DNA extracted from DNase I treated resting spores or from spheroplasts of Plasmodiophora brassicae is highly homologous to DNA extracted from Brassica, supporting previous reports of the uptake of host DNA by P. brassicae. Screening of a random genomic library made from DNA extracted from resting spores revealed two clones which hybridized to Brassica DNA. Sequence analysis demonstrated that these clones were highly homologous to a family of repetitive DNA elements previously cloned from B. nigra. (C) 1995 Academic Press Limited