Important virus diseases of orchids [Cymbidium mosaic, Odontoglossum ringspot] and some problems with control measures
1980
Lesemann, D.E.
Orchid viruses present one of the major dangers for the cultivation of orchids, and have been effectively distributed by the very intensive world wide exchange of plants by the growers. Three viruses are of major importance, i.e. Cymbidium mosaic (CyMV), Odontoglossum ringspot (ORV), and "short" orchid rhabdoviruses (KORV). Viruses of more limited importance in Germany are Dendrobium vein necrosis, "long" orchid rhabdoviruses, bean yellow mosaic, an isometric virus in Trichopilia, and a filamentous virus in Cypripedium. Further viruses of orchids have been reported in Japan and the USA. The problem of sensitive and efficient testing for the presence of virus is technically solved for CyMV and ORV but not for KORV or the other viruses. A main problem in the control of viruses is the high proportion of latent infections which may occur with each of the three important viruses. KORV can up to now not be detected with any known method in latently infected plants. Tissue cultures for mass propagation of orchids should be started only from plants that have been critically tested for virus. This is important in view of the difficulties in the elimination of virus from totally infected cultivars by meristem tip culture. Explants have to be very small for efficient virus elimination and consequently they do not grow as good as larger explants which can be used for mere propagation purposes. Adventitious plantlets, which are occasionally formed in some orchids were in three instances found to be free of the virus which was present in the mother plants. Such plantlets might be useful virus free sources for the start of tissue culture propagation of totally infected cultivars.
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