Tobacco Mosaic Virus

The causative agent, Tobacco mosaic virus, belongs to the genus Tobamovirus and is an RNA-containing virus with rigid rod-shaped virions. Under field conditions, Tobacco mild green mosaic virus (TMGMV) is also encountered. There are four main strains of TMV: common mosaic, aucuba strain, ring spot, and ribgrass strain, which differ in symptom expression and severity of damage.

Symptoms of infection include vein clearing, the appearance of alternating light and dark green patches, leaf curling, and the development of necrotic spotting. The virus is extremely persistent in the environment and is transmitted through contact. Tobacco resistance to the virus is conferred by the N gene, which triggers a hypersensitive response, localizing the infection at the site of entry through the formation of necroses.