Plants have different defence mechanisms to protect themselves from biotic and abiotic stressors. In addition, some of these stressors can effectively prime plant defence responses and make them more resistant to herbivory. In this study, we examined the effects of two entomopathogenic fungi (EPFs), Metarhizium anisopliae strain F01 and Beauveria bassiana strain GHA, on priming plant defence mechanisms in tomato (Solanum lycopersicum). First, we examined the potential of our entomopathogenic fungal isolate for systematic growth in tomatoes from leaf tissue to other sites over time. We found that following the inoculation of tomatoes with these endophytic fungi, the growth of aerial and underground tissues of treated tomatoes was affected, and the total phenolic and flavonoid contents and DPPH scavenging activity changed in different tissues (leaves, stem, and root) over the time compared to the control. Both B. bassiana and M. anisopliae as endophyte in tomato can reduce the preference of Tuta absoluta in choice and no-choice experiment. In addition, T. absoluta developmental parameters decreased after rearing on tomatoes colonized by fungal endophytes. In this study, for the first time, we found that pre-inoculation with B. bassiana or M. anisopliae strongly induced PR-10, ERF, and TGA gene responses in the phytohormone pathways of tomatoes after T. absoluta attack compared to infested plants grown in the absence of the fungus. Also, in the phenylpropanoid pathway, P450, as well as other defence-related genes, PRODH, nsLTP, and WIP, were strongly induced in endophytically colonized tomatoes after T. absoluta herbivory compared to non-colonized tomatoes. These results indicate that EPFs as endophytes can effectively prime plant defence responses, making them more resistant to herbivory with faster and stronger reactions when the stress recurs. These findings provide useful information for understanding the mechanisms of B. bassiana and M. anisopliae in tomato plant growth promotion and quicker responses to T. absoluta attack by priming the immune response, which would facilitate further improvement of EPFs for use in plant production.

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