TMV (Tobacco mosaic virus) is the most serious pathogen affecting tobacco plants. It causes mosaic symptoms on the leaves and stunts plant growth. TMV has a rod-shaped structure and is composed of RNA inside a protein capsid. The viral RNA directs the production of coat proteins and other proteins upon entry into host cells. TMV spreads through mechanical transmission via contact with infected plant matter and can contaminate seeds, but is not insect-transmitted. Management of TMV involves crop rotation, sanitation practices, and the use of resistant varieties.