scholarly journals Stream Monitoring for Detection of Phytophthora ramorum in Oregon Tanoak Forests

Plant Disease ◽  
2009 ◽  
Vol 93 (11) ◽  
pp. 1182-1186 ◽  
Author(s):  
W. Sutton ◽  
E. M. Hansen ◽  
P. W. Reeser ◽  
A. Kanaskie
Keyword(s):  
Host Plants ◽  
Selective Medium ◽  
Phytophthora Ramorum ◽  
Sudden Oak Death ◽  
Chain Reaction ◽  
Stream Monitoring ◽  
Lithocarpus Densiflorus ◽  
Bait Station ◽  
Mesh Bags ◽  
Polymerase Chain

Stream monitoring using leaf baits for early detection of Phytophthora ramorum has been an important part of the Oregon Sudden Oak Death (SOD) program since 2002. Sixty-four streams in and near the Oregon quarantine area in the southwest corner of the state were monitored in 2008. Leaves of rhododendron (Rhododendron macrophyllum) and tanoak (Lithocarpus densiflorus) were placed in mesh bags, and bags were floated in streams. Leaf baits were exchanged every 2 weeks throughout the year. Leaves were assayed by isolation on selective medium and by multiplex rDNA internal transcribed spacer polymerase chain reaction (ITS PCR). The two methods gave comparable results, but multiplex PCR was more sensitive. P. ramorum was regularly recovered at all seasons of the year from streams draining infested sites 5 years after eradication treatment. In streams with lower inoculum densities, recovery was much higher in summer than in winter. P. ramorum was isolated from streams in 23 watersheds. When P. ramorum was detected, intensive ground surveys located infected tanoaks or other host plants an average of 306 m upstream from the bait station. P. ramorum was isolated from stream baits up to 1,091 m from the probable inoculum source.

Surveying For and Eradicating Phytophthora ramorum in Agricultural Commodities

2004 ◽  
Vol 5 (1) ◽  
pp. 8 ◽  
Author(s):  
Nancy K. Osterbauer ◽  
John A. Griesbach ◽  
Jan Hedberg
Keyword(s):  
Host Plants ◽  
Selective Medium ◽  
Phytophthora Ramorum ◽  
Tree Plantations ◽  
Chain Reaction ◽  
Pcr Assay ◽  
Plant Materials ◽  
Disease Symptoms ◽  
Polymerase Chain ◽  
First Time

Since 2001, Oregon nurseries, Christmas tree plantations, and other sites have been surveyed for the federally regulated pathogen Phytophthora ramorum. Host plants at each site were visually surveyed for disease symptoms and symptomatic tissues tested in the laboratory by isolation onto a selective medium and by a polymerase chain reaction (PCR) assay. In 2002 and 2003, we detected PCRpositive plants that later proved to be infected with another Phytophthora, suggesting there are limitations to the PCR assay tested. In 2003, P. ramorum was detected for the first time in Viburnum, Pieris, Rhododendron, and Camellia plants in six nurseries. All infected and neighboring plant materials were destroyed by incineration and the nurseries and surrounding environs subsequently surveyed for the pathogen. Phytophthora ramorum was not detected, indicating the pathogen was successfully eradicated. Accepted for publication 10 February 2004. Published 9 March 2004.

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.

scholarly journals Phytophthora Blight and Dieback in North Carolina Nurseries During a 2003 Survey

Plant Disease ◽  
2008 ◽  
Vol 92 (3) ◽  
pp. 474-481 ◽  
Author(s):  
C. Y. Warfield ◽  
J. Hwang ◽  
D. M. Benson
Keyword(s):  
North Carolina ◽  
Polymerase Chain Reaction ◽  
Disease Incidence ◽  
Phytophthora Ramorum ◽  
Sudden Oak Death ◽  
Individual Plant ◽  
Phytophthora Blight ◽  
Chain Reaction ◽  
Phytophthora Spp ◽  
Polymerase Chain

