Capsid protein properties of cowpea aphid-borne mosaic virus and blackeye cowpea mosaic virus confirm the existence of two major subgroups of aphid-transmitted, legume-infecting potyviruses.

A study of the capsid proteins of different legume-infecting potyviruses using specific monoclonal antibodies on immunoblots of crude extracts from infected plants revealed that cowpea aphid-borne mosaic virus (CAMV) and blackeye cowpea mosaic virus (BICMV) have coat protein M(r) values of 32K and 35K, respectively. Immunoblot comparisons of BICMV, peanut stripe mosaic virus (PStV), bean common mosaic virus (BCMV) and azuki bean mosaic virus (AzMV) revealed equal reactivity of their 35K coat proteins. Similar comparisons between CAMV and the necrotic strain of BCMV (isolate NL3) showed a serological relationship between their 32K coat proteins, results providing the first evidence of a possible similarity between CAMV and BCMV NL3. Peptides from trypsin digests of the coat proteins of several of these legume-infecting potyviruses were analysed by HPLC. Comparison of the peptide profiles confirmed the serological results in distinguishing the two subgroups. Peptide profiles of coat protein from BICMV, PStV, AzMV and BCMV were almost identical, results suggesting that they could be considered as strains of one virus. In contrast, peptide profiles of various CAMV serotypes and BCMV NL3 were distinct from the first group and exhibited limited similarities to each other.