Related Experiment Video
Updated: Oct 16, 2025
Isolation and Selection of Entomopathogenic Fungi from Soil Samples and Evaluation of Fungal Virulence against Insect Pests
Published on: September 28, 2021
Timing and duration of light exposure during conidia development determine tolerance to ultraviolet radiation
Guilherme T P Brancini1, Luciano Bachmann2, Gilberto Ú L Braga1
1Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, 14040-903, Brazil.
Abstract:
Metarhizium is an important genus of soil-inhabiting fungi that are used for the biological control of insects. The efficiency of biocontrol is dependent on the maintenance of inoculum viability under adverse field conditions such as solar ultraviolet (UV) radiation. Therefore, increasing the tolerance of Metarhizium to UV radiation is necessary. It was previously established that, in mycelium, exposure to visible light increases tolerance to UV radiation. Similarly, growth under visible light for 14 days induces the production of tolerant conidia. However, a study evaluating if and how visible light affects conidia and their relationship with UV radiation was never performed. Here, we report that a relatively short and timed exposure to light around the time of conidiation is sufficient to induce the production of conidia with increased photoreactivating capacity and UV tolerance in Metarhizium acridum. Conidia produced by this method retain their characteristic higher tolerance even after many days of being transferred to the dark. Furthermore, we show that mature conidia of M. acridum and Metarhizium brunneum can still answer to light and regulate UV tolerance, suggesting that gene expression is possible even in dormant spores. Being able to respond to light in the dormant stages of development is certainly an advantage conferring improved environmental persistence to Metarhizium.
Insights
Visible light exposure enhances UV tolerance in Metarhizium fungi spores. This light-induced tolerance in conidia persists even after dark incubation, improving environmental persistence for biological control applications.
Area of Science:
- Mycology
- Biological Control
- Photobiology
Background:
- Metarhizium fungi are vital for insect biocontrol.
- Maintaining inoculum viability under UV radiation is crucial for biocontrol efficacy.
- Previous studies showed light enhances UV tolerance in Metarhizium mycelium and conidia production.
Purpose of the Study:
- To investigate the effect of visible light on Metarhizium conidia and their UV radiation tolerance.
- To determine if light exposure during conidiation induces lasting UV tolerance in Metarhizium conidia.
- To explore the capacity of dormant Metarhizium conidia to respond to light and regulate UV tolerance.
Main Methods:
- Exposing Metarhizium acridum to timed visible light during conidiation.
- Assessing UV tolerance and photoreactivating capacity of induced conidia.
- Evaluating the persistence of UV tolerance in conidia transferred to dark conditions.
- Investigating light-induced UV tolerance regulation in dormant conidia of M. acridum and Metarhizium brunneum.
Main Results:
- Short, timed light exposure during conidiation significantly increases UV tolerance and photoreactivation in Metarhizium acridum conidia.
- This enhanced UV tolerance is retained by conidia even after prolonged periods in darkness.
- Mature, dormant conidia of M. acridum and M. brunneum can still modulate UV tolerance in response to light, indicating gene expression is possible in spores.
Conclusions:
- Visible light exposure during conidiation is an effective strategy to enhance UV tolerance in Metarhizium conidia.
- This light-induced tolerance provides improved environmental persistence for Metarhizium, beneficial for biocontrol.
- The ability of dormant spores to respond to light suggests a sophisticated mechanism for environmental adaptation in Metarhizium.
