Pathogenicity of an isolate of Plasmodiophora brassicae from Fukuoka Prefecture.

概要

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An isolate of Plasmodiophora brassicae WORONIN from Katsuura, Tsuyazaki, Fukuoka Prefecture, where clubroot has recently become problem in some cruciferous crops, was investigated with regard to pathogenicity and control by several inoculation tests. The isolate showed high pathogenicity to clubroot-resistant (CR) cultivars of broccoli (cvs. Atsumori and Kasamori) but showed only negligible pathogenicity to some CR cultivars of Chinese cabbage, turnip and cabbage. The isolate was identified as WILLIAMS' race 4 and was evaluated to be the high virulent strain which severely attacks susceptible cultivars of Chinese cabbage (cv. Nozaki Ni-go) even at low inoculum density (1×103 spores/g dry soil). Of three fungicides tested, flusulfamide and fluazinam constantly showed high efficacy against the isolate even at high inoculum density (1×106 spores/g dry soil) . Turnip seedlings were grown in soils collected from fields, nurseries and a canal bed in Katsuura in order to investigate the infesting level of the clubroot fungus in these places. The results indicated that the level varied according to the place and whether or not the canal had also been infested by the fungus.
九州病害虫研究会の論文