Researchers make breakthrough in fight against major threat to food supply: 'We can take more effective action'

Wheat accounts for approximately 20% of the calories and protein people around the globe consume. Cereal, in particular, is one of the most-eaten staple foods, and wheat is a key ingredient, making continued wheat production vital. 

However, while wheat has natural resistance to certain fungi, its production is threatened by others, particularly powdery mildew. 

That's why researchers at the University of Zurich studied how wheat might be able to outsmart powdery mildew by looking at the mechanism that allows this fungus to bypass wheat's immune system. The team has now published their findings in Nature Plants, and the results are promising, as they could lead to the targeted development of powder mildew fungus-resistant wheat varieties.

Typically, the agricultural industry uses fungicides to prevent plant disease, but this often proves ineffective in the long term against powdery mildew, as the fungus evolves quickly to overcome immune resistance.

The way powdery mildew fungus works is by introducing a plethora of effectors, or tiny proteins, into the cells of the wheat, where they then establish an infection. Wheat, though, has resistance genes that recognize many of these effectors; once recognized, wheat's immune system kicks in to stop the infection. Typically, powdery mildew gets around the immune system by evolving to lose the recognized effectors or by modifying them. 

The team of researchers from the University of Zurich found that this fungus has a novel powdery mildew effector (AvrPm4), which is recognized by the resistance protein Pm4. However, rather than losing or modifying the effector, the fungus's way of tricking wheat is putting forth a second effector that prevents wheat from recognizing AvrPm4. 

Not only does this second effector prevent recognition, but it is also recognized by a different resistance protein. 

How does this benefit wheat production? Per Phys.org, Lukas Kunz, a postdoctoral researcher, explained: "This means that, by combining the two resistance proteins in the same variety of wheat, it might be possible to lure the fungus down an evolutionary dead end in which it can no longer escape the immune response of wheat."

As wheat crops worldwide experience reduced yields due to disease and extreme weather, this method of combining resistance genes to create resistant wheat could prove crucial to continued food supplies.

The research team conducted a handful of tests in the lab that proved successful by combining resistance genes that turned off both the second effector and the AvrPm4 effector, but much more testing will be needed to determine whether this method will work in the field.

However, the professor who led the team, Beat Keller, said, per Phys.org: "Because we now know these mechanisms and the pathogenic factors of the fungus involved, we can take more effective action to prevent powdery mildew from breaking through wheat's resistance."

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