Enzyme-assisted immune detection of plant virus proteins electroblotted onto nitrocellulose paper

A technique for the detection of plant virus coat proteins in plant sap is described. The method entails the electroblotting of sodium dodecyi sulphate-polyacrylamide gel electrophoresis-fractionated plant extracts onto nitrocellulose paper, probing the paper with virus-specific rabbit antisera, and indirect detection of virus proteins with horseradish peroxidase-conjugated goat anti-rabbit globulins. The sensitivity and specificity of the technique were tested using brome mosaic and barley stripe mosaic viruses. As little as 1 ng per track of virus protein was detectable, either as pure virus or when mixed with plant sap. Distant serological relationships were detected amongst tobamoviruses, and amongst the bromoviruses, with single antisera. The uses of the technique in probing capsid configuration in a presumed aphid picornavirus, and in routine diagnostic practice, are described.