Abstract

Entomopathogenic fungi considerably vary in their action and virulence mode. The contamination mainly depends on the adhesion and penetration of the fungus in the host integument. Four isolates from Beauveria bassiana and Metarhizium anisopliae were molecularly characterized by rDNA-ITS sequencing. Their virulence against last instar larvae of Galleria mellonella and Tenebrio molitor at four conidia concentrations: 1×10⁶, 1×10⁷, 1×10⁸ and 1×10⁹ conidia.ml^-1 were in vitro evaluated and the lethal concentrations (LC₅₀ and LC₉₀) as lethal time (LT₅₀ and LT₉₀) were determined. Sequencing of rDNA-ITS 500 bp fragments allowed the identification of Ma10MI, Ma12MI, Ma58MI and Ma11MI isolates as M. anisopliae and Bb11MI, Bb79MI, Bb53MI and Bb27MI isolates as B. bassiana by sequence comparison to GenBank. According to the pathogenicity test, B. bassiana strains with higher performance for G. mellonella were Bb53MI and Bb79MI with LC₅₀= 3.98×10⁷ and 1.04×10⁷ conidia.ml^-1 and LT₅₀= 5.46 and 5.27 days, respectively, as well as to T. molitor was Bb79MI with LC₅₀= 1.03×10⁷ conidia.ml^-1 and LT₅₀= 5.57 days. The M. anisopliae strains with the best performance were Ma58MI and Ma10MI both T. molitor (LC₅₀= 1.0×10⁶ and 1.0×10⁷ conidia.ml^-1 and LT₅₀= 4.06 and 5.22 days, respectively) and G. mellonella (LC₅₀= 6.3×10⁷ and 1.1×10⁸ conidia.ml^-1 and LT₅₀= 5.18 and 6.37 days, respectively), these isolates might be considered as new promising candidates for the microbial pest control.

Key words: Pathogenicity, molecular taxonomy, entomopathogenic fungi, microbial control.