Isolation and characterization of eight bacteriophages infecting Erwinia amylovora and their potential as biological control agents in British Columbia, Canada

Nineteen active bacteriophages against Erwinia amylovora, the causal agent of fire blight, were collected from apple and pear orchards in the Okanagan and Fraser Valleys of British Columbia. Eight survived the isolation, purification and storage processes. Five bacteriophage isolates included in this study lysed more than 50% of the 20 E. amylovora strains tested from BC. Examination by transmission electron microscopy revealed that all eight phages belong to the order Caudovirales, the tailed phages, and included members of the families Myoviridae and Podoviridae. Bacteriophages were characterized by digestion of the phage DNA with four restriction endonucleases and two sets of PCR primers. Two novel groups, RFLP groups 7 and 8, were identified based on differences in restriction fragment patterns. Phages Phi Ea1337-26 and Phi Ea2345-6 reduced infection by 84% and 96%, respectively, when tested on detached pear blossoms using the epiphyte bacterium Pantoea agglomerans Eh21-5 as a carrier. In addition, bacteriophage Phi Ea2345-6, applied in combination with Eh21-5, reduced infection of fire blight on apple flowers of potted apple trees by 56% and compared well with the antibiotic streptomycin.