@article {JPH:JPH1810, title = {Enhanced recovery of Phytophthora ramorum from soil following 30 Days of storage at 4{\textdegree}C}, journal = {Journal of Phytopathology}, year = {2011}, pages = {no{\textendash}no}, publisher = {Blackwell Publishing Ltd}, abstract = {

Chlamydospores of Phytophthora ramorum were used to infest field soil at densities ranging from 0.2 to 42 chlamydospores/cm3 soil. Recovery was determined by baiting with rhododendron leaf discs and dilution plating at time 0 and after 30\ days of storage at 4{\textdegree}C, as recommended by USDA-APHIS. Baiting was slightly more sensitive than dilution plating in recovering P.\ ramorum immediately following infestation of soil and allowed detection from samples infested with as little as 0.2\ chlamydospores/cm3 compared with 1 chlamydospore/cm3 for dilution plating. After 30\ days of infested soil storage at 4{\textdegree}C, P.\ ramorum was detected at significantly (P\ =\ 0.05) higher levels than at time 0 with both recovery methods. The results indicate that storage of P.\ ramorum-infested soil at 4{\textdegree}C may allow for pathogen activity, such as sporangia production, which may enhance recovery from soil.

}, keywords = {chlamydospore, ramorum blight}, issn = {1439-0434}, doi = {10.1111/j.1439-0434.2011.01810.x}, url = {http://dx.doi.org/10.1111/j.1439-0434.2011.01810.x}, author = {Tooley, Paul W. and Carras, Marie M.} } @article {4209, title = {Effects of Inoculum Density and Wounding on Stem Infection of Three Eastern US Forest Species by Phytophthora ramorum}, journal = {Journal of Phytopathology}, volume = {162}, year = {2014}, month = {Jan-03-2014}, pages = {683 - 689}, abstract = {

Seedlings of three Eastern US forest species Quercus rubra (northern red oak), Quercus prinus (chestnut oak) and Acer rubrum (red maple) were inoculated by applying Phytophthora ramorum sporangia to stems at different inoculum densities with and without wounding. Disease occurred in all treatments involving wounds, and no disease was observed in unwounded treatments. Younger seedlings (2{\textendash}3\ years old) did not differ significantly from older seedlings (5{\textendash}6\ years old) in disease incidence, but older seedlings sustained smaller lesions compared with younger seedlings. For both old and young seedlings, disease on wounded stems was observed down to the lowest sporangia concentration utilized (500 sporangia/ml for old seedlings and 100 sporangia/ml for young seedlings). The results show that in the presence of wounding, even very low sporangia concentrations can result in disease, and further suggest that wounding caused by insects and other factors may play an important role in P.\ ramorum epidemiology in forest environments.

}, doi = {10.1111/jph.12251}, url = {http://doi.wiley.com/10.1111/jph.12251}, author = {Tooley, Paul W. and Browning, Marsha and Leighty, Robert M.} } @article {4556, title = {The Effect of Exposure to Decreasing Relative Humidity on the Viability of Phytophthora ramorum sporangia}, journal = {Journal of Phytopathology}, volume = {164}, year = {2016}, month = {Aug 2016}, pages = {874 - 881}, abstract = {

Sporangia of three isolates of Phytophthora ramorum representing three different clonal lineages were subjected to relative humidity (RH) levels between 80 and 100\% for exposure periods ranging from 1 to 24\ h at 20{\textdegree}C in darkness. Plastic containers (21.5\ {\texttimes}\ 14.5\ {\texttimes}\ 5\ cm) were used as humidity chambers with 130\ ml of glycerine solution added to each container. Glycerine concentrations corresponded to 100, 95, 90, 85 and 80\% RH based on refractive index measurements. Sporangia suspensions were pipeted onto nitrile mesh squares (1.5\ {\texttimes}\ 1.5\ cm, 15 micron pore size) which were placed in the humidity chambers and incubated at 20{\textdegree}C in darkness. Following exposure periods of 1, 2, 4, 8, 12 and 24\ h, mesh squares were inverted onto Petri dishes of selective medium and sporangia germination assessed after 24 and 48\ h. At 100\% RH, we observed a mean value of 88\% germination after 1\ h exposure declining to 18\% germination following 24\ h incubation. At 95\% RH, a steeper decline in germination was noted, with means ranging from 79\% at 1\ h to less than 1\% at 24\ h exposure. At 90\% RH, no germination was noted after 8 or more h exposure, and values were 57\%, 22\% and 3\% germination for the 1, 2 and 4\ h exposures, respectively. Germination was only observed at 1\ h exposure for both the 85\% RH treatment (52\% germination) and the 80\% RH treatment (38\% germination). The three isolates responded similarly\ over the range of RH values tested. The germination response of P.\ ramorum sporangia to RH values between 80\% and 100\% was comparable to that reported for other Phytophthora species. Knowledge of conditions that affect P.\ ramorum sporangia germination can shed light on pathogenesis and epidemic potential and lead to improved control recommendations.

}, doi = {10.1111/jph.2016.164.issue-11pt1210.1111/jph.12506}, url = {https://doi.org/10.1111/jph.12506 }, author = {Tooley, Paul W. and Browning, Marsha} }