Orthotospovirus

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Orthotospovirus
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Transmission electron micrograph of tomato yellow ring virus
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(unranked): Virus
Realm: Riboviria
Kingdom: Orthornavirae
Phylum: Negarnaviricota
Class: Ellioviricetes
Order: Bunyavirales
Family: Tospoviridae
Genus:Orthotospovirus
Species

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Orthotospovirus is a genus of negative-strand RNA viruses, in the family Tospoviridae of the order Bunyavirales, which infects plants. Tospoviruses take their name from the species Tomato spotted wilt orthotospovirus (TSWV) which was discovered in Australia in 1919. TSWV remained the only known member of the family until the early 1990s when genetic characterisation of plant viruses became more common. There are now at least twenty species in the genus with more being discovered on a regular basis. Member viruses infect over eight hundred plant species from 82 different families. [1]

Contents

Genome

Tospoviruses have a negative-sense, single-strand RNA genome. The genome resembles that of the genus Phlebovirus . It is linear and is 17.2 kb in size. It is divided into three segments termed S (2.9kb), M (5.4kb), and L (8.9kb). The M and S RNA segments encode for proteins in an ambisense direction.

Transmission

Tospoviruses are arboviruses usually vectored by thrips. At least ten species of thrips belonging to family Thripidae have been confirmed as vectors for the transmission of thirteen or more tospoviruses. [2] The thrips vectors are not closely related, implying an independent origin of infection for each thrips, [3] possibly transmitted horizontally through shared hosts. There may be other species of thrips competent to transmit similar viruses, but they have not been documented on crops of economic significance.

Recent research concludes that thrips can only be infected by tospovirus during the larval phases of development, as pupation and metamorphosis separate the connection between the salivary glands and the infected muscle tissue of the mid-gut. [4] Adults transmit the virus from infected salivary glands, and uninfected adults will not transmit the virus. Obviously, controlling the infection by limiting transmission from infected plants to larval thrips or by preventing adult dispersal from infected plants are key strategies in preventing an epidemic of the disease. [5] [6]

Agricultural importance

Infection with these viruses results in spotting and wilting of the plant, reduced vegetative output, and eventually death. [7] No antiviral cures have been developed for plants infected with a Tospovirus, and infected plants should be removed from a field and destroyed in order to prevent the spread of the disease.

A large number of plant families are known to be affected by viruses of the Tospovirus genus. These include both food crops (such as peanuts, watermelons, capsicums, tomatoes, zucchinis, et al.) as well as ornamental species which are important to flower farms (calla lily, impatiens, chrysanthemums, iris, et al.). For a more complete list of hosts examine the Tospovirus host list [8] at Kansas State University.

Diagnosis

Pepper infected with Tomato spotted wilt virus. Plant of Pimiento L sweet pepper. Plant infected with virus..jpg
Pepper infected with Tomato spotted wilt virus. Plant of Pimiento L sweet pepper.

Early symptoms of infection are difficult to diagnose. In young infected plants the characteristic symptoms consist of inward cupping of leaves and leaves that develop a bronze cast followed by dark spots. As the infection progresses additional symptoms develop which include dark streaks on the main stem and wilting of the top portion of the plant. Fruit may be deformed, show uneven ripening and often have raised bumps on the surface. Once a plant becomes infected the disease cannot be controlled.

Serological and molecular tests are commercially available [1] to diagnose TSWV as well as a second common tospovirus found in ornamentals, Impatiens necrotic spot virus (INSV). Cytological studies of TSWV and INSV have shown that these viruses produce granular inclusions in the cytoplasm of infected plants. These inclusions can be seen in the light microscope with proper staining techniques. [9] These inclusions can be diagnostic. [10]

Epidemiology

Tospoviruses are prevalent in warm climates in regions with a high population of thrips. For instance TSWV is an agricultural pest in Asia, America, Europe and Africa. Over the past 15 years outbreaks of Tomato spotted wilt disease have become more prevalent in these regions. Therefore, TSWV is described as an emerging viral disease of plants. The increased prevalence is largely because of the successful survival of the thrips vector Frankliniella occidentalis . Another thrips, Scirtothrips dorsalis , has also been implicated in the transmission of at least three tospoviruses, but there remains some controversy over its efficiency as a vector. [11] Immunological testing and vector-competence studies suggest that S. dorsalis may represents a non-transmitting carrier for some strains of virus.

