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Local and Trans-Canadian Clonal Distribution of Sclerotinia sclerotiorum on Canola. Y. Kohli, Department of Botany, Erindale College, University of Toronto, Mississauga, Ontario, Canada L5L 1C6; R. A. A. Morrall(2), J. B. Anderson(3), and L. M. Kohn(4). (2)Department of Biology, University of Saskatchewan, Saskatoon, Canada S7N 0W0; (3)(4)Department of Botany, Erindale College, University of Toronto, Mississauga, Ontario, Canada L5L 1C6. Phytopathology 82:875-880. Accepted for publication 6 April 1992. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/Phyto-82-875.

Clonal variability within and among field populations of Sclerotinia sclerotiorum isolated from canola petals in western Canada was determined by analysis of two independent criteria, mycelial compatibility and DNA fingerprinting. Strains were considered to belong to the same clone if they were mycelially compatible and also had identical DNA fingerprints. Thirty-nine clones were identified among 66 strains from seven locations in Alberta, Saskatchewan, and Manitoba. The most widely distributed clone, accounting for 18% of the isolates, was found in all three provinces. Seven other clones were found in two provinces. In 33 out of 36 mycelial compatibility groups (MCGs), each MCG had a unique DNA fingerprint; each of the remaining three MCGs included strains with one of two fingerprints and was interpreted as two clones. A comparison of strains from western Canada with those from a previous study of two fields in Ontario showed that the one clone identified in both Ontario fields was also present in Manitoba and Saskatchewan. This study demonstrates that clones of S. sclerotiorum are distributed over long distances geographically and confirms the results of the Ontario study in demonstrating that field populations of S. sclerotiorum on canola are composed of more than one clone. Analysis of monosporous siblings from homothallic sexual reproduction in each of two clones showed no meiotic segregation for determinants of either mycelial compatibility or DNA fingerprints. Therefore, intact clonal genotypes can potentially be dispersed as ascospores.

Additional keywords: Sclerotinia stem rot.