| Barley yellow dwarf viruses | |
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Scientific classification  | |
| (unranked): | Virus |
| Realm: | Riboviria |
| Kingdom: | Orthornavirae |
| Groups included | |
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Barley yellow dwarf (BYD) is a plant disease caused by the barley yellow dwarf virus (BYDV), and is the most widely distributed viral disease of cereals. It affects the economically important crop species barley, oats, wheat, maize, triticale and rice.
Barley yellow dwarf is caused by barley yellow dwarf viruses. They contain genomes made of ribonucleic acid (RNA). Seven species of barley yellow dwarf virus are recognized, classified as follows: [1]
When aphids feed on the phloem of the leaf, the virus is transmitted to the phloem cells. Once inside the plant, the virus begins to replicate and assemble new virions. This process requires significant metabolic input from the plant, and causes the symptoms of barley yellow dwarf disease.
The symptoms of barley yellow dwarf vary with the affected crop cultivar, the age of the plant at the time of infection, the strain of the virus, and environmental conditions, and can be confused with other disease or physiological disorders. Symptoms appear approximately 14 days after infection. Affected plants show a yellowing or reddening of leaves (on oats and some wheats), stunting, an upright posture of thickened stiff leaves, reduced root growth, delayed (or no) heading, and a reduction in yield. The heads of affected plants tend to remain erect and become black and discoloured during ripening due to colonization by saprotrophic fungi. Young plants are the most susceptible.
The virus is transmitted from the phloem when the aphid feeds. When the aphid feeds, virions go to the aphid's hind gut, the coat protein of the virus is recognised by the hindgut epithelium, and the virion is allowed to pass into the insect's hemolymph, where it can remain indefinitely, but the virus cannot reproduce inside the aphid. [2] The virus is actively transported into the accessory salivary gland to be released into salivary canals and ducts. The virus is then excreted in the aphid saliva during its next feeding.
The host range of BYDVs consists of more than 150 species in the Poaceae; a large number of grasses both annual and perennial are alternate hosts to BYVD and can serve as reservoirs of the virus.
There are two main sources by which a cereal crop might be infected
1. By non-migrant wingless aphids already present in the field and which colonise newly emerging crops. This is known as "green-bridge transfer".
2. By winged aphids migrating into crops from elsewhere. These then reproduce and the offspring spread to neighbouring plants.
One aphid species in particular, Rhopalosiphum rufiabdominale , known as the rice root aphid, is commonly known to vector the virus to a range of cereal crops. [3]
This is variable since it depends on viral strain, time of infection and rate of spread. Most severe losses are from early infections and can be as high as 50%.
"Green bridge" sources must be ploughed in as early as possible. Alternatively, a desiccant herbicide should be applied 10 days prior to cultivation. Insecticide sprays may be used at crop emergence.
Drilling dates prior to mid-October favors attacks from winged migrant aphids. However, yield penalties may be experienced from late drilling. Insecticide sprays in this instance are therefore aimed at killing the aphids before significant spread can occur.
Synthetic pyrethroid insecticides
Potato leafroll virus (PLRV) is a member of the genus Polerovirus and family Solemoviridae. The phloem limited positive sense RNA virus infects potatoes and other members of the family Solanaceae. PLRV was first described by Quanjer et al. in 1916. PLRV is transmitted by aphids, primarily the green peach aphid, Myzus persicae. PLRV is one of the most important potato viruses worldwide but particularly devastating in countries with limited resources and management. It can be responsible for individual plant yield losses of over 50%. One estimate suggests that PLRV is responsible for an annual global yield loss of 20 million tons. Symptoms include chlorosis, necrosis and leaf curling.
Citrus tristeza virus (CTV) is a viral species of the genus Closterovirus that causes the most economically damaging disease to its namesake plant genus, Citrus. The disease has led to the death of millions of Citrus trees all over the world and has rendered millions of others useless for production. Farmers in Brazil and other South American countries gave it the name "tristeza", meaning sadness in Portuguese and Spanish, referring to the devastation produced by the disease in the 1930s. The virus is transmitted most efficiently by the brown citrus aphid.
Aster yellows is a chronic, systemic plant disease caused by several bacteria called phytoplasma. The aster yellows phytoplasma (AYP) affects 300 species in 38 families of broad-leaf herbaceous plants, primarily in the aster family, as well as important cereal crops such as wheat and barley. Symptoms are variable and can include phyllody, virescence, chlorosis, stunting, and sterility of flowers. The aster leafhopper vector, Macrosteles quadrilineatus, moves the aster yellows phytoplasma from plant to plant. Its economic burden is primarily felt in the carrot crop industry, as well as the nursery industry. No cure is known for plants infected with aster yellows. Infected plants should be removed immediately to limit the continued spread of the phytoplasma to other susceptible plants. However, in agricultural settings such as carrot fields, some application of chemical insecticides has proven to minimize the rate of infection by killing the vector.
