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Community composition, host range and genetic structure of the fungal entomopathogen Beauveria in adjoining agricultural and seminatural habitats
Authors:NICOLAI V MEYLING  METTE LÜBECK†  ELLEN P BUCKLEY‡  JØRGEN EILENBERG  STEPHEN A REHNER§
Institution:Department of Agriculture and Ecology, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark;, Center for Biotechnology and Bioenergy, Department of Biotechnology, Chemistry and Environmental Engineering, Aalborg University, Lautrupvang 15, DK-2750 Ballerup, Denmark;, USDA-ARS, Office of National Programs, Natural Resources and Sustainable Agriculture, Beltsville, MD 20705, USA;, Systematic Mycology and Microbiology Laboratory, USDA-ARS, Beltsville, MD 20705, USA
Abstract: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.
Keywords:agro-ecosystem  community  ecological host range  fungi  genetic diversity  recombination
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