Biopesticides as a Novel Management Strategy for Sclerotinia in Canola

Term: 6 years
Status: Complete
Researcher: Susan Boyetchko, Tim Dumonceaux, Fengqun Yu, Chrystel Olivier, AAFC
SaskCanola Investment: $448,530
Total Project Cost: $598,040
Funding Partners: MCGA

Grower Benefits

This project has identified a highly effective biocontrol agent (BCA) against stem rot of canola. This soil-derived bacterium suppresses disease development in plants challenged with a very high dose of Sclerotinia ascospores, in conditions that greatly favor disease development. Formulated to industrial standards, this BCA has proven to be effective and is a promising option for producers to provide natural disease control in canola crops. Industrial partners in Canada and the USA have expressed interest in making this BCA available to producers.

Project Summary

This project has identified several soil-derived bacteria that are effective at inhibiting disease progression caused by Sclerotinia sclerotiorum, a fungal pathogen of canola and other plants that causes stem rot, yield decline, and plant death. The mechanisms of action of the most effective biocontrol agent were investigated, and the bacterium was grown in formulations according to commercial standards. These industry-ready formulations were demonstrated to be as effective as the laboratory cultures, resulting in a biocontrol product that will soon be available as an option for producers.

Stem rot is detrimental to canola production, causing serious yield loss and plant death. The fungal pathogen, Sclerotinia sclerotiorum, can be controlled with chemical fungicides, but the development of fungal resistance, timing of fungicide applications, and environmental concerns are limitations to their use. This project aimed to exploit natural microbial interactions to identify antagonistic bacteria that can suppress disease development upon application. Screening on artificial growth medium identified several bacteria as biocontrol agents (BCA) with potential utility, and a strain coded PENSV20 performed very well on pathogen-challenged plants (Figure 1). Potential mechanisms of action were investigated using bacterial genome sequencing and RNA sequencing of inoculated plants. Finally, PENSV20 was formulated to industrial standards and applied to plants, bringing this effective BCA closer to being available to producers as an effective biocontrol option.

Figure 1. Pathogen challenge of B. napus cv. Westar (fully susceptible) and the protective effect of PENSV20. (i) pathogen only; (ii) pathogen+PENSV20 (day -1); (iii) water control. This is a representative example from three technical and biological replications.

We used culture-based growth antagonism assays to identify soil-derived bacteria that can inhibit the growth of Sclerotinia sclerotiorum, a fungus that causes stem rot in canola. The biocontrol agent was tested in greenhouse assays on canola plants that had been sprayed with Sclerotinia ascospores. The mechanisms of inhibition were investigated using chemical analysis and gene sequencing methods. Finally, the protective bacterium was formulated using common industrial protocols, and these commercial formulations were demonstrated to be effective in protecting canola plants from disease in greenhouse conditions.

Most of the research was conducted in greenhouse conditions, using a high dose of Sclerotinia ascospores and growth conditions that highly favored pathogen growth. Field trials to validate these results will not have such controlled conditions but are expected to be generally less favorable to disease progression.

This project has resulted in the identification of a soil-derived biocontrol agent (BCA) that protects canola plants from infection with Sclerotinia sclerotiorum, which causes stem rot. We assessed the effect of this BCA (PENSV20) on fully susceptible and partially resistant canola lines and identified the mechanisms by which PENSV20 protects canola from the worst effects of S. sclerotiorum. We examined the effect of BCA/pathogen challenge on the induction of gene synthesis in canola and identified three pathways that were overexpressed in B. napus upon treatment. These were associated with systemic acquired resistance, induced systemic resistance, and cellular detoxification. Our second line of investigation focused on the inhibitory chemicals produced by PENSV20. Examination of the PENSV20 genome identified 11 regions that can produce inhibitory metabolites. Finally, we evaluated formulations of PENSV20 for efficacy, utility, and applicability. We evaluated 6 formulations varying in composition on canola plants and demonstrated that all were effective, suggesting that there is flexibility in terms of formulation parameters. We are preparing for a greenhouse-scale replicated experimental trial with a limited number of formulations to determine the efficacy of the industrial-grade formulations on canola plants challenged with pathogen. We are preparing for larger-scale field trials by forming a Bioproducts Partnership with industrial collaborators, with the aim of undertaking the final stages of getting this now-proven BCA into the hands of producers.

Full Report PDF: Biopesticides as a Novel Management Strategy for Sclerotinia in Canola

Other References to this Research Project

• Canola Watch podcast - Plants, microbes and new tools (January 28, 2022)