Endophytes and their significance in plant health and agricultural sustainability

Endophytic Microbes in Plants: Mechanisms, Functions, and Agricultural Applications

Endophytic microorganisms—bacteria and fungi that colonise internal plant tissues without inducing overt disease—are a functionally important and still partly hidden component of the plant microbiome. Advances in cultivation-independent methods and multi-omics technologies have, over the past two decades, turned endophyte research from a largely descriptive, taxonomy-led pursuit into a mechanistic science with real bearing on sustainable crop production. This review critically synthesises the literature on the biology, mechanisms, and agricultural relevance of plant-associated endophytic microbes. It examines how endophytes colonise host tissues, the routes by which they are transmitted within and between plant generations, and the ecological logic underlying host specificity and core microbiome assembly. The principal mechanisms through which endophytes promote plant growth—phytohormone biosynthesis, biological nitrogen fixation, phosphate solubilisation, siderophore-mediated iron acquisition, and modulation of ethylene via 1-aminocyclopropane-1-carboxylate deaminase—are discussed alongside indirect mechanisms of pathogen suppression, including antibiosis, competitive exclusion, and induced systemic resistance. Particular attention is paid to the role of endophytes in conferring tolerance to drought, salinity, heavy-metal contamination, and temperature extremes, and to specialised symbioses such as those formed by Serendipita indica, dark septate endophytes, and Epichloë species. The review then considers how this biology has been, or might be, translated into biofertilisers, biopesticides, biostimulants, seed-applied inoculants, and phytoremediation strategies, before evaluating the contribution of omics technologies and synthetic microbial communities to rational inoculant design. Persistent obstacles to field-scale reliability, formulation stability, and regulatory harmonisation are critically appraised. The review concludes that endophytic microbes represent a scientifically mature but commercially underexploited resource for climate-resilient agriculture, and identifies where mechanistic understanding still needs to be reconciled with the variability of field performance.

THE ROLE OF PLANT BIOSTIMULANTS AND GROWTH REGULATORS IN CLIMATE-RESILIENT AGRICULTURE: A REVIEW

The need for the most up-to-date, environmentally friendly techniques of controlling plant diseases and pests necessitates keeping an eye out for effective tools that provide a safe environment for human and animal fitness. In recent years, the usage of plant biostimulants (BS), which are derived from various organic materials through hydrolysis reactions, has increased. Soil microbes and plants immediately absorb these Biostimulants, which often consist of peptides, amino acids, polysaccharides, humic acids and phytohormones  with less energy requirement. This benefits not only growth but also the yield and quality of the harvested grain or fruit. These items are intended to promote and increase plant metabolism, reduce stress, etc., rather than to supply nutrients. These days, a variety of biotic and abiotic stresses hinder plant development, seed germination and seedling growth due to shifting climatic conditions, which reduces biological and economic yields. Plant growth regulators (PGRs) helps plant in mitigating different abiotic stresses and also enhances the adaptability of plants in stress conditions. A variety of PGRs, including ethylene (ET), salicylic acid (SA), abscisic acid (ABA) and jasmonates (JAs), are linked to improving plants' ability to respond to various stimuli. On the other hand, under both normal and stressful environmental conditions, PGRs like auxin, cytokinins (CKs), gibberellins (GAs) and relatively novel PGRs like strigolactones (SLs) and brassinosteroids (BRs) are engaged in plant growth and development. These PGRs are crucial for regulating stress adaptation through modulates physiological, biochemical  and molecular processes and activation of the defense system, upregulating of transcript levels, transcription factors, metabolism genes, and stress proteins at cellular levels.

Functional diversity and ecological consequences of endophytic Bacillus-plant interactions.

The genus Bacillus, particularly endophytic species, has been widely studied as a source of plant growth-promoting bacteria in agricultural systems. These microorganisms contribute to plant performance through nutrient acquisition, phytohormone production, pathogen suppression, microbiome modulation, and enhanced tolerance to biotic and abiotic stresses. However, their ecological roles, functional plasticity, and genomic diversity remain poorly integrated into conceptual frameworks that extend beyond crop-based applications. Functional plasticity is reflected in their ability to colonize diverse plant hosts and tissues and to promote similar plant responses through distinct molecular mechanisms. Likewise, genomic diversity is evidenced by variation in accessory genomes, biosynthetic gene clusters, and regulatory networks that shape ecological functions and metabolite production. This review examines endophytic Bacillus as a model for understanding how metabolically versatile and genomically plastic bacteria establish functional, but context-dependent, associations with plants. Drawing on evidence from functional genomics, pangenomics, metabolomics, and microbial ecology, we discuss mechanisms associated with plant growth promotion and emphasize their dependence on host identity, environmental conditions, and microbial interactions. We address functional convergence arising from distinct genetic and metabolic routes, the contribution of accessory genomes and regulatory variation, and the ecological consequences of microbial inoculation in resident plant-associated microbiomes. We also highlight the limitations of in vitro screening approaches and the need for experimental validation across multiple biological scales to establish robust genotype-phenotype relationships. Finally, we extend the discussion beyond agricultural systems to consider the use of endophytic Bacillus in wild plant systems and ecological restoration, emphasizing the importance of evaluating both functional outcomes and ecological impacts.

“Current Applications of Trichoderma in Agriculture Biocontrol of Fungal Pathogens And Enhancement of Plant Growth”

Filamentous fungi of the genus Trichoderma, commonly found in the rhizosphere, are a prevalent component of various soil ecosystem mycobiomes and are known for their ability to colonize plant roots. Understanding Trichoderma's characteristics, including its metabolic activity and interactions with plants and other microorganisms, is crucial for its effective application in agriculture. Interest in Trichoderma is growing due to its direct and indirect biocontrol capabilities against a wide spectrum of soil-borne phytopathogens. These fungi employ a range of complex mechanisms, such as mycoparasitism, degradation of pathogen cell walls, competition for nutrients and space, and activation of plant defence responses. Given the continuous threat posed to plants by various pathogens, particularly filamentous fungi, and the increasing resistance of these pathogens to chemical pesticides, there is a pressing need to develop alternative biological protection strategies. Among non-pathogenic microorganisms, Trichoderma stands out as a promising candidate for sustainable agricultural practices due to its extensive biofertilization and bio stimulatory properties. Most Trichoderma species function as plant growth-promoting fungi, capable of producing phytohormones and the enzyme 1-aminocyclopropane-1-carboxylate (ACC) deaminase. This review consolidates current knowledge on the role of Trichoderma, emphasizing its significance in promoting plant growth and its effectiveness in the biocontrol of fungal phytopathogens.

Revisiting plant-microbe interaction mechanisms for developing efficient biostimulants.

Multifaceted Roles of Trichoderma in Sustainable Agriculture: Mechanisms, Applications, and Future Perspectives

Overall, this review presents the versatile function of Trichoderma spp.