Secondary metabolites play a pivotal role in the antagonistic activities of some biocontrol species of
Trichoderma sp. T. harzianum used previously as biological control agent against different pathogens. In this work,
the effect of F. oxysporum f. sp. gladioli on the major secondary metabolites secreted by biocontrol strain of T.
harzianum in Potato Dextrose Broth (PDB) cultures were investigated and quantified; followed by investigating the
effect of the previous microorganisms on T. harzianumsecondary metabolites secreted in Gladiolus grandiflorus
corms tissues under controlled conditions. Thin Layer Chromatography (TLC), Liquid chromatography Mass
spectroscopy (LC/MS), and Nuclear Magnetic Resonance (NMR) techniques were used in this study to determine
the major secondary metabolites. This is the first report recording the isolation, characterization and quantification
of 6-n-pentyl-6H-pyran-2-one (6PP) and harzianic acid (HA) from the treated corms with T. harzianum. The
secreted amounts from both metabolites were increased in the pre treated corms with T. harzianum followed by
infection with F. oxysporum f. sp. gladioli. Results provided better understandings of the interaction mechanism
between T. harzianum, F. oxysporum f. sp. gladioli which could be used in the future in different gene expression
studies and will help in using them as bio fertilizers in biocontrol field.