Plant-mediated effects of the entomopathogenic fungus Beauveria bassiana on Spodoptera littoralis

Beneficial microorganisms constitute a significant and promising alternative to agrochemicals thanks to their capacity to promote plant growth and their defence barriers against different biotic stress agents. Beauveria bassiana is one of the most important entomopathogenic fungi and can colonize a wide variety of plant species. Experimental evidence has already shown that it can contribute to limit growth and survival of plant pests and pathogens. Here we further contribute to this research topic by studying the effect on Spodoptera littoralis (Lepidoptera, Noctuidae) of tomato plants colonized by B. bassiana. Unexpectedly, endophytic colonization of plants has no effect survival of larvae feeding on them, which also showed a weight increase. These larvae proved to be more sensitive to B. bassiana infection, given their reduced immune competence. These results shed new light on the complex network of plant multitrophic interactions which underlie the evolution of entomopathogenic lifestyle in soil fungi.