[COMPARATIVE ANALYSIS OF THE IMMUNE REACTIONS IN COLORADO POTATO BEETLE LARVAE UNDER DEVELOPMENT OF MYCOSES CAUSED BY...

Area of Science:

• Entomology
• Immunology
• Microbiology

Background:

• Colorado potato beetle (Leptinotarsa decemlineata) is a major agricultural pest.
• Entomopathogenic fungi, such as Metarhizium species, are potential biocontrol agents.
• Understanding insect immune responses to fungal pathogens is crucial for developing effective biocontrol strategies.

Purpose of the Study:

• To comparatively investigate the humoral and cellular immune responses of Colorado potato beetle larvae to three Metarhizium fungal species.
• To correlate larval immune reactions with fungal virulence and mycosis development.

Main Methods:

• Larvae of Leptinotarsa decemlineata were infected with Metarhizium robertsii, M. brunneum, and M. pemphigi.
• Conidia germination rates in epicuticular extracts were assessed.
• Humoral (phenoloxidase activity) and cellular (hemocyte counts) immune responses were measured at different time points post-infection.
• Larval hemocoel colonization was examined.

Main Results:

• Larvae exhibited high susceptibility to M. robertsii and M. brunneum, but lower susceptibility to M. pemphigi.
• Fungal susceptibility did not correlate with conidia germination rates.
• M. pemphigi, a non-specific pathogen, did not induce significant immune changes or hemocoel colonization.
• Infection with virulent M. robertsii and M. brunneum caused initial hemocyte increases followed by sharp decreases, particularly in plasmatocytes and granulocytes.
• Phenoloxidase activity in hemolymph and cuticle was enhanced following infection with virulent strains.

Conclusions:

• Larval immune responses, including hemocyte counts and phenoloxidase activity, are critical factors influencing the outcome of Metarhizium infections.
• The virulence of Metarhizium species directly correlates with the observed changes in the Colorado potato beetle's immune system.
• Differential immune reactions explain the varying levels of mycosis development caused by different Metarhizium species.