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Title: Mortality of container-grown blueberry plants inoculated with Phytophthora cinnamomi Rands

item Smith, Barbara
item Miller Butler, Melinda
item CURRY, KENNETH - University Of Southern Mississippi

Submitted to: Mississippi Academy of Sciences Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 12/25/2014
Publication Date: 12/26/2015
Citation: Smith, B.J., Miller Butler, M.A., Curry, K.J. 2015. Mortality of container-grown blueberry plants inoculated with Phytophthora cinnamomi Rands. Mississippi Academy of Sciences Proceedings. 60:43.

Interpretive Summary:

Technical Abstract: We conducted four studies to evaluate the effect of Phytophthora cinnamomi isolates and inoculum delivery methods on root rot development and mortality of container-grown blueberry plants. Phytophthora cinnamomi isolates were obtained from the root zone of symptomatic blueberry plants and identified using morphological and molecular techniques. Plants were inoculated using one to four delivery methods (mycelial slurry, zoospore suspension, isolates grown on rice or vermiculite). Some studies incorporated a drought/flood treatment. In all studies inoculated plants had higher disease scores than “not inoculated” plants. Study 1: More ‘Biloxi’ plants died (91%) compared to ‘Tifblue’ (12%), suggesting that rabbiteye cultivars are more tolerant of this disease than southern highbush cultivars. Study 2: Significant differences were found in delivery method. Plants inoculated with rice grown inoculum had a mortality rate of 31% compared to 12% for those inoculated with mycelium or zoospores. Study 3: Comparison of virulence of five recently recovered isolates showed no significant differences between disease score and plant vigor due to isolate or delivery method. Study 4: Plants were subjected to three drought/flood treatments and those subjected to a 48-hour flood every three weeks were least vigorous and had the highest mortality rate. There were no differences in plant vigor or disease scores due to drought treatments. In Studies 3 and 4 ‘Biloxi’ received higher vigor ratings, but succumbed to the disease more readily than ‘Star’. Results of these trials will be used to develop procedures for evaluating chemical and biological controls for Phytophthora root rot on blueberries.