Isolation and characterisation of phages against Pseudomonas syringae pv. actinidiae

Purpose: Pseudomonas syringae pv. actinidiae causes bacterial canker of kiwifruit and is responsible for severe economic losses and emergence of drug-resistant bacteria. Bacteriophages are viruses that infect target bacterial hosts and may be the best strategy to prevent and control kiwifruit canker disease. The objective of this experiment was to monitor the prevalence of Pseudomonas syringae pv. actinidiae and provide insight for the use of phages in biological control. Materials and methods: In this study, 52 strains of Pseudomonas syringae pv. actinidiae were isolated from 68 stem samples of kiwi plant (cv. Hongyang & Jinkui). Following polymerase chain reaction (PCR) analysis, 15 isolates belonging to biovar 3 were identified, one of which was named XWY0007 and used as the target strain to isolate the phages. Thirty-six phages were isolated and purified from a total of 51 surface water samples collected in Shanghai. All phages were identified by transmission electron microscopy (TEM) and their host ranges were evaluated. Three phages, designated phi XWY0013, phi XWY0014 and phi XWY0026 were selected and further characterised using one-step growth curve and stability at different temperatures and pH. Results and conclusions: The isolated phages are promising for use as antimicrobials against bacterial canker in kiwi. This report is regarding Pseudomonas syringae pv. actinidiae and its phages from major areas of kiwifruit cultivation.