Isolation and characterization of two novel phages, ?Rspv1 and ?Rspv2, with a potential for biocontrol of Ralstonia solanacearum

Abstract: Bacteriophages offer an effective biocontrol strategy, presenting an environmentally friendly alternative to combat the issues of antibiotic and copper-based bactericide resistance in bacterial phytopathogens. In this study, two phages targeting Ralstonia solanacearun (designated as ?Rspv1 and ?Rspv2) were identified as potential biocontrol agents against solanaceous wilt, a highly destructive disease causing significant economic losses globally. Both phages demonstrated resistance to chloroform, while ?Rspv1 exhibited a broader host range compared to ?Rspv2 across five isolates of R. solanaceraum. The replication cycle for ?Rspv2 was determined to be 90 min. for a single growth cycle, with a burst size of 85 PFU per cell. Morphologically, ?Rspv1 featured icosahedral heads with long tails, characteristic of the Myoviridae family, whereas ?Rspv2 displayed a filamentous particle shape typical of Inoviridae viruses. Additionally, a Random Amplified Polymorphic DNA (RAPD) analysis using four random primers revealed a diverse nature of the two phages, suggesting their potential utility in disease management strategies. This research unveils two novel virulent phages, and their characterization highlights promising for phage therapy with future investigations aim to field level evaluation against R. solanacearum.