Insect pathogens as biological control agents: Back to the future.

Entomopathogenic fungi in the Order Hypocreales are important pathogens of pest and beneficial insects. Entomopathogenic Hypocreales have one of the widest spectra of host ranges among entomopathogens and, as such, many have been commercialized as biopesticides. Traditionally, classical microbiological methods have been used to isolate and identify hypocrealean fungi. While classical methods are still heavily utilized, the application of molecular methods, alone or in combination with classical methods, have provided valuable insights into the biology of entomopathogenic Hypocreales. In this chapter, we provide an overview of both classical and molecular techniques used to study entomopathogenic hypocrealean fungi. Due to the diversity of entomopathogenic fungi and the very wide range of hosts that they infect, we provide information in the form of generalizations as well as via specific examples. In many cases, readers will need to adapt these techniques to their specific requirements.

Laboratory techniques used for entomopathogenic fungi: Hypocreales

Although intensively investigated for biological control of insect pests, little is known about the ecology of the fungal entomopathogenic genus Beauveria in natural or agricultural habitats. In this study, we used molecular phylogenetic and genotypic information to infer species diversity, reproductive potential and genetic structure of Beauveria occurring within a single arable field and bordering hedgerow in Denmark. Isolates were sampled from cultivated field and hedgerow soils, from insects harbouring latent fungal infections, and from the phylloplanes of three plant species common in the hedgerow flora. A nuclear phylogeny of this local Beauveria assemblage resolved seven phylogenetic species, including (i) five phylogenetic species within Beauveria bassiana sensu stricto; (ii) Clade C, a taxonomically uncharacterized species that is morphologically indistinguishable but phylogenetically distant from B. bassiana s.s.; and (iii) Beauveria brongniartii. All seven species were present throughout the hedgerow habitat, including as infections in insects. Significantly, only B. bassiana s.s. phylogenetic species Eu_1 was isolated from tilled soils. Mating type polymerase chain reaction assays demonstrated that all five B. bassiana s.s. phylogenetic species possess bipolar outcrossing mating systems. Of these, only the Eu_1 population contained two mating types; however, a 31:2 skew in MAT1:MAT2 mating types suggests a low frequency of sexual reproduction in this population. The four remaining B. bassiana s.s. phylogenetic species were fixed for single mating types and these populations are evidently clonal. Multilocus microsatellite genotyping revealed polymorphism in all five phylogenetic species of B. bassiana s.s.; however, all show evidence of clonal genetic structure.

Community composition, host range and genetic structure of the fungal entomopathogen Beauveria in adjoining agricultural and seminatural habitats.

Genetic diversity and population structure among strains of the entomopathogenic fungus, Beauveria bassiana, as revealed by inter-simple sequence repeats (ISSR).

S.P. Wraight

Papers

Strain-specific detection of introduced Beauveria bassiana in agricultural fields by use of sequence-characterized amplified region markers.