Tobacco Mosaic Virus (TMV)
Tobacco Mosaic Virus is a disease-causing virus that was first found in tobacco plants leave. That attack on tobacco plant leaves and cause significant loss of crop plant. it’s also attack many other crops.
Morphology of tobacco mosaic virus:
Size and shape:
- Tobacco mosaic disease cause by rod shape virus.
- it about 300 nm in length and 15 nm in diameter.
- It consists of a single stand of RNA which is protected by protein sub unit know as capsid.
- Capsid is made of about 2130 molecule of protein sub unit. RNA is also part of TMV which consist of 6400 bases long.
- The coat self-assembles to the rode shape helical structure out side the RNA that make a hairpin loop like structure.
- One unit of protein contain with 158 amino acid monomer which are assemble into four alpha helices and arrange into helix.
- Tobacco mosaic virus remain stable at 93 C, so that reason it also called thermostable virus.
TMV infect nine plant families, particularly they infect Solanaceae family and 125 individual species, tobacco, tomato, cucumber and many ornamental flowering plants.
- In early stages affected plants young leaves show light green color between the veins.
- Later they developed quickly and show molten pattern of light and dark green color on leaves.
- Blister like area develop on leaf and most of leave area dead.
- Due to dead area plant growth stunted and curling and distortion of leaf occur.
- Leaves become narrow and elongated.
- Mosaic virus infection not result plant dead, but early season virus attack stops the leaf and plant growth.
- Lower side leaf burns due to virus attack in dry or hot season. Its also called destructive phase.
- TMV also attack on apple and grapes crop and show same symptom on it.
How TMV transmit and cause infection?
- TMV have ability to survive in infected leaf and stalk, soil surface and seed of plants. Firstly, virus enter in plant through wounded tissue seed or transplant plant from nursery. TMV attack first on parenchyma tissue than enter phloem.
- It’s also transmitted through sap, dodder and grafting.
- It’s also transmitted through with the help of worker that work in field from infected plant to healthy.
- They enter plasmodesmata and infect new cell.
- Firstly, they enter in host cell via inoculation.
- Then uncoated itself and release viral RNA.
- Viral RNA will replicate to produce mRNAs.
- mRNAs encode several protein coats, RNA polymers and movement of protein.
- Then TMV can replicate own genome.
- After this protein coat and genome of tobacco mosaic virus synthesis.
- At the end they assemble and make new TMV virions.
How to Control TMV Disease?
- Sanitation is a big problem that spread the TMV. So, update sanitation system to control it.
- Do not grow crop in that field where already TMV present for 2-3 year at least.
- Remove the effect plants from the field to stop the life cycle of TMV.
- Trisodium phosphate 3% solution use for hand wash after working in field.
- Use new varieties of tobacco that resist the TMV attack.
- Coconut also help to control the TMV attack on crop.