A survey of 14 nurseries growing hybrid rhododendron, Pieris spp., or Viburnum spp. was conducted as part of the 2003 Sudden Oak Death Pilot National Survey to determine if Phytophthora ramorum, the causal agent of sudden oak death, had been introduced to nurseries in North Carolina. Over 220,000 hybrid rhododendrons, 1,700 plants of Pieris spp., and 2,800 plants of Viburnum spp. were surveyed. Across nurseries, blight and dieback incidence averaged 2.4% for Pieris spp. and 10% for rhododendron. P. ramorum was not recovered by isolation or detected by polymerase chain reaction in the 347 plant samples collected. Three species of Phytophthora were isolated from hybrid rhododendron and Pieris spp., but no Phytophthora isolates were recovered from Viburnum spp. P. citricola and P. cambivora were isolated most frequently (61 and 39 isolates, respectively), while 2 isolates of P. cactorum were recovered. Occasionally, two Phytophthora spp. were found in the same block of rhododendrons within a nursery, but only one species was recovered from an individual plant. Most cultivars of rhododendron surveyed, including ‘English Roseum,’ ‘Nova Zembla,’ and ‘Roseum Elegans,’ had less than 0.5% incidence of Phytophthora blight and dieback, whereas ‘Lee's Dark Purple’ had 3.8% disease incidence across all nurseries surveyed.

scholarly journals Apparent Outbreaks of Clostridium Difficile-Associated Diarrhea in Horses in a Veterinary Medical Teaching Hospital

1995 ◽  
Vol 7 (3) ◽  
pp. 343-346 ◽  
Author(s):  
Bruce R. Madewell ◽  
Yajarayma J. Tang ◽  
Spencer Jang ◽  
John E. Madigan ◽  
Dwight C. Hirsh ◽  
...  
Keyword(s):  
Polymerase Chain Reaction ◽  
Clostridium Difficile ◽  
Teaching Hospital ◽  
Polymerase Chain Reaction Amplification ◽  
Acute Onset ◽  
Selective Medium ◽  
Chain Reaction ◽  
Medical Teaching ◽  
Polymerase Chain ◽  
Toxigenic Strains

Intestinal colonization with toxigenic strains of Clostridium difficile was documented in 9 of 10 horses with acute onset diarrhea in a veterinary medical teaching hospital, whereas a similar isolate was detected in only 1 of 23 other horses without diarrhea in the hospital. One horse with diarrhea was infected simultaneously with both C. difficile and Salmonella krefeld. Clostridium difficile was detected by fecal culture on selective medium, confirmed with a latex particle agglutination test, and identified as toxigenic by polymerase chain reaction amplification of toxin A and toxin B gene sequences. Using an arbitrarily-primed polymerase chain reaction, 6 distinct C. difficile isolates were detected in the feces of the 9 affected horses at the time of the outbreak of diarrhea.

scholarly journals Rare Pyrenophora teres Hybridization Events Revealed by Development of Sequence-Specific PCR Markers

2017 ◽  
Vol 107 (7) ◽  
pp. 878-884 ◽  
Author(s):  
Barsha Poudel ◽  
Simon R. Ellwood ◽  
Alison C. Testa ◽  
Mark McLean ◽  
Mark W. Sutherland ◽  
...  
Keyword(s):  
Host Plants ◽  
Fragment Length Polymorphism ◽  
Putative Hybrid ◽  
Pyrenophora Teres ◽  
Net Blotch ◽  
Pcr Markers ◽  
Chain Reaction ◽  
Specific Pcr ◽  
Polymerase Chain ◽  
Pathogenic Variability

Pyrenophora teres f. teres and P. teres f. maculata cause net form and spot form, respectively, of net blotch on barley (Hordeum vulgare). The two forms reproduce sexually, producing hybrids with genetic and pathogenic variability. Phenotypic identification of hybrids is challenging because lesions induced by hybrids on host plants resemble lesions induced by either P. teres f. teres or P. teres f. maculata. In this study, 12 sequence-specific polymerase chain reaction markers were developed based on expressed regions spread across the genome. The primers were validated using 210 P. teres isolates, 2 putative field hybrids (WAC10721 and SNB172), 50 laboratory-produced hybrids, and 7 isolates collected from barley grass (H. leporinum). The sequence-specific markers confirmed isolate WAC10721 as a hybrid. Only four P. teres f. teres markers amplified on DNA of barley grass isolates. Amplified fragment length polymorphism markers suggested that P. teres barley grass isolates are genetically different from P. teres barley isolates and that the second putative hybrid (SNB172) is a barley grass isolate. We developed a suite of markers which clearly distinguish the two forms of P. teres and enable unambiguous identification of hybrids.

