Endophytic Mushroom-Associated Fungi for Enhancing Plant Immunity and Resistance to Phytopathogens

Abstract

Endophytic mushroom-associated fungi represent an underexploited biological resource for sustainable crop protection, offering environmentally compatible alternatives to synthetic agrochemicals. While Ascomycota have historically dominated endophyte research, Basidiomycota particularly mushroom-forming Agaricomycetes possess sophisticated enzymatic systems, expansive secondary metabolic pathways, and complex immunomodulatory capabilities that remain largely untapped. This review comprehensively examines the taxonomic diversity, colonization dynamics, and dual mechanisms of pathogen suppression mediated by endophytic macrofungi. Direct antagonism operates through antimicrobial secondary metabolite synthesis (including phenolics, terpenoids, and alkaloids), lytic enzyme secretion (chitinases, β-1,3-glucanases, proteases), mycoparasitism, siderophore-mediated iron sequestration, and competitive niche displacement. Indirect defense mechanisms involve reprogramming host plant physiology via induced systemic resistance (ISR) and systemic acquired resistance (SAR), stabilization of reactive oxygen species (ROS) dynamics through enhanced antioxidant enzyme activity (SOD, CAT, POD), and reinforcement of structural barriers via lignin and callose deposition. Model endophytic systems, particularly Serendipita indica (formerly Piriformospora indica), demonstrate significant disease suppression across diverse crops including onion, chickpea, tomato, and cabbage, reducing pathogen severity by up to 69.5% in field trials. Emerging biotechnological innovations including nanoparticle biosynthesis, multi-omics integration, and activation of silent biosynthetic gene clusters through epigenetic modulation and microbial co-culturing promise to unlock the full metabolic potential of these fungi. This review synthesizes current knowledge on endophytic mushroom-associated fungi and proposes their integration into integrated pest and disease management frameworks, addressing the urgent need for sustainable agricultural practices that maintain crop productivity while reducing ecological damage from conventional agrochemicals.