The success of this virus has also been attributed to the acquisition of a gene in the M segment of the genome which encodes a movement protein. This protein allows the virus to infect a wide range of hosts. The gene encoding this protein was likely acquired by recombination from either a plant host or from another plant virus.

Management

Control of these diseases is difficult. One of the reasons for this is that the wide host range allows the viruses to successfully overseason from one crop to the next. To prevent spread of the virus infected plants should be immediately removed away from neighbouring plants. Control of insects, especially thrips, is important to reduce spread of the virus by vectors.

Taxonomy

The following species are recognized: [12]


Resources

Related Research Articles

<span class="mw-page-title-main">Leaf spot</span> Damaged areas of leaves

A leaf spot is a limited, discoloured, diseased area of a leaf that is caused by fungal, bacterial or viral plant diseases, or by injuries from nematodes, insects, environmental factors, toxicity or herbicides. These discoloured spots or lesions often have a centre of necrosis. Symptoms can overlap across causal agents, however differing signs and symptoms of certain pathogens can lead to the diagnosis of the type of leaf spot disease. Prolonged wet and humid conditions promote leaf spot disease and most pathogens are spread by wind, splashing rain or irrigation that carry the disease to other leaves.

<i>Nepovirus</i> Genus of viruses

Nepovirus is a genus of viruses in the order Picornavirales, in the family Secoviridae, in the subfamily Comovirinae. Plants serve as natural hosts. There are 40 species in this genus. Nepoviruses, unlike the other two genera in the subfamily Comovirinae, are transmitted by nematodes.

<i>Beet necrotic yellow vein virus</i> Species of virus

Beet necrotic yellow vein virus (BNYVV) is a plant virus, transmitted by the plasmodiophorid Polymyxa betae. The BNYVV is a member of the genus Benyvirus and is responsible for rhizomania, a disease of sugar beet that causes proliferation of thin rootlets, and leads to a smaller tap root with reduced sugar content. Infected plants are less able to take up water, and wilting can be observed during the warm period of the year. If the infection spreads to the whole plant, vein yellowing, necrosis and yellow spots appear on the leaves, giving the virus its name.

<i>Impatiens necrotic spot orthotospovirus</i> Species of virus

Impatiens necrotic spot orthotospovirus(INSV) is a plant pathogenic virus of the order Bunyavirales. It was originally believed to be another strain of Tomato spotted wilt virus, but genetic investigations revealed them to be separate viruses. It is a negative-strand RNA virus which has a tripartite genome. It is largely spread by the insect vector of the western flower thrips. The virus infects more than 648 species of plants including important horticultural and agricultural species such as fuchsia, tomato, orchids, and lettuce (especially romaine). As the name implies, the main symptom on plants is necrotic spots that appear on the leaves. The INSV virus infects by injecting the RNA the virus contains into the cell which then starts using the cell resources to transcribe what the virus RNA states. Viral infection can often result in the death of the plant. The disease is mainly controlled by the elimination of the western flower thrip vector and by destroying any infected plant material.

Prune dwarf virus (PDV) is an economically important plant pathogenic virus affecting Prunus species globally. PDV is found worldwide due to easy transmission through seed, pollen, and vegetative propagation. The virus is in the family Bromoviridae an important family of plant RNA viruses containing six genera, including Alfamovirus, Ilarvirus, Bromovirus, Amularvirus, Oleavirus, and Cucumovirus. PDV belongs to the genera Ilarvirus. It can cause dwarfism of leaves on certain prune and plum plants. It will also cause yellows in sour cherry, especially when present with Prunus necrotic ringspot virus. There are no known transmission vectors, though the pollen of infected cherry trees has been found to infect other cherry trees a small percent of the time.

<i>Prunus necrotic ringspot virus</i> Species of virus

Prunus necrotic ringspot virus (PNRSV) is a plant pathogenic virus causing ring spot diseases affecting species of the genus Prunus, as well as other species such as rose and hops. PNRSV is found worldwide due to easy transmission through plant propagation methods and infected seed. The virus is in the family Bromoviridae and genus Ilarvirus. Synonyms of PNRSV include European plum line pattern virus, hop B virus, hop C virus, plum line pattern virus, sour cherry necrotic ringspot virus, and peach ringspot virus.

