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Title: Survival of Phytophthora ramorum chlamydospores at high and low temperatures

item Tooley, Paul
item Browning, Marsha

Submitted to: Sudden Oak Death Science Symposium
Publication Type: Abstract Only
Publication Acceptance Date: 12/5/2006
Publication Date: 3/1/2008
Citation: Tooley, P.W., Browning, M.E. 2008. Survival of Phytophthora ramorum chlamydospores at high and low temperatures. Page 475 in: Frankel, Susan J; Kliejunas, John T; Palmieri, Katherine M., tech. coords. 2008. Proceedings of the sudden oak death third science symposium. Gen. Tech. Rep. PSW-GTR-214. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station. 491 p.

Interpretive Summary:

Technical Abstract: Phytophthora ramorum causes Sudden Oak Death, a destructive disease that imacts forest species, as well as, nursery crops in the U.S. and elsewhere. Chlamydospores were produced as described by Colburn and Shishkoff (Phytopathology 96:S25). Samples (5cc) of chlamydospores in sand inoculum were placed in 15 ml conical plastic test tubes and incubated at selected temperatures for 1, 2, 3, 4, and 7 days. Following incubation, tube contents were resuspended in 0.2% water agar and 1 ml was plated onto PARPH selective medium amended with 4% clarified V8 juice. Numbers of colonies resulting from germinated chlamydospores were assessed microscopically. High temperature treatments included 30, 35, and 40 degrees C while low temperature treatments included 0, -10, and -20 degrees C. All experiments also included chlamydospores placed at 20 degrees C as positive controls. Near 100% survival was observed at temperatures of 0 degree C and for the 20 degree C controls for up to 7 days, while in the low temperature treatments almost no survival occurred at -10 or -20 degrees C over the 7 day period. For the high temperature treatments, high levels of chlamydospore germination were observed over the 7 day period at 30 degrees C and for the 20 degrees C controls, while no growth was observed at 40 degrees C. At 35 degrees C, high levels of chlamydospore germination were observed at day 1, but growth declined steadily and was zero by 7 days. These results help define the temperature conditions under which chlamydospores of P. ramorum survive, and provide information to help define treatments aimed at inactivating chlamydospores in soil substrates.