Kharbanda: Biocontrol of economical important diseases of canola by using a bacterium and compost
Date: August 2001
Term: 3 years
Status: Completed
Researcher(s): Dr. Prem D. Kharbanda and Jian Yang, Alberta Research Council, Vegreville, AB
SaskCanola Investment: n/a
Total Project Cost: n/a
Funding Partners: Alberta Agricultural Research Institute
Project Summary
Blackleg, rhizoctonia seedling blight and sclerotinia stem rot are economically important diseases of canola, which have caused millions of dollars of losses in western Canada. Researchers initiated a three-year study (1998 – 2000) to evaluate an effective technique for applying biocontrol agents to seeds and soil. Although the results of using PKB1 bacterium spores as a seed coating or for inoculating compost showed some activity against some of the diseases, it did not significantly reduce disease. More testing to optimize PKB1 activity is needed. Researchers also tested several different composts and found that generally disease suppression was achieved through the presence of beneficial microbes in the composts. Supplementing compost with known biocontrol agents may be an effective strategy for canola disease suppression.
Blackleg, rhizoctonia seedling blight and sclerotinia stem rot are economically important diseases of canola, which have caused millions of dollars of losses in western Canada. Although resistant cultivars have been used to control blackleg, no resistant cultivars are available for sclerotinia and rhizoctonia diseases. Researchers conducted a study to evaluate an effective technique for applying biocontrol agents to seeds and soil.
In this three-year study conducted from 1998 to 2000, researchers tested a bacterium strain Paenibacillus polymyza PKB1, which had an inhibitory effect against several fungal pathogens of canola, including Leptosphaeria maculans, Rhizoctonia solani, Sclerotinia sclerotiorum and other pathgogenic fungi. Research was conducted to evaluate the effect of seed treatments and compost amended with the bacterium PKB1 in controlling seed-borne diseases of canola under controlled and field conditions. Studies also evaluated the suppressive effect of composts made from different raw materials on soil-borne diseases in the growth chamber and in the field.
Seed Treatments
Canola seeds were treated with PKB1 spores by using polymers and peat moss methods, both in the growth chamber and in the field. Bacterial coated seeds had lower infection and higher plant survival inoculated with L. maculans in growth chamber tests. However, seed coating with the bacterium had no significant effect on the control of Rhizoctonia seedling blight under field conditions. Researchers need to continue this research to determine how to promote germination and optimize the activity of PKB1 when used as a seed coating.
Compost Inoculated with PKB1
Compost made from cattle manure and wood chips amended with 5% soybean meal was inoculated with PKB1 spores and evaluated for disease control under controlled and field conditions. The compost significantly inhibited germination of sclerotia of S. sclerotiorum in both controlled and natural field conditions, but did not significantly reduce blackleg seedling infection or Rhizoctonia damping-off under field conditions. Researchers suspect that environmental conditions were not suitable for the bacterial growth and activity, and need more research to determine and optimize the conditions for the biocontrol agent.
Effect of Compost in Disease Suppression
Composts made from different starting materials, including municipal wastes, pulp sludge, wood chips and cattle manure were evaluated for their chemical and biological properties to understand the mechanisms involved in disease suppression with compost. In this study, various composts were found to contain microbes showing inhibitory effects against pathogenic fungi, including Bacillus spp, Trichoderma spp., Gliocladium sp. and Penicillium spp. The microbial population and activity were high in all composts, except wood chip-based compost.
General disease suppression was achieved through the presence of beneficial microbes in the composts. The research indicates that the introduction of beneficial bacteria into the compost could enhance its disease-suppressive effect and obtain consistent results. Supplementing compost with known biocontrol agents may be an effective strategy for canola disease suppression.