First occurence of fire blight (Erwinia amylovora) on Prunus species in Hungary

Appearance of shoot blight was observed in a ten-year-old plum (Prunus domestica L. 'd'Agen'), cherry plum (Prunus cerasifera 'Nigra') and apricot (Prunus armeniaca 10/13 hybrid) tree near Budapest, Hungary during 2011-2014. The stone fruits shoots showed typical symptoms of fire blight: blighted, young succulent terminal shoot with brown to black necrotic lesion, wilting and shepherd's crook on affected stems, leaf blighting, and stem cankers on one-year-old shoots. The pathogens examined by classical and molecular features. Isolations on general (King's B agar) medium yielded pure cultures of a bacteria. The isolates showed typical colony morphology on the medium. The isolates were gram negative and induced a hypersensitive reaction in tobacco (Nicotiana tabacum L. 'White Burley') leaves. Biochemical tests API 20E (Biomerieux, France) were also used for identification. The pathogenicity was tested by injecting healthy plum and apricot fruits and plum, cherry plum and apricot shoots with a bacterial suspension (5x10(7) CFU mL(-1)). Controls were injected with sterile distilled water. Fifteen and five days after inoculation dark brown to black lesions and shepherd's crook and the water-soaked tissue lesions were observed only on inoculated shoots and fruits. For molecular identification of the pathogens, the 16S rDNA region were amplified with universal bacterial primer pair. The PCR products were cloned into a pGEM T-Easy plasmid vector and were transformed into Escherichia coli DH5 alpha cells. Recombinant plasmids were sequenced by M13 forward and reverse primers. The sequences were deposited in GenBank (Accession No. HE610678, HF546214, HF564622). On the basis of the classical and molecular features the pathogens were identified as E. amylovora. According to our knowledge, this is a first report of a natural outbreak of fire blight on plum, cherry plum and apricot in Hungary.