Submitted to: American Phytopathology Society
Publication Type: Abstract Only
Publication Acceptance Date: March 11, 2004
Publication Date: June 1, 2004
Citation: Shishkoff, N., Tooley, P.W. 2004. Persistence of Phytophthora ramorum in nursery plants and soil. Phytopathology. 94:S95. Publication no. P-2004-0649-AMA. Technical Abstract: Phytophthora ramorum causes cankers, dieback, and foliar symptoms on a number of hosts, but its behavior in soil has not been intensely examined. When Rhododendron x'Cunningham's White' were inoculated on foliage in the greenhouse, tissue taken weekly from the edge of lesions gave rise to colonies of P. ramorum on selective medium for at least 90 days, whether the leaves remained on the plant or fell to the soil surface. When leaf tissue containing chlamydospores was buried in mesh bags below the soil surface in pots containing nursery stock and sampled monthly, chlamydospores plated on selective media formed colonies for at least 155 days after burial. When mycelium that included chlamydospores was buried in a similar fashion and sampled monthly, chlamydospores also formed colonies for at least 155 days. When roots of rhododendron were dipped in a sporangial solution (approx. 2,500 sporangia/mL) and then planted in coarse soil-less medium, P. ramorum could be isolated from unsterilized or 5% bleach-sterilized roots 10-66 days later. These results indicate that P. ramorum may persist in the soil of nursery stock, even if above-ground symptoms are not evident.