ABSTRACT.- Societal Impact Statement: Arbuscular mycorrhizal (AM) fungi support plant development by enhancing growth and resistance to pathogens through mycorrhiza-induced resistance (MIR). However, the varying capacities of individual AM fungal species to induce MIR are not well-understood, limiting their agricultural potential. This study reveals that specific AM fungal isolates differ in their ability to enhance tomato growth and reduce biomass losses due to Rhizoctonia solani infection, a major root pathogen. By identifying MIR-effective fungal isolates and linking them to shifts in root-associated chemical composition, we highlight potential to improve crop resilience and productivity, advancing agriculture by enabling more efficient use of AM fungi.© 2025 The Author(s). Plants, People, Planet published by John Wiley & Sons Ltd on behalf of New Phytologist Foundation.