Electrophoretic karyotype of the obligate biotrophic parasite Plasmodiophora brassicae Wor.

Classical genetic analysis is not possible with the protist Plasmodiophora brassicae due to the intracellular life of this obligate biotrophic parasit e. An electrophoretic karyotype has been obtained using contour-clamped hom ogeneous electric field gel electrophoresis to facilitate gene mapping of P . brassicae. Using two different separation conditions 16 chromosomal bands of P. brassicae were distinguished ranging in approximate size from 2.2 Mb to 680 kb. According to this determination of chromosome number and size, the total genome size of P. brassicae was estimated to be 20.3 Mb. The chro mosomal bands were further designated by their hybridization pattern with r epetitive elements of P. brassicae. The repetitive element H4 (1800 bp) hyb ridized with 14 chromosomal bands, but the sequence of H4 showed no homolog y to known centromere or telomere structures and revealed no repetitive mot ifs.