Erwinia amylovora strains isolated in Romania from outbreaks of fire blight disease: phenotypic characterization.

The fire blight disease was described for the first time in Romania, in 1992. Since then by continuous spreading, this disease has caused severe damages of the fruit trees production, particularly of the pear and quince orchards in different regions of the country, being advantaged by certain weather conditions (high temperatures and humidity). An epidemiological surveillance of this disease that was spreading over different regions of the country, has been instituted since 2002. During the year 2005 a total number of 785 samples were collected from the affected areas. The isolation and identification of Erwinia (E.) amylovora were performed on NSA and King's media and by indirect immunofluorescence (IFA) assay using monoclonal antiserum. Four hundred and fifty strains proved levan-type colonies on sucrose nutrient-agar and were IF-positive. Biochemical characterization of 46 selected strains, by help of the API 20E system, revealed a great homogeneity, for 80% of the strains, belonging to one of the two major API 20E profiles described for E. amylovora, the 20% remaining strains showing minor differences. Hypersensitivity test performed on tobacco leaves was positive. Six of the selected strains were susceptible to streptomycin. The present study can be considered as the first attempt of phenotypic characterization of E. amylovora strains isolated from Romanian area.