The effects of Phytophthora ramorum infection on hydraulic conductivity and tylosis formation in tanoak sapwood

2009 ◽  
Vol 39 (9) ◽  
pp. 1766-1776 ◽  
Author(s):  
Bradley R. Collins ◽  
Jennifer L. Parke ◽  
Barb Lachenbruch ◽  
Everett M. Hansen
Keyword(s):  
Hydraulic Conductivity ◽  
Water Transport ◽  
Specific Conductivity ◽  
Phytophthora Ramorum ◽  
Sudden Oak Death ◽  
Inoculation Site ◽  
Lithocarpus Densiflorus ◽  
Stem Water ◽  
Spread Of Infection ◽  
Flow Over Time

Tanoak ( Lithocarpus densiflorus (Hook. and Arn.) Rehder) is highly susceptible to sudden oak death, a disease caused by the oomycete Phytophthora ramorum Werres, De Cock & Man in’t Veld. Symptoms include a dying crown, bleeding cankers, and, eventually, death of infected trees. The cause of mortality is not well understood, but recent research indicates that water transport is reduced in infected trees. One possible mechanism causing the reduction in hydraulic conductivity is the presence of tyloses in xylem vessels. The development of tyloses was studied in relation to hydraulic conductivity in P. ramorum-infected sapwood. Inoculated logs showed a greater abundance of tyloses than noninoculated logs after 4 weeks. Inoculated trees with xylem infections had significantly more tyloses than noninoculated trees. In addition, the increase in number of tyloses was associated with a decrease in specific conductivity, suggesting that tyloses induced by infection with P. ramorum may interfere with stem sap flow. Over time, tylosis development increased in tissues farther from the inoculation site, in advance of the vertical spread of infection. The results suggest that infected sapwood contains numerous tyloses, which could significantly impede stem water transport.

scholarly journals Phytophthora ramorum Colonizes Tanoak Xylem and Is Associated with Reduced Stem Water Transport

2007 ◽  
Vol 97 (12) ◽  
pp. 1558-1567 ◽  
Author(s):  
J. L. Parke ◽  
E. Oh ◽  
S. Voelker ◽  
E. M. Hansen ◽  
G. Buckles ◽  
...  
Keyword(s):  
Specific Conductivity ◽  
Vessel Diameter ◽  
Phytophthora Ramorum ◽  
Heat Diffusion ◽  
Sap Flux ◽  
Tissue Samples ◽  
Lithocarpus Densiflorus ◽  
Polymerase Chain ◽  
Stem Water ◽  
Radial Spread

Isolation, detection with diagnostic polymerase chain reaction (PCR), and microscopy demonstrated the presence of Phytophthora ramorum in the sapwood of mature, naturally infected tanoak (Lithocarpus densiflorus) trees. The pathogen was strongly associated with discolored sapwood (P < 0.001), and was recovered or detected from 83% of discolored sapwood tissue samples. Hyphae were abundant in the xylem vessels, ray parenchyma, and fiber tracheids. Chlamydospores were observed in the vessels. Studies of log inoculation indicated that P. ramorum readily colonized sapwood from inoculum placed in the bark, cambium, or sapwood. After 8 weeks, radial spread of P. ramorum in sapwood averaged 3.0 to 3.3 cm and axial spread averaged 12.4 to 18.8 cm. A field study was conducted to determine if trees with infected xylem had reduced sap flux and reduced specific conductivity relative to noninfected control trees. Sap flux was monitored with heat-diffusion sensors and tissue samples near the sensors were subsequently tested for P. ramorum. Adjacent wood sections were excised and specific conductivity measured. Both midday sap flux and specific conductivity were significantly reduced in infected trees versus noninfected control trees. Vessel diameter distributions did not differ significantly among the two treatments, but tyloses were more abundant in infected than in noninfected trees. Implications for pathogenesis, symptomology, and epidemiology are discussed.

