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Evaluation of a quantitative (q)PCR assay as the basis for a stem rot of canola (Sclerotinia sclerotiorum) risk assessment tool
B. R. ZIESMAN (1), T. K. Turkington (2), U. Basu (1), E. J. deMilliano (3), S. E. Strelkov (1). (1) University of Alberta, Edmonton, AB, Canada; (2) Agriculture and Agri-Food Canada, Lacombe, AB, Canada; (3) Crop Production Services, Fort Saskatchewan, AB, Canada

Stem rot of canola, caused by <i>Sclerotinia sclerotiorum</i>, is a sporadic disease that can reduce yields by up to 50%. In western Canada, stem rot is primarily managed with routine application of fungicides, often without any indication of disease risk. A <i>S. sclerotiorum</i> specific quantitative (q)PCR assay has been evaluated as the basis for a risk assessment tool to reduce non-economic application of fungicides. Canola petals collected from central Alberta in 2011, 2012 and 2013 at early bloom (EB) and late bloom (LB) were analyzed with the qPCR assay to provide an estimate of the amount of <i>S. sclerotiorum</i> DNA present. Non-linear regression was used to determine the relationship between qPCR estimates of petal infestation and final disease levels in the field. For all three years, LB qPCR estimates were more strongly related to final disease incidence than the EB estimates. The strength of the relationship for the LB samples in 2011, 2012 and 2013 varied considerably (R2= 0.4, 0.7 and 0.2 respectively) which is consistent with different environmental conditions. In 2013, there appeared to be a significant effect of seeding date, when only early seeded crops were considered the regression became significant (R2=0.9). Results indicate that the qPCR assay has potential as a risk assessment tool particularly if used at multiple flowering stages and if environmental conditions are taken into consideration to account for differences between years.

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