Bioactive secondary metabolites from Trichoderma against phytopathogenic bacteria in rice ( Oryza sativa L.): a review

Bacterial diseases of rice (Oryza sativa L.) pose severe threats to global food security, inflicting significant yield losses across vegetative, reproductive, and grain-filling stages. The growing limitations of conventional bactericides, including resistance development and environmental concerns, have strengthened interest in microbial secondary metabolites as alternative tools for sustainable disease management. This review synthesizes current evidence on the antibacterial potential of Trichoderma-derived secondary metabolites against phytopathogenic bacteria in rice. Recent studies indicate that peptaibols, particularly trichokonins, provide one of the clearest compound-level examples of antibacterial activity against Xanthomonas oryzae pv. oryzae (Xoo). Recent evidence also identifies polyketide-related metabolites, particularly bisvertinolone, as emerging antibacterial compounds with activity against Xoo and X. oryzae pv. oryzicola (Xoc). Other metabolites, including volatile organic compounds (VOCs) and terpenoids, have shown inhibitory or anti-virulence relevance against rice phytopathogenic bacteria. Direct antibacterial evidence is strongest for membrane disruption and cell leakage. In contrast, quorum-sensing interference, enzymatic signal degradation, and signal mimicry represent relevant anti-virulence mechanisms that require further validation in rice-associated bacterial pathosystems. However, current evidence remains heavily concentrated on Xanthomonas-associated diseases, field-scale metabolite characterization is largely absent, and bioformulation development remains underdeveloped. Future research should prioritize metabolomics-guided field validation, expanded pathogen screening across rice growth stages, and development of stable field-adaptable bioformulations to realize the full potential of Trichoderma secondary metabolites in sustainable rice disease management.