First record of bacterial canker caused by Pseudomonas syringae pv. syringae, on apricot trees in Turkey

Abstract

During the spring and summer of 1999 and 2001, a serious disease with typical bacterial canker symptoms was observed on nearly 80% of apricot trees (Prunus armeniaca) grown in commercial orchards and home gardens in the provinces of Erzurum, Erzincan and Artvin in Turkey. Initial characteristic symptoms were small, water-soaked lesions on blossoms, young expanding leaves and twigs. Subsequent development of the disease was expressed as blossom blast, dried leaves attached to trees, twig dieback, bark necrosis and trunk cankers. A fluorescent, Gram-negative bacterium was consistently isolated from diseased tissues onto King's B medium. A total of 33 bacterial strains were isolated that were oxidase- and arginine dihydrolase-negative, and levan-positive. None of these isolates utilized erythritol and dl-lactate as sole source of carbon (Jones et al., 1986). Fatty acid analysis of the isolates identified the bacterium Pseudomonas syringae pv. syringae with similarity indices of 66–87% (Janse et al., 1992). All isolates were able to induce a hypersensitive response on tobacco plants (Nicotiana tabacum cv. Samsun) (Klement, 1982). Pathogenicity of the strains was confirmed by spray-inoculating 1-year-old host twigs with 108 CFU mL−1 bacterial suspensions in sterile water (Şahin et al., 1999). Inoculated and sterile water-sprayed controls were maintained in the growth chamber with 90% RH for 6–7 days at 24 ± 2°C. Symptoms similar to the original were observed on inoculated plants within 5–7 days. No symptoms developed on controls. Bacteria reisolated from inoculated plants were identified as strains of Pseudomonas syringae pv. syringae. This appears to be the first record of the occurrence and outbreak of a bacterial canker disease on apricot trees in Turkey. This study was supported by a grant from the Research Funds appropriated to Atatürk University.