Characterization and genetic diversity of causal agent of stone fruit bacterial canker Pseudomonas cerasi, a new pathogen of cherry

Based on phenotypic tests, 49 out of 168 isolates of Pseudomonas syringae obtained from various organs of diseased tissue originating from various regions in Poland, were identified as P. syringae pv. morsprunorum race 1 (Psm1), 10 as race 2 of this pathovar (Psm2), 53 as pathovar syringae (Pss) and 56 as an atypical taxon. The pathogenicity test on immature sweet cherry fruits divided the tested strains into two groups: one with isolates causing black brown necrosis and the second containing isolates inducing water soaked superficial lesions. Phenotypic and genetic studies on toxins production by bacteria showed that all Pss produced syringomycin. However, only some Psm1 isolates have the gene for coronatine production. All strains belonging to Psm2 possessed genes encoding yersiniabactin. Results of genetic analyses (rep-PCRs, PCR MP) confirmed the homogeneity of isolates within pathovar morsprunorum and the atypical taxon and revealed diversity within pathovar syringae. A detailed polyphasic approach including phenotypic and genetic characterization applied for eight strains from the atypical taxon showed that the strains represent a novel species of the genus Pseudomonas for which Pseudomonas cerasi sp. nov. (non Griffin, 1911) is proposed