First occurrence of fire blight on apricot (Prunus armeniaca) in Czech Republic.
During June 2007, a severe bacterial disease was observed on young shoots of an apricot tree. Symptoms of the bacterial disease were observed on 42% of young shoots on a five-year-old apricot tree cultivar 'Veharda' (Prunus armeniaca). This apricot tree was located near pear seedlings (Pyrus ussuriensis) that are very susceptible to Erwinia amylovora, and routinely have fire blight every year. Samples of the leaves with symptoms were macerated and spread on sucrose nutrient agar and King's medium B. After 24 hours of incubation at 27°C, bacteria morphologically similar to E. amylovora were detected (M/07/01). The isolate showed typical colony morphology on King's medium B and CCT medium. The Biolog GN2 MicroPlateTM System and Sherlock®; Microbial Identification System were used to identify the isolated bacteria. A pathogenicity test was positive on immature pear fruits and the strain induced a hypersensitivity response on tobacco leaves (Nicotiana tabacum L. 'Burley SH'). Similar symptoms of fire blight were observed after artificial inoculation of young shoots of apricot with the isolate from apricot and other known strains of E. amylovora. This is a first record of a natural outbreak of fire blight on an apricot tree in the Czech Republic.