into the Joe Hall area eventually spread to several regions: mostly north but also east and southwest. A new introduction into Hunter Creek appears to correspond to a second introduction not clustering with the early introduction. Our data are best explained by both introductions originating from nursery populations in California or Oregon and resulting from two distinct introduction events. Continued vigilance and eradication of nursery populations of P. ramorum are important to avoid further emergence and potential introduction of other clonal lineages.

Novel introductions and epidemic dynamics of the sudden oak death pathogen Phytophthora ramorum in Oregon forests

2020 ◽  
Author(s):  
Nicholas C Carleson ◽  
Hazel Daniels ◽  
Paul Reeser ◽  
Alan Kanaskie ◽  
Sarah Navarro ◽  
...  
Keyword(s):  
Principal Component Analysis ◽  
Population Dynamics ◽  
Microsatellite Loci ◽  
Forest Ecosystems ◽  
Principal Component ◽  
Phytophthora Ramorum ◽  
Sudden Oak Death ◽  
Clonal Lineage ◽  
Epidemic Dynamics ◽  
One Year

Sudden oak death caused by Phytophthora ramorum has been actively managed in Oregon since the early 2000’s. To date, this epidemic has been driven mostly by the NA1 clonal lineage of P. ramorum, but an outbreak of the EU1 lineage has recently emerged. Here we contrast the population dynamics of the NA1 outbreak first reported in 2001 to the outbreak of the EU1 lineage first detected in 2015. We tested if any of the lineages were introduced more than once. Infested regions of the forest were sampled between 2013-2018 (n = 903) and strains were genotyped at 15 microsatellite loci. Most genotypes observed were transient, with 272 of 358 unique genotypes emerging one year and disappearing the next. Diversity of EU1 was very low and isolates were spatially clustered (< 8 km apart), suggesting a single EU1 introduction. Some forest isolates are genetically similar to isolates collected from a local nursery in 2012, suggesting introduction of EU1 from this nursery or simultaneous introduction to both the nursery and latently into the forest. In contrast, the older NA1 populations were more polymorphic and spread over 30 km2. Principal component analysis supported two to four independent NA1 introductions. The NA1 and EU1 epidemics infest the same area but show disparate demographics owing to initial introductions of the lineages spaced 10 years apart. Comparing these epidemics provides novel insights into patterns of emergence of clonal pathogens in forest ecosystems.

scholarly journals Sudden Oak Death Caused by Phytophthora ramorum in Oregon

Plant Disease ◽  
2002 ◽  
Vol 86 (4) ◽  
pp. 441-441 ◽  
Author(s):  
E. M. Goheen ◽  
E. M. Hansen ◽  
A. Kanaskie ◽  
M. G. McWilliams ◽  
N. Osterbauer ◽  
...  
Keyword(s):  
San Francisco ◽  
Aerial Survey ◽  
Selective Medium ◽  
Phytophthora Ramorum ◽  
Its Sequences ◽  
Sudden Oak Death ◽  
Usda Forest Service ◽  
Plant Materials ◽  
Solid Media ◽  
Lithocarpus Densiflorus

Sudden oak death, caused by Phytophthora ramorum (1,2), has been found for the first time in Oregon, killing tanoak, Lithocarpus densiflorus, trees. To our knowledge, this is the first report of the disease outside of the San Francisco to Monterey area in California, (300 km to the south). Nine areas of infestation, all within a 24-km2 area, were discovered on forest lands near Brookings, in southwest Oregon. Mortality centers ranged in size from 0.2 to 4.5 ha and included 5 to approximately 40 diseased trees. P. ramorum was isolated from stem cankers using Phytophthora-selective medium. Isolates had distinctive morphological features characteristic of P. ramorum, including abundant production of chlamydospores and caducous, semipapillate sporangia on solid media. Internal transcribed spacer (ITS) sequences of isolates of P. ramorum from Oregon were identical to ITS sequences of isolates from California (1). The pathogen also was isolated from necrotic lesions on leaves and stems of native Rhododendron macrophyllum and Vaccinium ovatum growing beneath diseased tanoaks. In July 2001, the disease was located by an aerial survey conducted cooperatively by the USDA Forest Service and Oregon Department of Forestry. All lands within 1.6 km (1 mile) of the mortality centers are subject to Oregon quarantine, which bars the transport of any host plant materials. An eradication effort is currently underway. Symptomatic plants and all known host plants within 15 to 30 m of symptomatic plants are being cut and burned in the first phase of this operation. The total treated area is approximately 16 ha. References: (1) D. M. Rizzo et al. Plant Dis. In press. (2) S. Werres et al. Mycol. Res. 105:1155, 2001.

