AIMTo examine whether isolates of the entomopathogenic fungus Beauveria bassiana are more closely associated to their summer hosts compared with overwintering hosts, with recently developed molecular tools based on mitochondrial regions.METHODS AND RESULTSPrimers for the traditional ITS1-5.8S-ITS2 region and two mitochondrial intergenic regions, namely, nad3-atp9 and atp6-rns, were used. All amplified products were sequenced, aligned and Neighbour-Joining (NJ), parsimony and Bayesian phylogenetic inference analyses were performed. The isolates examined were grouped with very good support into three distinct groups, two of them showed geographical correlation, but no clear association to their host.CONCLUSIONSThe mitochondrial intergenic regions used were more informative than the nuclear ITS1-5.8S-ITS2 sequences. The sequence variability observed, that allowed the phylogenetic placement of the isolates into distinct groups, depended on the geographical origin of the isolates and can be exploited for designing group-specific and isolate-specific primers for their genetic fingerprinting. No clear associations with summer Sunn Pest populations were observed.SIGNIFICANCE AND IMPACT OF THE STUDYStudies on the genetic variability of biocontrol agents like B. bassiana are indispensable for the development of molecular tools for their future monitoring.