Barley yellow mosaic virus
| Barley mosaic virus | |
|---|---|
| Virus classification | |
| Group: | Group IV ((+)ssRNA) |
| Family: | Potyviridae |
| Genus: | Bymovirus |
| Species: | Barley mosaic virus |
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.
Barley (Hordeum vulgare) is the only current known host for the virus. Other species of Hordeum have been experimentally innocultated and exhibited similar symptoms, but this has since been categorized as a different strain of disease called barley mild mosaic virus. When dealing with viruses, it is important to understand that symptoms are not reliable in diagnosing the specific virus. That being said, the signature symptom exhibited by the barley from the virus is a yellowing and mosaic flecking of the youngest leaves that often appears in the winter or early spring. Early on the plant leaves begin to show a pale green color, and over time the changes become more drastic with severe yellowing and mosaic patterns. In addition, leaf curl, stunting, and necrosis can all be observed.
The symptoms are categorized as systemic, due to the spread of the disease throughout the plant. Once the virus enters the plant through the root cells via Polymyxa graminis it is able to multiply and spread throughout the plant. The symptoms arise due to the virus's ability to hack into the plant cells' machinery, which disrupts the normal cycle of the plant.
Barley Yellow Mosaic Virus (BaYMV) is a virus, and therefore doesn’t divide, produce energy, or have any reproductive structures. The only way BaYMV is able to multiply is by "taking over" host cells and manufacturing more viruses. It is spread through the protist Polymyxa graminis, so its disease cycle largely depends on that of P. graminis.P. graminis is a soil-borne pathogen, so it is spread by tools, water, animals, and other means of physically moving soil. BaYMV overwinters in the resting spores of P. graminis, and can survive decades in this state. When P. graminis invades the roots of a plant and begins growing in the root cells, the BaYMV is transmitted from protist to barley through zoospores. It then can enter barley plant cells and use the cell machinery to make more virus, thus infecting the plant. The virus does this by using its coat protein to gain access into plant cells, and then taking over cell machinery in the nucleus. It uses the cell machinery to manufacture more virus, and can rapidly reproduce this way. Once a plant is infected, there is no known way to "cure" the plant, so the plant stays infected indefinitely. The virus remains in the resting spores in the soil, and in this way it can infect other plants, overwinter, or be spread via cultivation or harvest (spreading the soil).
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