ABSTRACT
Tobacco necrosis (TNV) is the only approved member of the group. The virus has polyhedral particles about 30 nm in diameter sedimenting as a single component of about 118S and containing positive-sense RNA of Mr about 1.4 × 106. A number of TNV strains have been characterized and found to vary considerably in their biological properties, stability, and serological specificity. The reported diameter of TNV varies from 26 to 30 nm. When stained in uranyl acetate, the particles have hexagonal outlines and diameters of about 30 nm. The TNV genome consists of a single molecule of single-stranded, positive-sense RNA which sediments at between 24 and 27S. Edwardson and his colleagues were the first to detect TNV particles in infected tobacco leaves. It would appear that their isolate was free of satellite virus. They observed TNV particles, many forming crystalline aggregates, throughout the cytoplasm of necrotic cells.
