Pathotypes of Plasmodiophora brassicae in Washington, Oregon, and California. R. L. Dobson, Research Assistant, Western Washington Research and Extension Center, Puyallup 98371. J. Robak, Research Associate, and R. L. Gabrielson, Plant Pathologist, Western Washington Research and Extension Center, Puyallup 98371. Plant Dis. 67:269-271. Accepted for publication 23 July 1982. Copyright 1983 American Phytopathological Society. DOI: 10.1094/PD-67-269.

This study analyzes the pathotypes or races of Plasmodiophora brassicae occurring in crucifer-production areas of Washington, Oregon, and California. On the European Clubroot Differential set (ECD), all collections were similar in virulence. ECD code designations of the collections were either 16/02/31 or 16/03/31, both corresponding to race 7. Collecting spores from one ECD host with limited infection and reinoculating with these spores onto the same and other ECD host was important for verifying virulence genes present at low frequencies.