Isolation and characterization of Erwinia amylovora-specific phages for biocontrol of fire blight disease in Tunisia

This study investigates the isolation and characterization of Erwinia amylovora-specific phages for potential biocontrol of fire blight disease (FBD). A total of nine phages were isolated from infected pear trees and soil using a single plaque purification method, with four phages (pHEa1, pHEa2, pHEa3, and pHEa4) demonstrating the ability to initiate a lytic cycle on the E. amylovora strains. Morphological analysis classified pHEa1 and pHEa2 as Myovirus-like, while pHEa3 and pHEa4 were identified as Podovirus-like. The optimal multiplicity of infection (MOI) was determined to be 0.1, revealing varying latency periods and burst sizes among the phages. In vitro assays indicated that the phages effectively reduced E. amylovora populations, with plant-isolated phages exhibiting superior efficacy. Environmental stability tests showed that phages pHEa3 and pHEa4 maintained activity across a broader temperature range (5 °C–40 °C) and under neutral pH conditions. In vivo experiments utilizing a phage cocktail comprising all four isolated phages demonstrated that treated pear plants exhibited delayed disease symptoms and reduced mortality compared to untreated controls, with only one dead plant observed in the phage-treated group after two months, compared to eight in the untreated group. These findings underscore the potential of E. amylovora-specific phages, particularly in cocktail form, as a sustainable biocontrol strategy for managing fire blight disease in pear orchards.