Plum 'prune d'Agen' is a new host plant of Erwinia amylovora in Hungary.
Appearance of shoot blight was observed in a ten-years-old plum tree in Budaörs, Hungary during the summer of 2011. The naturally infected shoots were on European plum, Prunus domestica L. 'd'Agen'. The plum 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 shoot. The pathogen examined by classical and molecular features. Isolations on general (King's B agar) medium yielded pure cultures of a bacterium. The isolate showed typical colony morphology on the medium. The isolate was gram negative and induced a hypersensitive reaction in tobacco (Nicotiana tabacum L. cv. White Burley) leaves. Biochemical tests, API 20E and API 50 CH (Biomérieux, France) were also used for identification. The pathogenicity was tested by injecting healthy plum shoots with a bacterial suspension (107 CFU/ml). Controls were injected with sterile distilled water. Ten days after inoculation dark brown to black lesions and shepherd's crook were observed only on inoculated shoots. For molecular identification of the pathogen the 16S rDNA region was amplified with general bacterial primer pair (63f forward and 1389r reverse). The PCR products were cloned into a pGEM T-Easy plasmid vector and were transformed into Escherichia coli DH5α cells. A recombinant plasmid was sequenced by M13 forward and reverse primers. The sequence was deposited in GenBank (Accession No. HE610678). On the basis of the classical and molecular features the pathogen was identified as E. amylovora. According to our knowledge, this is a first report of a natural outbreak of fire blight on plum in Hungary. The project was funded by TÁMOP- 4.2.1./B-09/1-KMR-2010-0005 and TÁMOP- 4.2.2./B-10/1-2010-0023 grants.