In order to develop robust management strategies against bacterial plant pathogens, it is necessary to understand the context of pathogen introduction and infection which includes the phyllosphere microbiome. Included in the microbiome are bacteriophages which are viruses that infect bacteria, impacting virulence and pathogenicity of their bacterial hosts.The longterm goal of the proposed project is to explore the genetic and phenotypic diversity of bacteriophage infecting Xanthomonas species and investigate the role of this diversity in determining phage host range and specificity as well as pathogenicity of their bacterial hosts. Outcomes from this work can be used to inform management strategies that could include bacteriophage capable of reducing bacterial populations in an effort to protect agricultural supply chains and availability of healthy food for consumers. To achieve this goal, the following objectives will be addressed:1. Characterize the phenotypic diversity and bacterial host range of phage Xanthomonas arboricola pv. pruni. a.Standardize phage inoculum for host-range studies and phenotypic diversity assays. b.Assess phenotypic diversity of phage-bacterial host interactions. c.Select phage and bacterial hosts for whole genome sequencing.2.Explore genetic components contributing to phage - bacterial interactions. a.Whole-genome sequencing of selected phage isolates representative of phenotypic and host range diversity. b.Whole-genome sequencing of Xanthomonas bacterial strains representing a range in phenotypic and host range diversity based on phageassays. c.Comparative genomic analyses to identify genes and/or gene clusters associated with host specificity in phage isolates.3. Characterize spatiotemporal dynamics of phage-bacteria interactions. a.Profile changes in phage genomes over time and geography. b.Examine patterns of horizontal gene transfer in bacteria resulting from interactions between phage isolates and their Xanthomonas spp. hosts. c.Effect of phage-bacteria interaction on bacterial host pathogenicity and virulence.