Endophytic development of the entomopathogen Beauveria bassiana reduces the immunocompetence of Spodoptera littoralis larvae

Beneficial microorganisms can promote plant growth and defence barriers, offering a valuable alternative to synthetic agrochemicals. Beauveria bassiana is one of the most important entomopathogenic fungi that can colonize a wide variety of plant species as an endophyte, limiting the growth and survival of plant pests and pathogens. Here we contribute to this research topic by studying the effect of tomato plants colonization by B. bassiana on the survival, development, and immunity of Spodoptera littoralis (Lepidoptera, Noctuidae). Endophytic colonization of plants did not affect the survival of larvae feeding on them, which showed a weight increase associated with a higher pupal mortality. Interestingly, encapsulation and nodulation responses of larvae fed with B. bassiana colonized plants were reduced, while, in contrast, phagocytosis slightly increased. These larvae proved to be more sensitive to B. bassiana or Bacillus thuringiensis infection, given their reduced immune competence. “Omic” studies are currently being performed to unravel the molecular mechanism underlying these changes. Our results shed new light on the complex network of multitrophic interactions which underlie the evolution of entomopathogenic lifestyle in soil fungi. KEY