Wheat dwarf virus
Wheat dwarf virus (WDV) is a plant pathogenic virus of the family Geminiviridae. The two isolates of this virus effect both wheat and barley. It is spread by the leafhopper Psammotettix alienus.
| Wheat dwarf virus | |
|---|---|
Virus classification  | |
| (unranked): | Virus |
| Realm: | Monodnaviria |
| Kingdom: | Shotokuvirae |
| Phylum: | Cressdnaviricota |
| Class: | Repensiviricetes |
| Order: | Geplafuvirales |
| Family: | Geminiviridae |
| Genus: | Mastrevirus |
| Species: | Wheat dwarf virus |
Hosts And Symptoms
There are two main types of strains for Wheat Dwarf Virus, which can be distinguished by their host preference for either wheat (Triticum aestivum) or barley (Hordeum vulgare). Wheat Dwarf Viruses can cause a range of symptoms on their host plant that are both localized and systemic (Schubert et al., 2007). For example, the growth of the plant can be stunted, appearing bush-like. The plant can have fewer tillers (stem produced by grass) and leaves than normally observed. Small parts of the leaf may also be affected by chlorosis, which can eventually take over the entire leaf. The number of spikes on the plant may be reduced or existing ones may be stunted. This virus is vector-transmitted by leafhoppers, which suck phloem sap from the vegetative sections of wheat with its mouthparts, passing on the virus (Plantix, 2019). This is a circulative, non-propagative transmission process.
A study done by the Department of Virology in Prague-Ruzyně, Czech Republic, observed the reaction of selected winter wheat varieties to autumnal infection with Wheat Dwarf Virus. Results were measured by examining the reduction in height of the plant and the grain yield. The Ludwig wheat, a very susceptible variety, has a reduction in height between 78–97.0%. They also had a reduction of grain yield, which was nearly 100%. Other less susceptible wheat varieties, like Banquet, still had a height reduction of about 70.0%, with a grain yield reduction of about 36%. Each wheat variety had several symptoms including necrotic spots and dying leaves ( ŠirlovÁ et al., 2010). This study showed that large impacts that Wheat Dwarf Virus can have on the growth of wheat during the winter in terms of height and overall yield.
Importance
About 10,000 years ago, wheat became a domesticated crop in Europe. However, during the domestication process, some traits of wheat which occurred in the wild ancestors were lost. Therefore, diseases including Wheat Dwarf Virus have been detrimental occurrences in the past century in several European countries. In Sweden, characteristics symptoms for wheat dwarf were detected and seemed to be identical to symptoms of a disease called Slidsjuka, which was found in the early 1900s. Slidsjuka destroyed numerous wheat fields and had not been an issue since the 1940s, until it was recently identified as Wheat Dwarf Virus (Lindsten et al., 1999). This disease has led to large crop yields losses of up to 75% on major wheat fields throughout Europe. It has been shown that up to 50% of winter wheat in one field can be infected by Wheat Dwarf Virus during the summer in Sweden. The recent causes of this disease have been found to be a result of changing agricultural practices that have been favorable for the disease. One of agricultural practice used recently has been chemical insecticides, which targets the vector in autumn.
Wheat cultivation for farmers in Sweden have been severely threatened by this disease. As climate change is becoming an increasingly large problem worldwide, the incidence of vector-transmitted virus (like wheat dwarf virus) is becoming a more prominent problem (Lindblad et al., 2004)
Management
Management and control of this disease focuses mainly on targeting the vector, the leafhopper, Psammotettix alienus. Although there are no biological controls for this virus, there are chemical controls that when integrated with preventative measures, could have a large impact. Insecticides are one source of chemical control, but are only to be used when there are a large number of vector insects found within the plant. These insecticides can be used in the fall when winter wheat and barley begin to emerge because primary infection occurs via adults feeding at this time. Spraying of insecticides again in the spring can also be done as adult vectors cause secondary spread of the virus (Garthwaite et al.,2012). Another way to control the virus is by treating seeds with imidacloprid. Treating the wheat plant itself with pyrethroid can help to avoid the transmission of the virus.
Preventative measures are also very important to stop the development of the virus. For example, using more resistant varieties, like Banquet (referenced above), can make the effects of the virus less dramatic. Demolishing infected plant material can help stop the proliferation of the leafhopper (Plantix, 2019).
Notes
Garthwaite DG, Hudson S, Barker I, Parrish G, Smith L & Pietravalle S (2012) Pesticide Usage Survey Report 250: Arable Crops in the United Kingdom (Statistics N ed.). Department for Environment, Food and Rural Affairs.
Lindblad, M. & Sigvald, R. (2004). Temporal spread of wheat dwarf virus and mature plant resistance in winter wheat. Crop Protection 23(3), 229–234.
Lindsten K., Lindsten B. (1999): Wheat dwarf – an old disease with new outbreak in Sweden. Z. Pfl.-Krankh. Pfl.-Schutz, 106: 325–332.
Schubert, Jörg, et al. “Surveying Cereal-Infecting Geminiviruses in Germany—Diagnostics and Direct Sequencing Using Rolling Circle Amplification.” Virus Research, vol. 127, no. 1, 2007, pp. 61–70., doi:10.1016/j.virusres.2007.03.018.
Širlová, L., et al. “Reaction of Selected Winter Wheat Varieties to Autumnal Infection with Wheat Dwarf Virus.” Plant Protection Science, vol. 41, no. No. 1, 2010, pp. 1–7., doi:10.17221/2732-pps.
“Wheat Dwarf Virus: Plant Disease Library.” Plantix, Plantix, 2019, plantix.net/plant-disease/en/200038/wheat-dwarf-virus.