Guidelines for the Identification and Characterization of Plant Viruses

Introduction. Several hundred virus diseases of plants have been described and apparent new ones continue to be reported. Often the causal agents are described as new viruses on totally inadequate grounds. Within the last 10 years, virologists in the Plant Virus Subcommittee of the International Committee on Taxonomy of Viruses have established 23 virus groups and two families (Matthews, 1979) (Table 1). An additional 200 or more viruses in various stages of characterization remain ungrouped.

When an unknown virus disease is being investigated, it has to be determined if the virus (or viruses) concerned is identifiable with any that are already known. This ‘diagnostic phase’, in some instances may not need to go beyond determination of particle morphology to determine to which group the virus belongs, followed by an appropriate serological test to identify the virus.