Endophytic entomopathogenic fungus, individually and in combination with rhizobacteria, enhances resistance in wild and cultivated tomatoes to Tuta absoluta

Several beneficial microbes have been shown to activate defensive mechanisms in plants, enhancing their resistance against herbivores. However, it remains unclear whether different beneficial microbes can synergize to improve defenses in wild plants, similar to their effects in cultivated plants against insect pests. Here, we investigated the effect of the endophytic entomopathogenic fungus Metarhizium robertsii, both individually and in combination with the growth-promoting rhizobacteria Bacillus amyloliquefaciens, on plant growth and volatile emissions in the cultivated Solanum lycopersicum and its two wild parents, S. pimpinellifolium and S. habrochaites. We also assessed the ovipositional preference of the destructive pest Tuta absoluta and the olfactory responses of its natural enemy, the mirid predator Macrolophus basicornis, toward these treatments across each tomato species. Both wild and cultivated plants inoculated with M. robertsii exhibited enhanced growth and emitted higher levels of specific volatile compounds than non-inoculated plants. Furthermore, T. absoluta females laid fewer eggs on S. lycopersicum and S. habrochaites inoculated with M. robertsii. Additionally, the inoculation of this beneficial fungus resulted in increased attraction of M. basicornis to the volatiles of S. lycopersicum and S. pimpinellifolium. Interestingly, the combined inoculation of B. amyloliquefaciens and M. robertsii generally did not yield an additive effect on volatile emissions and resistance against T. absoluta compared to M. robertsii alone in wild and cultivated tomato plants. These results suggest that the inoculation of M. robertsii could be a promising tool for protecting tomato plants against T. absoluta and enhancing the attraction of its natural enemy, M. basicornis.