Issue 9, June 18, 2012
Rose Mosaic Virus
Wherever there are roses, there is also the lurking threat of rose mosaic virus. This viral disease is distributed throughout the world and can infect a wide range of plants. Its causal pathogen, rose mosaic virus (RMV) has been associated with Prunus necrotic ringspot virus (PNRSV). However, symptoms that are similar have also been seen on roses with single or mixed infections of PNRSV, Apple mosaic virus (ApMV), and Arabis Mosaic virus (ArMV). That is because the combination of PNRSV, ApMV and ArMV can induce similar symptoms to RMV. Therefore, ArMV, ApMV, and PNRSVE separately or together have been reported to cause the range of symptoms on roses which is recognized as the disease rose mosaic.
The symptoms of RMV are hard to categorize because they can depend on the virus or combination of virus (ArMV, ApMV, and/or PNRSVE) infection, host species, and environmental conditions. But, a chlorotic pattern of some sort on foliage can usually result from a RMV infection. This chlorosis can be present in a multitude of patterns ranging from irregular lines, ringspots, and mottling on leaves. If infected, the overall plant growth might suffer, resulting in stunted or dwarfed plants. Fortunately, flower production does not seem to be affected by the virus, though the plants can be unmarketable due to unappealing leaves.
Irregular patterns of chlorotic lines on leaves.
Infected leaves all display similar symptoms
Chlorotic mottling on the leaves
In roses, this virus can be spread when growers perform bud-grafting, a process in which two or more plant parts are joined together in asexual propagation.
Management of the disease
Because the virus can cause unsightly plants, it is desirable to control the disease as soon as possible. When purchasing rose plants, only buy from credible sources where the rose stocks grew from disease-free nurseries and propagates. Once the symptoms appear on the rose plant, it cannot be used for further grafting and must be destroyed as promptly as possible. However, some buds can still be salvaged from these infected plants. These plants have to undergo heat treatment of 38 degrees Celsius for up to 4 weeks to obtain virus-free plant material.
How do you tell if your plant is infected with RMV?
It is very hard to determine rose mosaic virus from symptoms alone because the symptoms are not often visible. Serological tests such as enzyme-linked immunosorbent assay (ELISA) can be done to detect ApMV and PNRSV in rose. Detection of these viruses are best from young, succulent leaves or petals in the spring and fall. Immunocapture polymerase chain reaction (PCR) is even more accurate for identifying and differentiating the viruses that cause RMV. Another method is to ‘bud' a RMV infected rose with a indicator plant. Some of the rose cultivars such as ‘Queen Elizabeth' and ‘Madame Butterfly' show very severe symptoms, and can be used as indicator plants.
Can the rose die from rose mosaic disease?
The virus itself does not kill the plant directly. However, it can weaken plant such that it is susceptible to other environmental factors and stress. For example, infected plants tend to have a low survival rate after transplanted and are subjected to winterkill.
For more information regarding rose mosaic disease, visit: http://aces.nmsu.edu/ces/plantclinic/documents/rose-mosaic-virus-_od-9__final.pdf (Adobe PDF).
For more information regarding rose viruses in general: http://web.aces.uiuc.edu/vista/pdf_pubs/632.pdf (Adobe PDF).
(Stephanie Porter and Zu Dienle Tan)