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Washington State University
WSU Puyallup Ornamental Plant Pathology

Nursery research


Nursery research

Effect of Surface Sterilization Treatments on the Detection and Viability of Phytophthora ramorum on Various SubstratesIMG_0007 sm

Katie Coats, Kathy Riley, Gary Chastagner and Marianne Elliott, Washington State University, Puyallup Research and Extension Center, 2606 W. Pioneer, Puyallup, WA 98371; kpcoats@wsu.edu

An accurate evaluation of asymptomatic colonization of plant tissue by Phytophthora ramorum requires the ability to distinguish between the surface contamination or epiphytic growth of the pathogen and the colonization of plant tissues. Growth on selective media, such as CARP, following the surface sterilization of plant tissue is often used to confirm P. ramorum colonization of the tissue. The use of PCR to detect asymptomatic colonization of tissues requires that treatments kill pathogen propagules as well as render residual pathogen DNA on the surface of substrates undetectable. A series of surface sterilization tests were performed with two commonly used laboratory surface sterilants to determine their efficacy in killing epiphytic propagules of P. ramorum and rendering pathogen DNA undetectable in several different P. ramorum experimental scenarios. Substrates tested include detached rhododendron leaves, rhododendron leaf discs, and freshly harvested Douglas-fir wood. Whatman filter paper was included to represent an inert surface.

Results from preliminary tests indicate that the efficacy of a treatment varies by experimental scenario and detection method. Based on post-sterilization growth on CARP media, a 30-second treatment in a 10% solution of household bleach (0.6% sodium hypochlorite) one hour after a spore suspension of P. ramorum was applied to rhododendron leaves and leaf discs was as effective as higher concentrations of bleach and longer treatments in bleach in killing the pathogen on the surface of this host.  When spore suspensions were placed on Douglas-fir wood samples, a 30-second treatment in a 10% solution of bleach was not as effective as a 30-second treatment with 95% ethanol, based on CARP isolation data post-treatment. When spore suspensions were placed on Whatman filter paper and incubated for 2 days, a 10% bleach solution, 95% ethanol, and water each appeared equally as effective in preventing the detection of P. ramorum by isolation on CARP media post-treatment. When post-treatment quantitative PCR was used to detect the pathogen on Whatman filter paper and Douglas-fir, 10% bleach effectively removed DNA evidence of the pathogen while 95% ethanol and water were ineffective, leaving behind DNA at quantities comparable to those on non-treated substrates.

Additional studies are in progress and will be presented at the symposium.

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Proceedings of the Sudden Oak Death Fourth Science Symposium 2010
Susan J. Frankel, John T. Kliejunas, and Katharine M. Palmieri, tech. coords.

Gen. Tech. Rep. PSW-GTR-229. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station. 378 p

Abstract pdf Poster pdf

 

Contact: Gary Chastagner, 253-445-4528 | WSU Puyallup Research & Extension Center, 2606 West Pioneer, Puyallup, WA, 98371-4998 USA
Last updated January 2, 2013

Biology of P. ramorum


Biology of P. ramorum

Phenotypic variation in Phytophthora ramorum: wild type vs non-wild type isolates wt and nwt

M. Elliott, Washington State University, Puyallup Research and Extension Center, Puyallup, WA, USA 98371; melliott2@wsu.edu ; G. Sumampong, S. F. Shamoun, E. Becker, Canadian Forest Service, Pacific Forestry Centre, Victoria, BC, Canada V8Z 1M5; A. Varga, D. James, S. Masri, Sidney Laboratory, Canadian Food Inspection Agency, Sidney, BC, Canada V8L 1H3; and N. J. Grünwald, Horticultural Crops Research Laboratory, USDA ARS, Corvallis, OR, USA 97330

In earlier studies unusual culture morphology and behavior were noticed among some NA1 isolates of Phytophthora ramorum. This “non-wild type” behavior was not observed in our collection of isolates from the EU1 or NA2 lineages, even though the isolates had been in culture for a similar amount of time. It has been suggested that subculturing in vitro cause culture instability and loss of virulence, and passage through the host can revive the isolate back to its original state.  To study this, we compared four less virulent isolates (non-wild type; nwt) with four isolates of normal virulence (wild type; wt) in our culture collection.  One objective of this study was to determine whether wt behavior could be restored to nwt isolates of P. ramorum by successive re-isolation from host material. Detached leaves of rhododendron “Cunningham’s White” were inoculated with each of the isolates, which were re-isolated and tested for pathogenic aggressiveness, growth rate at maximum, optimum, and minimum temperatures, and chlamydospore production in vitro.

