Response of soil microbial communities to the application of a formulated Metarhizium brunneum biocontrol strain

Entomopathogenic fungi are used for biological control of insect pests. Metarhizium brunneum Petch (Hypocreales) has potential to control Diabrotica virgifera virgifera LeConte (Chrysomelidae), which is a major pest of maize in North America and has recently invaded Europe. The inundative application of an entomopathogenic fungal strain in biological control results in high densities of fungal propagules in the soil which can potentially affect soil microbial communities and their multiple functions in soil. The objective of the present study was to assess potential effects of M. brunneum on soil fungal and prokaryotic communities in a pot experiment over a time course of 4 months using high-throughput sequencing (HTS) of ribosomal markers. The application of M. brunneum formulated as fungus colonised barley kernels (FCBK) led to a significant increase of the applied strain in soil, as assessed by cultivation-dependent (plating on selective medium followed by genotyping of Metarhizium isolates) and cultivation-independent (HTS of ribosomal markers) approaches. Data revealed that soil fungal and prokaryotic community structures did not change after the application of M. brunneum. Temporal changes of the fungal and prokaryotic communities were observed and the prokaryotic communities showed minor changes to barley kernels (BK), the matrix of the formulation. Results of this study are in accordance with other investigations lacking any evidence for adverse effects on microbial communities caused by applied entomopathogenic fungi.