Serological relationship and detection of bean common and bean yellow mosaic viruses in agar gel

Microprecipitin tests demonstrated a distant serological relationship between intact virus particles of BCMV and BYMV. Antiserum titres of 2048–4096 and 16–128 (reciprocals of dilution end-points) were found for homologous and heterologous antigens, respectively. Cross-reactivity, however, was not obtained in agar immunodiffusion tests when the antigens, in purified preparations or crude infective sap, were treated with pyrrolidine or when the reactants were placed in agar gels containing sodium dodecyl sulphate. Only homologous antigens produced a precipitin line; homologous antiserum titre was 16. In comparative immunodiffusion trials, single-radial-diffusion tests (antiserum incorporated in agar) were much more sensitive than double-diffusion tests for detecting low virus concentrations. Analyses of virus proteins by polyacrylamide-gel electrophoresis demonstrated that coat protein of each virus was composed of a single polypeptide chain with a molecular weight of 35000.