The collaboration of AAFC, MCVET and Manitoba Agriculture through field surveys and additional testing has shown changes within the crown rust pathogen populations in Manitoba where virulence has developed on a number of oat varieties. Varieties that contain the Pc91 gene, including AAC Justice, CDC Morrison, HiFi, Souris and Stainless, have been redefined for crown rust resistance in Seed Manitoba 2016 (www.seedmb.ca). The variety Summit, which is postulated to carry different resistance genes, is also losing its resistance to virulent races in the Eastern Prairies; therefore, it has also been redefined for crown rust resistance.
This is not the first time crown rust resistance ratings has been changed in Seed Manitoba, nor will it be the last. As the pathogen population is highly variable, it can happen quite regularly where genes are defeated and lines once resistance to crown rust can become more susceptible.
There are a number of steps used to determined if changes are occurring within the crown rust pathogen populations, and then whether changes in variety disease resistance ratings are required. Please take the time to read the attached article to learn more about how and why the crown rust resistance ratings did change in Seed Manitoba 2016.
Submitted by: Pam de Rocquigny, Provincial Cereal Crops Specialist, Manitoba Agriculture
With information from Dr. Jim Menzies, Phytopathologist, AAFC Morden & Dr. Jennifer Mitchell-Fetch, Oat Breeder, AAFC Brandon