<i>Tobacco ringspot virus</i> Species of virus

Tobacco ringspot virus (TRSV) is a plant pathogenic virus in the plant virus family Secoviridae. It is the type species of the genus Nepovirus. Nepoviruses are transmitted between plants by nematodes, thrips, mites, grasshoppers, and flea beetles. TRSV is also easily transmitted by sap inoculation and transmission in seeds has been reported. In recent cases it has also been shown to appear in bees, but no transmission to plants from bees has been noted.

<i>Tobacco streak virus</i> Species of virus

Tobacco streak virus (TSV) is a plant pathogenic virus of the family Bromoviridae, in the genus Ilarvirus. It has a wide host range, with at least 200 susceptible species. TSV is generally more problematic in the tropics or warmer climates. TSV does not generally lead to epidemics, with the exception of sunflowers in India and Australia, and peanuts in India.

<i>Carlavirus</i> Genus of viruses

Carlavirus, formerly known as the "Carnation latent virus group", is a genus of viruses in the order Tymovirales, in the family Betaflexiviridae. Plants serve as natural hosts. There are 53 species in this genus. Diseases associated with this genus include: mosaic and ringspot symptoms.

<i>Thrips palmi</i> Species of thrip

Thrips palmi is an insect from the genus Thrips in the order Thysanoptera. It is known commonly as the melon thrips.

<i>Watermelon mosaic virus</i> Species of virus

Watermelon mosaic virus (WMV) also known as Marrow mosaic virus, Melon mosaic virus, and until recently Watermelon mosaic virus type 2 (WMV-2), is a plant pathogenic virus that causes viral infection in many different plants. The virus itself is referred to as Watermelon Mosaic Virus II or WMV-2 and is an isolate of the U.S. WMV-2 is a ssRNA positive strand virus that is part of the Potyviridae or Potyvirus clade. Like all RNA viruses, it contains a protein capsid which protects the inner viral RNA. First described on squash in Florida, WMV arose from a unique recombination of genetic material contributed by Soybean mosaic virus (SMV) and Bean common mosaic virus (BCMV) along with Peanut Stripe virus (PSV).

Orchid fleck dichorhavirus, commonly called Orchid fleck virus (OFV), is a non-enveloped, segmented, single-stranded (ss) RNA negative-strand virus, transmitted by the false spider mite, Brevipalpus californicus. OFV causes necrotic and chlorotic lesions on the leaves of many genera in the family Orchidaceae.

<i>Melon necrotic spot virus</i> Species of virus

Melon necrotic spot virus (MNSV) is a virus that belongs to the genus Gammacarmovirus of the family Tombusviridae. It has been observed in several countries of the Americas, Africa, Asia, and Europe. It is considered to be an endemic virus in greenhouses and field productions of Cucurbitaceae crops, including melon, cucumber, and watermelon. MNSV is mainly spread through infected soil, seedlings, insects, and by the root-inhabiting fungus vector Olpidium bornovanus. Symptoms vary between Curbitaceae crops, but generally consist of chlorosis, brown necrotic lesions, leaf wilt, fruit decay, and plant death. Management of the disease consists of preventing infection by rotating fields and crops, steam sterilization, and disposal of infected plants. Also, treated seeds with heat or chemicals are efficient in preventing infection. MNSV is important in melon plants as it causes vast economical damage worldwide reducing significant yields.

Soybean vein necrosis orthotospovirus is a plant pathogenic virus of soybeans. SVNV is a relatively new virus, which was discovered in Tennessee in 2008 and has recently been found in many US states from the Southeast and East coast to some western states including CA. This pathogen initially causes intraveinal chlorosis (yellowing) in leaves. This chlorosis then spreads throughout the leaf and eventually these chlorotic areas can become necrotic. It is a member of the order Bunyavirales, family Tospoviridae and genus Orthotospovirus, which is the only genus within this virus family that infects plants. Like other members of Bunyavirales, this virus is enveloped and has a negative sense single-stranded RNA (−ssRNA) genome composed of three genomic segments. It encodes proteins on the M and S segments in an ambisense manner.

Maize lethal necrosis disease is a viral disease affecting maize (corn) predominantly in East Africa, Southeast Asia and South America, which was recognised in 2010. It is caused by simultaneous infection with two viruses, MCMoV and any of several Potyviridae.

