Efficient root infection with single resting spores of Plasmodiophora brassicae

Abstract

An efficient method of inoculation with single resting spores of Plasmodiophora brassicae has been developed. After purification of spore suspensions through step-wise density gradient centrifugation, the frequency of viable spores detected by staining with calcofluor white and ethidium bromide was ∼ 80%. Approximately 90% of resting spores had one nucleus, the remainder were larger with two nuclei. Single resting spores which were small and considered to be viable were isolated under a microscope, and inoculated into 1-d-old seedlings of Brassica campestris by using the automatic system transferring single cells. A few small galls were observed on roots ∼ 2 months after inoculation. Plasmodia were recognized mainly in galls on some roots. We concluded that the fungus grown in the host plants resulted in the formation of plasmodia. The frequency of successful infection with single resting spores was 48%.