Symptom severity on differential host lines is currently used to characterize and identify pathotypes of Plasmodiophora brassicae, which is an obligate, soil-borne chromist pathogen that causes clubroot disease on canola (Brassica napus) and other brassica crops. This process is slow, variable and resource intensive; development of molecular markers could make identification of important pathotypes faster and more consistent for deployment of cultivars with pathotype-specific resistance. In the current study, a variant of gene 9171 was identified in the whole-genome sequences of only the highly virulent pathotypes of P. brassicae from around the world, including the new cohort of virulent pathotypes in Canada; its presence was confirmed using three KASP marker pairs. The gene was not present in the initial cohort of pathotypes identified in Canada. The putative structure, domains, and gene ontogeny of the protein product of gene 9171 were assessed using on-line software resources. Structural analysis of the putative protein produced by gene 9171 indicated that it was localized in the cytosol, and likely involved in cellular processes and catalytic activity. Identification of gene 9171 represents a potentially useful step toward molecular identification of the pathotypes of P. brassicae.