Tomato spotted wilt virus | |
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Symptoms of Tomato spotted wilt tospovirus on tomato | |
Virus classification | |
(unranked): | Virus |
Realm: | Riboviria |
Kingdom: | Orthornavirae |
Phylum: | Negarnaviricota |
Class: | Ellioviricetes |
Order: | Bunyavirales |
Family: | Tospoviridae |
Genus: | Orthotospovirus |
Species: | Tomato spotted wilt virus |
Synonyms | |
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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. [1]
The circulative propagative transmission of TSWV is carried out by at least ten different species of thrips. [2] The most common species is Frankliniella occidentalis (western flower thrips) as it is the vector that predominantly transmits TSWV globally and in greenhouses. [3] [4] The rapid developmental and reproductive rate of the thrips contributes to the spread of TSWV. The amount of time it takes for insects to acquire the virus (acquisition period) and the amount of time it takes for the virus to move from the insect to the plant (inoculation) for TSWV varies depends on the vector species. [2] For F. occidentalis, the acquisition and inoculation of TSWV can be as short as 5 minutes. However, the acquisition and inoculation periods for optimal transmission is 21.3 hours and 42.7 hours, respectively. [5]
Transmission of TSWV can only occur when larvae stage thrips acquire TSWV. The larvae stage for thrips lasts around 1–3 days. [6] TSWV is acquired by thrips when they feed on infected plants. Adult thrips cannot be infected with TSWV as their midgut barrier successfully prevents infection. [7] However, thrips that have successfully become infected with TSWV in the larvae stage can transmit the virus throughout their lifetime. [2] In order to protect their eggs, thrips insert their eggs into various types of plant tissue. Eggs can be found in the stems, leaves, or flowers of plants. [8] Thrips hatch in 2–3 days and complete their life cycle in 20–30 days. [2] Adult thrips feed on the flower bud, stem and leaf parts of the plant. [8]
TSWV infects a variety of hosts, contributing to its global economic impact on crops. There are over a thousand different hosts for TSWV. [2] The host range of TSWV includes agronomically important crops like tomatoes and tobacco. [2] The symptoms of TSWV vary from host to host. [2] There is also variability of symptoms within a single type of host due to the age of the plant, nutrition and the environment (especially temperature). [9] Common symptoms include stunting, ringspots on fruit and necrosis of leaves. [10] There are many different strains of TSWV, and differences in symptoms may also be attributed to the differences in the number of strains present. [3]
TSWV is a spherical negative-sense RNA virus that has a diameter between 80 and 110 nanometers. [2] TSWV tripartite genome are named RNAs L (8.9 kb), M (4.8 kb), and S (2.9 kb). The RNA S has two genes which encode nucleocapsid (N) and nonstructural protein (NSs), respectively. [11] [12]
p202/3WT, Tarquinia, and p105 isolates were always positioned in three different lineages according to phylogenetic analysis based on full genome, RdRp, GcGn, NSm, N, and NSs genes. [13] [14] TSWV isolates from worldwide shared high nucleotide and amino acid identities in N gene region. [15] Additionally, the highly conserved N gene was found to be under very strong negative selection pressures with estimated dN/dS values = 0.0638 [16] and 0.0557. [15]
Prevention is key in managing TSWV. Once a plant becomes infected with TSWV, there are no practical ways to cure the virus infected plant. The most efficient method of containing this disease is genetic resistance. [9] There are several different resistance genes identified in multiple crops. In some crops the resistance genes have been effective, however, in others, some strains of TSWV have been discovered to overcome the resistance gene, such as the Sw-5 resistance gene in tomato. [17] The Sw-5 resistance gene in tomato is a dominant resistant gene. [17] The Sw-5 gene gives resistance to the TSWV through a hypersensitive response. [18] A hypersensitive response is when the plant cells that surround the infection undergo cell death which would then deprive the virus of the cell machinery it needs to replicate and infect the plant further. There have been several strains of TSWV detected in countries such as Australia, Spain and the United States that can overcome the Sw-5 resistant gene. [17] However, those strains of TSWV have not been spread worldwide so the Sw-5 gene is still useful. [18]
Other important prevention techniques include buying virus and thrips-free transplants and managing thrips populations. Introducing species that naturally prey on thrips, such as the minute pirate bugs ( Orius insidiosus ) and big eyed bugs ( Geocoris punctipes ), may help reduce transmission of TSWV. [10] Insecticides are not an efficient way to decrease the vector population because the vectors rapidly develop resistance. [19] [10] Removing weeds and infected plants is a good way to prevent more infections in the greenhouse. [3] Sanitation practices such as the destruction or removal of old crops by plowing or physical removal are often used in the field. [4]
Bunyavirales is an order of segmented negative-strand RNA viruses with mainly tripartite genomes. Member viruses infect arthropods, plants, protozoans, and vertebrates. It is the only order in the class Ellioviricetes. The name Bunyavirales derives from Bunyamwera, where the original type species Bunyamwera orthobunyavirus was first discovered. Ellioviricetes is named in honor of late virologist Richard M. Elliott for his early work on bunyaviruses.
