Fusarium culmorum is a widespread fungal pathogen that affects many crops worldwide. When it infects cereals, such as wheat, it causes a disease called Fusarium head blight, which can reduce crop yields and contaminate grains with toxins harmful to humans and animals. Farmers constantly battle Fusarium, using environmentally unfriendly fungicides to fight back.
But what if we could fight the fungus using biology?
Just like all living organisms, fungi can be infected by viruses, called mycoviruses. Some mycoviruses can change how their fungal hosts behave, and even make harmful fungi weaker. Luckily, they are strictly restricted to infecting closely related fungi and are harmless to other organisms, including humans.
In our study, we investigated a virus called Fusarium culmorum phenuivirus 1, which infects the fungus Fusarium culmorum. We wanted to understand how this virus affects the fungus and whether it changes the fungus’ ability to infect plants.
To do this, we compared fungal strains with and without the virus. By transferring the virus into a recipient strain marked with an antibiotic resistance gene, we created identical strains, except for either the presence or the absence of the virus. We studied their growth in the laboratory and tested how well they infected wheat plants in a greenhouse and a shaded semi-field.
In the laboratory, the virus did not seem to change how the fungus behaved. The infected fungi looked, grew and produced spores much like those without the virus. However, the virus was easily passed on to fungal spores and could even spread to other fungal strains and species.
When we moved to plant experiments, the story became more interesting. In greenhouse conditions, the virus appeared to make the fungus more aggressive, making the disease worse. But under shaded semifield conditions, the opposite effect was observed, with the fungus becoming less harmful when infected. We also found that the virus changed toxin levels in infected wheat. For example, the amount of one toxin produced by F. culmorum decreased by about 40% when the virus was present.
Our results show that the relationship between fungi and their viruses can be surprisingly complex. The effects of mycoviruses may only appear under certain environmental conditions, so testing should include a variety of conditions. However, by understanding these hidden viral infections inside fungi, we may eventually develop new strategies to manage crop diseases without harmful chemicals.
Zivile Buivydaite, Anne Winding, and Rumakanta Sapkota published this study in Plant Pathology Journal:
Mixed Impacts of the Mycovirus Fusarium Culmorum Phenuivirus 1 on Fusarium culmorum: Laboratory and In Planta Investigations
Cover Image: Testing mycovirus effects on fungal disease
