First Report of Cucumber Mosaic Cucumovirus on Wasabi in Australia.

Wasabi (Wasabia japonica (Miquel) Matsum.), a native perennial of Japan and Shakhalin Island used to produce a condiment for Japanese dishes, is under commercial development in Tasmania, Australia. Plants propagated within shade houses showed systemic necrotic flecks and veinal necrosis in leaves and sunken necrotic stem lesions similar to those, reported in Japan (1), caused by cucumber mosaic cucumovirus (CMV). Necrosis progressed rapidly, resulting in death of plants transferred to or mechanically inoculated in a glasshouse (15 to 30°C) under full light. Disease progression in plants maintained in shade houses (5 to 20°C) was slower and symptoms less severe. Presence of CMV in symptomatic plants was confirmed by enzyme-linked immunosorbent assay (ELISA), using antiserum from Agdia (Elkhart, IN), and by sap transmission tests to healthy wasabi and Chenopodium quinoa plants. Incidence of CMV among plants in the shade houses was estimated at 10%. A survey of a commercial planting of 400 to 500 plants in November 1997, using ELISA, showed an incidence of 2.6% CMV-infected plants. They were concentrated at the field margins, suggesting that the inoculum originated from external sources rather than from transplants. This pathogen could have significant impact on the longevity and production of this crop in Australia. Reference: (1) S. Adachi. 1987. Wasabi cultivation. Shizuoka Pref. Agric. Exp. Sta. Pub., Shizuoka, Japan.