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Vector of virus


[R] Organism (insect, nematode, mite) carrying a pathogenic virus and transmitting it to a plant. 90% of vectors belong to the Homoptera, especially aphids, the Cicadellidae and the Aleyrodidae.
These insects can transmit viruses in 3 ways:.
- the stylet-borne or non-persistent way, in which aphids are mere mechanical vectors transferring the virus from the sap of an infected plant to a healthy plant. Viruses cannot survive long in these vectors and their short infectious power shows itself immediately after they have caught the virus during feeding. These vectors are capable of transmitting several types of virus and, conversely, a specific virus can be transmitted by several different vectors. For example, the peach-potato aphid (Myzus persicae) is capable of transmitting more than 20 viruses.
- the persistent way, in which aphids are biological vectors transmitting only 1 or 2 types of virus, which cannot be transmitted experimentally with direct injections but can be transmitted with grafts. After it has caught the virus during feeding, the insect becomes infectious only after an incubation period corresponding to the period of the multiplication and the migration (from the intestine to the haemolymph and from the haemolymph to the salivary glands) of the virus. This latent period finished, the insect retains its infectious power for a very long time. The glasshouse and potato aphid (Aulacorthum solani) is an active vector of the potato leaf roll virus (PLRV). Being polyphagous, it also transmits the cabbage mosaic virus (CMV) to various cultivated plants and the beet yellows virus (BYV) to beet. The bird-cherry aphid (Rhopalosiphum padi) is the vector of several cereal virus diseases and mainly transmits barley yellow dwarf virus (BYDV).
Some viruses can be transmitted both by a biological vector and mechanicaly. The ability of a vector to transmit a virus also depends on the feeding site, the species feeding on the phloem being more efficient than those feeding on the parenchyma.
Nematodes known to be vectors of viruses are all ectophytes of the family Dorylaimidae and include , which is harmful to vine, and , which causes damage to strawberry.


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