Dr Viet-Cuong Han, from the Centre for Crop and Disease Management
Photo Credit: Courtesy of Curtin University
Scientific Frontline: Extended "At a Glance" Summary: Natural Soil Suppression of Crop Diseases
The Core Concept: Certain agricultural soils function as dynamic living systems capable of naturally inhibiting the infection and survival of devastating fungal pathogens, such as Sclerotinia sclerotiorum.
Key Distinction/Mechanism: Unlike passive growing mediums that rely entirely on chemical fungicides, naturally suppressive soils utilize a specialized microbiome to actively antagonize pathogens. Beneficial bacteria prevent the fungus from infecting plants and inhibit the germination of its survival structures.
Major Frameworks/Components:
- The Soil Microbiome: The community of microscopic organisms that drives the disease-suppressing effect.
- Biocontrol Organisms: Specific naturally occurring bacteria, heavily featuring the genera Bacillus and Streptomyces, which actively stunt fungal growth.
- Soil Chemistry: Suppressive traits are closely linked to specific properties, with less acidic soils and those possessing lower carbon-to-nitrogen ratios showing higher efficacy.
- Microbiome Inoculation: The suppressive effect can be successfully transferred to vulnerable (conducive) soils by inoculating them with microbes from suppressive soils.
Branch of Science: Agricultural Science, Soil Ecology, Microbiology, and Plant Pathology.
Future Application: The discovery paves the way for microbiome-informed crop protection strategies. This includes using native soil microbes as bio-indicators or inoculants, and promoting agronomic practices (like maintaining organic matter and minimizing soil disturbance) to cultivate disease-suppressing biology naturally.
Why It Matters: Sclerotinia stem rot causes massive yield losses in broadacre crops like canola and pulses. Harnessing the natural suppressive power of soil offers a highly sustainable, biologically driven alternative to chemical pathogen control, ensuring better crop resilience and global food security.
Curtin University researchers have discovered some agricultural soils can naturally suppress one of Australia’s most damaging broadacre crop diseases.
The research, published in the international journal Applied Soil Ecology, found some soils can inhibit the infection and survival of Sclerotinia sclerotiorum—the fungus responsible for Sclerotinia stem rot, a disease that causes significant yield losses in broadacre crops such as canola and pulses.
Lead author Dr. Viet-Cuong Han from the Centre for Crop and Disease Management said the study highlights the role of soil as a living biological system rather than a passive growing medium.
“We identified a soil that naturally suppresses Sclerotinia sclerotiorum by preventing the fungus from infecting plants and by inhibiting the germination of its survival structures in the soil,” Dr. Han said.
“In field conditions, by comparing a suppressive soil with a nearby disease-conducive soil, we found clear differences in microbial community structure. Suppressive soils were enriched with well-known, naturally occurring biocontrol organisms, particularly bacteria from the genera Bacillus and Streptomyces. These microbes actively ‘antagonize’ the pathogen. This suppressive effect is driven by the soil microbiome—the community of microscopic organisms living in the soil—and, under controlled and experimental conditions, the effect can be expressed in soils that are normally conducive to disease by inoculating the conducive soil with the microbiome from the suppressive soil.”
Dr. Han said the research showed that Bacillus bacteria are central to disease-suppressing soils, while both Bacillus and Streptomyces help stop fungal growth and reduce disease in lab and plant tests.
“The study also identified bacteria from Western Australian soils that had not previously been shown to fight Sclerotinia sclerotiorum, suggesting that disease-suppressing soils could be a source of native microbes that may be helpful in controlling crop disease,” Dr. Han said. “We also found certain soil properties were linked to disease suppression, with less acidic soils and those with lower carbon-to-nitrogen levels better able to suppress the pathogen.”
Professor Sarita Bennett, coauthor and deputy head of the School of Molecular and Life Sciences, said the findings have important implications for Australia’s broadacre cropping industries.
“Sclerotinia stem rot is becoming increasingly prevalent in agricultural systems,” Professor Bennett said. “This research shows that soil microbial communities can play a crucial role in limiting disease prevalence, providing a foundation for microbiome-informed approaches to crop protection.”
Dr. Han said the findings open the door to future disease management strategies that work with soil biology rather than relying solely on chemical control.
“Agronomic practices that support soil health—such as maintaining soil organic matter and minimizing unnecessary disturbance—may help support microbial communities associated with natural disease suppression,” Dr. Han said. “Understanding which microbes are responsible, and how soil conditions influence them, brings us closer to managing disease through biology. Ultimately, this work supports the possible future use of soil microbes as indicators and tools for the more sustainable management of Sclerotinia stem rot and other soilborne crop diseases.”
Funding: The Centre for Crop and Disease Management is a national co-investment of the Grains Research and Development Corporation and Curtin University.
Published in journal: Applied Soil Ecology
Authors: Viet-Cuong Han, Nicole E. White, Pippa J. Michael, Bec Swift, Duong Vu, and Sarita Jane Bennett
Source/Credit: Curtin University | Lucien Wilkinson
Edited by: Scientific Frontline
Reference Number: agri052826_01