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.
Highlights
It is well known that synthetic insecticides have deleterious effects on the worldwide environment and attention has addressed to biocontrol agents as suitable alternatives (Safavi et al, 2007).Entomopathogenic fungi are natural common enemies of arthropods, insects, and they might be used in the management of pest populations in agroforestry and urban ecosystems (Lacey and Kaya, 2007)
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
Analysis of ITS-rDNA sequences have been applied to determine the genetic diversity of M. anisopliae and B. bassiana (Wall et al, 2005; Entz et al, 2005; Becerra et al, 2007; Carneiro et al, 2008; Freed et al, 2011)
Summary
Entomopathogenic fungi are natural common enemies of arthropods, insects, and they might be used in the management of pest populations in agroforestry and urban ecosystems (Lacey and Kaya, 2007). Insect pathogenic fungi have to meet several host challenges producing enough new infectious spores in each generation maintaining viable populations. Spores should germinate and initiate penetration of the solid insect exoskeleton relatively quickly (Cole and Hoch, 1991). The fungal cells must proliferate inside the hemocell, muscles, or other host body tissues collapsing the host immune system in order to the host dies shortly after (Vega et al, 2012). The fungal pathogen should manage the host cadaver optimizing spore production and dispersal under prevailing environmental conditions (Roy et al, 2006)
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