Improving the production and virulence of entomopathogenic fungi for biological control using insect-derived in vitro culture medium

The environment in which a fungus grows can directly influence their development, transmission, and pathogenic potential. This environment encompasses factors like nutrient availability, biotic and abiotic stressors, as well as host-derived chemical cues. In fungal pathogens, where conidia act as the infectious agents, the environment impacts the quantity and quality of these spores, thereby affecting their ability to infect and kill hosts. In the present study, we investigated the effect of host-derived medium types on various phenotypes, including spore production, growth rate, and virulence in two entomopathogenic fungi, Metarhizium acridum and Metarhizium brunneum. Three medium types derived from insect material were compared to a standard laboratory medium. Conidia produced on the insect-derived media exhibited enhanced sporulation and reduced time to sporulation, while conidial germination and maximum growth rate were comparable across medium types, suggesting that some of the medium-induced phenotypic effects were transient. Notably, conidia derived from two of the insect medium types demonstrated higher virulence, indicating that host-derived cues may prime virulence. These results highlight that the composition of growth substrates can regulate fungal reproductive strategies and virulence, with implications for developing high-throughput phenotyping and for the biotechnological optimization of mass production and efficacy of entomopathogenic fungi in biological control applications.