First Report of Phytophthora ramorum Infecting Camellia Flower Buds in North America

2006 ◽  
Vol 7 (1) ◽  
pp. 52
Author(s):  
Steve A. Tjosvold ◽  
David L. Chambers ◽  
Samantha L. Thomas ◽  
Cheryl L. Blomquist
Keyword(s):  
North America ◽  
North American ◽  
Phytophthora Ramorum ◽  
Sudden Oak Death ◽  
Flower Buds ◽  
Flower Bud ◽  
First Report ◽  
The North ◽  
Landscape Plants ◽  
North American Genotype

Camellias are important nursery and landscape plants and are known to be highly susceptible hosts of Phytophthora ramorum, the pathogen that causes Sudden Oak Death. This is the first report of camellia flower bud infection in the field with the North American genotype of P. ramorum Accepted for publication 31 May 2006. Published 25 August 2006.

scholarly journals Monitoring Using a Sentinel Plant System Reveals Very Limited Aerial Spread of Phytophthora ramorum From Infected Ornamental Plants in a Quarantine Research Nursery

2017 ◽  
Vol 18 (1) ◽  
pp. 9-16
Author(s):  
Tomas Pastalka ◽  
Suzanne Rooney-Latham ◽  
Kathleen Kosta ◽  
Karen Suslow ◽  
Vernon Huffman ◽  
...  
Keyword(s):  
Short Distance ◽  
Host Plants ◽  
Novel Species ◽  
Disease Incidence ◽  
Ornamental Plants ◽  
Phytophthora Ramorum ◽  
University Of California ◽  
Sudden Oak Death ◽  
Phytophthora Spp ◽  
Sentinel Plants

The potential aerial spread of Phytophthora ramorum, causal agent of sudden oak death and Ramorum blight, from infected plants in a quarantine research nursery at the National Ornamentals Research Site at Dominican University of California (NORS-DUC) to the environment was monitored weekly for five years (2011 to 2016) using a sentinel system. Phytophthora ramorum was never detected on any of the sentinel plants (Rhododendron, Viburnum, and Loropetalum spp), indicating very limited aerial spread under suboptimal meteorological and environmental conditions. An infection experiment with host plants placed in the immediate vicinity of symptomatic plants proved the potential for short-distance (1 to 2 m) aerial transmission of P. ramorum. Other Phytophthora spp. causing symptoms similar to P. ramorum were detected during the rainy season (January to May) on the sentinel plants, among them potentially two novel species. These data reveal how sentinel monitoring at NORS-DUC allows for seasonal assessments of disease incidence and provide longitudinal data to assess the threat of P. ramorum movement in nurseries.

scholarly journals Steaming Inactivates Phytophthora ramorum, Causal Agent of Sudden Oak Death and Ramorum Blight, from Infested Nursery Soils in California

2014 ◽  
Vol 15 (1) ◽  
pp. 43-47 ◽  
Author(s):  
Wolfgang Schweigkofler ◽  
Kathleen Kosta ◽  
Vernon Huffman ◽  
Supriya Sharma ◽  
Karen Suslow ◽  
...  
Keyword(s):  
Thermal Inactivation ◽  
Ornamental Plants ◽  
Soil Layer ◽  
Central Valley ◽  
Phytophthora Ramorum ◽  
Causal Agent ◽  
Sudden Oak Death ◽  
Long Distance ◽  
Top Soil ◽  
Heating Up

Nursery trade plays a major role in the long-distance spread of Phytophthora ramorum, the causal agent of Sudden Oak Death (SOD) and ramorum blight of ornamental plants. Under federal regulations, nurseries found positive for P. ramorum must destroy infected plants and treat infested soils. The use of steam is an effective method to thermally inactivate P. ramorum from nursery soils as demonstrated at the National Ornamental Research Site at Dominican University (NORSDUC) and one commercial nursery in the Central Valley of California. Heating up the top soil layer (0-30 cm) to 50°C for 120 minutes resulted in complete thermal inactivation of P. ramorum. Consequently, the commercial nursery was released from federal quarantine. Steaming can be a fast, reliable and sustainable option for treating nursery soils. Accepted for publication 21 January 2014. Published 13 March 2014.

Observations of the Coyote Lake, California earthquake sequence of August 6, 1979

1980 ◽  
Vol 70 (2) ◽  
pp. 559-570 ◽  
Author(s):  
R. A. Uhrhammer
Keyword(s):  
San Francisco ◽  
Fault Zone ◽  
Strong Earthquake ◽  
Main Shock ◽  
B Value ◽  
Aftershock Sequence ◽  
The South ◽  
The North ◽  
Temporal And Spatial Characteristics ◽  
Largest Aftershock

abstract At 1705 UTC on August 6, 1979, a strong earthquake (ML = 5.9) occurred along the Calaveras fault zone south of Coyote Lake about 110 km southeast of San Francisco. This strong earthquake had an aftershock sequence of 31 events (2.4 ≦ ML ≦ 4.4) during August 1979. No foreshocks (ML ≧ 1.5) were observed in the 3 months prior to the main shock. The local magnitude (ML = 5.9) and the seismic moment (Mo = 6 × 1024 dyne-cm from the SH pulse) for the main shock were determined from the 100 × torsion and 3-component ultra-long period seismographs located at Berkeley. Local magnitudes are determined for the aftershocks from the maximum trace amplitudes on the Wood-Anderson torsion seismograms recorded at Berkeley (Δ ≊ 110 km). Temporal and spatial characteristics of the aftershock sequence are presented and discussed. Some key observations are: (1) the first six aftershocks (ML ≧ 2.4) proceed along the fault zone progressively to the south of the main shock; (2) all of the aftershocks (ML ≧ 2.4) to the south of the largest aftershock (ML = 4.4) have a different focal mechanism than the aftershocks to the north; (3) no aftershocks (ML ≧ 2.4) were observed significantly to the north of the main shock for the first 5 days of the sequence; and (4) the b-value (0.70 ± 0.17) for the aftershock sequence is not significantly different from the average b-value (0.88 ± 0.08) calculated for the Calaveras fault zone from 16 yr of data.

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