Mycelial Incompatibility and Molecular Markers Identify Genetic Variability in Field Populations of<i>Sclerotinia sclerotiorum</i>

Sixty-three sclerotial strains of Sclerotinia were obtained from transects in two fields of canola (Brassica napus) in Ontario. Mycelial pairings of the strains in all combinations on agar medium produced either an incompatible reaction in which a reaction line between the two strains developed in the interaction zone, or a compatible reaction in which no reaction line developed. The reaction line was a distinct discontinuity between the two strains, visible as a red line on the colony reverse in pairings made on medium amended with red food coloring. Among the 33 strains from the first field, six mycelial compatibility groups (MCGs) were recognized, the largest group including 19 strains (...)