Single cell sequences of Plasmodiophora brassicae reveal genome diversity in a single club.

Plasmodiophora brassicae Wor. is an obligate soil-borne Chromist that causes clubroot of brassica crops. Several pathotypes often co-exist in a field or even a single clubbed root, which likely contributes to rapid breakdown of genetic resistance. However, the extent of genetic diversity has not been directly assessed because of the difficulties with sequencing a soil-borne obligate pathogen. We sequenced single protoplasts of resting spores and identified 3 to 6 substantially different genotypes in the single clubbed root, likely resulting from simultaneous infection of the host plant by spores of different genotypes.