Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: 7/28/2005
Publication Date: 8/5/2005
Citation: Colburn, G.C., Sechler, K.E., Shishkoff, N. 2005. Survivability and pathogenicity of Phytophthora ramorum chlamydospores in soil [abstract]. Phytopathology. 95:S20.
Technical Abstract: Chlamydospores are produced by most Phytophthora spp. and are important long term survival propagules in the soil. Phytophthora ramorum produces abundant chlamydospores but their purpose in the disease cycle of Sudden Oak Death is unknown. Chlamydospores of A1 and A2 isolates of P. ramorum were produced to infest soils at 100 spores/cm3 soil in sand, potting soil mix, and natural biologically active forest soil. Direct plating was used to quantify the viable chlamydospore population. The soils were maintained in bags at 22 C and 4 C and in plastic pots under normal greenhouse conditions. After 4 months, there was no decline in the population of chlamydospores held at 4 C in any of the soil types. The decline was gradual for chlamydospores held at 22 C, but was much more rapid for soils kept in the greenhouse. Survival of chlamydospores was lowest in the forest soil under greenhouse conditions. To examine chlamydospore pathogenicity, Rhododendron 'Cunningham's White' plants were inoculated with soils infested with 40 chlamydospores/cm3. After 4 weeks, the rhododendron plants had healthy root systems, but P. ramourm could be isolated from the roots indicating infection had occurred.