ABSTRACT
This chapter provides a brief account of the development of studies on structure, composition, properties, cytopathology, and taxonomy of Tobamoviruses. The name Tobamovirus is derived from the type member of the group, tobacco mosaic virus (TMV). The number of isolates and strains of Tobamoviruses that have been studied and named is very large. The particles of all true Tobamoviruses are indistinguishable in the electron microscope. They are rigid, helically constructed nucleoprotein tubes having external and internal diameters of 18 and 4 nm, respectively and a modal length of 300 nm. Cells of different hosts infected with various Tobamoviruses, though predominantly with TMV, have been a favoured subject for examination by electron microscopy of thin sections. Sometimes techniques such as autoradiography and cytochemistry have also been used. Examination of thin sections of plants infected with possible Tobamoviruses has revealed virus particles in the cytoplasm only.
