Transmission of Virus in Plants

Transmission of Virus:

Viruses are transferred from infected plants to healthy ones by a number of agencies and this is known as transmission of virus.

1. By Grafting: A large number of plants are vegetatively propagated. Grafting is the most common method used in propagating fruit and ornamental plants. When an infected plant is used for grafting with a healthy plant, the virus is transmitted through the cell solutions flowing from the infected part into the healthy parts.

2. By Seeds: Seed transmission of viruses isn’t common. Mosaic viruses of cucurbits and legumes are transmitted by seeds. But in the crops which are vegetatively propagated by the use of setts, tubers, rhizomes, bulbs, corms, etc. Viruses are transmitted by these organs.

3. By Contact: Viruses can be transmitted merely by contact or slight rubbing of the infected and healthy plant organs. Such transmission is quite easy in a thickly populated field where one plant is always in close contact with the other and even the slightest movement of the wind can help in rubbing the organs of one with the other. Viruses usually gain entry through the injuries caused on plant surfaces.

4. By Air and Water: Unlike fungi and bacteria viruses aren’t easily transmitted by air and water. The tobacco necrosis virus has been observed to be transmitted by both air and water.

5. By Soil: Tobacco mosaic virus lies in the soil with the plant debris after the harvest of the crop and infects the new crop, when sown in the same field.

6. By Tools and Agricultural Operations: At the time of agricultural operations such as topping, pruning, weeding, roguing, or irrigation, the agricultural tools and the hands of the worker may get contaminated by the juice of an infected plant if it gets injured. These tools and the hands of the workers transfer the viruses to healthy plants, the contact with which can’t be avoided ordinately.

7. By Smokers: Tobacco mosaic virus remains infective in dry tobacco leaves for as long as 31 years. This virus is very resistant to high temperatures. It can spread by the fingers of the smokers by the smoke and the unburnt pieces of cigarettes, cigars, and biris. Tobacco chewer’s sputum can also transmit viruses if it is there in the tobacco leaves.

8. By Store House: Viruses such as tobacco mosaic are transmitted to the new stock of tobacco when it is stored in the same storehouse, where the infected leaves were stored.

9. By Insects: In nature, viruses are ordinarily transmitted by aphids, jassids, and white flies which are the sucking insects. Most crop diseases viruses are transmitted by insects and for this simple reason, some virologists believe that there would have been no virus diseases if there were no insects. One Virus can be transmitted by several species of insects and vice versa.