Cucumber mosaic virus
Cucumber mosaic virus (CMV) is a plant pathogenic virus in the family Bromoviridae. It is the type member of the plant virus genus, Cucumovirus. This virus has a worldwide distribution and a very wide host range. In fact it has the reputation of having the widest host range of any known plant virus. It can be transmitted from plant to plant both mechanically by sap and by aphids in a stylet-borne fashion. It can also be transmitted in seeds and by the parasitic weeds, Cuscuta sp. (dodder).
|Cucumber mosaic virus|
|Cucumber mosaic virus symptoms|
Cucumber mosaic virus
Hosts and symptomsEdit
In plant tissue this virus makes characteristic viral inclusion bodies which can be diagnostic. They are hexagonal in shape (Fig.1) and stain both in a protein stain and a nucleic acid stain. The inclusions can also be rhomboidal (Fig. 2b), may appear hollow (Fig. 1) and can form larger aggregates (Fig. 3b). The inclusions are not uniformly distributed and can be found in epidermal (Figs. 1 and 2b), mesophyll (Fig. 3b), and stomatal cells (Fig. 4b). These inclusions are made up of virus particles.
This virus was first found in cucumbers (Cucumis sativus) showing mosaic symptoms in 1934, hence the name Cucumber mosaic. Since it was first recognized, it has been found to infect a great variety of other plants. These include other vegetables such as squash, melons, peppers, beans, tomatoes, carrots, celery, lettuce, spinach and beets, various weeds and many ornamentals and bedding plants, such as Narcissus. Symptoms seen with this virus include leaf mosaic or mottling (Fig. 2a), yellowing (Fig. 3a), ringspots (Fig. 4a), stunting, and leaf, flower and fruit distortion.
CMV shows symptoms on leaves known as the "shoestring" effect for most host species. This effect causes young leaves to appear narrow and the entire plant to be stunted.
Specifically CMV can cause cucumbers to turn pale and bumpy. The leaves of these plants turn mosaic and their rugosity is often changed, making leaves wrinkled and misshapen. Growth of these plants is usually stunted and produces few flowers. Often cucumber fruits are oddly shaped and appear gray. This appearance often leads to cucumbers being referred to as "white pickles". Often infected cucumbers are bitter.
In celery, CMV can cause streaking and spotting and can be often confused with symptoms of the celery mosaic virus.
Symptoms of CMV in lettuce can be similar to those of lettuce mosaic virus. Infected plants show symptoms of chlorosis, stunting and often do not properly head.
Some of the most important fruits and vegetables affected by CMV are peppers, bananas, tomatoes and cucurbits.
CMV in peppers causes slightly different symptoms than the previously mentioned. Pepper plants often have severe foliar damage, shown as mosaic and necrotic rings. Often the peppers themselves are misshapen and contain chlorotic rings and spots.
Tomato plants are usually stunted and have poorly shaped leaves, or "fernleaf", when infected by CMV. Also certain strains of CMV can cause partial or total crop loss.
Fig.4a. Symptoms in Commelina diffusa
As CMV is easily spread, it can be found worldwide. It is transmitted by more than 60 different aphid species, among other vectors, and it can infect over 1200 plant species, including important crops and ornamental species. In its plant host, CMV can cause severe damage, which can lead to economical losses, as it can lead to 10-20% loss of field yield .
CMV is mainly transmitted by aphids, but it can also be mechanically spread by humans in some cases. However, the mechanically spreading of this virus is not as common as the case of other virus (such as Tobacco Mosaic Virus, TMV), because CMV is not a very stable virus. When it is transmitted by aphids, this virus has an acquisition period of five to ten seconds and an inoculation period of about a minute. Nevertheless, after two minutes, the probability of inoculation largely decreases, and within two hours it is practically impossible to transmit it. Moreover, CMV can overwinter in perennial plants and weeds, as it can survive the winter in the roots of the plant and move to the aerial parts in spring, where it can be transmitted by aphids to other plants.
Once the virus penetrates into the host cell, it releases its RNAs into the host cytoplasm. Then, proteins 1a and 2a are produce to enable the virus replication, which takes place in viral factories, which are subcellular compartments which increase the efficiency of this process. There, a dsRNA genome is synthetized from the ssRNA(+) and transcribed in order to obtain viral mRNAs as well as new ssRNAs. Afterwards, the capsid proteins are produced and the new viral particles are assembled. Finally, the virus is ready to move to a new cell by triggering the formation of tubular structures which mediate the movement of the virions . The short-distance (cell-to-cell) movement of the virus is achieved via plasmodesmata, while the long-distance one (within the plant) occurs via the phloem.
