Lettuce mosaic virus | |
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Lettuce aphid, a carrier of LMV | |
Virus classification | |
(unranked): | Virus |
Realm: | Riboviria |
Kingdom: | Orthornavirae |
Phylum: | Pisuviricota |
Class: | Stelpaviricetes |
Order: | Patatavirales |
Family: | Potyviridae |
Genus: | Potyvirus |
Species: | Lettuce mosaic virus |
Lettuce mosaic virus (LMV) is a typical potyvirus (genus Potyvirus, family Potyviridae ), which causes one of the major virus diseases of lettuce crops worldwide.
LMV is seed-borne at a low but significant rate (1-10% of the seeds produced by an infected mother plant germinate into infected seedlings). This provides the primary inoculum in lettuce crops. LMV, and thus the mosaic disease, is then spread locally from plant to plant by the feeding stylets of aphids.
Like all plant viruses, LMV is totally harmless to the consumer but causes defects in heading, leaf distortions and leaf colour anomalies, which altogether result in the infected lettuce plants to be unmarketable. Disease rates can reach 100% locally, and therefore cause complete loss of the harvest. LMV can also infect other crops such as spinach and peas, as well as ornamentals (especially the Cape Daisy Osteospermum spp) and wild plants (especially the prickly lettuce Lactuca serriola and the oxtongue Helminthia echioides). All these plants, and probably others, can serve as local sources from which LMV can spread to crops.
Lettuce mosaic virus (LMV) has a wide host range. All types of lettuce are susceptible, including Crisphead, Romaine, Butterhead, and leaf lettuces. And in nature, the virus infects members of that same family (Asteraceae), including crop plants such as lettuce, endive, escarole, as well as various weeds and wild lettuce species. Perennial weeds and ornamental hosts are also of great importance as they can be reservoirs for inoculum. The most commonly infected cultivated plants are endive, escarole, and lettuce. Other plants such as pea, safflower, and spinach may also become infected. [1]
Lettuce mosaic virus has a wide range of symptoms which depend on the cultivar or the type of lettuce, the age of the plant when infected, and the conditions of the environment. [1] The disease gets its name from the characteristic green and yellow mottling and mosaic pattern that develops on the leaves of infected plants. [2] Other symptoms of LMV often include yellowing of the leaves and vein clearing. In certain lettuce cultivars such as Crisphead, LMV-infected plants experience stunting and distortion of leaves. Leaves often develop a downward rolling of the leaf tips. Some infected plants also fail to form small heads, grow irregularly-shaped leaves, and experience stunting. Necrotic spots on stems and leaves may grow into widespread necrosis. [1]
Depending on the time of infection, infected lettuce cultivars develop different symptoms. Plants that were infected at later stages of growth develop mottling on leaves ranging from light-green to yellow in color. Infected lettuce plants that have flowered develop symptoms such as chlorosis of the leaves and stunting of the plant. [1]
Diagnosis of Lettuce mosaic virus can be difficult despite having characteristic symptoms. Numerous viruses may infect the species, which makes the diagnosis particularly difficult. [3] Diagnosis of LMV infection in lettuce requires diagnostic tests to confirm the disease. Diagnostic tests that may be used to confirm the infection include serological methods such as lateral-flow devices and enzyme-linked immunosorbent assay. Reverse transcription-polymerase chain reaction and sequencing can also be used to confirm the infection. The development of these diagnostic techniques has led to an increase in the speed of diagnosis, allowing for it to occur in-field for lettuce crops. [1]
While also spread by infected seeds, significant spread of Lettuce mosaic virus occurs from aphids (Denis, 2010). The virus can be spread by many species, including the cotton aphid (Aphis gossypii), the potato aphid (Macrosiphum euphorbiae), and the green peach aphid (Myzus persicae). [1] Spread of the virus by non-persistent aphids has a short feeding period of less than one minute for transmission. Aphids that migrate from crop to crop briefly lead to increased exposure and spread of the virus. [4]
Certain symptoms of LMV are more pronounced in particular climates. Necrotic-like symptoms are more likely to occur in warmer seasonal conditions. Symptoms such as mosaic and mottling are more evident in leaf lettuces and Crisphead lettuces that grow in humid weather conditions. [1] The incidence of plants infected by seed infection is determined by time of year in certain climates. In cultivars grown in California, the percentage of plants infected is significantly higher during the month of June rather than the spring months of March and April. [5] Transmission of the virus in cultivars is considerably affected by the temperature in certain climates. Transmission rate is reduced significantly in high day temperatures compared to low day temperatures. [6]
Lettuce mosaic virus is a very common and economically important viral disease that affects lettuce worldwide. The virus spread due to an increased exchange of seeds of various lettuce varieties between countries. [3] It was first recorded in 1921 in lettuce crops in Florida. [1] Since then it has been found in most of the world's major lettuce growing countries. It has occurred in the United Kingdom, and all of Europe generally. [7] It also impacts regions of South America (Argentina, Brazil, Uruguay), Asia (China, Japan, Syria) and the Middle East (Egypt, Israel, Jordan). [3] It is found commonly in the United States as well, especially in lettuce cultivars in California.
