Strawberry crinkle cytorhabdovirus

SCV in its family tree

Based on the Baltimore classification, which is a virus classification system the groups viruses into families based on their genome type, we can know the steps the virus must take in order to produce mRNA and how the genome is copied to create more genomes. All viruses want to get to mRNA in order to go through the process of translation; however, only positive sense single stranded RNA virus (+RNA) have the capability to do this. (-)RNA viruses, such as SCV, are not able to be translated by the host because cells do not have the machinery to copy it, indicating that the virus needs to bring their own enzyme, RNA-dependent RNA polymerase, in order to copy the negative strand into mRNA. This allows viruses, such as SCV, to produce (+)RNA, which can therefore be translated by the host.

SCV is enveloped with a bacilliform morphology. The virus is roughly 163-383 nm long and 74-88 nm in diameter. Glycoproteins are likely said to be the primary surface projections that occur in the cytoplasm, which are either coated or uncoated. Its nucleocapsids is enclosed in a host-derived envelope and are typically helical with a linear genome that is a negative sense single stranded RNA (- RNA). Typically, SCV’s viral genome is roughly 13kb and contains four proteins. The four proteins involved in this virus are glycoprotein (G), nucleocapsid (N), phosphoprotein (P), and the matrix (M) with their respective sizes of 77 kDa, 55 kDa, 45 kDa, and 23 kDa. Like other plant rhabdoviruses there is a fifth protein involved, a large protein (L) that is 230 kDa.

The organization of these five proteins in SCV’s genome is highly conserved. The genome’s order is as follows: N, P, M, G, L, while regions in between these proteins exist. It is important to note that the accumulation of M and G proteins are responsible for the bacilliform shaped morphology of SCV.[4][1]

Aphid Vectors during their growth and development stages.

Strawberry aphid vectors, such as Chaetosiphon fragaefolii, is of genus Chaetosiphon, which are the primary causes of  problems seen in strawberry plants worldwide. These vectors infiltrate strawberry plants, and appear to be either translucent yellow-white to pale green-yellow in color. The body length of C. fragaefolii is roughly 0.9–1.8 millimetres (5⁄128–9⁄128 in) long, while the antennae are 0.9-1.1 times the body length. Damage to plants are caused by aphid vectors sucking on the sap from plants, causing the observed symptoms of SCV. These vectors can be infected with this virus in as little as 24 hours from birth, while a latent period of 10–19 days are observed. Once infected, this vector can transmit SCV for up to 2 weeks.[7][8]  

• Strawberry latent virus, strains A and B
• Strawberry lesion-A and lesion-B viruses
• Strawberry vein chlorosis virus[9]

The symptoms of Strawberry Crinkle Virus varies between different varieties of plants, and they can also vary in the severity. Common symptoms can include spotting of the plant veins. The spotting can be chlorotic (yellowish spot on the leaf surface) or necrotic with areas of black indicating tissue death in these areas. The petals of the flowers can also be deformed, and thee petals can also have abnormal streaking. The virus can also cause malformed leaflets, crinkled leaves, and also uneven leaf distribution in the plant. Another symptom can be the formation of lesions or areas of damage in the petioles and stolons of the plant. Episnasty can also occur from the virus, which causes increased growth of the upper region of the plant, which in turn makes the plant top-heavy causing it to bend downward.[9]

• SCV is seen worldwide and geographical regions affected include, but are not limited to:
  • Europe: Belgium, Bulgaria, Czech Republic, France, Germany, Italy, Netherlands, Poland, UK, Yugoslavia
  • Asia: China (Hebei, Hubei, Heilongjiang, Jilin, Jiangxi, Liaoning, Shandong, Shanxi, Zhejiang), Israel, Japan, Kazakhstan
  • Africa: South Africa
  • North America: Canada, USA (California, Oregon)
  • South America: Chile
  • Oceania: Australia (New South Wales, Tasmania, Victoria), New Zealand[9]

The natural host range of SCV is narrow, including the wild strawberries F. vesca, F. virginiana and F. chiloensis, as well as on the cultivated species, F. ananassa.[6]

In a study, the virus was isolated from strawberry leaf material; however, more experiments are necessary to conclude which strawberry plant tissues are optimal for the virus.[1]

Strawberries are one of the most important berry crops that are grown in the temperate regions. Due to this, the strawberry industry is a multibillion dollar industry across the temperate regions of the world.  Viruses are considered a minor factor of pathogens that cause major arm to crop productions. In order to control SCR, it is advised to control the vectors of this virus, aphids Chaetosiphon fragaefolii and C. jacobi. However, it is important to note that insecticides are not used to regulate aphid vectors due to possible harmful interactions with bumblebees, which are essential for pollinating the plants. Additionally cultivating healthy, virus-free plants can help control the spread of SCR. Plant material that has been infected by the virus should be eradicated. When trading strawberry plants, it is important to verify that the plant material has met the conditions of a virus-free certification scheme; however, apical meristems from diseased plants can be obtained and made virus-free by growing them on culture medium. This is most successful when the parent plants had been treated with heat of 35 °C-41 °C for several months.[6][10][7]

• ICTVdB - The Universal Virus Database: Strawberry crinkle virus
• Family Groups - The Baltimore Method