Salicylic acid (SA), Jasmonic acid (JA) and ethylene (ET) have the significant roles in the plants physiologically and in defense against pathogens. To elucidate the role of these three phytohormones in the development of Induced systemic resistance (ISR), it is a systemic immune response that occurs when the roots are colonized by beneficial microbes. The study model of SRI is the combination of specific beneficial strains of Pseudomonas fluorescens PTA-CT2 with Arabidopsis thaliana, the course of camalexin levels was monitored before and after infection with the fungus Botrytis cinerea. To conduct this, we use different mutants and transgenic plants that fail in the pathway of JA (jar1), ethylene (ein2) or NahG (transgenic line degrading salicylic acid [SA]).  We are therefore monitoring the evolution of camalexin, a highly lipophilic phytoalexin, before and after bacterization and/or infection. As a consequence of the study, the bacterization induces potentiation of the defenses, which depends on the three signaling pathways.  In addition, the recognition of the beneficial bacteria is reduced by JA and ET.