Lange: Sclerotinia stem rot field nursery for evaluation of resistance and fungicide efficacy
Date: March 2008
Term: 2 years
Status: Completed
Researcher(s): Ralph Lange and Rodney Werezuk, Alberta Research Council
SaskCanola Investment: n/a
Total Project Cost: n/a
Funding Partners: n/a
Project Summary
Sclerotinia sclerotiorum is the causal agent of Sclerotinia stem rot (SSR), and can cause severe economic damage to Argentine canola. Researchers know that if it were available, genetic resistance to SSR would be an attractive option to canola growers They initiated a two-year project to develop a field scale SSR disease nursery for screening of genetic resistance. As a result of the research, the methods developed to produce enough ascopores to inoculate the field nursery have since been expanded. Researchers have supplied inoculum to other researchers and breeders across Canada to develop sclerotinia-resistant cultivars.
Sclerotinia sclerotiorum is the causal agent of Sclerotinia stem rot (SSR), and can cause severe economic damage to Brassica napus. Currently, the most effective methods of managing SSR in canola are rotation with non-host crops and application of foliar fungicides. Because of the persistent nature of sclerotia of S. sclerotiorum as well as migration of inoculum from neighbouring fields, crop rotation alone is not always an effective SSR management tool. Foliar fungicides require application at the correct crop and fungal developmental stages. They are a significant input cost, and efficacy is influenced by environmental conditions. Therefore, if genetic resistance to SSR was available, it would be an attractive option to canola growers, since reliance on fungicides would lessen, and canola production would become more profitable.
Based on previous success in building and running SSR field nurseries, and applying past experience gained with a small SSR nursery structure, researchers initiated a two year study to design, construct and make operational a field scale Sclerotinia stem rot (SSR) disease nursery structure. With this research structure, infection would hopefully be guaranteed due to the controlled environment within the nursery. The objective was to construct a large structure, relative to other controlled environment structures like greenhouses and growth chambers, which would allow larger plot sizes. Systems could be expanded to accommodate a commercially viable number of entries. Using this information, researchers planned to build a full scale nursery to use for cultivar and fungicide evaluation.
The first year of the study resulted in a disappointing performance with no SSR symptoms observed in the pilot-scale nursery. Therefore, the expansion of the nursery planned for year two was cancelled; however improvements to the structure were made to improve the chances of developing infection. The operational data gained in 2006 were valuable and used to modify nursery design and operation in 2007. Despite the improved performance in 2007, statistically significant treatment effects could only be measured on plants treated with fungicides because overall disease severity and incidence remained low. Effects of genotype on disease development were either too subtle to be detected, or the genotypes tested were in fact not SSR-resistant.
As a result of the research, the methods developed to produce enough ascopores to inoculate the field nursery have since been expanded. Researchers have supplied inoculum to other researchers and breeders across Canada to develop sclerotinia-resistant cultivars. It was previously thought that it was impractical to produce sufficient inoculum to apply adequate quantities to field nurseries, but researchers have worked out the methods needed to do this, based on an initial method used by Dr. Greg Boland at the University of Guelph.