Hormonal crosstalk in endophyte-mediated biotic stress resilience: from colonization to defence for sustainable agriculture

The unprecedented pressure from a rising global population places heavy demands on agriculture to ensure secure and sustainable food production. Synthetic agrochemicals have contributed to yield enhancement, but their excessive use has led to residual toxicity, environmental pollution, and long-term health hazards, necessitating the search for eco-friendly alternatives. In this scenario, non-pathogenic microbial endophytes residing within plant tissues have emerged as promising biological resources capable of enhancing crop productivity sustainably by increasing resistance to both biotic and abiotic stresses. Through modulation of various phytohormonal signalling pathways, endophytes directly influence plant development and physiology and indirectly suppress pest and pathogen invasion. Apart from promoting stress tolerance, these organisms enhance disease resistance by activating systemic responses. Utilizing these capabilities in the form of bioinoculants represents a sustainable strategy to reduce the dependency on chemical fertilizers and pesticides and to promote plant health along with environmental quality. This review discusses the role of endophytes in engineering plant immunity and stress mitigation through phytohormone regulation, highlighting their function as biocontrol agents within the host-endophyte-pathogen signalling network. Additionally, it also provides an insight into developing broad-spectrum microbial inoculants suitable for challenging environments and emphasizes the potential of OMICS-based research to unravel plant-endophyte interactions, identify novel functional genes and accelerate next-generation inoculant development for improved crop performance under stress conditions.