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POSTERS: Population biology and genetics

Characterization of Pseudomonas syringae pv. papulans strains isolated from ‘NY-1’ apple fruit in New York
Sr?an A?imovi? - Cornell University, Hudson Valley Research Laboratory. Daniel Donahue- Cornell Cooperative Extension, Eastern New York Commercial Horticulture Program, Ricardo Delgado Santander- Cornell University, Hudson Valley Research Laboratory

Pseudomonas syringae pv. papulans (Psp) is the causal agent of apple blister spot, a disease typically affecting the cultivar ‘Mutsu’ and causing economical losses due to symptoms reducing the apple fruit marketability. Disease symptoms on other cultivars usually occur when infected ‘Mutsu’ trees are in the vicinity. However, in 2018 immature ‘NY-1’ apple fruit showing blister spot characteristic symptoms were sampled from an orchard in New York with no ‘Mutsu’ trees in the surroundings. In this work, for the first time, we isolated, identified and characterized Psp isolates from ‘NY-1’ fruit by classical and molecular methods. Characteristic levan-negative colonies on SNA were identified as Psp by specific PCR and 16S rDNA partial sequencing. The isolates were negative for cytochrome oxidase, arginine dihydrolase and pectin degradation, but triggered a strong hypersensitive response in Pelargonium sp. After inoculation, symptoms of blister spot and necrosis were reproduced on immature ‘NY-1’ fruit and leaves, respectively. The Psp isolates were streptomycin sensitive, but showed a high copper tolerance compared to other phytopathogenic bacteria. Studies on apple ‘NY-1’ as a possible new overwintering host for Psp, or on the characterization of copper resistance mechanisms in this bacterial species are currently ongoing, and will provide useful data for the management of blister spot disease.