In both wt and nwt groups, there were significant differences in lesion size on detached rhododendron leaves between the original culture and the first re-isolation. Successive re-isolations were not different from the original culture and the first re-isolation. After re-isolation from the host, nwt isolates were still less aggressive than wt isolates. Along with lower aggressiveness on rhododendron leaves, nwt isolates produced fewer chlamydospores in V8 agar than did wt isolates.  There was no difference in growth rate between the original culture and the first re-isolation for most isolates.  However, nwt isolates were found to be more sensitive to temperatures below 2°C and above 28°C. The optimum growth temperature was 20°C.

Our preliminary results show that non-wild type isolates were more variable than wild type isolates in all of the characters tested, and were generally lower in aggressiveness, chlamydospore production, and growth rate at all temperatures for both the original culture and when re-isolated from a host. The greater variability suggests that these isolates are unstable or that slightly deleterious mutation(s) have accumulated in accordance with Muller’s ratchet resulting in reduced fitness. Wild type isolates performed better than non-wild type isolates in all of the phenotypic characters examined. Why nwt survives and proliferates is still a mystery. To understand the cause of these phenotypic differences, the role of cytoplasmic elements and differences in mitochondrial and nuclear DNA are being examined.

in

Proceedings of the Sudden Oak Death Fourth Science Symposium 2010
Susan J. Frankel, John T. Kliejunas, and Katharine M. Palmieri, tech. coords.

Gen. Tech. Rep. PSW-GTR-229. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station. 378 p

Abstract pdf Poster pdf
 

Contact: Gary Chastagner, 253-445-4528 | WSU Puyallup Research & Extension Center, 2606 West Pioneer, Puyallup, WA, 98371-4998 USA
Last updated January 2, 2013

Phytophthora ramorum in waterways


Phytophthora ramorum in waterways

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Spread of Phytophthora ramorum to water, soil, and vegetation outside a nursery in Pierce County, Washington
G. CHASTAGNER (1), K. Coats (1), M. Elliott (1)
(1) Washington State University, Puyallup, WA, U.S.A.
Phytopathology 101:S32

 

Volunteer stream monitoring for invasive Phytophthora species in western Washington
M. ELLIOTT (1), G. Chastagner (1), K. P. Coats (1), A. DeBauw (1), K. Riley (1)
(1) Washington State University, Puyallup Research and Extension Center, Puyallup, WA, U.S.A.
Phytopathology 101:S48

 

Mystery on the Sammamish: What are the sources of Phytophthora ramorum infesting this Washington State waterway?
G. Chastagner (1), K. COATS (1), D. Omdal (2), A. Ramsey-Kroll (2), M. Elliott (3)
(1) Washington State University, Puyallup, WA, U.S.A.; (2) Washington State Department of Natural Resources, Olympia, WA, U.S.A.; (3) Washington State University, Puyallup Research and Extension Center, Puyallup, WA, U.S.A.
Phytopathology 101:S32

 

 

Marianne Elliott, Gary Chastagner, Katie Coats, and Gil Dermott
In Frankel, S.J.; Kliejunas, J.T.; Palmieri, K.M.; Alexander, J.M. tech. coords. 2013. Proceedings of the Sudden Oak Death Fifth Science Symposium. Gen. Tech. Rep. PSW-GTR-243. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station. 169 p.

Spread of P. ramorum from Nurseries into Waterways—Implications for Pathogen Establishment in New Areas 243 KB
Gary Chastagner, Steven Oak, Daniel Omdal, Amy Ramsey-Kroll, Katie Coats, Yana Valachovic, Chris Lee, Jaesoon Hwang, Steven Jeffers, and Marianne Elliott.

In Frankel, Susan J.; Kliejunas, John T.; Palmieri, Katharine M.  2010.  Proceedings of the Sudden Oak Death Fourth Science Symposium.   Gen. Tech. Rep. PSW-GTR-229. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station. 378 p.

