Virus Turns Deadly Plant Fungus From Foe to Friend

The fungus Sclerotinia sclerotiorum on a bush bean plant. (By Wikipedia user Rasbak, CC BY-SA 3.0, Link)

(CN) — A dangerous fungus, one so deadly to plant life it can kill them in a mere matter of days, could actually hold the secret to giving plants a much needed boost to their health and protect them from future diseases, according to a new study.

For centuries throughout human history, humankind has long battled with the ever-ongoing threat of crop loss, a threat that has singlehandedly made disastrous contributions towards economic loss and worsening world poverty. For as long as farmers and growers have sought to cultivate plants that sustain life, dangerous diseases and fungi with the ability to devastate crop yield and crop health have presented a near constant threat.

Fungi in particular have long presented perhaps the gravest threat to plant life, given that fungi are behind roughly 80% of most plant-based diseases and destroy around a third of food crops around the world each year. One such fungus that has plagued growers is the Sclerotinia sclerotiorum, which can lead to drastic stem loss and even death among plants within just days of infection.

New research, however, shows that there may be a way to combat such fungi — and the key to it is another fungal plant virus.

In a study published Tuesday in Molecular Plant, researchers reveal they have discovered a new plant virus known as a mycovirus that can transform deadly fungal pathogens into a natural booster to a plant’s immune system. Once the pathogens have been naturally reconstructed by the virus to protect the host plant instead of killing it, the result is a plant that is not only healthier, but more resistant to other types of diseases it may contract down the road.

Daohong Jiang, a professor at Huazhong Agricultural University in China and senior author of the study, said that researchers have essentially turned a potential threat to plant survival into a critical plant aid, and that the evolution of fungi throughout history may have helped make it possible.

“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,” Jiang said with the release of the study. “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.”

To test this idea, researchers experimented with a plant that has been historically vulnerable to these fungal pathogens: rapeseed. These bright yellow plants that often coat entire farm fields are not only the source of perhaps one of the most common cooking staples found in kitchens throughout the world — canola oil — but also serve as a critical ingredient to animal feed and biodiesel around the world.

Despite their varied uses however, rapeseed crops around the world are routinely threatened by the Sclerotinia sclerotiorum fungus, making it an ideal candidate for researchers.

They discovered that after they infected a series of rapeseeds with the mycovirus, done so by inoculating the seeds with virus-infected fungus fragments, the once-deadly fugus seemingly lost its interest in being destructive. Rather than turn against the plant, researchers found that the fungus actually boosted rapeseed weight and root growth by 18% and generally improved the plant’s immune system.

“The fungal virus might be a good thing for the fungus because the fungus now recognizes the plant as ‘home’ instead of killing it,” Jiang said. “The virus turned a foe to a friend.”

Researchers further found the fungus-infected fragments helped to notably suppress stem rot, stimulated plant growth and improved overall seed yield. Researchers were also encouraged to see that the virus can be easily transmitted to other plants and fungi in a rapeseed field, a transmissibility that could prove valuable when it comes to creating plant vaccines to inoculate and protect plants for their entire lives.

Jiang is hopeful these discoveries could also be used to help safeguard other crop types outside of just rapeseed, and that its myriad of uses could help to give those in agriculture some much needed relief in their battle against plant diseases.

“This fungal disease is also prevalent in the United States,” Jiang said. “Besides rapeseeds, the fungus also attacks sunflowers, beans and other crops Our prevention method and research idea may benefit many others who are engaged in similar work and benefit agricultural production. It has a lot of potentials.”

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