The Virulence of Metarhizium rileyi to Locusta migratoria Is Determined by the Ability of the Fungus to Respond to Carbon and Nitrogen Sources

Insects are among the most diverse and abundant organisms on Earth, and their population dynamics are strongly influenced by entomopathogenic fungi. This study examines the role of carbon and nitrogen metabolism in the virulence of the entomopathogenic fungus <i>Metarhizium rileyi</i> against the migratory locust, <i>Locusta migratoria</i>. The findings demonstrate that the capacity of <i>M. rileyi</i> to utilize different carbon and nitrogen sources is a key factor in its virulence. Specifically, two strains of <i>M. rileyi</i> (PPDB201006 and SZCY201010) exhibited distinct metabolic abilities, with PPDB201006 displaying superior growth and enzyme activities on various carbon and nitrogen sources compared to SZCY201010. These metabolic differences were associated with significant variations in virulence, as PPDB201006 induced higher mortality rates in <i>L. migratoria</i> than SZCY201010. Metabolomics analysis revealed that infection by <i>M. rileyi</i> led to substantial alterations in the hemolymph metabolites of <i>L. migratoria</i>, particularly in organic acids, amino acids, sugars, and lipids. These results emphasize the significance of carbon and nitrogen metabolism in the pathogenicity of entomopathogenic fungi and offer new perspectives for optimizing their application as biological control agents. This study not only improves our understanding of fungal virulence mechanisms but also contributes to the development of more effective and sustainable pest management strategies.