Isolation of entomopathogenic microorganisms from soil: study of the pathogenicity of an Aspergillus strain and its toxins against Galleria mellonella

Abstract

This study aims at finding an alternative to control bee enemies in order to protect this precious insect. Entomopathogenic microorganisms are isolated from the rhizosphere, and an Aspergillus strain was chosen to be tested against the wax moth Galleria mellonella and the poliniphagous beetle Trogoderma sp. The work of the first part was oriented towards the isolation of bacteria and fungi from soil and phenotypic identification of the fungal strain chosen. Then production and characterization of toxins produced by Aspergillus sp. by submerged fermentation using Maltose medium were done. The double extraction of the supernatant with dichloromethane and its separation by TLC allowed us to reveal the production of Ochratoxin A and Fumagillin. Biotests using different fungal suspensions (D1 = 5.2 * 10 3 sp/ml; D2 = 5.2 * 10 5 sp/ml, D3 = 5.2 * 10 7 sp/ml) and mycotoxins against the two pests allowed us to observe that the treatment did not affect Trogoderma beetle. By contrast, the wox moth was infected by the fungus. This result was confirmed by the qualitative and quantitative determination of the haemolymphatic metabolites which revealed a clear disturbance. The verification of the harmlessness of the fungus tested against *Corresponding author h.mohandkaci@univ-boumerdes.dz Apis mellifera showed that the highest dose 10 7 spores/ml is moderately toxic in honey bees. Finally, the application of minimum inhibitory doses of biocontrol agent Aspergillus will allow to avoiding possible mortalities to bees