Fourteen strains of cucumber mosaic virus (CMV) from Australia have been characterized by their host range and symptomatology. They were classified as subgroup I or II strains by a dot‐blot molecular hybridization assay between their total viral RNAs and selected cDNAs. The strains FNY and LNy, both from the USA, were used as the subgroup I‐ and subgroup II‐type strains, respectively. A range of serological tests was used to compare these isolates. Gel immunodiffusion tests, with standard antigens homologous to the antisera prepared against glutaraldehyde‐fixed virus of 11 strains, showed that they could be divided into three serogroups on the basis of spur formation in heterologous reactions. Two of the serogroups included either subgroup I or subgroup II isolates, whereas the third serogroup consisted of only one strain (YWA) which was homologous to all the strains tested. Use of heterologous standard antigens in this test failed to show further subgrouping of the antigens. Double‐antibody sandwich (DAS) ELISA using polyclonal antibodies to distinct virus strains also placed the 14 strains in the same three serogroups. When eight different monoclonal antibodies (MAbs) were used in indirect ELISA, one of them distinguished subgroup‐I strains and another distinguished subgroup‐II strains; the YWA strain fell into subgroup II. Other MAbs showed narrower or broader specificity. Thus both molecular hybridization with total RNA and specific MAbs may be useful for separating isolates of CMV into subgroups I and II. Spur formation using heterologous standard antigens to the antisera, as well as being more difficult to interpret, was not a reliable criterion for classification.

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The symptoms and host ranges of 16 strains of cucumber mosaic virus (CMV) from both Subgroup I and II were compared on selected pasture and grain legumes. None infected either Arachis hypogea or Glycine max, although 13 other plant species were infected. The observation that success of inoculation varied with the time of year, may limit the usefulness of the biological differentiation of strains. No hosts tested distinguished Subgroup I or II isolates. The distribution of symptoms and virus in Medicago spp. was uneven and the virus was first detected in some cultivars 6-12 weeks after inoculation, indicating that any test for resistance to CMV in these species would have to be prolonged. Most cultivars of lupin tested were severely affected by several strains of CMV, which caused necrosis and death under conditions which excluded other pathogens.