Contact: Gary Chastagner, 253-445-4528 | WSU Puyallup Research & Extension Center, 2606 West Pioneer, Puyallup, WA, 98371-4998 USA
Last updated January 2, 2013

Presentations for First Detector Training


Presentations and Workshops

Presentations and workshops are available on a variety of topics related to Sudden Oak Death. Presentations can be downloaded for viewing or contact Marianne Elliott (melliott2@wsu.edu) to arrange a presentation or workshop for your group.

Presentations

 

SOD Symptom ID and Nursery Management

A presentation for nursery professionals on recognizing symptoms of P. ramorum on nursery crops and best management practices to minimize the impact of P. ramorum on a nursery.

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Life Cycle of P. ramorum as it Relates to Soil and Water

Learn how P. ramorum survives and spreads in soil and water environments. Best management practices for nurseries are also discussed.

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Sudden Oak Death and Other Phytophthora Diseases of Rhododendron

Rhododendron is the most important host of P. ramorum in Washington nurseries. Learn how to recognize symptoms of P. ramorum and other Phytophthora diseases of Rhododendron. Some results of a study screening a large number of Rhododendron species and cultivars are also presented.

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Sudden Oak Death and other Phytophthora diseases in Washington ecosystems

Sudden Oak Death is devastating California forests, but what about in Washington? For those interested in the potential effects of P. ramorum on WA forests, native plants, and implications to trade in forest products. Other Phytophthora species and their role in forest ecosystems will be discussed.

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Sudden Oak Death, Madrone Canker, and Systemic Acquired Resistance

A not so random grouping of subjects that will interest tree care professionals and others.

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“What’s killing my tree?”

A presentation from the Master Gardener Advanced Education Conference, Sept 22-24 2011, Ocean Shores, WA. Includes information about tree diseases with special sections on SOD and madrone blight. PDF, ~10 MB.

Decaying Oaks
Decaying Oaks killed by P. ramorum

 

Workshops

First Detector Workshops

Sudden Oak Death First Detector workshops are available for interested groups and industry professionals. The purpose of these workshops is to train participants as first detectors, in the event that P. ramorum is introduced to Washington’s landscape. Master Gardener volunteers and horticultural and natural resource professionals are encouraged to attend a training session.


Managing Phytophthora diseases in the nursery

Phytophthora diseases are very costly to nurseries, and a positive P. ramorum find can have huge economic consequences. At this hands-on workshop methods for reducing damage by Phytophthora diseases in the nursery will be demonstrated.

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For information, please contact:

Marianne Elliott
Puyallup Research and Extension Center
2606 W. Pioneer
Puyallup, WA 98371-4998
253-445-4596
melliott2@wsu.edu

Contact: Gary Chastagner, 253-445-4528 | WSU Puyallup Research & Extension Center, 2606 West Pioneer, Puyallup, WA, 98371-4998 USA
Last updated January 2, 2013

The Sentinel Plant Network


The Sentinel Plant Network

sm191-9188_IMGThe American Public Gardens Association (APGA) is working with the National Plant Diagnostic Network to develop a Sentinel Plant Network, under a grant funded by USDA-APHIS under the 2008 Farm Bill.

APGA recently launched a SPN web page that provides an overview of the program, and its mission, the benefits of participation and information on how member gardens can get involved.

APGA has been working closely with NPDN to develop two “train-the-trainer” modules for public gardens. The first module addresses the impact of plant pests and pathogens and the importance of early detectors as well as providing an overview of the SPN, its primary partners, and the role of participating gardens. The second module, which is focused on the “best practices” of pest /pathogen scouting and reporting and outlines the proper methods of sample collection and submission, will provide valuable instruction to public garden professionals and volunteers. Gardens participating in SPN will be encouraged to use this module in classes offered to the general public, thereby giving them the necessary training to be effective citizen scientists contributing to the early detection of potential threats. Preliminary versions of these modules are expected prior to APGA’s conference in June and will undergo beta testing over the summer before being integrated into the SPN regional professional development workshops this fall and winter.

APGA is also developing a freestanding website marketed towards kids and educators and will work with a curriculum specialist to develop a teacher / parent guide to these resources.

 

 

Contact: Gary Chastagner, 253-445-4528 | WSU Puyallup Research & Extension Center, 2606 West Pioneer, Puyallup, WA, 98371-4998 USA
Last updated January 2, 2013