Abstract: Fusarium oxysporum f. sp. lycopersici (FOL) has proved to be a protective agent inpepper against several pathogens, namely, Verticillium dahliae, Phytophthora capsici andBotrytis cinerea (Díaz et al., 2005). The mechanism of such protection seems to be inducedresistance and ethylene signalling is needed for it (Díaz et al., 2005). Induction by FOL caused anincrease in chitinase activity and cell wall phenolics as well as enhancement of expression ofdefense genes (Díaz et al., 2005; Silvar et al., 2009). The induction of resistance in plants is dueto the recognition by the plant of MAMPs that trigger a response that prime or activate theresistance mechanisms. In the present study, we just started the research to try to unravel theeffects of MAMPs derived from FOL. In practice, FOL could not be used for biocontrol becauseit is a pathogen of tomato, but a MAMP derived from FOL would be agronomically acceptable.Our approach was using an autoclaved extract of Fusarium oxysporum f. sp. lycopersici toinduce plants. The plant roots were exposed to the extract and 48 hours later plants werechallenged with a pathogen. Plant challenge was carried out in some plants on the leaves with theairborne fungus Botrytis cinerea. In other plants, the roots were challenge inoculated with thesoilborne fungus Verticillium dahliae. The extract treatment controlled partially the infection ofthe leaves by the necrotroph Botrytis cinerea while it did not protect the plant against the fungusVerticillium dahliae.Samples of the root and leaves were taken after the induction and after the infection forenzyme and gene expression assays. Peroxidase and chitinase activities were measured, but nochanges were observed. The expression level of a set of genes related with resistancemechanisms was obtained through Real Time RT-PCR. All the genes were up-regulated by theFOL extract, both in the roots and the leaves.