Comparative analysis of molecular and biological characteristics of strains of Beauveria brongniartii isolated from insects

Variations within the ribosomal DNA gene of the entomopathogenic filamentous genus Beauveria were examined in 28 strains of B. brongniartii and 2 strains of B. bassiana . These strains were isolated from diverse geographical and biological origins, more especially from the white grub Hoplochelus marginalis . Internal transcribed spacer regions (ITS1 and ITS2) were analysed by polymerase chainreaction amplification and restriction fragment-length polymorphism. The analysis revealed a high degree of polymorphism within B. brongniartii species and allows separation of the strains into seven distinct groups. One of these groups contains specifically all strains isolated from H. marginalis . The genetic separation of these strains is supported by their biological origin, since they are the only strains virulent against H. marginalis . Sequence data from the ITSs confirm the conclusions of PCR-RFLP analysis and allow estimation of the genetic distances between the different groups. Intraspecific variability due to point mutation is 0·70–14·67% in ITS1 and 1·80–16·67% in ITS2. This surprisingly high level of polymorphism is discussed.