The immunoreactivity of a panel of polyclonal antibodies and monoclonal antibodies (MAbs) raised against African isolates ofpotyviruses from cowpea and African yam bean was examined in ELISAs. A serological study including reference isolates followed by further characterization in differential hosts resulted in separation of the potyviruses into two distinct serogroups, one containing blackeye cowpea mosaic virus (B1CMV) and the other containing cowpea aphid-borne mosaic virus (CAMV). Using biotin-labelled MAbs, the BICMV isolates were further subdivided into two serotypes and the CAMV isolates into five serotypes. Because both B1CMV and CAMV induce a very similar mosaic disease in cowpea, different ELISA procedures using mixed MAbs were evaluated and a single protocol was developed which allowed reliable diagnosis of both viruses.

A study of the capsid proteins of different legumeinfecting 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 (B1CMV) have coat protein Mr 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 B1CMV, 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.

Large-scale surveys in Africa for blackeye cowpea mosaic (B1CMV) and cowpea aphid-borne mosaic (CABMV) showed that several CABMV isolates from Southern Africa were either not or poorly recognized by monoclonal antibodies prepared to isolates collected in West Africa. Selection of three new monoclonal antibodies prepared against the Maputo (Mozambique) isolate of CABMV, and their incorporation into a revised panel of monoclonal antibodies, resulted in the assignment of four of these new CABMV isolates to existing serotypes (II, IV, and V) and three others to a new serotype (VI). The South African isolate of passiflora mosaic virus was shown to be related to CABMV isolates in serotype IV. It is proposed that CABMV isolates be assembled into a distinct species in the legume-infecting, aphid-transmissible potyviruses.

In order to develop a reliable diagnostic test for pepper veinal mottle virus (PVMV), a panel of monoclonal antibodies (mAbs), raised to a Nigerian isolate (PVMW‐Ni), was evaluated by double‐antibody sandwich enzyme‐linked immunosorbent assay (DAS‐ELISA) on infected pepper samples from seven West African countries. PVMV from different geographical locations was serologically very homogeneous and no significant epitope differences were detected even with a very sensitive double‐mAb sandwich ELISA. This ELISA format was optimized with mAb 6C12 and its application in a diagnostic test resulted in the identification of PVMV in Burkina Faso, Togo and Sénégal where it had not been previously reported.