Trophic and Symbiotic Interactions between Endophytic Fungi, Soil Microfauna and Plants: Implications for Sustainable Agriculture and Soil Ecology

Endophytic fungi, or endobionts, are microscopic fungi that inhabit plant tissues without causing disease symptoms, playing a key role in enhancing plant growth and improving resilience to both biotic and abiotic stresses if their growth is controlled or balanced. Beyond their agricultural importance, these fungi also form vital trophic and symbiotic relationships with soil microfauna such as nematodes, protozoa, and microarthropods. These relationships affect nutrient cycling, organic matter breakdown, and the regulation of soil microbial communities, thereby influencing both plant vitality and faunal diversity in the rhizosphere. Endophytic fungi can function as food sources, mutualistic allies, or antagonists for soil fauna, while microfauna contribute to fungal dispersal and regulate their population dynamics. Together, these intricate interactions support soil food web stability and ecosystem health. Through the production of phytohormones, antimicrobial compounds, and other bioactive metabolites, endophytic fungi not only benefit their host plants directly but also shape the living conditions for soil-dwelling animals indirectly. This review brings together current knowledge on plant–fungus–microfauna interactions, emphasizing their importance for sustainable farming, soil health preservation, and the creation of bioinoculants and biocontrol agents adaptable to various stress environments. It also outlines the challenges and future directions for applying these three-way relationships in ecological and agricultural management.