Immunodiagnosis of plant viruses by a virobacterial agglutination test

A new virobacterial agglutination (VBA) test for the immunodiagnosis of plant viruses is described. The test is based on the agglutination of Staphylococcus aureus cells by virus particles after treatment of the cells with homologous antiserum. The agglutination occurs within 1–5 min. The sensitivity of the test is 0·1-0·4 μg virus/ml and is not affected by the shape of the virus particle. The use of affinity purified antibodies for sensitisation of S. aureus cells increases the sensitivity of the reaction 50-fold and enables the detection of tobacco mosaic and cucumber green mottle mosaic viruses at a concentration of 2 ng/ml. The VBA test allows the estimation of potato viruses X, S, M and Y in the eyes and sprouts of infected tubers and in the leaves of infected plants. The diagnosis of carnation mottle virus in carnation plants and of mushroom viruses in mushroom (Agaricus bisporus) fruit-bodies and mycelium are also described.