First report of Sclerotinia stem rot on quinoa ( Chenopodium quinoa ) caused by Sclerotinia sclerotiorum in Canada

A new disease, Sclerotinia stem rot, was observed in quinoa (Chenopodium quinoa) fields in Northwest Saskatchewan, Canada, during the 2022 agricultural season. The disease incidence was low, ranging from 0.03% to 0.1%, with symptomatic plants exhibiting leaf discoloration, bleached stems, and black sclerotia. The pathogen was identified as Sclerotinia sclerotiorum (Lib.) de Bary based on its cultural characteristics, and this identification was confirmed through rDNA-ITS sequencing. Additional molecular characterization was performed using TU1/TU2/TU3 and SscadF1/SscadR1 primers targeting the β-tubulin and calmodulin genes, respectively. Pathogenicity tests demonstrated that quinoa cultivars Kailey, NQ20W, NQBlack, and NQRed inoculated with S. sclerotiorum isolate IMSS218 were highly susceptible. Sclerotinia sclerotiorum was consistently re-isolated from symptomatic tissues, fulfilling Koch’s postulates and confirming it as the causal agent of Sclerotinia stem rot in quinoa. To our knowledge, this is the first report of Sclerotinia stem rot in quinoa in Canada.