Invasive Species Compendium

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Abstract

Fire blight disease appeared on apricot (Prunus armeniaca 10/13 hybrid) and cherry plum (Prunus cerasifera 'Nigra') in Hungary.

Abstract

Appearance of shoot blight was observed in a ten-years-old cherry plum (Prunus cerasifera 'Nigra') and apricot (Prunus armeniaca 10/13 hybrid) trees near Budapest, Hungary during the period 2012-2014. The shoots of stone fruits 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 pathogen was examined and identified by classical and molecular methods. Isolations on King's B agar medium yielded pure cultures of a bacterium. The isolates showed typical colony morphology on the medium. The isolates were Gram negative and induced a hypersensitive reaction in tobacco (Nicotiana tabacum L. cv. White Burley) leaves. Biochemical tests API 20E (Biomérieux, France) were also used for identification. The pathogenicity was tested by injecting healthy cherry plum and apricot shoots with a bacterial suspension (5*108 CFU/ml). Controls were injected with sterile distilled water. Fifteen days after inoculation dark brown to black lesions and shepherd's crook were observed on the inoculated shoots, while control remained healthy. For molecular identification of the pathogen the 16S rDNA region were amplified by PCR with universal bacterial primer pair (63f forward and 1389r reverse). The PCR products were cloned into pGEM T-Easy plasmid vector and were transformed into Escherichia coli DH5α cells. Sequences were deposited in GenBank (Accession No. HF546214, HF564622). On the basis of the classical and molecular features the pathogen was identified as E. amylovora in case of all isolates. According to our knowledge, this is a first report of a natural outbreak of fire blight on cherry plum and apricot in Hungary.