Badnavirus is a genus of viruses, in the family Caulimoviridae order Ortervirales. Plants serve as natural hosts. There are 67 species in this genus. Diseases associated with this genus include: CSSV: leaf chlorosis, root necrosis, red vein banding in young leaves, small mottled pods, and stem/root swelling followed by die-back. Infection decreases yield by 25% within one year, 50% within two years and usually kills trees within 3–4 years.

Cocoa necrosis virus (CoNV) is a plant pathogenic virus of the genus nepovirus that infects Theobroma cacao en natura causing cacao necrosis disease. CoNV is considered synonymous with Strain S of cacao swollen shoot virus. Unlike Cacao swollen shoot virus, it is not transmitted by mealybugs nor vectored by aphids, beetles, or leafhoppers that also commonly infest cacao. It is serologically, distantly related to Tomato black ring virus and very distantly related to Grapevine chrome mosaic virus.

<i>Thrips tabaci</i> Species of thrip

Thrips tabaci is a species of very small insect in the genus Thrips in the order Thysanoptera. It is commonly known as the onion thrips, the potato thrips, the tobacco thrips or the cotton seedling thrips. It is an agricultural pest that can damage crops of onions and other plants, and it can additionally act as a vector for plant viruses.

<span class="mw-page-title-main">Tomato spotted wilt orthotospovirus</span> Species of virus

Tomato spotted wilt orthotospovirus (TSWV) is a spherical negative-sense RNA virus. Transmitted by thrips, it causes serious losses in economically important crops and it is one of the most economically devastating plant viruses in the world.

<span class="mw-page-title-main">Viral diseases of potato</span>

Viral diseases of potato are a group of diseases caused by different types of Viruses that affect potato crops worldwide and, although they do not affect human or animal health since they are viruses that only infect vegetables, they are a source of great economic losses annually. About 28 viruses have been reported infecting potato crops. However, potato virus X (PVX), potato virus Y (PVY), and potato leafroll virus (PLRV) are the most important viruses worldwide. Some others are of economic importance only in some regions. Such is the case of potato virus M (PVM) in some Asian and European countries.

References

  1. 1 2 "PP-212/PP134: Tospoviruses (Family Bunyaviridae, Genus Tospovirus)". Edis.ifas.ufl.edu. Retrieved 2014-06-15.
  2. ↑ Jones, D. R. 2005. Plant viruses transmitted by thrips. European Journal of Plant Pathology 113: 119–157.
  3. ↑ Mound, L. A. 2002. So many thrips – so few tospoviruses?, pp. 15 - 18. In L. A. Mound and R. Marullo [eds.], Thrips and Tospoviruses: Proceedings of the 7th International Symposium on Thysanoptera. CSIRO Entomology, Reggio Calabria, Italy.
  4. ↑ Moritz, G., S. Kumm, and L. A. Mound. 2004. Tospovirus transmission depends on thrips ontogeny. Virus research 100: 143–149.
  5. ↑ Groves, R. L., J. F. Walgenbach, J. W. Moyer, and G. G. Kennedy. 2003. Seasonal Dispersal Patterns of Frankliniella fusca (Thysanoptera: Thripidae) and Tomato Spotted Wilt Virus Occurrence in Central and Eastern North Carolina. Journal of Economic Entomology 96: 1 - 11.
  6. ↑ Nault, B. A., J. Speese III, D. Jolly, and R. L. Groves. 2003. Seasonal patterns of adult thrips dispersal and implications for management in eastern Virginia tomato fields. Crop Protection 22: 505–512.
  7. ↑ "Destructive onion virus evolving, spreading". WSU Insider. Washington State University. 7 January 2022. Retrieved 13 January 2022. Iris yellow spot virus is continuing to pose a danger to onion crops …
  8. ↑ "Tospovirus Host List". Archived from the original on 2007-11-22. Retrieved 2007-11-20.
  9. ↑ "Materials and Methods for the Detection of Viral Inclusions". Freshfromflorida.com. Archived from the original on 13 October 2014. Retrieved 20 December 2017.
  10. ↑ "Inclusions of Tomato spotted wilt virus and Impatiens necrotic spot". Freshfromflorida.com. Retrieved 20 December 2017.
  11. ↑ Whitfield AE, Ullman DE, German TL (2005). Tospovirus-thrips interactions. Annual Review of Phytopathology. 43: 459–89.
  12. ↑ "Virus Taxonomy: 2020 Release". International Committee on Taxonomy of Viruses (ICTV). March 2021. Retrieved 19 May 2021.

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