Identification of the causal agent of bacterial canker on hazelnut trees in Guilan province

Two species of Pseudomonas bacteria including P. avellanae and P. syringae pv. syringaehave been identified till now as pathogenic agents on hazelnut trees. During the year 2004, hazelnut trees of Guilan province were visited and samples were taken from trees showin suspicious symptoms. After culturing extracts of the infected tissues on NA and King’s B media, dark white, fluorescent colonies were isolated. The isolates were gram negative, oxidase and pectinase negative, Levan and catalase positive and obligate oxidative. They caused hypersensitive reaction on tobacco leaves and could not hydrolyze gelatin. Based on these characteristics, isolates were identified as the genus Pseudomonas. The isolates had the ability to produce ice nucleation and syringomycin toxon, but they could not produce indole, reduce nitrate, produce H2S, tolerate NaCl 7% and hydrolyze starch, but they hydrolyzed Tween 80 and casein. The isolates also could use tartarate, L-cystein, lysin, lactose, rhamnose, maltose, Larabinose, ribose, glycin, triptophan and dextrin, but they used D-sorbitol, rafinose, trehalose and sucrose. Pathogenicity test of isolates on leaves, fruit and buds of hazelnut branches wasalso positive. Based on all physiological and biochemical characteristics, the isolates wereidentified as P. syringae pv. syringae. Comparison of protein profile of isolates with reference strain of this pathovar also showed a high similarity percentage. Pathogenicity of this pathovar on hazelnut trees in Guilan province was proved for the first time as a result of the current research. P. avellanae was not observed and isolated from any of the suspected samples and existence of it was not proved in this province.