Impacts of Metarhizium anisopliae on mortality, energy reserves, and carbohydrase of Trogodermagranarium
2022
Trogoderma granarium Everts is a serious insect pest of the stored products like: wheat, barley, cotton, groundnut, millet, maize, rice, sesame and sorghum. Development of resistance against insecticides is becoming a major issue. So, the current study was planned to assess the bio-pesticidal capacity of Metarhizium anisopliae, which is an entomopathogenic fungus to control this notoriously destructive pest. Toxicity of M. anisopliae was assessed in terms of LC₅₀ by exposing larval T. granarium to five concentrations i.e., 1 × 10⁸, 1 × 10⁷, 1 × 10⁶, 1 × 10⁵ and 1 × 10⁴ conidia/mL suspensions for 7, 14 and 21 days. The increase concentration of conidial suspensions and prolonged exposure time was responsible for higher mortality. The protein concentration and chitinolytic, proteolytic and lipolytic activities of M. anisopliae were found elevated in induced medium containing T. granarium exoskeleton as compared to chitin containing medium. Protease activity level was highest among all of the digestive enzymes, so, in silico analysis was performed to determine whether it could interact with N-acetyl-D-glucosamine the major constitute of exoskeleton. The protease was predicted to bind with N-acetyl-D-glucosamine having a binding energy of 1069.7 kcal/mol and their structure was stabilized by the hydrogen bonds. Moreover, contents of glycogen, total protein, trehalose, total lipids, and soluble protein were significantly decreased 30.211, 6.94, 14.49, 22.02, and 14.8% respectively, while concentration of free amino acid, glucose, DNA and RNA were increased significantly 3.47, 21.65, 6.14 and 28.81% respectively, in infected individuals exposed to LC₂₀ of fungus as compared to controls. For carbohydrase, activities of invertase, catalase and trehalase were increased 10.54, 27.88, and 42.66% while amylase activity was significantly decreased 48.90% in infected individuals exposed to LC₂₀ as compared with control group. The current findings may be used in the production and development of novel myco-pesticide with biodegradable properties and to combat insecticide resistance.
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