Use ofMetarhizium anisopliaeChitinase Genes for Genotyping and Virulence Characterization

Abstract

Virulence is the primary factor used for selection of entomopathogenic fungi (EPF) for development as biopesticides. To understand the genetic mechanisms underlying differences in virulence of fungal isolates on various arthropod pests, we compared the chitinase genes,chi2andchi4, of 8 isolates ofMetarhizium anisopliae. The clustering of the isolates showed various groups depending on their virulence. However, the analysis of their chitinase DNA sequenceschi2andchi4did not reveal major divergences. Although their protein translates have been implicated in fungal virulence, the predicted protein structure ofchi2was identical for all isolates. Despite the critical role of chitin digestion in fungal infection, we conclude thatchi2andchi4genes cannot serve as molecular markers to characterize observed variations in virulence amongM. anisopliaeisolates as previously suggested. Nevertheless, processes controlling the efficient upregulation of chitinase expression might be responsible for different virulence characteristics. Further studies using comparative “in vitro” chitin digestion techniques would be more appropriate to compare the quality and the quantity of chitinase production between fungal isolates.