Restriction fragment length polymorphism markers to characterize Plasmodiophora brassicae single-spore isolates with different virulence patterns

Plasmodiophora brassicae-specific clones were used to establish restriction fragment length polymorphism (RFLP) markers for four single-spore isolates of P. brassicae, which were originally selected from the field isolate 'e' and could be distinguished by infection tests with a small differential Ar abidopsis thaliana set. The poor yield of DNA from the obligate biotrophic parasite was overcome by extracting DNA from young diseased roots of Brassi ca rapa. This mixture of host and parasite DNA was employed for RFLP and fi ngerprint studies utilizing selected P. brassicae-specific clones as hybrid ization probes.