PHAGE-BASED BIOPESTICIDES: CHARACTERIZATION OF PHAGE RESISTANCE AND HOST RANGE FOR SUSTAINABILITY

A host range study was done to establish the efficacy of 7 phage biopesticides on a number of Erwinia amylovora isolates, closely related Erwinia species and non-Erwinia species from geographically distinct regions. The Ontario E. amylovora isolates were 100% phage-sensitive and similarly 5 of 6 Quebec isolates were also 100% sensitive. In British Columbia, sensitivity was reduced by at least 14%. Korean Erwinia pyrofolia isolates were 100% sensitive, but the Japan isolates had a variable sensitivity. Within Ea110 and Ea29-7 E. amylovora phage-sensitive populations, 27 and 6 phage-resistant colonies were isolated and characterized, respectively. Dualplex real-time PCR confirmed the isolates as E. amylovora and simultaneously checked for the presence of a prophage. Prophages were detected in 24 of the phage-resistant Ea110 isolates, resulting in lysogeny as responsible for their resistance. There was no detectable prophage in the 6 Ea29-7 phage-resistant isolates therefore resistance is thought to be the result of mutation. For all phage-resistant isolates, resistance was gained against multiple phages used in our biopesticides.