Exploring diversity of Erwinia amylovora population in Serbia by conventional and automated techniquesand detection of new PFGE patterns

Forty Erwinia amylovora strains originating from different host plants and locations in Serbia and one strain from Montenegro were characterized by conventional, automated and molecular techniques. All strains were Gram-negative, nonfluorescent, facultative anaerobes, oxidase negative, levan positive, produced necrotic lesions followed by bacterial exudate on artificially inoculated immature pear fruits and caused HR on tobacco. Based on carbon source utilization, all strains tested with the Biolog system were identified as E. amylovora. Based on fatty acid profiles all tested strains clustered into three groups in which strains from north Serbia differed from strains isolated in central and south parts of the country. Restriction analysis of genomic DNA using XbaI and PFGE resulted in six different patterns differentiating the strains into six groups. Most of the investigated strains clustered in one group having the pattern type similar to Pt2 group described earlier as dominant in East Europe and the Mediterranean region. Two strains showed PFGE pattern similar to the previously described Pt3 pattern and one strain had pattern similar to Pt6. Based on size and number of the bands, new restriction patterns, assigned as Pt7, Pt8 and Pt9 were observed. PFGE results showed that the E. amylovora population in Serbia is not homogenous and was possibly introduced from different directions. This is the first characterization of E. amylovora collection of strains from Serbia using fatty acid analysis and PFGE.