Screening Peas for Resistance to Sclerotinia sclerotiorum
In the quiet fields where peas stretch toward the sun, an unseen enemy lurks beneath the soil, capable of wiping out entire crops in its path.
Imagine a pathogen so resilient it can survive in soil for up to a decade, so ruthless it attacks over 400 plant species, and so destructive it can cause total crop failure under the right conditions. This isn't a fictional threat but the reality of white rot (also called stem rot), a devastating disease caused by the fungal pathogen Sclerotinia sclerotiorum (Lib.) de Bary that threatens pea production worldwide 1 7 9 .
Sclerotinia sclerotiorum is a cosmopolitan, polyphagous fungal pathogen, meaning it's found worldwide and feeds on many different plant species—over 500 by some estimates 7 8 . It's what plant pathologists call a necrotroph, a pathogen that kills host tissue and then feeds on the dead matter 8 .
What makes S. sclerotiorum particularly challenging to control is its production of sclerotia—hard, black, seed-like structures that form in or on infected plant tissue 7 9 . These survival structures can persist in soil for many years, with research indicating viability of up to 8-10 years under certain conditions 7 9 .
Managing white rot through cultural practices alone presents significant challenges for growers. While techniques like crop rotation are recommended, the extended rotation breaks needed—often 6-8 years or more—conflict with efforts to increase pea production to meet the growing demand for plant-based protein 4 .
This challenging landscape makes the identification of partial resistance and the development of tolerant varieties absolutely critical for sustainable pea production. While complete immunity may not be achievable, finding peas that can limit disease progression and maintain reasonable yields under infection pressure would represent a major advancement for growers.
Screening pea accessions for resistance to S. sclerotiorum involves carefully designed procedures that allow researchers to evaluate the response of different pea lines to the pathogen under controlled conditions.
The process typically begins with the collection of S. sclerotiorum isolates from infected plant materials, often in the form of sclerotia recovered from diseased crops 7 . These sclerotia are surface-sterilized and placed on potato dextrose agar (PDA) medium to grow pure cultures of the fungus 7 .
For screening purposes, pea seedlings are typically grown in controlled environments and inoculated at specific growth stages. Common inoculation methods include:
After inoculation, researchers regularly monitor disease development using standardized assessment scales. While specific scales vary between research groups, they typically evaluate:
The inoculated plants are maintained under conditions favorable for disease development—typically temperatures around 21±1°C with high relative humidity (85% or above) 7 .
21±1°C
Temperature≥85%
HumidityMaintaining a diverse collection of isolates is important since S. sclerotiorum shows significant cultural, morphological, and genetic variability between isolates from different hosts and geographical regions 7 .
While traditional screening focuses on finding genetic resistance, complementary approaches explore biological control methods. A 2025 study investigated the potential of Trichoderma-based bioformulations for managing S. sclerotiorum on field peas, providing an excellent example of innovative thinking in white rot management 1 .
The researchers selected six indigenous Trichoderma isolates known for their biocontrol capabilities against various plant pathogens 1 . These beneficial fungi were mass-produced using solid-state fermentation techniques on three different low-cost substrates: rice, sorghum, and wheat 1 .
| Substrate | Level of Sporulation | Efficiency |
|---|---|---|
| Rice | Maximum | |
| Sorghum | Moderate | |
| Wheat | Minimum |
Interestingly, the researchers found that rice substrate supported maximum sporulation of the Trichoderma isolates compared to sorghum and wheat, leading them to select rice for the final bioformulation development 1 .
The results demonstrated significant potential for Trichoderma-based biocontrol. Seed treatment with specific Trichoderma bioformulations, particularly T. harzianum AMUTH-1 and T. asperellum AMUTV-3, led to impressive outcomes compared to untreated controls:
Notably, the effect of these bioformulations was comparable to the fungicide treatment, suggesting they could serve as effective alternatives to chemical fungicides in integrated disease management programs 1 .
Screening pea accessions for resistance to white rot requires specialized materials and methods. The table below highlights key research reagents and their applications in this important work.
| Research Reagent/Material | Function and Application |
|---|---|
| S. sclerotiorum isolates | Pathogen source for inoculation; maintaining genetic diversity of isolates is crucial for comprehensive screening 7 . |
| Potato Dextrose Agar (PDA) | Culture medium for growing and maintaining pure cultures of S. sclerotiorum 7 . |
| Potato Dextrose Broth (PDB) | Liquid medium for mass production of sclerotia for soil infestation studies 1 . |
| Trichoderma bioformulations | Biocontrol agents mass-produced on low-cost substrates like rice for eco-friendly disease management 1 . |
| Surface sterilants | Solutions like mercuric chloride (0.1%) or sodium hypochlorite (5%) for disinfecting sclerotia and seeds 1 7 . |
| ISSR primers | Molecular markers for analyzing genetic variability among different S. sclerotiorum isolates 7 . |
The development of effective bioformulations represents just one approach in the multifaceted battle against white rot. Researchers continue to explore:
Identifying markers linked to resistance traits for more efficient breeding programs.
Tools like LAMP (Loop-Mediated Isothermal Amplification) for rapid pathogen detection 6 .
Combining genetic resistance, cultural practices, and biological controls for enhanced protection.
As climate change creates increasingly favorable conditions for disease development in some regions, the importance of this research grows exponentially . Warmer temperatures and periods of drought followed by intense rainfall can create ideal conditions for root rot pathogens .
The silent battle against white rot in peas continues in laboratories and research fields worldwide. While S. sclerotiorum remains a formidable adversary, the systematic screening of pea accessions for resistance, coupled with innovative management strategies like Trichoderma bioformulations, offers hope for more sustainable pea production.
The research journey continues, with each screened accession bringing us closer to pea varieties that can stand firm against the white rot threat, ensuring this valuable crop remains a viable and sustainable protein source for future generations.
As scientists persist in their work, the vision of fields filled with healthy, productive pea plants—protected through nature-inspired solutions—comes increasingly within reach.