Table of Contents hide
Last Updated on January 13, 2020 by Sagar Aryal
Plant viruses are transmitted from plant to plant in several ways. The mode of transmission includes:
- Vegetative propagation
- Mechanically through sap
- Through seed, pollen, dodder
- By specific insects, mites, nematodes, and fungi
Image Sources: Crop Nutrition Laboratory Services Ltd. and https://doi.org/10.1111/1744-7917.12470
Transmission by Vegetative Propagation
- Whenever plants are propagated vegetatively by budding or grafting, any viruses present in the mother plant will almost always be transmitted to the progeny
- By cuttings, by bulbs, by corms, by rhizomes, by tubers, by runners or through natural root grafts of adjacent plants
Mechanical Transmission of Viruses through Sap
- In nature, the direct transfer of sap through contact of one plant with another is uncommon and relatively unimportant
- This method of transmission happens when the plants are wounded during cultural practices by tools, hands, or clothes, or by animals feeding on the plants
- In the mechanical transmission of viruses, a virus from one kind of plant may be transmitted to dozens of unrelated herbaceous plants
- However, several viruses, especially of woody plants, are difficult or impossible to transmit through the sap
- Examples of plant viruses transmitted through sap: potato virus X, tobacco mosaic virus and cucumber mosaic virus
Transmission of Viruses by Dodder
- Transmitted from one plant to another through the bridge formed between two plants by twining the stem of parasitic plants, dodder (Cuscuta sp.)
- Examples: sugar beet curly top virus (BCTV), cucumber mosaic virus
Seed Transmission
- More than 100 viruses are transmitted by seed
- The frequency of transmission varies with the host-virus combination and with the stage of growth of the mother plant when it is infected with the viruses
- The viruses seem to come primarily from the ovule of infected plants
- Examples: Barley stripe mosaic virus, Southern bean mosaic virus
Pollen Transmission
- Result in reduced fruit set, may infect the seed and the seedling
- In some cases, can spread through the fertilized flower and down into the mother plant
- Example: sour cherry with Prunus necrotic ringspot virus
Insect Transmission
- Most common and economically most important means of transmission
- Insect vectors of plant viruses:
- Order Homoptera- Aphididae (aphids), Cicadellidae (leafhoppers), Delphacidae (planthopper), Aleyrodidae (whiteflies), Coccoidae (mealybugs), Membracidae (treehoppers)
- Order Hemiptera- true bugs
- Order Thysanoptera- chewing/sucking thrips
- Order Coleoptera- beetles
- Order Orthoptera- grasshoppers
- Insects with piercing and sucking mouthparts (stylet): aphids, leafhoppers, whiteflies, thrips, other groups of Homoptera, and true bugs
- Insects with chewing mouthparts: beetles and grasshoppers
- Examples: Grapevine virus A (transmitted by mealybugs and aphids), Turnip yellow mosaic virus (transmitted by beetles)
Mite Transmission
- Mites of family Eriophyidae is known as gall mites, family Tetranychidae
- These mites have piercing and sucking mouthparts
- Examples: wheat streak mosaic virus, peach mosaic virus, Ryegrass mosaic virus
Nematode Transmission
- One or more species of three genera of soil-inhabiting, ectoparasitic nematodes
- Nematodes of genera Longidorus, Paralongidorus, and Xiphinema
- transmit several polyhedral-shaped viruses (nepoviruses), such as grape fanleaf, tobacco ring spot
- Nematodes of genera Trichodorus and Paratrichodorus
- transmit at least two rod-shaped tobraviruses, tobacco rattle, and pea early browning
- Transmit by feeding on roots of infected plants and moving on to roots of healthy plants
Fungus transmission
- Root-infecting fungal-like organisms, the plasmodiophoromycetes Polymyxa and Spongospora, and the chytridiomycete Olpidium transmit at least 30 plant viruses
- Transmitted by zoospores of root-infecting fungus and fungal-like organisms
- Examples of plant viruses vectored by zoospores:
- Tobacco necrosis-type viruses
- single-stranded RNA genome
- Viruses are carried on the surface of zoospores, not internally
- Acquired from the soil when the virus particles adhere to the surface of zoospore
- Tobacco stunt type viruses
- Rod-shaped viruses containing double-stranded RNA
- Carried internally in the zoospores
- They also enter the resting spores and survive in the soil
- Barley yellow mosaic group viruses
- Filamentous, single-stranded RNA viruses
- These viruses acquired by the fungus within the plant cells and carried internally in both the zoospores and the resting spores
- With very long persistence time in the soil
- Furovirus group
- Characteristically vectored by plasmodiophorid zoospores
- Have a single-stranded RNA genome, which divided into two segments (RNA-1 and RNA-2) that occur in different virus particles
- Acquired by fungus within the plant cells and carried internally in both the zoospores and resting spores
- Example: Beet necrotic yellow vein virus
- Tobacco necrosis-type viruses
References
- http://www.biologydiscussion.com/viruses/transmission-of-plant-viruses-8-methods-virology/64193
- https://www.thoughtco.com/plant-viruses-373892
- https://apsjournals.apsnet.org/doi/full/10.1094/PBIOMES-10-18-0045-R
- https://www.thoughtco.com/plant-viruses-373892
- https://www.annualreviews.org/doi/abs/10.1146/annurev.phyto.34.1.87
- https://www.sciencedirect.com/science/article/pii/B9780444887283500160
- https://www.ncbi.nlm.nih.gov/pubmed/15012536