Electro‐Blot Immunoassay—A Means for Studying Serological Relationships among Plant Viruses?

The coat proteins of tymo‐, tombus‐, como‐, nepo‐, tobamo‐, potex‐, carla‐ and potyviruses were subjected to sodium dodecylsulphate (SDS)‐polyacrylamide gel electrophoresis, electro‐blotted onto nitrocellular membranes and reacted with homologous and heterologous antìsera to intact plant viruses. Immune complexes were detected after reaction with alkaline phosphatase‐labelled goat anti‐rabbit antibodies. SDS coat proteins of comoviruses reacted only with antisera which were homologous for their intact particles. In all other groups, however, a rather broad range of serological relationships was detected. With a number of viruses, serological relations to other members of the same group were demonstrated for the first time. SDS coat proteins of maclura mosaic virus, a possible potyvirus, and of beet necrotic yellow vein virus, a possible tobamovirus, did not react with antisera to definitive members of the respective groups. Several unexpected reactivities of SDS coat proteins of viruses from one group with antisera to viruses in other groups were, however, also observed. This indicated that electro‐blot immunoassay, like other serological methods, cannot be used reliably to assign a virus to a certain group. The SDS coat proteins of several tombusviruses were able to mimic serological reactions by a direct binding of enzymelabelled antibodies which occurred also without serum treatment.