PROJECT OVERVIEW

Biological Control of Sclerotinia in Canola

ARDI Project:

Total Approved:

Date Approved:

Project Status:

#00-465

$40,000

April 9, 2001

In Progress

Sclerotinia stem rot of canola has been recognized as a serious threat to the Canadian canola industry. It is further confounded by environmental concerns with application of fungicides as there is the potential of the pathogen becoming resistant to the chemicals applied. There is also a real threat of fungicides being taken off the market by regulation enacted by governments without much prior notice. Canola Council of Canada has recognized these impending threats to the canola industry and has funded a program designed to develop a biological pesticide that would be environmentally friendly and act as an alternative management strategy to chemical pesticides. An extremely potent and antibiotic-producing bacterial strain, Pseudomonas aureofaciens strain PA-23, has shown consistent reduction of mycelial growth of the fungus in lab studies. In addition, it completely shuts down the production of sclerotia, the hard, black over-wintering structures that give rise to ascospores that would fall on the petals of the new crop in the following season.

The aim of this ongoing project is to develop a biosystem targeting the infection stage of the pathogen. Specifically, ARDI funding will be used to enhance the knowledge of the biopesticide by supporting research under field conditions. This would help researchers to understand the efficacy of the biocontrol agent and optimum inoculum concentrations and conditions needed to inhibit the pathogen in the field. The field experiment for this project will examine the effect of the biocontrol agent on Sclerotinia during two years of study. Treatments will include inoculation with Pseudomonas aureofaciens strain PA-23, inoculation with a mutant of the biocontrol agent that cannot produce antibiotics, a Ronilin fungicide treatment and, finally, an uninoculated control with no fungicide application. Disease severity and incidence will be assessed and the population size of the biocontrol bacterium on blossoms will be determined at various intervals. In addition, the effect of cropping practices on biological control will be investigated using a field naturally infested with Sclerotinia. The main plots will be conventional or zero-tilled and subplots will consist of treatments to investigate the effects of the following on Sclerotinia control: biocontrol agent and fungicide applied in combination, time of inoculation, number of inoculations and concentration of inoculum.

Mechanisms of the biocontrol protection will also be examined. The interaction of bacterial antibiotics with the pathogen in-planta will be investigated using different techniques including light and electron microscopy. Along with the production of antibiotics by the beneficial bacteria, plant tissues will be tested for their capacity to respond to the bacterial treatment in terms of building up barriers against further infection by the parasite. This will show whether or not the mode of action of the biocontrol agent occurs through an indirect elicitation of plant defense mechanisms. Finally, changes in fungal biology and structure will be investigated after exposure to bacterial antibiotics and/or plant-accumulated molecules. This will give a better understanding of the parasites susceptibility towards biological pesticides, which can be used for further control strategies.

Funding for this project has also been provided by the Canola Council of Canada.

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