Friendly fungus could help protect wheat from disease

A naturally occurring fungus found inside wheat seeds could help protect one of the world's most important food crops from one of its most damaging diseases, researchers say.

The fungus, known as Chaetomium globosum, was shown to significantly suppress Septoria tritici blotch (STB), a disease that can cut wheat yields by up to half during severe outbreaks.

This is the first time it has been found in wheat seeds, but it had previously been identified in tomatoes, cotton, hemp, apples and tobacco.

Dr Amir Mirzadi Gohari from the University of Tehran made the initial discovery, and is working with Heriot-Watt's Dr Angela Feechan on the research, with the fungus being tested extensively in the laboratory to find out how it fights STB.

The current findings are published in the journal Scientific Reports.

Tackling a threat to global food security

STB is caused by a fungus, Zymoseptoria tritici, and 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 the disease.

Dr Amir Mirzadi Gohari said: “STB is a huge problem and a real threat to global food security.

“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.”

A 'friendly' fungus

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.

Dr Mirzadi Gohari 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.”

Fighting fungus with fungus

Dr Angela Feechan, from Heriot-Watt’s School of Energy, Geoscience, Infrastructure and Society, said: “Chaetomium globosum seems to fight the disease 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.

“We also found that it secretes antifungal compounds that attack rival fungi, like Zymoseptoria tritici, which causes STB.

“We grew the fungus in liquid and sprayed the liquid extract 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.

“It may also promote plant growth. It produces ammonia and the plant hormone auxin, along with mechanisms that help plants take up iron.

“We need to investigate this further, but it does seem that the fungus has real benefits for wheat plants, and potentially other crops.”

Further study required

The scientists are now trying to pinpoint exactly which antifungal compound the fungus produces and have sequenced its genome to search for the responsible genes.

Dr Feechan said longer-term research and field trials will help determine whether farmers could use Chaetomium globosum to tackle STB in wheat crops.

“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 work was a collaboration between the University of Tehran, Heriot-Watt University and University College Dublin led by the University of Tehran, funded by the Iran National Science Foundation.