First report of wasabi mottle virus causing ringspot and vein-clearing symptoms on wasabi (Wasabia japonica) in North America


MacDonald, J.L., Punja, Z.K., Xiang, Y., Bouthillier, M.J., Reade, R., DeYoung, R.M., Bhagwat, B., Betz, E.C., Li, Y.Q., Chen, X. (2020). First report of wasabi mottle virus causing ringspot and vein-clearing symptoms on wasabi (Wasabia japonica) in North America,

Plain language summary

Agriculture and Agri-Food Canada and Simon Fraser University researchers successfully isolated and described a new virus to wasabi in North America – wasabi mottle virus. By characterizing the symptoms caused by this viral infection – leaf mottling and vein-clearing, in extreme cases with necrotic lesions – growers will be able to identify infected plants and take appropriate management measures to reduce the spread among their crops. Using electron microscopy and genetic detection techniques, they were able to identify what species of virus was present in the plants. Further genetic investigations linked it to closely related strains of the virus in Taiwan and in Japan, where it was previously known. After identification and description of the virus, an isolate was contributed to the Canadian Plant Virus Collection, to be maintained so that future researchers have access to this strain.


Symptoms of ringspots and vein-clearing were observed on wasabi (Wasabia japonica (Miq) Matsum) plants in three greenhouses in British Columbia during 2017. Ten indicator plant species, including four Nicotiana species, were inoculated with sap extracts from symptomatic leaves; after 4–11 days, necrotic lesions developed on all plants. Transmission electron microscopy revealed rod-shaped virions, 250–300 nm in length, in leaves of N. occidentalis and N. clevelandii. Total RNA from symptomatic wasabi tissues was used in RT-PCR with universal primers corresponding to five virus genera and specific primers for turnip ringspot virus and alfalfa mosaic virus. Amplicons ~400 bp in size were obtained with tobamovirus primer set TobN up3/TobN do4 and amplicons of ~300 and ~600 bp were obtained with ilarvirus primer set Ilar1F5/Ilar1R7. Sequencing and MegaBLAST (NCBI) query of the Ilar amplicons showed 99% identity to wasabi mottle virus (WMoV), a member of the genus Tobamovirus. Next-generation Sequencing confirmed WMoV as the only virus present in diseased plants. BC isolates (GenBank accession no. MK431779) showed 99.43% sequence identity to isolate ‘Alishan’ (GenBank accession no. KJ207375.1) and 98.62% identity to ‘Tochigi’ strain (GenBank accession no. AB017504.1). Mechanical inoculation of wasabi cultivars ‘Green Thumb’ and ‘Daruma’ produced ringspots and vein-clearing symptoms after 22–23 days on the former while the latter was asymptomatic, but WMoV was detected in all plants by RT-PCR. WMoV may have been introduced into Canada on imported infected ‘Green Thumb’ plants and subsequently spread through commercial vegetative propagation. The effects on yield or rhizome quality are yet unknown.

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