A Virus-based Approach to Combat Bacterial Spot: Cationic Phage Supplementation for Enhanced Lytic Activity against Xanthomonas euvesicatoria

Xanthomonas euvesicatoria, an etiological agent of tomato and pepper Bacterial Spot disease, has developed resistance to copper-based antimicrobial agents due to their excessive usage. Increased risks of antimicrobial resistance and copper-associated plant/soil toxicity presents challenges for crop disease management. An emerging alternative for controlling Bacterial Spot is the use of bacteriophages (viruses that infect and kill bacteria). By implementing a plaque assay approach, this study aimed to test the effects of K+, Na+, Zn2+, and Mg2+ at various concentrations, on the lytic infection cycle of Xanthomonas phage FFC20. It was hypothesized that ≤0.1mM divalent cation supplementation would induce a significant effect on lytic activity against X. euvesicatoria. Our results demonstrated that supplementation of FFC20 with each selected cation increased lytic activity against the host bacterium, irrespective of the concentration level. These results highlight the potential benefits of including supplementary cations in phage-based crop disease biocontrol formulations.