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

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.

Analysis of genetic diversity among different isolates of Beauveria bassiana by RAPD-PCR

“…It infects a variety of insects from different orders and has the potential for insect pest control (Meyling et al, 2009). B. bassiana based mycoinsecticides are used against agricultural, veterinary and medical insect pests.…”

A multidisciplinary approach to study virulence of the entomopathogenic fungus Beauveria bassiana towards malaria mosquitoes

“…coluzzii). shown that B. bassiana is not monophyletic, however it is composed of several cryptic species that are morphologically identical (Ghikas et al, 2010;Meyling et al, 2009;Rehner et al, 2006). For instance, Ghikas et al (2010) described seven phylogenetic clusters in B. bassiana that consisted of isolates which did not show any geographic distribution but had common climate characteristics, and studies from Meyling et al (2009) found isolates that were distributed in five clusters in a particular hedgerow habitat.…”

“…shown that B. bassiana is not monophyletic, however it is composed of several cryptic species that are morphologically identical (Ghikas et al, 2010;Meyling et al, 2009;Rehner et al, 2006). For instance, Ghikas et al (2010) described seven phylogenetic clusters in B. bassiana that consisted of isolates which did not show any geographic distribution but had common climate characteristics, and studies from Meyling et al (2009) found isolates that were distributed in five clusters in a particular hedgerow habitat. Furthermore, a comparative genomic study of seven isolates of the plant pathogen Penicillium expansum showed that the genetic diversity found was between 1.27-7.13 SNPs/kb (Julca et al, 2016), while in two isolates of Aspergillus niger it was on average 7.8 SNPs/kb (Andersen et al, 2011).…”

“…When taking into consideration the phylogenetic clusters found, we realized that only Bb8028 and B5078 belong to the same cluster and had the lowest number of SNPs/kb, compared to the other possible combinations. If we take into consideration that B. bassiana could be polyphyletic, and reports have found a single mating type in several populations (Meyling et al, 2009), it is not surprising that B. bassiana is limited mainly to asexual reproduction. The ability to obtain sexual reproduction under lab conditions would have been useful to perform GWAS of quantitative virulence between offspring of two isolates that differ in virulence, e.g.…”

“…The mating type alleles MAT1-1-1 and MAT1-2-1 were also determined by PCR with the primer pairs MAT112.F4/ MAT111.R5 and MAT2.F4/ MAT2.R5 (Meyling et al, 2009), respectively.…”