Plant viruses are viruses that affect plants. Like all other viruses, plant viruses are obligate intracellular parasites that do not have the molecular machinery to replicate without a host. Plant viruses can be pathogenic to vascular plants.
Agroinfiltration is a method used in plant biology and especially lately in plant biotechnology to induce transient expression of genes in a plant, or isolated leaves from a plant, or even in cultures of plant cells, in order to produce a desired protein. In the method, a suspension of Agrobacterium tumefaciens is introduced into a plant leaf by direct injection or by vacuum infiltration, or brought into association with plant cells immobilised on a porous support, whereafter the bacteria transfer the desired gene into the plant cells via transfer of T-DNA. The main benefit of agroinfiltration when compared to the more traditional plant transformation is speed and convenience, although yields of the recombinant protein are generally also higher and more consistent.
Papaya ringspot virus (PRSV) is a pathogenic plant virus in the genus Potyvirus and the virus family Potyviridae which primarily infects the papaya tree.
Alfalfa mosaic virus (AMV), also known as Lucerne mosaic virus or Potato calico virus, is a worldwide distributed phytopathogen that can lead to necrosis and yellow mosaics on a large variety of plant species, including commercially important crops. It is the only Alfamovirus of the family Bromoviridae. In 1931 Weimer J.L. was the first to report AMV in alfalfa. Transmission of the virus occurs mainly by some aphids, by seeds or by pollen to the seed.
Rice hoja blanca tenuivirus (RHBV), Spanish for "white leaf rice virus", is a plant virus in the family Phenuiviridae. RHBV causes Hoja blanca disease (HBD), which affects the leaves of the rice plant Oryza sativa, stunting the growth of the plant or killing it altogether. RHBV is carried by an insect vector, Tagosodes orizicolus, a type of planthopper. The virus is found in South America, Mexico, throughout Central America, the Caribbean region, and the southern United States. In South America, the disease is endemic to Colombia, Venezuela, Ecuador, Peru, Suriname, French Guiana and Guyana.
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.
Potato virus Y (PVY) is a plant pathogenic virus of the family Potyviridae, and one of the most important plant viruses affecting potato production.
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.
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.
Tomato yellow leaf curl virus (TYLCV) is a DNA virus from the genus Begomovirus and the family Geminiviridae. TYLCV causes the most destructive disease of tomato, and it can be found in tropical and subtropical regions causing severe economic losses. This virus is transmitted by an insect vector from the family Aleyrodidae and order Hemiptera, the whitefly Bemisia tabaci, commonly known as the silverleaf whitefly or the sweet potato whitefly. The primary host for TYLCV is the tomato plant, and other plant hosts where TYLCV infection has been found include eggplants, potatoes, tobacco, beans, and peppers. Due to the rapid spread of TYLCV in the last few decades, there is an increased focus in research trying to understand and control this damaging pathogen. Some interesting findings include the virus being sexually transmitted from infected males to non-infected females, and an evidence that TYLCV is transovarially transmitted to offspring for two generations.
Soybean mosaic virus (SMV) is a member of the plant virus genus Potyvirus. It infects mainly plants belonging to the family Fabaceae but has also been found infecting other economically important crops. SMV is the cause of soybean mosaic disease that occurs in all the soybean productions areas of the world. Soybean is one of the most important sources of edible oil and proteins and pathogenic infections are responsible for annual yield losses of about $4 billion in the United States. Among these pathogens, SMV is the most important and prevalent viral pathogen in soybean production worldwide. It causes yield reductions of about 8% to 35% but losses as high as 94% have been reported.
Sweet potato feathery mottle virus (SPFMV) is a member of the genus Potyvirus in the family Potyviridae. It is most widely recognized as one of the most regularly occurring causal agents of sweet potato viral disease (SPVD) and is currently observed in every continent except Antarctica. The number of locations where it is found is still increasing; generally, it is assumed that the virus is present wherever its host is. The virus has four strains that are found in varying parts of the world.
The western flower thrips [Frankliniella occidentalis (Pergande)] is an invasive pest insect in agriculture. This species of thrips is native to the Southwestern United States but has spread to other continents, including Europe, Australia, and South America via transport of infested plant material.
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.
Thrips palmi is an insect from the genus Thrips in the order Thysanoptera. It is known commonly as the melon thrips.
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.
Frankliniella schultzei, the common blossom thrips or cotton thrips, is a species of thrips in the family Thripidae. It is found in many parts of the world and is an important pest insect in agriculture.
Carrot virus Y (CarVY) is a (+)ss-RNA virus that affects crops of the carrot family (Apiaceae), such as carrots, anise, chervil, coriander, cumin, dill and parsnip. Carrots are the only known crop to be infected in the field. Infection by the virus leads to deformed roots and discolored or mottled leaves. The virus is spread through insect vectors, and is currently only found in Australia.
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