Tobacco mosaic virus (TMV) is a positive-sense single stranded RNA virus that infects plants, especially tobacco and other members of the family Solanaceae. The infection causes characteristic patterns (mottling and discoloration) on the leaves (hence the name). TMV was the first virus to be discovered. Although it was known from the late 19th century that an infectious disease was damaging tobacco crops, it was not until 1930 that the infectious agent was determined to be a virus.
Symptoms:In young tobacco plants the first visible Symptoms are downward curling and distortion of leaves accompanied with chlorosis. As the leaves enlarge abnormally dark green spots appear which develop into irregular crumpled blister like areas while the remainder of the tissue becomes more and core chlorotic. Old leaves may not show mottling but may contain scattered chlorotic or necrotic spots. In pink flower forms, light colouring areas appear on floral parts or the colour is completely suppressed.
Causal agents:Tobacco mosaic virus.
Disease Cycle:Sources of primary infection consist of plant debris in soil in warehouse and certain manufactured tobacco products (cigaretes), contaminated hands of worker. Dissemination from plant to plant is by Mechanical means. The virus is not known to be transmitted by insects from tobacco to tobacco but aphids are known to transmit it from tomato to tomato.
Control:
- Avoid infested soil.
- Avoid contamination of hands while working in the field.
- Do not chew tobacco, while working in tobacco or tomato fields.
- Rouging: Gently remove the diseased plant from the soil and bury it deep in the soil.
- Insect (aphid) control.
- Remove susceptible weeds, e.g.Solanum nigrum
