Abstract: We previously reported that the composite application of the plant growth-promoting fungi (PGPF) with the arbuscular mycorrhizal fungus (AMF) Glomus mosseae (Gm) to the soil during planting improved plant growth and suppressed plant diseases caused by pathogens with different lifestyles. To elucidate the mechanisms by which the PGPF and Gm suppress symptom development of leaf pathogens in cucumber plants, we carried out a molecular study. Leaf and/or root samples were taken from plants grown in soil medium amended with the PGPF and/or Gm at sowing, at different periods after challenge inoculation with the pathogens. Results indicated an elevated expression of defense-related genes. We hypothesize the involvement of multiple defense mechanisms leading to ISR in cucumber against the leaf pathogen Colletotrichum orbiculare and the Cucumber mosaic virus-Y (CMV-Y).