Status of Fire Blight (Erwinia amylovora) Disease in Romania: Distribution, Pathogen Characterization and Disease Control

Fire blight (Erwinia amylovora) was first observed on apple trees in 1992 in Pitesti (Maracineni) and Braila counties of southeast Romania. Due to several factors, including climate, underestimated loss and lack of efficient control measures, the disease spread to 42 counties in Romania by the year 2000. From 2004 to 2006, 34,785.3 ha (46% of cultivated areas) were inspected for fire blight occurrence. Our results showed an increase in infected areas (35% in 2004, 35.85% in 2005 and 40.3% in 2006) and in the number of positive samples (58% in 2004, 54.74% in 2005 and 67% in 2006). Biochemical characterization of 46 selected strains, using the API 20E system, revealed a great homogeneity. 80% belong to one of the two major API 20E profiles described for E. amylovora. The random amplified polymorphism DNA (RAPD) technique did not allow the detection of genetic markers in E. amylovora strains isolated in Romania and proved not to be discriminating among strains of this pathogen. In the biocontrol experiments, in which pomelo (Citrus maxima) oil was used to control E. amylovora, the CLSM studies showed an inhibition of bacterial development on quince (Cydonia oblonga) leaves when treated for 5 minutes.