A naturally occurring fungus found inside wheat seeds could help protect one of the world’s most important food crops from a damaging disease, researchers have found.
The fungus, known as Chaetomium globosum, was shown to significantly suppress a disease known as STB, which can cut wheat yields in half during severe outbreaks.
The study is the first time the fungus has been identified in wheat seeds – though it has previously been found in cotton, hemp, apples and tobacco.
STB, which stands for Septoria tritici blotch, is one of the most destructive wheat diseases worldwide.
Northern Europe’s biggest wheat producers, which include the UK, Germany, France and Denmark, are among the worst affected because the region’s rain and humidity create ideal conditions for it.
Dr Amir Mirzadi Gohari, from the University of Tehran, made the initial discovery.
“STB is a huge problem and a real threat to global food security,” he said.
“Farmers currently rely on chemical fungicides to control the disease.
“But it is becoming incredibly resistant to these treatments, and there are growing concerns about the environmental and financial costs of spraying wheat crops.
“Finding a naturally occurring fungus that fights this pathogen could be a huge step forward; it’s a very exciting discovery.”
Dr Mirzadi Gohari’s team screened 45 fungal endophytes, which are fungi that live inside plants without harming them, in a similar way to friendly gut bacteria in humans, searching for one that could hold STB at bay.
The winner came from an unexpected source: the seeds of a wheat variety that is highly susceptible to the disease.
Wheat producers in northern Europe are particularly vulnerable to STB (Joe Giddens/PA)
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The scientist said: “We treated different varieties of wheat with our new fungus three days before exposing them to STB.
“The results were incredible.
“Even in the worst-hit variety, lesions covered 74% less of the leaf area, and the structures that produce the disease-spreading spores were reduced by 82%.
“We tested wheat varieties that are susceptible to STB, and across all of these, disease severity fell by more than half.”
STB is caused by a fungus called Zymoseptoria tritici, which is difficult to control because of its resistance to many fungicides.
Dr Angela Feechan, from Heriot-Watt University in Edinburgh, is working with Dr Mirzadi Gohari on the research.
She explained that Chaetomium globosum appears to fight STB in three main ways.
“As a fungus, it puts the plant’s defences on alert and its immune system kicks in, similar to how vaccines work in humans,” she said.
“We also found that it secretes antifungal compounds that attack rival fungi, like Zymoseptoria tritici, which causes STB.”
She explained that part of the research involved growing the fungus in liquid and spraying it onto STB-infected wheat.
“It inhibited germination of the spores by more than 80%, and spraying it onto plants in the greenhouse test also reduced the disease,” she said.
“It may also promote plant growth. It produces ammonia and the plant hormone auxin, along with mechanisms that help plants take up iron.”
She said further investigation is necessary, but that it appears the fungus has “real benefits for wheat plants, and potentially other crops”.
The team is now trying to pinpoint exactly which antifungal compound the fungus produces, and they have sequenced the fungus’s genome to search for the genes responsible.
Dr Feechan said longer-term research and field trials will help determine whether farmers could use Chaetomium globosum to tackle STB in wheat crops.
She said: “We could potentially coat seeds with the fungus before they are planted, which would mirror how wheat would encounter fungus naturally in the soil, or a spray-on treatment could be developed.”
The study was a collaboration between the University of Tehran, Heriot-Watt University and University College Dublin, led by the University of Tehran and funded by the Iran National Science Foundation.
The findings are published in the journal Scientific Reports.