scholarly journals Diversity of Ampeloviruses in Mealybug and Soft Scale Vectors and in Grapevine Hosts from Leafroll-Affected Vineyards

2009 ◽  
Vol 99 (10) ◽  
pp. 1177-1184 ◽  
Author(s):  
M. Fuchs ◽  
P. Marsella-Herrick ◽  
G. M. Loeb ◽  
T. E. Martinson ◽  
H. C. Hoch
Keyword(s):  
New York ◽  
Heat Shock Protein 70 ◽  
Host Plants ◽  
Protein Gene ◽  
Nucleotide Sequence Analysis ◽  
Rt Pcr ◽  
Chain Reaction ◽  
Pcr Products ◽  
Polymerase Chain ◽  
Pseudococcus Maritimus

The occurrence and diversity of Grapevine leafroll-associated virus 1 (GLRaV-1) and Grapevine leafroll-associated virus 3 (GLRaV-3) in the soft scales Parthenolecanium corni and Pulvinaria innumerabilis and in the mealybug Pseudococcus maritimus was determined in leafroll-affected vineyards in the Finger Lakes region of New York. Groups of 1 to 4 specimens were collected under loose grapevine bark and tested by reverse-transcription polymerase chain reaction (RT-PCR) for segments of the second diverged copy of the GLRaV-1 coat protein gene or GLRaV-3 heat-shock protein 70-homologue gene. Virus-specific RT-PCR products were amplified from immature insect vectors and adult mealybugs. Single viral amplicons were obtained mostly from immature vectors (35%, 30 of 85) and dual viral amplicons from immature (16%, 10 of 61) and adult (100%, 14 of 14) mealybugs, including individuals. These observations suggested a simultaneous uptake of GLRaV-1 and GLRaV-3 by individual mealybugs. Furthermore, a comparative nucleotide sequence analysis of viral amplicons from soft scales, mealybugs, and grapevines from which vectors were collected showed identical or highly similar haplotypes, indicating that uptake of GLRaV-1 and GLRaV-3 likely occurred by direct feeding of vectors on their host plants.

scholarly journals Detection of Multiple Verticillium Species in Soil Using Density Flotation and Real-Time Polymerase Chain Reaction

Plant Disease ◽  
2011 ◽  
Vol 95 (12) ◽  
pp. 1571-1580 ◽  
Author(s):  
J. Debode ◽  
K. Van Poucke ◽  
S. C. França ◽  
M. Maes ◽  
M. Höfte ◽  
...  
Keyword(s):  
Polymerase Chain Reaction ◽  
Real Time ◽  
Selective Medium ◽  
Soil Samples ◽  
New Method ◽  
Small Samples ◽  
Chain Reaction ◽  
Polymerase Chain ◽  
Pcr Assays ◽  
Wet Sieving

Wet sieving of soil samples, followed by plating on semi-selective medium and microscopic analysis, is the most commonly used technique to quantify microsclerotia-forming Verticillium species in soil. However, the method is restricted to small samples, does not allow easy differentiation between species, and takes several weeks to complete. This study describes an alternative method to test 100-g soil samples for three Verticillium species (V. tricorpus, V. dahliae, and V. longisporum) using density flotation-based extraction of microsclerotia followed by new real-time polymerase chain reaction (PCR) assays. Primers for these real-time PCR assays were designed to the ribosomal DNA internal transcribed spacer for V. tricorpus and the β-tubulin gene for V. dahliae + V. longisporum and V. longisporum. Tests with artificially and naturally infested soils showed that the new method is reproducible and sensitive (0.1 to 0.5 microsclerotia/g soil), allows differentiation among the three species, and can be completed in one day. The results of the new method and the wet-sieving method were highly correlated for V. tricorpus (R2 = 0.78), but not for V. dahliae/V. longisporum, probably due to the loss of germinability of V. dahliae/V. longisporum microsclerotia during prolonged dry storage of the soil.

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