Efficacy of and pv phages to control fire blight and black rot .

Phytopathogens, such as and , pose significant threats to agriculture, leading to substantial economic losses. Traditional chemical pesticides can harm soil fertility, contaminate water, and impact non-target organisms such as natural predators and pollinators, highlighting the need for sustainable pest control methods. This study explores the use of bacteriophages as biocontrol agents against , which causes fire blight, and pv. , responsible for black rot in cruciferous vegetables. Bacteriophages were isolated from urban wastewater and tested for their lytic activity against these pathogens. Three virulent phages were identified: ɸEF1 and ɸEF2 against and ɸXF1 against pv. . Genetic analysis confirmed the absence of known lysogeny-related genes, indicating that these phages are ideal candidates for biocontrol applications. assays demonstrated significant bacterial population reductions. Specifically, ɸEF1 killed 92.1% of the population at a multiplicity of infection (MOI) of 1 after 3 h, while ɸEF2 reduced the population by 98.1%. When combined in a 1:1 ratio, the two phages reduced populations by 99.7%, and no regrowth of resistant cells was observed, which was not the case when the phages were applied individually. ɸXF1 killed 99.9% of pv. populations at an MOI of 1 after 5 h. experiments using pears and kohlrabi as infection models further validated the phage effectiveness. Treated pears showed reduced fire blight symptoms, and kohlrabi plants exhibited markedly less necrosis from black rot compared to untreated controls.IMPORTANCEThree new virulent phages have been isolated: two targeting and one targeting pv. . All phages were able to rapidly reduce the population of their corresponding phytopathogens and alleviate disease symptoms in plant models. These findings highlight the potential of these phages as biocontrol agents for managing bacterial plant diseases, offering an alternative to traditional chemical treatments.