Host-pathogen interactions between Brassica oleracea genotypes and single spore derived isolates of Plasmodiophora brassicae

Single-spore derived isolates (SSDI) were produced from 4 field population isolates of Plasmodiophora brassicae. Thirty three SSDI were characterized using a restricted set of 3 Brassica napus lines. Seven distinct pathotypes were obtained. Most of the SSDI differed consistently from the original population and from each other, confirming the heterogeneity of populations of P. brassicae. The assessment of 5 different B. oleracea genotypes for response to P. brassicae showed that the reaction of a given genotype may be different according to the type of isolate used. A genotype resistant to a given population isolate may become susceptible to some SSDI derived from this population. Data obtained in the study of the host-pathogen relationships showed that components of resistance in B. oleracea are either differential or non-differential.