Clonal genomic population structure of Beauveria brongniartii and Beauveria pseudobassiana: Pathogens of the common European cockshafer (Melolontha melolontha L.)

Authors: PEDRAZZINI, CHIARALUISA - Agroscope; Rehner, Stephen; STRASSER, HERMANN - University Of Innsbruck; ZEMP, NIKLAUS - Eth Zurich; HOLDEREGGER, ROLF - Eth Zurich; WIDMER, FRANCO - Agroscope; ENKERLI, JURG - Agroscope

Submitted to: Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/7/2024
Publication Date: 4/16/2024
Citation: Pedrazzini, C., Rehner, S.A., Strasser, H., Zemp, N., Holderegger, R., Widmer, F., Enkerli, J. 2024. Clonal genomic population structure of Beauveria brongniartii and Beauveria pseudobassiana: Pathogens of the common European cockshafer (Melolontha melolontha L.) Environmental Microbiology. 26:e16612. https://doi.org/10.1111/1462-2920.16612.
DOI: https://doi.org/10.1111/1462-2920.16612

Interpretive Summary: Insects can cause serious damage or even kill many species of plants, but in some cases, fungi can be used to control them. The insect biocontrol fungus Beauveria brongniartii is used to suppress outbreaks of the plant insect pest Melolantha melolantha (also known as doodle bug) in Europe. DNA analyses are useful tools to determine the genetic diversity of naturally occurring isolates of the fungus to estimate potential effectiveness and other effects of the application of biocontrol strains. This study found that two species of fungi infect M. melolantha, B. brongniartii and B. pseudobassiana, and that both have low levels of genetic diversity. The results of this study will help insect mycologists, fungal ecologists and IPM managers using Beauveria for insect biological control.

Technical Abstract: Beauveria brongniartii is a fungal pathogen of Melolontha melolontha, an agricultural pest in Europe. Prior investigations focused on the use of B. brongniartii to control M. melolontha, however its population genomic structure is unknown, and whether it is affected by its interaction with M. melolontha, geography, year of isolation or reproductive mode. Here, genome-wide SNP polymorphisms were analyzed to infer the population genomics of Beauveria spp. isolated from M. melolontha adults in an Alpine region. One-third of the isolates was identified as B. brongniartii, whereas two-thirds were apportioned among four cryptic species within B. pseudobassiana, a previously unrecognized M. melolontha pathogen. No spatial or temporal patterns emerged in Beauveria spp. population genomics and no correlation was found with M. melolontha population genomics, suggesting that fungal dispersal is not beetle dependent. Both Beauveria spp. displayed clonal structures, with B. brongniartii fixed for MAT 1-1-1 mating type. In contrast, B. pseudobassiana included both mating types, implying factors other than mating compatibility limit sexual reproduction. We conclude that Beauveria spp. population genomics is primarily shaped by asexual reproduction, clonal longevity, dispersal, and establishment capacity. Through population genomics, this study improves understanding of a long-term monitored insect-pathogen interaction, providing new ecological insights.