CMV is a linear positive-sense, tripartite single-stranded RNA virus . Its genome size is 8.623 kb and it is divided among RNA1 (3357 pb) , RNA2 (3050 pb)  and RNA3 (2216 pb) , all of which has a tRNA-like structure . These three RNAs encode five proteins, proteins 1a, 2a, 2b, movement protein (MP) and coat protein (CP). While proteins 1a and 2a are responsible for the replication of the virus, protein 2b is the host-silencing suppressor .
Its total genome size 8.621 kb and is broken into three parts. The largest part is 3.389 kb; the second largest is 3.035 kb; the third largest is 2.197 kb. The RNA is surrounded by a protein coat consisting of 32 copies of a single structural protein which form isometric particles.
This virus presents non-enveloped, icosahedral or bacilliform virions of 26-35 nm in diameter. The different RNAs are encapsidated in distinct particles, which results in a variety of virions .
CMV is naturally found in temperate areas, where aphids, one of its main vectors, are also found  .
Nowadays, there is not any chemical capable of removing this virus from an infected plant. Therefore, the best control in this case is prevention of the infection and eradication . To achieve this, it is crucial to remove weeds and diseased plants from the field, as well as use clean and sanitized tools. Another option consists of the use of resistant varieties or the so-called "trap crops".
- Description of Plant Viruses:What are viruses?
- Description of Plant Viruses: Bromovirideae
- "About Plant Viruses / Material and Methods for the Detection of Viral Inclusions / Florida Plant Viruses and Their Inclusions / Science / Plant Industry / Divisions & Offices / Home - Florida Department of Agriculture & Consumer Services".
- Description of Plant Viruses:Cucumovirus
- Plant Viruses Online:Cucumber mosaic host range
- Crop Knowledge Master: Cucumber Mosaic Virus
- "Material and Methods for the Detection of Viral Inclusions / Florida Plant Viruses and Their Inclusions". Florida Department of Agriculture & Consumer Services.
- Price, W.C. 1934. Phytopathology 24: 743.
- Douine, L., Quiot, J.B., Marchoux, G. and Archange, P. 1979. Annls. Phytopath. 11: 439
- Vegetable MD Online: Bean – Cucumber mosaic Cucumovirus
- Vegetable MD Online: Virus Diseases of Leafy Vegetables and Celery
- Iwaki 1972.
- Vegetable MD Online: Important New York Vegetable Diseases
- "Cucumber Mosaic Virus (CMV)" (PDF). AVRDC. Archived from the original (PDF) on 2006-05-26.
- Stephen A. Ferreira; Rebecca A. Boley. "Cucumber mosaic virus - cucumber mosaic". University of Hawaii at Manoa.
- Stephen H. Brown; Tom Becker; Bonnie Farnsworth. "Cucumber Mosaic Virus (CMV): A Growing Problem for American Beautyberry (Callicarpa americana)" (PDF). UF/IFAS.
- "Cucumber mosaic virus".
- ICTVd Descriptions:Cucumber mosaic virus
- Kong, J.; Wei, M.; Li, G.; Lei, R.; Qiu, Y.; Wang, C.; Li, Z. H.; Zhu, S. (2018-04-06). "ScienceDirect". Biochemical and Biophysical Research Communications. 498 (3): 395–401. doi:10.1016/j.bbrc.2018.01.072. PMID 29407169.
- ICTVdB - Picture Gallery:Images of CMV
- Jude Boucher. "Pepper IPM: Aphids and Viruses". University of Connecticut Integrated Pest Management Program. Archived from the original on 2001-02-25.
- Pest Alert: Cucumber mosaic virus
- IWAKI, Mitsuro; KOMURO, Yasuo (1972). "Viruses Isolated from Narcissus (Narcissus spp.) in Japan". Japanese Journal of Phytopathology. 38 (2): 137–145. doi:10.3186/jjphytopath.38.137.
Other on-line Links about CMV for growers and gardeners
- Texas Plant Disease Handbook: Cucumber Mosaic
- Weekend Gardener: Cucumber mosaic virus
- Ohio Floriculture:
- ICTVdB - The Universal Virus Database: Cucumber mosaic virus
- Family Groups - The Baltimore Method
- Plant Viruses Online – VIDE Database
- Descriptions of Plant Viruses
- Weekendgardner Monthly Web Magazine: Cucumber Mosaic Virus
- Crop Knowledge Master: Cucumber Mosaic Virus
- AVRDC - The World Vegetable Center Fact Sheet: Cucumber Mosaic Virus
- University of Illinois Extension - Report on Plant Disease: Mosaic Diseases of Cucurbits
- APSnet: Cucumber Mosaic Virus
- Alabama Cooperative Extension System - Alabama A&M and Auburn Universities Plant Disease Notes: Cucumber Mosaic Virus
- Florida Tomato Scouting Guide: Cucumber Mosaic Virus
- HYPP Pathology: Cucumber Mosaic Virus
- ICTVdB Virus Descriptions: Cucumber Mosaic Virus