Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: 5/16/2006
Publication Date: 8/2/2006
Citation: Colburn, G.C., Shishkoff, N. 2006. Density of phytophthora ramorum chlamydospores in soil necessary to cause infection. Phytopathology: 96:S25
Technical Abstract: Phytophthora ramorum produces abundant chlamydospores but their significance in the disease cycle is unknown. Chlamydospores of A1 and A2 isolates of P. ramorum were produced in V8 broth cultures which were transferred to sand moistened to holding capacity. Direct plating of the sand onto PARPH was used to quantify the viable chlamydospore population. To examine chlamydospore infectivity, Rhododendron (Cunningham's White) plants were inoculated with potting soil infested with 1, 10, or 100 chlamydospores/cm3. After 8 weeks, plants inoculated with the A2 isolate at all three concentrations had significantly less weight than the uninoculated control plants. Plants inoculated with the A1 isolate did not significantly differ in weight from the control. However, plants inoculated with the A1 isolate at 10 and 100 chlamydospores/cm3 had significantly higher incidences of root infection than plants inoculated with the A2 isolate. The incidence of root infection ranged from 0% in plants inoculated with the lowest concentration of the A2 isolate to 72% in plants inoculated with the highest concentration of the A1 isolate.