Curly top is a viral disease that affects many crops. This disease causes plants to become smaller in size, have shriveled petals and leaves, and are twisted and pulled out of shape. They are often caused by curtoviruses, members of the virus family Geminiviridae. This disease is important in western United States, such as California, Utah, Washington, and Idaho.
Luteovirus is a genus of viruses, in the family Tombusviridae. There are 13 species in this genus. Plants serve as natural hosts. The geographical distribution of Luteoviruses is widespread, with the virus primarily infecting plants via transmission by aphid vectors. The virus only replicates within the host cell and not within the vector. The name 'luteovirus' arises from the Latin luteus, which is translated as 'yellow'. Luteovirus was given this name due to the symptomatic yellowing of the plant that occurs as a result of infection.
Banana bunchy top virus (BBTV) is a plant pathogenic virus of the family Nanoviridae known for infecting banana plants and other crops. It is aphid transmitted.
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.
Groundnut rosette virus (GRV) is a peanut pathogenic virus found in Sub-Saharan Africa. It is transmitted between plants by insect vectors such as the groundnut aphid.
Maize dwarf mosaic virus (MDMV) is a pathogenic plant virus of the family Potyviridae. Depending on the corn plant’s growth stage, the virus can have severe implications to the corn plant’s development which can also result in economic consequences to the producer of the crop.
Wheat yellow leaf virus (WYLV) is a wheat (Triticum spp. L.), barley (Hordeum vulgare L.), rye (Secale cereale M.Bieb.), and oat (Avena sativa L.) pathogenic virus of the family Closteroviridae. WYLV virions are 1600–1850 nm in length and 10 nm in diameter. The virus, like other members of its genus, is transmitted by aphids. Identified vectors include Rhopalosiphum padi L. and R. maidis Fitch. (Aphididae). The virus has been identified in crop plants in Japan, China, and Italy. Native host plants include Italian ryegrass (Festuca perennis Lam.) in Europe and Agropyron tsukushiense var. transiens Ohwi in Japan. The virus proliferates in the phloem of its host plants, interfering with the plant's ability to produce sufficient chlorophyll (Chlorosis), causing the leaves to yellow and the plant to die.
Wheat dwarf virus (WDV) is a plant pathogenic virus in the family Geminiviridae. The two isolates of WDV affect wheat and barley. It is spread by the leafhopper Psammotettix alienus.
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 production 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.
Barley, a member of the grass family, is a major cereal grain grown in temperate climates globally. It was one of the first cultivated grains; it was domesticated in Eurasia some 9,000 years ago. Globally 70% of barley production is used as animal feed, while 30% is used as a source of fermentable material for beer, or further distilled into whisky, and as a component of various foods. It is used in soups and stews, and in barley bread of various cultures. Barley grains are commonly made into malt in a traditional and ancient method of preparation.
Rhopalosiphum maidis, common names corn leaf aphid and corn aphid, is an insect, and a pest of maize and other crops. It has a nearly worldwide distribution and is typically found in agricultural fields, grasslands, and forest-grassland zones. Among aphids that feed on maize, it is the most commonly encountered and most economically damaging, particularly in tropical and warmer temperate areas. In addition to maize, R. maidis damages rice, sorghum, and other cultivated and wild monocots.
Bird cherry-oat aphid is an aphid in the superfamily Aphidoidea in the order Hemiptera. It is a true bug and sucks sap from plants. It is considered a major pest in cereal crops, especially in temperate regions, as well as other hosts in parts of Northern Europe. It is the principal vector of many viruses in economically important field crops.
Rhopalosiphum rufiabdominale, the rice root aphid or red rice root aphid, is a sap-sucking insect pest with a wide host range and a global distribution. As a member of the superfamily Aphidoidea, it is one of 16 species of the genus Rhopalosiphum. Adults and nymphs are soft-bodied and usually dark green with brown, red, or yellow tones. Like all aphids, reproduction is sexual and asexual, depending on the environmental conditions and host plant. Rice root aphids cause injury to external plant parts, namely the roots or stem, by feeding on plant sap and vector several important plant viruses. The hosts of this pest extend across multiple plant families with most belonging to Rosaceae, Poaceae, and Solanaceae. R. rufiabdominale is universally associated with Prunus species but also infests various field crops, greenhouse vegetables, cannabis, and other ornamental plants. While this aphid originates from east Asia, it spans nearly every continent. Dispersal is particularly widespread across the United States, India, and Australia, with crop damage documented in multiple instances, although economic losses are primarily associated with Japanese rice crops. Nonetheless, it remains a pest of serious concern due to its high mobility, discrete habitat, and adaptive plasticity, giving it the rightful reputation as a successful invader.
Metopolophium dirhodum, the rose-grain aphid or rose-grass aphid, is a species of sap-sucking insect in the family Aphididae found worldwide. Its primary host is rose, and its secondary host is a grass, including cereals such as wheat, barley, oats and rye. It is an important vector of the barley yellow dwarf virus (BYDV) which causes serious reductions in yields of affected crops.
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.
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.
| Authority control databases: National |
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