| Banana bunchy top virus | |
|---|---|
Virus classification  | |
| (unranked): | Virus |
| Realm: | Monodnaviria |
| Kingdom: | Shotokuvirae |
| Phylum: | Cressdnaviricota |
| Class: | Arfiviricetes |
| Order: | Mulpavirales |
| Family: | Nanoviridae |
| Genus: | Babuvirus |
| Species: | Banana bunchy top virus |
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.
Banana bunchy top is a viral disease caused by a single-stranded DNA virus called the banana bunchy top virus (BBTV). It was first identified in Fiji in 1879, and has spread around the world since then. [1] Like many viruses, BBTV was named after the symptoms seen, where the infected plants are stunted and have "bunchy" leaves at the top. [2] The disease is transmitted from plant-to-plant in tropical regions of the world by aphids, [3] banana aphids which can also feed on Heliconia and flowering ginger (from the family Zingiberaceae), which is an important factor in control of the disease. There are no resistant varieties, so controlling the spread by vectors and plant materials are the only management methods. [1] Symptoms include spotting any deformed plant appearance.[ citation needed ]
All babuviruses are aphid transmitted including BBTV. Information is lacking regarding vector-virus interactions. [3]
Banana bunchy top disease affects the banana fruit and foliage, and is caused by a single-strand DNA virus, the banana bunchy top virus. [4] BBTV can infect species of the family Musaceae, which includes bananas, plantains, abaca, and more. [1] The aphids also feed on Heliconia and flowering ginger, which are grown in the same regions as bananas and must be considered in management of the disease. It is best to establish a banana production area where these alternate hosts are not present. Any age plants can be infected by this virus, but some varieties of banana, including the Cavendish, are more susceptible to the virus. [2] In areas where the virus is less common, the disease is usually spread by planting diseased suckers at the beginning of the season, which means the season is started with a diseased crop. [1]
The pathogen causes cytopathological effects in the phloem tissue, which is the damaging of the host cells caused by the virus. [1] The damage causes many effects that help to diagnose and characterize the disease. The name of the disease comes from the symptom which occurs in older plants, in which the new leaves that are produced are narrower than normal, yellow, and flat, which causes a “bunchy” appearance at the top of the tree. [2] If any fruit is produced, which is unusual, it will be deformed. [2] In addition, one of the most distinctive symptoms is “Morse code streaking” [2] where the infected cells die and are lighter in color, causing irregular spots and dashes on the leaves that are easier to see when the waxy coating over the petiole is rubbed away.[ citation needed ]
BBTV is a widespread disease in the tropics, and is present in Southeast Asia, the Philippines, Taiwan, Oceania [3] including most of the South Pacific islands and Hawaii, [3] Pakistan (first found 1988, first identified 1991 or 1992), [5] East Asia, [3] parts of India, [2] and is invading Africa as of 2021 [update] . [3] [2] It is especially problematic in East Asia, Oceania, and Hawaii. [3] It was first observed in Hawaii in 1989, and is now widespread on Oahu, in the Kona area, and on Kauai. [2] The disease is currently not present in Central or South America. [2] The pathogen is not present everywhere bananas are grown, but is present in most areas where the vector is also present. [6] : 301–03 These aphids are most likely native to Southeast Asia, but they are present in most areas in the tropics, and almost everywhere bananas are grown. [7] BBTV is spread to new areas by poor agricultural practices, and can be transmitted on plant material from the family Musaceae, the virus' host. [2]
BBTV is the sole member of the genus Babuvirus in the family Nanoviridae. [4] The genome of BBTV is made up of at least six circular, single-stranded DNA components, each about 1 kilo-base pair in length. [4] Replication takes place by rolling circle replication, a unidirectional nucleic acid replication that can result in rapid synthesis of single-strands of DNA. [4] There are specific virus-like particles that have been proposed as the virions of BBTV but there are still discrepancies in the scientific world about the exact relationship between these virions and the single-stranded DNA virus. [8] Nevertheless, it was demonstrated that the associated ssDNA molecules are transmitted with the disease and therefore are designated as the pathogen. [8]
