This study evaluated the antibacterial efficacy of secondary metabolites from various Streptomyces species against the causative agents of bacterial wilt and soft rot in potatoes. Using morphological, biochemical, and 16 S rRNA-based molecular identification, Streptomyces rochei strain 3MKA was identified as the most potent, exhibiting the highest in vitro inhibition zones against all tested phytopathogenic bacteria. Crude extracts and fractionations were assessed through in vitro and in planta assays. In greenhouse trials, foliar and soil applications of extract fraction F5 from S. rochei 3MKA reduced Ralstonia solanacearum-induced wilt severity and AUDPC by 91%, suppressed pathogen populations in the rhizosphere and crown area to undetectable levels, and maintained potato yield. Pre-treatment of tubers with F5 also effectively inhibited soft rot symptoms caused by Pectobacterium carotovorum and P. atrosepticum. NMR and LC-MS analyses identified the active compound in F5 as palmitic acid (C₁₆H₃₂O₂), a known antibacterial agent. These findings highlight the potential of S. rochei 3MKA-derived metabolites as biocontrol agents for managing major bacterial diseases in potato under integrated pest management (IPM) frameworks. |
