To investigate reactions of potato cultivars in Japan to potato spindle tuber viroid (PSTVd), PSTVd was inoculated to seven potato cultivars. All cultivars inoculated showed some symptoms , but the severity of symptoms on both leaves and tubers were different among the seven cultivars. The cultivars Hokkaikogane, Norin No.1 and Danshaku-imo developed relatively severer symptoms than the other cultivars Waseshiro, Konahubuki, Mayqueen and Astarte. PSTVd in these plant leaves and tubers were

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... ted by dot blot hybridization using digoxigenin (DIG) labeled cDNA probe . PSTVd accumulation did not differ among cultivars significantly. The result indicated that all cultivars were susceptible to PSTVd and this hybridization method was applicable to diagnose PSTVd in potato leaves and tubers directly.