Identification of Pseudomonas syringae isolates causing bacterial blight symptoms on pear and quince trees in Yozgat province of Turkey

Pseudomonas syringae is a polyphagous phytopathogenic bacterial disease agent associated with more than 180 plants species. The bacterial agent causes economically important diseases on several species of fruit trees in Turkey. In 2019, pear and quince trees in several orchards in districts of Yozgat province located in the Central Anatolian Region of Turkey showed bacterial blight symptoms that differed from symptoms of fire blight caused by Erwinia amylovora. Bacterial isolates were obtained from necrotic pear and quince tissue on King’s medium B. Occurrence of pure greyish colonies producing green-blue fluorescent pigment was checked after incubation at 26 °C for 48 h. All purified isolates (n = 5) were Gram-negative, aerobic, and negative for oxidase, induced hypersensitive reaction on tobacco leaves, did not cause soft rot on potato slices, and formed levan-positive colonies on Nutrient Sucrose Agar medium. The identification of bacterial isolates was further confirmed by MALDI-TOF MS and molecular analysis. Identification of these isolates was confirmed by matching with reference Pseudomonas syringae pv. syringae DSM6693 type strain by using MAL-DI-TOF MS analysis. For molecular identification was performed by sequencing the rpoD gene that was amplified with primer pair PsrpoD-FNP1/Psrp-Dnprpcr1. Obtained partial sequences of rpoD gene of five representative isolates showed 100% nucleotide similarity with rpoD gene sequences of available P. syringae pv. syringae isolates from the GenBank. Pathogenicity test revealed that these isolates caused typical disease symptoms on the inoculated pear and quince parts. Re-isolation of the pathogen was obtained from the margins of necrotic lesions on inoculated plant parts. Based on the expressed symptoms, biochemical characteristics, pathogenicity and molecular analysis, the causal disease agent was identified as Pseudomonas syringae pv. syringae.