EFFICIENT ROOT INFECTION WITH SINGLE RESTING SPORES OF PLASMODIOPHORA-BRASSICAE

An efficient method of inoculation with single resting spores of Plasm odiophora brassicae has been developed. After purification of spore su spensions through step-wise density gradient centrifugation, the frequ ency of viable spores detected by staining with calcofluor white and e thidium bromide was similar to 80%. Approximately 90% of resting spore s had one nucleus, the remainder were larger with two nuclei. Single r esting spores which were small and considered to be viable were isolat ed under a microscope, and inoculated into 1-d-old seedlings of Brassi ca campestris by using the automatic system transferring single cells. A few small galls were observed on roots similar to 2 months after in oculation. Plasmodia were recognized mainly in galls on some roots. We concluded that the fungus grown in the host plants resulted in the fo rmation of plasmodia. The frequency of successful infection with singl e resting spores was 48%.