Endophytic entomopathogenic fungi enhance plant immune responses against tomato leafminer.

Plants employ various defense mechanisms to protect themselves from invaders such as microorganisms and herbivores. By recognizing these threats, plants can trigger a cascade of responses throughout their tissues, effectively priming their defenses and enhancing their resistance to future attacks. In this study, we examined the indirect effects of the entomopathogenic fungi Beauveria bassiana strain GHA and Metarhizium anisopliae strain F01 on tomato growth, expression of selected plant genes, production of secondary metabolites, and preference and performance of the tomato leafminer (Tuta absoluta). Both B. bassiana and M. anisopliae colonized tomato endophytically. Plants treated with B. bassiana had greater biomass than the untreated control and M. anisopliae treated plants. Oviposition was lower on plants treated with B. bassiana and M. anisopliae than on untreated controls in both choice and no-choice studies, and both endophytic EPF also affected the development of leafminer larvae. Gene expression analysis of tomato leaves inoculated with endophytic EPF provided evidence of triggering plant immune response genes, and of priming genes for herbivore attack, making plants more resistant to herbivory. These findings provide important insights into the mechanisms by which B. bassiana and M. anisopliae promote tomato plant growth and rapidly respond to T. absoluta infestation by priming the immune system. This knowledge could improve the development of entomopathogenic fungi for use in plant-protection strategies.