It is known that Banana aphid ( Pentalonia nigronervosa ) transmits the virus from infected to healthy plants by feeding. Aphids feed on the plant phloem tissues by injecting their thin, flexible stylet into the epidermis of the plant tissue until it reaches the phloem of the leaves. Then the aphid injects saliva and sucks the cell contents. This ingestion of viral components is done inadvertently by the aphid. Vector transmission of the BBTV is circulative and non-propagative, meaning that transmission of the virus occurs from and to the phloem tissues and the virus does not replicate within the aphid’s midgut. Acquisition of the virus by the banana aphid requires about 18 hours of feeding and then the aphid can retain the virus for approximately two weeks. [2] The retransmission of this virus can happen after as little as two hours of feeding on a healthy plant however it takes about a month for the BBTV symptoms to appear after infection. [2] To infect, the carrier aphid can feed on the banana plant for as few as 15 minutes, but more often a couple hours, as the longer feeding time will increase the odds of transmission. [1] The suckers produced on infected plants that would usually be used for planting the next season will also be diseased, which is one way the disease can spread from year to year. [1] Banana aphids also have the capability to feed on Heliconia and flowering ginger; however, these alternate hosts of the aphid vector are not hosts of the virus. [2] The ability of banana aphids to feed on alternate hosts is important to keep in mind when attempting to control the virus.[ citation needed ]
There are no resistant varieties of banana against BBTV, so the most common method of control is chemical control of the aphid vectors. [2] [9] Another way to help control the virus is to remove and destroy any infected plants before the virus can spread, which is a practice known as roguing. [2] Quarantines are also implemented to prevent the import of any potentially infected plant materials, including one in Hawaii that prevents the movement of anything except fruits from the island of Oahu to any other island, since BBTV is widespread in Oahu. [2] Fruit is not often produced on infected plants, but if it is, the fruit will be deformed, which easily identifies if there is any virus present in the fruits to comply with quarantine regulations. [2] Since bananas are not the only host, the alternate hosts for both the virus and the aphid must also be monitored for disease, and sprayed with pesticides to control the aphids more. [1] [2] When planting at the beginning of the season, the seed material or suckers should be obtained from BBTV free areas of the world or from cultures that are grown and developed to be free of the virus. [2] Currently, there is ongoing research into biopriming, or inducing systemic resistance by using bacteria that live inside the host but do not infect. [9]
Control of banana bunchy top is achieved by killing the banana aphids then destroying all infected material. First, the aphids should be killed on the infected banana material, and then all the plant material should be destroyed to prevent the spread of the virus. [2] Infected banana plants can be sprayed with an insecticide like Sevin to reduce or get rid of the aphid population, since control of viruses starts with control of the vectors. [2] The agriculture department, however, recently obtained an EPA waiver for the pesticide Provado is a means of controlling the aphids that spread the disease.[ citation needed ]
Banana bunchy top disease is the most serious virus disease of banana worldwide. [2] Diseased plants rarely produce fruit and when they do, the fruit is stunted and twisted. However, in the rare scenario that a diseased plant does produce fruit that reaches maturity, it is edible. The banana bunchy top disease has had a huge impact on the banana industry in Hawaii and Australia and among other areas of the world. The disease was first seen on the Hawaiian island of Oahu in 1989 and by 2002, only 13 years later, it was a major disease on four of the Hawaiian islands (Hawaii, Oahu, Kauai and Maui). [10] The movement of BBTD was mostly facilitated by human movement of diseased plant material and banana aphids from island to island. In the 1920s it almost completely destroyed the banana growing industry in Australia. [11]
| Island | Year | Month | City |
|---|---|---|---|
| Oahu | 1989 | July | Punaluu |
| Hawaii | 1995 | October | North Kona |
| Kauai | 1997 | September | Kilauea Town |
| Maui | 2002 | December | Pukalani |
While BBTV certainly has a huge impact on the industrial scale of banana production, it can also be devastating to subsistence farmers who depend on their crop to feed their families and provide income. Small farmers will often lose the uphill battle of fighting against BBTV in their crop. Once established, it is very difficult to eradicate and manage the disease. [9] The difficulty of eradication is perpetuated by a number of reasons. First of all, the disease is caused by a vector-transmitted virus and this virus is not completely understood yet. [8] Secondly, all bananas are susceptible to the disease and no resistant varieties have been discovered or made commercially available. Lastly, the control methods are quite demanding, including chemical treatment for the aphid vectors, removal of all infected tissue (aka roguing), quarantining plants and monitoring alternate vector feeding sites. [2]
Plant pathology is the scientific study of diseases in plants caused by pathogens and environmental conditions. Organisms that cause infectious disease include fungi, oomycetes, bacteria, viruses, viroids, virus-like organisms, phytoplasmas, protozoa, nematodes and parasitic plants. Not included are ectoparasites like insects, mites, vertebrate, or other pests that affect plant health by eating plant tissues. Plant pathology also involves the study of pathogen identification, disease etiology, disease cycles, economic impact, plant disease epidemiology, plant disease resistance, how plant diseases affect humans and animals, pathosystem genetics, and management of plant diseases.
