Endophyte-mediated pest resistance: mechanisms, evidence gaps, and translational opportunities
Escalating crop losses caused by insect pests, together with pesticide resistance, environmental persistence, and increasing regulatory scrutiny of conventional agrochemicals, have intensified interest in biologically based pest-management strategies. Endophytic bacteria and fungi represent a promising avenue for crop protection because they can influence plant defense, pest performance, and multitrophic interactions within plant tissues. This review critically synthesizes the ‘landscape’ of endophyte-mediated pest resistance—the ‘journey’ of microbes from colonization to field protection—through direct antagonism by insecticidal metabolites and enzymes, immune priming, signaling crosstalk (i.e., jasmonic acid, salicylic acid, and ethylene pathways), volatile organic compound-mediated indirect defense, and microbiome restructuring. We further evaluate the strength of evidence across laboratory, greenhouse, and field studies, distinguishing well-supported mechanisms from responses that remain context-dependent or insufficiently validated under agronomic conditions. This implies that endophyte-based pest resistance will remain difficult to translate unless colonization stability, host specificity, ecological trade-offs, formulation performance, biosafety, and regulatory requirements are addressed together. Future progress will require standardized efficacy testing, multiomics-based mechanism validation, improved delivery systems, predictive strain-selection pipelines, and transparent biosafety frameworks. By linking mechanism, evidence strength, and deployment barriers, this review provides a translational framework for moving endophyte-mediated pest resistance from experimental promise toward field-ready crop protection.