Surface disinfestation of resting spores of Plasmodiophora brassicae used to infect hairy roots of Brassica spp

Resting spores of Plasmodiophora brassicae were surface-disinfested by trea tment with 2% chloramine-T for 20 min and then with an antibiotic solution (1,000 ppm of colistin sulfate, 1,000 ppm of vancomycin hydrochloride, and 6,000 ppm of cefotaxime sodium) for 1 day. The disinfested resting spores w ere used to inoculate hairy roots of cabbage (Brassica oleracea var. capita ta cv. Fuji Wase), Chinese cabbage (B. pekinensis cv. Musou Hakusai), turni p (B. rapa var. rapifera cv. Wase Okabu), and rape (B. napus line Dc 119). Differences among hosts in susceptibility to clubroot in hairy roots were e vident. Chinese cabbage and turnip hairy roots supported the highest percen tages of root hair infection (53.3 to 80%) and the greatest production of z oosporangial groups (8.5 to 32.5 per root). Moreover, gall formation was ob served only on Chinese cabbage and turnip hairy roots. The morphology of zo osporangia, plasmodia, and resting spores in diseased hairy roots was found to be identical to that in infected intact plants by both light and scanni ng electron microscopy. Pathogenicity tests confirmed the infectivity of re sting spores produced in hairy roots. Thus, the hairy root culture techniqu e should prove useful as a dual culture system for P. brassicae.