Geminiviridae is a family of plant viruses that encode their genetic information on a circular genome of single-stranded (ss) DNA. There are 520 species in this family, assigned to 14 genera. Diseases associated with this family include: bright yellow mosaic, yellow mosaic, yellow mottle, leaf curling, stunting, streaks, reduced yields. They have single-stranded circular DNA genomes encoding genes that diverge in both directions from a virion strand origin of replication. According to the Baltimore classification they are considered class II viruses. It is the largest known family of single stranded DNA viruses.
Closteroviridae is a family of viruses. Plants serve as natural hosts. There are four genera and 59 species in this family, seven of which are unassigned to a genus. Diseases associated with this family include: yellowing and necrosis, particularly affecting the phloem.
The potato spindle tuber viroid (PSTVd) was the first viroid to be identified. PSTVd is a small, single stranded circular RNA molecule closely related to the chrysanthemum stunt viroid. Present within the viroidal RNA is the Pospiviroid RY motif stem loop common to its genus. The natural hosts are potatoes and tomatoes. All potatoes and tomatoes are susceptible to PSTVd and there is no form of natural resistance. Natural infections have also been seen in avocados and infections in other solanaceous crops have been induced in the laboratory. Until 2017 PSTVd was thought to be unable to infect Solanum sisymbriifolium. Then in May seeds exported by a Dutch company were noticed to be infected. These seeds were shipped from the company, but had been originally bred to their specifications in two Asian countries. Pstv also causes Tomato bunchy top and is seed transmitted in tomato.
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.
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.
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.
Papaya ringspot virus (PRSV) is a pathogenic plant virus in the genus Potyvirus and the virus family Potyviridae which primarily infects the papaya tree.
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.
Cassava mosaic virus is the common name used to refer to any of eleven different species of plant pathogenic virus in the genus Begomovirus. African cassava mosaic virus (ACMV), East African cassava mosaic virus (EACMV), and South African cassava mosaic virus (SACMV) are distinct species of circular single-stranded DNA viruses which are transmitted by whiteflies and primarily infect cassava plants; these have thus far only been reported from Africa. Related species of viruses are found in India and neighbouring islands, though cassava is cultivated in Latin America as well as Southeast Asia. Nine species of cassava-infecting geminiviruses have been identified between Africa and India based on genomic sequencing and phylogenetic analysis. This number is likely to grow due to a high rate of natural transformation associated with CMV.
Beet curly top virus (BCTV) is a pathogenic plant virus of the family Geminiviridae, containing a single-stranded DNA. The family Geminiviridae consists of nine genera based on their host range, virus genome structure, and type of insect vector. BCTV is a Curtovirus affecting hundreds of plants. The only known vector is the beet leafhopper, which is native to the Western United States.
Cacao swollen shoot virus (CSSV) is a plant pathogenic virus of the family Caulimoviridae that primarily infects cacao trees. It decreases cacao yield within the first year of infection, and usually kills the tree within a few years. Symptoms vary by strain, but leaf discoloration, stem/root swelling, and die-back generally occur. The virus is transmitted from tree to tree by mealybug vectors. It was first discovered in Ghana in 1936, and is currently endemic in Togo, Ghana and Nigeria. Over 200 million trees have already been claimed by this disease, which has prompted Ghana to launch the most ambitious and costly eradication effort of any country in the world against a viral plant disease.
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).
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 virus being sexually transmitted from infected males to non-infected females, and an evidence that TYLCV is transovarially transmitted to offspring for two generations.
Strawberry vein banding virus (SVBV) is a plant pathogenic virus and a member of the family Caulimoviridae.
Blueberry shoestring virus (BBSSV) is a disease-causing virus that is commonly transmitted by the aphid vector, Illinoia pepperi. The blueberry shoestring virus disease is very prominent in highbush and lowbush blueberry plants in the northeastern and upper Midwest of the United States. Symptoms can vary significantly depending on the environment, but the most common disease symptoms are reddish streaking on young stems, reduced vigor and strap-shaped leaves. The blueberry shoestring virus disease can be managed by eliminating the aphid vector through the use of biological, chemical or cultural controls. In severe cases, the disease leads to an extensive loss of yield and marketable fruit.
Babuvirus is a genus of viruses, in the family Nanoviridae. Musa species serve as natural hosts. There are three species in this genus. Diseases associated with this genus include: stunting, severe necrosis and early plant death. BBTV induces banana bunchy top disease (BBTD).
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.
