Enhanced growth and virulence of Metarhizium species using insect-derived in vitro culture medium

The environment in which a fungus grows directly influences fungal traits such as development, transmission, and pathogenic potential. The environmental niche encompasses factors such as nutrient availability, biotic and abiotic stressors, as well as host-derived chemical cues. In fungal pathogens, where conidia act as the infectious agents, the environmental niche impacts the quantity and quality of the produced conidia, thereby affecting the ability of conidia to infect and kill hosts. In the present study, we investigated the effect of host-derived medium types on various phenotypes, including fungal growth rate, conidial production, and virulence in two entomopathogenic fungi, Metarhizium acridum and Metarhizium brunneum. Three medium types derived from insect material were compared with a standard laboratory medium. When grown on insect-derived medium, cultures exhibited enhanced conidiogenesis and reduced time to conidiogenesis. Although the conidia produced on this host-derived medium germinated and grew at rates comparable to those generated on control medium, they demonstrated higher virulence in one isolate of M. brunneum. 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 optimization of mass production and efficacy of entomopathogenic fungi in biological control applications.