Rose rosette virus (RRV)
(Emaravirus Rose rosette virus)
Introduction
Rose rosette virus is a member of the Emaraviridae, a group of eriophyid mite-transmitted viruses. It is a negative-strand, multipartite RNA virus consisting of four to eight separate RNA particles. Double membrane-bound particles are seen with electron microscopy in infected rose tissue. Rose rosette virus was detected in 84 of 84 rose plants showing symptoms of rose rosette disease and in 0 of 30 asymptomatic rose plants by Laney, et al. (2011) and is thus has been identified as the cause of rose rosette disease.
Symptoms
Symptoms of rose rosette disease (RRD) are highly variable, depending on the species or cultivar of rose affected. This variability can complicate diagnosis. Symptoms can include rapid elongation of new shoots, followed by the development of witches' brooms or clustering of small branches. Leaves in the witches' broom are small, distorted, and may have a conspicuous red pigmentation, although red pigmentation is not a consistent symptom. Canes on some species or cultivars develop excessive growth of unusually soft and pliable red or green thorns that may stiffen later. When this symptom is present, it is diagnostic for RRD. Symptomatic canes may also be noticeably thicker than the parent cane from which they emerged, or they may grow in a spiral pattern. Flowers may be distorted with fewer petals than normal, and flower color may be abnormal. For example, flowers that are normally a solid color may be mottled. Buds may abort, be deformed, or be converted to leaf-like tissue. Infected rose plants often die within one to two years.
Some diseased plants develop very obvious red pigmentation, while others exhibit a less striking reddish-pink color on leaf undersides or along the margins of otherwise green leaves. On RRD-infected plants, the reddish color does not go away, whereas on healthy plants, the reddish color usually disappears as the leaf matures.
Other symptoms of rose rosette disease that may be expressed include blackening and death of the canes on some cultivars, short internodal distances, and blind shoots (shoots that do not produce a flower). Rose rosette-infected plants may also show increased susceptibility to powdery mildew.
Ecological Threat
The disease is transmitted by the eriophyid mite, Phyllocoptes fructiphilus, or by grafting. The wild multiflora rose (Rosa multiflora) is very susceptible to the disease and is a common source of inoculum. Cultivated roses planted downwind of infected multiflora rose are especially at risk because the mite vector travels on wind currents from infected to healthy plants. Some growers have observed symptoms on previously healthy plants within four weeks of being planted downwind of diseased multiflora rose. The causal agent of rose rosette disease is not soil-borne, so it is possible to successfully plant healthy roses in beds where diseased plants have been removed. However, because the pathogen is systemic in infected plants, the virus may persist in RRD-infected root pieces that remain in the soil. If plants regrow from these old root pieces, they can serve as an inoculum source for healthy plants. It is important to completely remove symptomatic plants.
Rose rosette virus is a member of the Emaraviridae, a group of eriophyid mite-transmitted viruses. It is a negative-strand, multipartite RNA virus consisting of four to eight separate RNA particles. Double membrane-bound particles are seen with electron microscopy in infected rose tissue. Rose rosette virus was detected in 84 of 84 rose plants showing symptoms of rose rosette disease and in 0 of 30 asymptomatic rose plants by Laney, et al. (2011) and is thus has been identified as the cause of rose rosette disease.
Symptoms
Symptoms of rose rosette disease (RRD) are highly variable, depending on the species or cultivar of rose affected. This variability can complicate diagnosis. Symptoms can include rapid elongation of new shoots, followed by the development of witches' brooms or clustering of small branches. Leaves in the witches' broom are small, distorted, and may have a conspicuous red pigmentation, although red pigmentation is not a consistent symptom. Canes on some species or cultivars develop excessive growth of unusually soft and pliable red or green thorns that may stiffen later. When this symptom is present, it is diagnostic for RRD. Symptomatic canes may also be noticeably thicker than the parent cane from which they emerged, or they may grow in a spiral pattern. Flowers may be distorted with fewer petals than normal, and flower color may be abnormal. For example, flowers that are normally a solid color may be mottled. Buds may abort, be deformed, or be converted to leaf-like tissue. Infected rose plants often die within one to two years.
Some diseased plants develop very obvious red pigmentation, while others exhibit a less striking reddish-pink color on leaf undersides or along the margins of otherwise green leaves. On RRD-infected plants, the reddish color does not go away, whereas on healthy plants, the reddish color usually disappears as the leaf matures.
Other symptoms of rose rosette disease that may be expressed include blackening and death of the canes on some cultivars, short internodal distances, and blind shoots (shoots that do not produce a flower). Rose rosette-infected plants may also show increased susceptibility to powdery mildew.
Ecological Threat
The disease is transmitted by the eriophyid mite, Phyllocoptes fructiphilus, or by grafting. The wild multiflora rose (Rosa multiflora) is very susceptible to the disease and is a common source of inoculum. Cultivated roses planted downwind of infected multiflora rose are especially at risk because the mite vector travels on wind currents from infected to healthy plants. Some growers have observed symptoms on previously healthy plants within four weeks of being planted downwind of diseased multiflora rose. The causal agent of rose rosette disease is not soil-borne, so it is possible to successfully plant healthy roses in beds where diseased plants have been removed. However, because the pathogen is systemic in infected plants, the virus may persist in RRD-infected root pieces that remain in the soil. If plants regrow from these old root pieces, they can serve as an inoculum source for healthy plants. It is important to completely remove symptomatic plants.
Selected Images
Invasive Listing Sources
Taxonomic Rank
| Domain: Viruses |
| Realm: Riboviria |
| Kingdom: Orthornavirae |
| Phylum: Negarnaviricota |
| Subphylum: Polyploviricotina |
| Class: Bunyaviricetes |
| Order: Elliovirales |
| Family: Fimoviridae |
| Genus: Emaravirus |
| Emaravirus Rose rosette virus |
Other System Links
NPDN Pest: FVRRVBB
References
Common Name Reference: Web Search - http://www.ext.vt.edu/pubs/plantdiseasefs/450-620/450-620.html
Scientific Name Reference: Web Search - http://www.ext.vt.edu/pubs/plantdiseasefs/450-620/450-620.html