Temperature-dependent germination, growth and co-infection of Beauveria spp. isolates from different climatic regions

ABSTRACT

Biological control agents based on entomopathogenic fungi traditionally contain a single strain that is efficient under certain biotic and abiotic conditions. Since particularly abiotic conditions vary, biological control efficiency may become more resilient at extreme temperatures if two or more fungal strains are combined based on their adaptations to their original environment. Here we evaluated the in vitro temperature-dependent germination and growth rate for six Beauveria spp. isolates originating from either arctic or tropical regions. Isolates of arctic origin showed higher germination and growth rate at 8°C and 12°C than isolates from the tropics while the latter group showed highest germination and in vitro growth at 32°C. Three of the isolates belonging to Beauveria bassiana were further tested in vivo for temperature-dependent infection in the mealworm beetle Tenebrio molitor both individually and combined. The same amounts of conidia were used in all bioassays. Virulence was isolate dependent at all temperatures with no additional effect at the low (12°C) and high (32°C) temperatures of combinations of arctic and tropical isolates. The results therefore indicate that adaptations to abiotic conditions in the natural environment do not directly reflect the effect of biotic environment (such as host infection) under similar conditions. Selection of isolates for biocontrol agents should not be based solely on in vitro experiments, while isolate selection based on virulence should also include considerations of the abiotic conditions the isolates are expected to function.

KEYWORDS:

• Temperature
• entomopathogenic fungi
• biological control
• Beauveria bassiana
• Tenebrio molitor
• co-infection
• climatic regions

Acknowledgements

We thank Louise Larsen and Charlotte Fischer for technical assistance.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Brian L. Fredensborg http://orcid.org/0000-0002-4837-5974

Nicolai V. Meyling http://orcid.org/0000-0003-3025-4370

Additional information

Funding

The study was funded by the Villum Foundation [grant number 00007457].