Using the fluorescein-labeled antibodies, slide agglutination tests were employed to detect several plant viruses under dark field illumination in a Nikon microscope connected with a mercury vapour lamp (Chiyoda AHL 250). Positive reactions were recognized with tobacco masaic virus, potato virus X and Y, and rice dwarf virus by their corresponding conjugated antisera.
A drop of crude sap from infected plants was mixed with about one third to one fourth its volume of the concentrated fluorescein-labeled antibody solution on a microscope slide, stirred with the corner of a cover glass and covered with same. This method is available for detecting the antigen-antibody complexes stained specifically in the mixtures despite the weak reaction.
This method is very excellent because it is easy to apply, and the quantity of both antiserum and antigen to be required is very little, and specificity of the reaction can be directly confirmed under a microscope. A high sensibility of the slide agglutination test was ascertained by experimental results with box titration using each virus and its homologous conjugated antiserum.
