Phenotypic and Genotypic Diversity of Erwinia amylovora Strains, Causing Fire Blight Disease of Pome Fruits in Semnan Province

Fire blight of pome fruits caused by Erwinia amylovora is one of the most devastating disease especially on pear and quince in Semnan province. A total of eighty strains were isolated from different localities and hosts including apple, pear, quince and rose during 2006-2007. Fifty strains were studied for their phenotypic characteristics, genotypic variability, pathogenicity and also resistance to streptomycin and cupper oxychloride. On the basis of physiological, biochemical and morphological features, tested strains were identified as E. amylovora. They were Gram negative, formed levan, facultative anaerobic and induced hypersensitivity reaction in tobacco leaves. They did not produce fluorescent pigment on King`s B medium. On the basis of Phenotypic features, host rang and geographical distribution, eight representatives were selected for evaluating the genetic diversity among them, by rep-PCR using ERIC and BOX primers. All strains were identical to ATCC 49946 strain. On the basis of these experiments no resistance to antibiotics and copper oxychloride was found among the E. amylovora strains causing fire blight of pome fruit trees in Semnan province, therefore chemical bactericides can be safely used in an integrated management program of the disease in Semnan province orchards and this similarity may help to follow a similar method in selecting resistant varieties and forecasting of the disease management.