Tobacco rattle virus
|Tobacco rattle virus (TRV)|
|Group:||Group IV ((+)ssRNA)|
|Species:||Tobacco rattle virus|
The virus causes the plant disease tobacco rattle in many plants, including many ornamental flowers. It causes the disease corky ringspot, or spraing, in potatoes. The disease manifests in various ways, and signs can include brown rings and arcs on the surface of a potato, and discolored spots on the interior.
Nematodes of the family Trichodoridae, the stubby-root nematodes, are vectors of the virus. The nematode species Paratrichodorus minor, for example, introduces the virus when it feeds on the roots of plants. The virus can also be spread on garden tools. It can be present in seeds, and cause disease in the plants that grow from them.
Hosts and Symptoms
Boning first discovered Tobacco Rattle Virus in 1931 in Germany. It was discovered in Nicotiana tabacum, which is a type of cultivated tobacco. Tobacco Rattle Virus is common and potentially serious in a variety of herbaceous ornamentals including, but not limited to, astilbe, bleeding heart, coral bells, daffodil, epimedium, gladiolus, hyacinth, marigold, tulip and vinca. Tobacco rattle can also affect vegetable crops such as beans, beets, peppers, potatoes, and spinach. On potatoes, the disease is referred to as corky ring spot.(11)
Symptoms of Tobacco Rattle virus vary based on the plant host, which varies widely in this disease. Common symptoms include mottling, cholortic or necrotic local lesion, ringspots or line patterns, and systemic necrosis.
Tobravirus is known to cause Tobacco Rattle Virus (TRV) on plants. Transmission of Tobravirus is supported by nematodes, such as Trichodorus and Paratrichodorus. These species of nematodes are known as stubby root nematodes (3). Transmission of the virus could be separated into four distinct steps: Acquisition, adsorption, retention, and virus particle release (2). At the beginning of the feeding cycle, the nematodes puncture a multiple individual cells by using its specialized stylet , onchiostyle. Among those penetrated but intact cells, the nematodes select a cell, which it will feed on. Upon selection, the nematodes begin sucking up cell contents, leading to death of the cell (4). During this process, adsorption of Tobravirus begins, the process where cytoplasm of infected cells containing Tobravirus was assimilated into the nematodes (2). Both juvenile and adult nematode can pick up Tobravirus particle (4). Once the Tobravirus transferred into the nematodes, the cycle is now at retention. Tobravirus consumed by the nematodes could linger in the nematodes for years (1). Eventually, the nematode loaded with Tobravirus starts its feeding cycle on uninfected root cell. During this period, Tobravirus will be transferred into the new cell, completing the virus transmission (4).
Interesting feature of the life cycle of stubby root nematodes is that these reproduce in the absence of sexual activity. Because the nematode does not require sexual activity for reproduction, male nematodes are rarely detected. In the consequence, female nematodes lay eggs without sexual activity. These eggs hatch. Juvenile nematodes undergo molting three times until it reach adult stage (3). Then, the life cycle begins again.
Tobacco Rattle Virus (TRV) is dependent to the nematodes’ activity. Therefore, environmental factors that support nematodes’ movement or life cycle would lead to prosperous dispersal of this virus. One such environmental inducer would be high soil moisture. Nematodes are obligate parasite; therefore, the nematode requires host around its presence. Otherwise, it would die. High soil moisture enables the nematodes to move easily in the soil. With high soil moisture, nematodes would have better access to the root or root hairs, subsequently either attaining or dispersing virus on those cells (4). Also, moderately warm temperature allows faster life cycle of the nematode. In other words, if temperature were at optimum for nematode’s life cycle, there would be a greater chance of dispersal of Tobravirus along the turf (5).
Tobacco Rattle Virus (TRV) can be managed through a variety of methods designed to make the environment unsuitable for transmission and viral propagation. Tubers or seeds of any susceptible plants should be purchased only from sellers certified as clean, and never planted in fields with a history of corky ringspot or TRV-related disease. While its requires a permit in many jurisdictions, the nematicide 1,3-dichloropropene may be employed against fields overrun by stubby root nematodes, a common vector of the virus.(5) Soil fumigants generally fail to penetrate the 40 inches necessary to ensure nematode eradication, and carmabates such a aldicarb and oxamyl are recommended. TRV is only found in nature in association with stubby root nematodes Trichodorus spp. And Paratrichodorus spp. Although otherwise considered harmless, they spread the infection during feedings. Nematodes may live and multiply within weeds in the field in between crop rotations, and it is advisable to employ plants it does not like, such as alfalfa, to compete against weeds that may otherwise harbor the viral vector. In contrast, nightshade is a very problematic weed as it is an ideal host for the virus and the nematode.(6) While the Russet Burbank cultivar proves to be highly susceptible to TRV corky ringspot, Merrimack and several old European varieties enjoy resistance. Too much soil moisture can encourage nematode overpopulation, but tightly packed fine soil, clay, or sand can drastically inhibit the vector movement responsible for widespread and erratic field decimations. (6) Once a plant is infected it cannot be treated and should be burned or disposed of as biohazard waste.
Tobacco Rattle Virus infects hundreds of plant species and is a virus commonly used in studies involving transgenic plants, as a vector for silencing specified target genes. It is thus an important tool to plant physiologists and in the field of plant developmental genetics.(7) The disease corky ringspot of potatoes was first reported in the United States in 1946, and was identified incorrectly as a novel virus until advances were made in genetics.(9) Corky ringspot from TRV has been known to cut yields from 6-55 percent in the Pacific Northwest, rendering those affected crops unmarketable.2 Other than severe cosmetic damage to the tuber crops, however, CRSD from TRV is not considered highly damaging to potato yields.(10)
|This plant virus article is a stub. You can help Wikipedia by expanding it.|