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Ontario Grain Farmer Magazine

Optimization of known and well-characterized beneficial microbes as biocontrol agents to protect soybean from Sclerotinia sclerotiorum

Principal Investigator: Zhongwei Zou

Research Institution: Wilfrid Laurier University

Timeline: April 2024 – March 2027  

Objectives:

  • Investigate the inhibitory effect of three biocontrol agents (BCAs) and a commercialized biocontrol, Serenade, on Sclerotinia sclerotiorum.
  • Examine the antifungal activities of PA23, DF41, BS6, and one commercialized biocontrol agent against ascospore germination in soybean petals.
  • Evaluate white mold disease incidence/severity of soybean plants after treatment with three BCAs.
  • Assess the adaptability and competitiveness of optimized BCA in control of Sclerotinia sclerotiorum infection on popularly used soybean varieties.
  • Conduct field trials to compare the efficacy and yield of optimized biological control products and conventional fungicides.
  • Investigate the influence of carbon source on BCA growth, antifungal activities, and metabolites.

Impacts:

  • The project aims to identify beneficial microbial strains that can mitigate yield loss in soybean caused by white mold, an economically important disease.
  • The results will enhance our understanding of the pathogen’s behavior, especially its interactions with beneficial microbes. In addition, the findings will advance our knowledge of plant-microbe interactions and the role of the rhizosphere in inhibiting plant disease progression.
  • The application of biocontrol could assist farmers in reducing their reliance on chemical fungicides for white mold management.

Scientific Summary:

White mould is a significant yield-robbing issue for soybean growers in Ontario and Quebec. The disease, caused by Sclerotinia sclerotiorum, is a near-perennial disease in some soybean fields. Biocontrol can be part of an integrated system to manage Sclerotinia stem rot (white mould) disease in soybean, and is applicable in both conventional and organic soybean production systems. While soybean growers often select varieties with enhanced resistance to the disease, only a few quantitative resistance genes have been identified against S. sclerotiorum in different crops. Therefore, growers frequently apply a variety of fungicides with single or multiple mode(s) of action to manage white mould (i.e., Cotegra, Delaro, Stratego Pro, Acapela, Proline, Miravis Neo, etc.). The application of various fungicides has been shown to increase yield from 3.8 bu/ac to 17.5 bu/ac. However, continuous use of fungicides may contribute to developing fungicide resistance and their use needs to be managed carefully in production systems.

This project will evaluate three biocontrol agents (BCAs) derived from bacteria, including Pseudomonas chlororaphis (PA23), Bacillus amyloliquefaciens (BS6), and Pseudomonas sp. (DF41), for their ability to control white mould disease in soybean. These BCAs have been demonstrated to exhibit strong biocontrol activity against S. sclerotiorum in canola. Further, studies have shown that these biocontrol agents can inhibit ascospore gemination of S. sclerotiorum through various metabolism activities in vitro and in field trials. Through this project, we are therefore aiming: 1) to evaluate the effectiveness of the three BCAs in control of S. sclerotiorum infection through in vitro assay and greenhouse trials; 2) to optimize the most effective BCA for potential commercialization based on the ascospore inhibitory effect on soybean petals and its impact on final disease severity in soybean; 3) to compare the competitiveness of effectiveness of candidate BCAs with current commercial products, such as Serenade, as well as conventional fungicide checks; and finally 4) to assess the adaptability and effectiveness of the BCAs on commonly used soybean varieties in Ontario.

External Funding Partners:

This project is supported in part by the Ontario Agri-Food Research Initiative (OAFRI). OAFRI is funded through the Sustainable Canadian Agricultural Partnership (Sustainable CAP), a five-year, federal-provincial-territorial initiative.