Transmission of plant viruses

Plant viruses are transmitted from plant to plant in a number of ways.

Transmission of viruses by vegetative propagation.
Mechanical transmission of viruses through sap.
Transmission of viruses by seed.
Transmission of viruses by Pollen.
Transmission of viruses by dodder.
Transmission by vectors.

1. Welcome To MY Presentation 1

2. Transmission of plant viruses Prepared by Md : Aminul Haque [email protected] 2

3. Contains Introduction Number of ways Transmission of plant viruses Details Conclusion 3

4. Introduction Plant pathology  is the study of plant disease  including the reasons why  plants  get sick and how to control or manage healthy  plants .  Viruses  are intracellular (inside cells) pathogenic particles that infect other living organisms. The total number of known viruses to date are 2000. Nearly half of known viruses causes diseases in plants . Common characteristics of viruses: Viruses are infectious agents, Viruses are visible under electron microscope but not visible under light microscope. Viruses show obligate relationship with plant . Elongate viruses have size of 10-15 X 300-2000 nanometers. Each plant viruses consist of at least nucleic acid and a protein coat.

5. Plant viruses are transmitted from plant to plant in a number of ways. Transmission of viruses by vegetative propagation Mechanical transmission of viruses through sap Transmission of viruses by seed Transmission of viruses by Pollen Transmission of viruses by dodder Transmission by vectors Insect transmission Mite transmission Nematode transmission Fungus transmission

6. Transmission by Vegetative Propagation: Plants are propagated vegetative by budding or grafting or by cutting or by the use of tubers, corms, bulbs or rhizome. Any virus present in the mother plant from which these organs are taken will almost always be transmitted to the progeny. Transmission of viruses may also occur through natural root grafts of adjacent plant .

7. Mechanical transmission of viruses through sap The  transmission  of a  virus from  infected to healthy tissues is a procedure fundamental to the study of  virus  diseases . In the laboratory this is usually accomplished by grinding the leaf of a diseased plant, and rubbing the infectious sap  on to the leaf of a healthy plant . after a strong wind injures the leaves of adjacent diseased and healthy plants or when plants are wounded during cultural practices by tools, hands, or clothes, or by animals feeding on the plants, and the sap carrying virus is transferred to wounded plants.

8. Transmission of viruses by seed About 100 viruses have been reported to be transmitted by seed only a small portion (1-30) of the seed derived from virus infected. Plant transmit the virus . Frequencies varies with the host virus combination. Tobacco ring spot virus is soybean may be transmitted by almost all 100% of the seed of infected plant. 28-94% in squash mosaic virus in musk melon. 50-100% in barley stripe mosaic virus in barley. Mosaic of Datura stramonium to the tune of 79%.

9. Transmission of viruses by Pollen Virus transmitted by pollen may infect not only the seed but also seedling that will grow form it. Ex. Tomato and Tobacco black ring virus . Cross pollination by pollen from virus infected plant may infect the seed and the seedling that will grow from it in some cases, can spread through the fertilized flower down into the mother plant.

10. Transmission of viruses by dodder Several plant virus can be transmit ted from one plant to another plant through the bridge formed between the two plants by twining the stem of parasitic plant, dodder ( Cuscuta species), green strain of cucumber mosaic virus on N. glutinosa , lucern ( alfa-alfa ) , mosaic virus to tobacco potato stem mottle virus to tobacco. Bennett (1940) showed dodder transmission, sugar beet curly top virus (BCTV), cucumber mosaic virus .

11. Transmission by vectors Insect transmission Mite transmission Nematode transmission Fungus transmission

12. Insect transmission Insects which chew or suck plant tissues are the ideal and the most common means of transmitting viruses to new hosts in the field. The most important virus vectors are aphids, leafhoppers, whiteflies, and thrips .

13. Mite transmission Mites of the family Eriophyidae transmit at least 6 viruses including Wheat streak mosaic virus Only 1 Tetranychidae and 5 eriophid mites have been proved to be the vectors of plant viruses . It also appears to be a nonspecific or casual vector of potato virus Y .

14. Nematode transmission Nematode plant viruses are transmitted by three genera of soil inhabiting ectoparasitic nematodes e.g. the genera Longidorus , Paralongidorus , and Xiphinema . Transmit several viruses such as grape fanleaf , tobacco ring spot and other viruses.

15. Fungus transmission Root-infecting fungal-like organisms, the Plasmodiophoromycetes Polymyxa sp. and Spongospora sp. and the Chytridiomycetes Olpidium sp., transmit at least 30 plant viruses.

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