Serological detection by sodium dodecyl sulphate (SDS)-immunodiffusion tests. Antigen wells contain SDS-treated sap: B = blackeye cowpea mosaic virus-infected cowpea: C = cowpea aphid-borne mosaic virus (Moroccan isolate)-infected cowpea: H = healthy cowpea. The antiserum in wells A is to blackeye cowpea mosaic virus treated with pyrollidine (Lima et al., 1979). In Fig. 6, the cross-reacting antibodies were removed by intragel absorption with sap from plants infected with Morocco cowpea aphid-borne mosaic virus. In Fig. 7, the antiserum was absorbed by intragel absorption with sap from non-inoculated cowpea plants.