TMV

TMV, or Tobacco mosaic virus, is a plant virus of the genus Tobamovirus in the family Virgaviridae. It is a rod-shaped, non-enveloped virion with a positive-sense, single-stranded RNA genome of about 6.4 kilobases. The virion measures roughly 300 nanometers in length and 18 nanometers in diameter and is built from a single type of coat protein that forms a rigid helix around the RNA.

The genome encodes two replicase proteins produced by read-through (approximately 126 kDa and 183 kDa), a movement protein (~30 kDa), and a coat protein (~17.5 kDa). The movement protein facilitates cell-to-cell spread in plants, while the coat protein encapsidates the RNA in the virion. TMV replication occurs in the cytoplasm of infected plant cells.

TMV has a broad host range, with many solanaceous crops such as tobacco, tomato, pepper, and some ornamental and weed species susceptible. Infected plants typically display mosaic or mottling patterns on leaves, combined with curling, necrosis, and reduced growth or yield. Transmission is primarily mechanical: the virus is spread by contaminated hands, tools, or plant sap during pruning or handling. It is exceptionally stable in the environment, persisting in dried plant material and on surfaces for extended periods, making sanitation and clean propagation stock essential.

Historically, TMV was central to early virology research and helped establish the concept of viruses as filtrable infectious agents. It remains a model system for studying virus structure and self-assembly. Detection methods include serology (ELISA) and molecular assays (RT-PCR). Management emphasizes sanitation, use of certified virus-free seeds and stock, removal of infected material, and, where available, deployment of resistant crop varieties.