Researchers are investigating how fungal pathogens recognise plant surfaces, opening the door to crop-protection strategies that disrupt infection before it begins.
The waxy surface of a crop leaf could hold the key to preventing fungal disease before infection takes hold, according to new research from Adelaide University.
Scientists found that two types of powdery mildew could germinate on artificial surfaces coated with leaf wax, even without the underlying structure of a leaf. The results suggest that chemical signals in the wax itself help fungal spores recognise a suitable host and begin growing.
The peer-reviewed study was published in Biointerphases, an AVS journal published by AIP Publishing.
Fungicide Resistance Raises the Stakes
Fungal diseases can cause severe losses in grain crops, threatening agricultural production and food security. Fungicides remain the main means of prevention, but their effectiveness is under pressure as pathogens become more prevalent and resilient, according to a press release.
Rather than relying on broad fungicide applications, the Adelaide team examined the point at which contact between a plant and a fungus begins: the leaf surface.
“Biomaterials research has developed sophisticated tools for producing highly uniform surface coatings and uses surface analysis to understand complex systems,” says study author Bryan Coad.
“Applying those techniques to a plant pathology problem allows us to ask new questions and investigate these interactions with a level of control that hasn’t previously been possible.”
Leaf Coating May Help Pathogens Find Their Hosts
Leaves are covered by a natural waxy layer known as the cuticle. Its primary role is to protect the plant from environmental stresses, including water loss and physical damage.
Research increasingly suggests, however, that the cuticle also sends chemical signals to other organisms. Those organisms can include fungal pathogens such as powdery mildew.
By recreating the leaf coating under controlled conditions, scientists can investigate which signals encourage fungal spores to germinate—and whether those signals can be blocked.
“The focus now is on identifying the specific surface signals involved in host recognition and exploring how that knowledge can eventually be translated into practical crop-protection strategies,” Coad says.
Artificial Surfaces Isolate the Effect of Wax
The researchers deposited leaf-cuticle wax on non-biological surfaces. This allowed them to separate the chemical effects of the wax from the physical effects of the leaf’s shape and structure.
Both powdery mildew species included in the study germinated on the wax-coated surfaces. The result indicates that leaf wax can influence fungal growth independently of the leaf’s underlying geometry.
The findings are preliminary, however. Successful fungal infection also depends on factors such as surface roughness, wettability and environmental conditions, as well as the interactions between them.
Crop Protection Could Begin Before Infection
A fuller understanding of these processes could support disease-control methods that reduce reliance on conventional fungicides.
One possibility is to develop treatments that mask, alter or interrupt the surface signals used by fungal pathogens to identify their host. Instead of killing the fungus after contact, such an approach would aim to stop the pathogen from initiating infection.
Reaching that point will require collaboration among chemists, crop scientists, fungal pathologists and materials scientists.
“Ultimately, the goal is to prevent fungal pathogens from recognizing their host in the first place,” Coad says. “If we can understand the surface signals that trigger infection, we can begin developing strategies to disrupt or block those signals before disease becomes established.”
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