|Carras, Marie - Former Ars Employee|
Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: 3/24/2010
Publication Date: 6/1/2010
Citation: Tooley, P.W., Carras, M.M. 2010. Detection of Phytophthora ramorum chlamydospores in soil by baiting and dilution plating. Phytopathology. 100:S208.
Technical Abstract: Chlamydospores of P. ramorum produced by mixing 20 percent V8 juice broth cultures with sand and incubating over a 1 month period were used to infest field soil at concentrations ranging from 0.2 to 42 chlamydospores/cc soil. Chlamydospore recovery was determined by baiting with rhododendron leaf discs and dilution plating both when soil infestation was performed (time 0) and following 30 days storage at 4 C, as recommended in the soil and growing medium sampling protocol on the APHIS website (http://www.aphis.usda.gov/plant_health/plantpestinfo/pram /downloads/pdf_files/soil_growingprotocol.pdf). Baiting was slightly more sensitive than dilution plating at time 0, allowing detection of P. ramorum down to 0.2 chlamydospores/cc compared with 1 chlamydospore/cc for dilution plating. Following 30 days of infested soil storage at 4 C, P. ramorum was detected using both methods at significantly (P = 0.05) higher levels than at time 0. The results indicate that storage of P. ramorum-infested soil at 4 C for 30 days can enhance recovery of the pathogen.