Immunodiffusion test showing the serological relationship of dasheen mosaic virus to blackeye cowpea mosaic virus. Centre well contains antiserum to dasheen mosaic virus. Peripheral wells contain extracts of: (a) P. selloum infected with dasheen mosaic virus, (b) cowpea (Vigna unguiculata) infected with blackeye cowpea mosaic virus, (c) healthy cowpea, and (d) healthy P. selloum. The diffusion medium contains 0.5% sodium dodecyl sulphate, and non-degraded antigens were tested.