When planted in cultivars of Little Gem and Saladin, LMV was found to cause devastating yield losses of 85% and 55%, respectively. [8] Most severe losses most often occur in field crops. However, the virus can also infect greenhouse crops if the seedlings are not raised in insect free conditions. [3]
Like other diseases caused by viruses in plants, there are no means to cure plants from LMV once they are infected. Prevention of LMV can however be relatively efficient based on:
In the late twentieth century, a novel type of LMV appeared in lettuce crops around the world: it was called LMV-Most (mo1-breaking, Seed-Transmitted) to account for its ability to infect and to spread through seeds even in the presence of mo1. [9] Therefore, LMV-Most can only be prevented by controlling seeds, which consumes time, effort and money.
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.
Plum pox, also known as sharka, is the most devastating viral disease of stone fruit from the genus Prunus. The disease is caused by the plum pox virus (PPV), and the different strains may infect a variety of stone fruit species including peaches, apricots, plums, nectarine, almonds, and sweet and tart cherries. Wild and ornamental species of Prunus may also become infected by some strains of the virus.
Zucchini yellow mosaic virus (ZYMV) is an aphid-borne potyvirus, regarded as a major pathogen of cucurbits in most regions of the world where these crops are cultivated.
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.
Papaya ringspot virus (PRSV) is a pathogenic plant virus in the genus Potyvirus and the virus family Potyviridae which primarily infects the papaya tree.
Bidens mottle virus (BiMoV) is a pathogenic plant virus in the plant virus family Potyviridae. BiMoV is a flexuous filamentous particle, 720 nm long, and belongs to the Potyviridae genus Potyvirus. Like other viruses in this genus, Bidens mottle virus is transmitted both mechanically by sap and by aphids in a stylet-borne fashion.
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).
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.
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.
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.
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.
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.
Tulip breaking virus is one of five plant viruses of the family Potyviridae that cause color-breaking of tulip flowers. These viruses infect plants in only two genera of the family Liliaceae: tulips (Tulipa) and lilies (Lilium).
Celery mosaic virus (CeMV) is a plant pathogenic virus in the genus Potyvirus and the virus family Potyviridae .
Commelina mosaic virus (CoMV) is a plant pathogenic virus in the genus Potyvirus and the virus family Potyviridae. Like other members of the Potyvirus genus, CoMV is a monopartite strand of positive-sense, single-stranded RNA surrounded by a capsid made for a single viral encoded protein. The virus is a filamentous particle that measures about 707-808 nm in length. This virus is transmitted by two species of aphids, Myzus persicae and Aphis gossypii, and by mechanical inoculation.
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).
The cardamom mosaic virus (CdMV) is a mosaic virus that affects the production of green cardamom (E. cardamomum). It is a member of the genus Macluravirus (recognized under the family Potyviridae by ICTV in 1988), and is transmitted through aphids (P.caladii) and infected rhizomes, the former in a non-persistent manner.
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.
The Lily mottle virus (LMoV), is a plant virus of the Potyviridae virus family that causes asymptomatic to mild diseases of individual plant parts in plants of the lily family (Liliaceae). However, a frequently occurring simultaneous infection with other plant viruses, which on their own only cause moderate or no disease, can cause the entire plant to perish. This coinfection leads to considerable crop damage in lily cultivation and is therefore of great economic importance. Lily mottle virus is spread by aphids and in horticulture during vegetative propagation by splitting the lily bulb. LMoV was regarded as a synonym for a subtype of the Tulip Breaking Virus (TBV) that occurs in lilies, although since 2005 it has been classified as a closely related but independent virus species of the genus Potyvirus.
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