A satellite is a subviral agent that depends on the coinfection of a host cell with a helper virus for its replication. Satellites can be divided into two major classes: satellite viruses and satellite nucleic acids. Satellite viruses, which are most commonly associated with plants, are also found in mammals, arthropods, and bacteria. They encode structural proteins to enclose their genetic material, which are therefore distinct from the structural proteins of their helper viruses. Satellite nucleic acids, in contrast, do not encode their own structural proteins, but instead are encapsulated by proteins encoded by their helper viruses. The genomes of satellites range upward from 359 nucleotides in length for satellite tobacco ringspot virus RNA (STobRV).
Plant viruses are viruses that have the potential to 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.
Tombusviridae is a family of single-stranded positive sense RNA plant viruses. There are three subfamilies, 17 genera, and 95 species in this family. The name is derived from Tomato bushy stunt virus (TBSV).
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.
Lettuce mosaic virus (LMV) is a typical potyvirus, which causes one of the major virus diseases of lettuce crops worldwide.
Potyvirus is a genus of positive-strand RNA viruses in the family Potyviridae. Plants serve as natural hosts. Like begomoviruses, members of this genus may cause significant losses in agricultural, pastoral, horticultural, and ornamental crops. More than 200 species of aphids spread potyviruses, and most are from the subfamily Aphidinae. The genus contains 190 species and potyviruses account for about thirty percent of all currently known plant viruses.
Fusarium oxysporum f.sp. betae is a destructive fungal plant pathogen. It causes Fusarium yellows or fusarium wilt, characterized by yellowing and dwarfing.
Arabis mosaic virus is a viral plant pathogen that is known to infect multiple hosts. The pathogen, commonly referred to as ArMV, is from the family Secoviridae, and it causes yellow dwarf of raspberry and is one of the causes of mosaic of rhubarb. Arabis mosaic virus infects multiple hosts, including strawberries, hops, hemp, grape, geraniums, raspberries, sugar beets, celery, horseradish, lilac, peach, and lettuces.
Apple mosaic virus (ApMV) is a plant pathogenic virus of the family Bromoviridae. It is named after its symptoms that were first present on apples. ApMV is a positive sense RNA based virus. The disease itself has several synonyms including Mild Apple Mosaic Virus, Hop Virus, Rose Mosaic Virus, and European Plum Line Patten Virus. It causes a severe yield reduction and decreased life-expectancy of fruit trees.
Barley yellow mosaic virus is plant pathogenic virus that causes the yellow mosaic disease of barley. Its shape is categorized as being flexuous filamentous, with lengths of 275 and 550 nanometers. The virus has a limited host range, and barley appears to be the only known susceptible host. The virus is transmitted via Polymyxa graminis, which is a plasmodiophorid protist, through the resting spores that survive in the soil, and eventually zoospores. Eastern Asia is the most affected region, but the virus can be found worldwide. Current agricultural practices have been ineffective at eliminating the virus, but breeding resistance appears to be the only way to help reduce the disease.
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.
Cucumber mosaic virus (CMV) is a plant pathogenic virus in the family Bromoviridae. This virus has a worldwide distribution and a very wide host range, having the reputation of 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).
Soil-borne wheat mosaic virus is a rod-shaped plant pathogen that can cause severe stunting and mosaic in susceptible wheat, barley and rye cultivars. The disease has often been misdiagnosed as a nutritional problem, but this has actually allowed in part for the fortuitous visual selection by breeding programs of resistant genotypes. Soil-borne wheat mosaic virus is part of the genus Furovirus. Members of this genus are characterized by rigid rod-shaped particles and positive sense RNA genomes consisting of two molecules that are packaged into separate particles that code for either replication, mobility, structure or defense against the host. The virus is spread by a fungal-like protist, Polymyxa graminis, whose asexual secondary and sexual primary cycles help the virus spread. The disease produces secondary symptoms from the root cell infection. The disease is a serious contributor to loss in crop yield.
Benyvirus is a genus of viruses, in the family Benyviridae. Plants serve as natural hosts. There are four species in this genus. Diseases associated with this genus include: BNYVV: rhizomania.
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.
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 in 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.
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.
Polerovirus is a genus of viruses, in the family Solemoviridae. Plants serve as natural hosts. There are 26 species in this genus. Diseases associated with this genus include: PLRV causes prominent rolling of the leaves of potato and a stiff upright habit of the plants; necrosis of the phloem and accumulation of carbohydrates in the leaves.
The Blueberry mosaic associated ophiovirus (B1MaV) is a plant virus which infects blueberry plants, causing a discoloration of the leaves of the plants in a mosaic-like pattern. The disease is found in blueberry plants in many regions of North America, as well as South America, Europe, New Zealand, and South Africa. Within these regions the virus is most often found in high blueberry-yielding areas, but can be spread to other locations. Blueberry mosaic associatedophiovirus is one of seven species in the genus Ophiovirus. It is a member of the Aspiviridae family, in the Serpentovirales order, and in the Milnevircetes class. The Ophioviridae viruses are characterized by a flexible and elongated nucleocapsid that is composed mostly of filamentous structures and is helically symmetrical. It also has a non-enveloped protein capsid that is capable of coiling around itself allowing for a super-coiled structure and the helical symmetry. The virus has the potential to be symptomatic or asymptomatic within plants causing the display of symptoms in only a few plants, but the ability to transmit the virus unknowingly in many plants. B1MaV often remains asymptomatic for long periods of time after initial infection allowing for blind transmission.
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.
