New research has shown that a fungal virus can convert deadly pathogens into beneficial fungus in rapeseed plants, Cell Press reported on 29 September.

Once transformed, the fungus boosted the plant’s immune system, making the plant healthier and more resistant to diseases.

The findings, published in the journal Molecular Plant, indicated that some fungal viruses could be used to develop ‘plant vaccines’ to improve crop health and enhance crop yield.

Rapeseed farmers suffered significant losses from the fungal pathogens, Sclerotinia sclerotiorum, which caused stem rot, lesions and killed the plants within a few days of infection, Cell Press said.

“The virus we identified can convert the fungus from a deadly pathogen in different plants to an endophytic fungus like a gentle sheep and protect these plants,” said senior author of the study Daohong Jiang, a professor at Huazhong Agricultural University in China.

Endophytic organisms live within a plant for at least part of its life cycle without causing diseases, maintaining a symbiotic relationship.

“The research is important because we know plants have endophytic fungus, but where did it come from? The fungal virus might have played a role in the evolution of these fungi and that’s something we can look into in the future,” Jiang added.

When infected by the fungal virus – also called a mycovirus – the rapeseed-threatening fungus lost its virulence. Instead of killing the plant, the virus-infected fungus lived peacefully within the plant and also had some added benefits.

The research team had infected the rapeseeds by inoculating seeds with virus-infected fungus fragments and had observed a boost in the plant’s immune system, an 18% increase in weight and more root growth, Cell Press said. These plants grew bigger and stronger and could also resist other diseases.

In the rapeseed trials, fungus-infected fragments also suppressed stem rot, stimulated plant growth and improved seed yield by 6.9%-14.9%.

The researchers also found that the fungal virus could be transmitted to other fungal pathogens quickly and efficiently throughout the field, which were ideal traits to develop ‘plant vaccines’.

Fungi caused more than 80% of crop diseases and destroyed one third of all food crops annually, causing economic loss and impacting global poverty, Cell Press said.

“This fungal disease is also prevalent in the USA. Besides rapeseeds, the fungus also attacks sunflowers, beans and other crops,” added Jiang.

The research work had financial support from the National Science Foundation of China, the National Key R&D Program, and the China Agriculture Research System.