Abstract
Immunoelectron microscopy with gold-labelled antibodies showed that homologous capsid proteins or virions are associated with cylindrical inclusions of wheat streak mosaic virus and of wheat spindle streak mosaic virus in vivo. Capsid proteins did not bind to any other structure in the cell. The specific association of capsid proteins with cylindrical inclusions is discussed in relation to cell-to-cell spread of virions through plasmodesmata.