Should northern rose growers be concerned about possible above ground spread of Rose Viruses?
This page gives the information that I have collected from my own literature searches and from others posting on the internet. Please let me know if you feel anything is not clear or is not addressed at all as I am continually updating/modifying it as I get feedback.
Bold print in quotes does not mean that the bold print appeared in the original; the bold print was added by me (H. Kuska) for emphasis.
As background material the term "rose mosaic virus" means different things to different people. Here are 2 scientific literature examples of the complexity of this subject (which illustrate why I decided to use the term "Rose Viruses" in the title instead of "Rose Mosaic Virus").
1)
Title: Roses: virus and virus-like diseases.
Author: V. Lisa
Published in: Colture-Protette. 1998, 27: 5 Supplement, pages 35-38.
Abstract: "Notes are given on the viruses and virus-like diseases that are
known to affect roses around the world. The most common and widespread virus
disease is rose mosaic, associated especially with prunus necrotic ringspot
ilarvirus (PNRSV), apple mosaic ilarvirus (ApMV), arabis mosaic nepovirus (ArMV)
and strawberry latent ringspot nepovirus (SLRV), but also with tobacco ringspot
nepovirus, tobacco streak ilarvius and tomato ringspot nepovirus. Tobacco mosaic
tobamovirus and an unidentified closterovirus are found sporadically. The
virus-like diseases of unknown aetiology include rose ring pattern, rose flower
break, rose streak, rose rosette (or rose witches' broom), rose leaf curl, rose
spring dwarf and rose wilt.
Other disorders are caused by hormonal imbalances or other types of
incompatibility between the graft and the rootstock of unknown aetiology, such
as rose bud proliferation, rose dieback (or rose stunt) and frisure. Techniques
for diagnosing viruses in roses and methods for their control are
described."
(The actual articles are copyrighted. This is why one will only see the abstract on public forums.)
AND 2)
Title: Characteristics of rose mosaic diseases
Author: Marek S. Szyndel
Published in: Acta Agrobotanica 57(1-2): 79-87, (2004)
( Marek S. Szyndel, is the author of the chapter "Viruses" (180-189) in the Encyclopedia of Rose Science (2003).)
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The current studies of the spread of virus in roses were done in Lakeland, Florida and Davis, California. (The light pink indicates that there are links to further information.)
As can be read in the link, the Florida article reported no spread, but the full California paper reported (in addition to what is in the linked abstract): that a significant percentage of uninoculated plants had become virused: "After two growing seasons, virus had spread to 15% of the uninoculated hedged plants and 19% of the uninoculated non-hedged plants. After three years virus had spread to 23% of the uninoculated hedged plants and 39% of the uninoculated nonhedged plants."
The authors of the California article raise the possibility that the virus was spread by "mechanical transmission" ( (page 220-221) "The possibility remains that spread occurred by mechanical transmission due to contact between the leaves of the closely spaced plants and experiments are underway to test that putative mechanism of spread.")
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Why is the temperature where the studies were done important?
A procedure based on treatment at 100 degrees F has been used to obtain "clean" roses of the more "common" rose viruses. Also, alternate day 100 degrees/night 82 degrees has been reported to actually be better for PNRSV in peach ( http://www3.interscience.wiley.com/journal/119341371/abstract
Thus, in hot climate areas, in the summer months, the above ground parts of the roses are expected to experience some "natural cleansing" by whatever mechanism is triggering the above "heat cleaning". And, when the virus concentration is low or non existent in the above ground parts of the roses, one would expect that the "above ground spread" mechanisms would not be important.
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EXPERIMENTAL STUDIES ON TEMPERATURE EFFECTS ON VIRUS BEHAVIOR Is there experimental evidence that in hot weather the most common rose virus (PNRSV) does experience some "natural cleansing" in plants related to roses? The following papers discusses this point: PNRSV infections in Peach have been reported to vary with the season (i.e. temperature). The following is the abstract of the published, refereed paper (please, keep in mind the reversal of our seasons with theirs). I have added bold print to indicate important sections. Their results are consistent with the casual observations that many have made that, in many roses, the symptoms are observable in the spring but disappear in the summer. This paper has been cited by 10 more recent papers according to Google Scholar.
END OF ABSTRACT Now, the question is: does PNRSV in roses have the same temperature behavior? Fortunately the next paper answers this question. --------------------------------------------------------------------------------------------------------------- This 2000 PNRSV in Roses published research paper by Moury et. al. is available free at the following web link: http://apsjournals.apsnet.org/doi/pdfplus/10.1094/PHYTO.2000.90.5.522 This paper has been cited by 15 more recent papers according to Google Scholar" Among other things, they studied the PNRSV Elisa readings on the hybrid tea rose Anna as a function of time of year. On December 8, 1998. The ratio of the absorbance of the infected leaves and the absorbance of the leaves of a healthy plant were (see Table 4, page 526) - 4.7 Same test on February 3, 1999 - ratio 7.8 Same test on March 31, 1999 - ratio 3.8 Same test on May 10, 1999 - ratio 18.9 Same test on July 15, 1999 - ratio 3.7 Same test on September 1, 1999 - all samples were ELISA negative - they could not detect the virus! Table 3, page 525 gives the percent of positive leaf samples for the
same 6 times. They are: 33.3%, 50.0%, 53.3%, 65.6%, 22.7%, and 0.0 %. (A less dramatic seasonal dependence (in a cooler climate) was reported by a later study in Poland. For your convenience: The average high temperature for Warsaw, Poland is 73.4 F June, 75.2 F July, and 73.4 F August.) Thus, the amount (concentration) of PNRSV in roses decreases in the above ground parts of the plant as the temperature increases (and in at least one case, until it can no longer be detected). The next question is: why (chemically) would the virus concentration decrease with temperature increase? ------------------------------------------------------------------------------------------------------------------ The following study appears to be the critical study for explaining why plant virus infections have high concentration at lower temperatures but are attenuated at higher temperature. This 2003 paper has been already cited by 211 more recent papers (according to Google Scholar). The abstract contains the following: "Therefore, in cold, plants become more susceptible to viruses,.....". The Introduction contains the following: "Plant-virus interactions are strongly modified by environmental factors; especially by temperature. High temperature is frequently associated with attenuated symptoms ('heat masking') and with low virus content of virus-infected plants (Johnson, 1922; Hull, 2002). In contrast, rapid spread of virus diseases and the development of severe symptoms are frequently associated with cold air temperature (Hine et al., 1970; Gerik et al., 1990). Harrison (1956) has speculated that the virus content of a plant represents an equilibrium between replication and degradation and that the activity of the virus degrading system increases with temperature. However, the underlying molecular mechanisms of these effects of temperature are still missing. We hypothesized that RNA silencing might be the postulated virus degradation system and temperature modifies plant-virus interactions through the regulation of RNA silencing." (page 633 and 634)) In the Conclusion section (page 638), they state: Please note that statements in a reviewed published scientific paper have to be approved by the editor based on the comments of the manuscript provided to him/her by the reviewers (normally at least 3). Here is a link that might be useful: Link to full paper ------------------------------------------------------------------------------------------------------------------ Summary Contrary to early "thinking" plants do have an immune system (natural defenses). As the temperature increases: the plant's natural defenses are better able to overcome the virus so the concentration of virus is decreased (or possibly even eliminated in the above ground parts of the rose. So any type of above ground spread such as: use of pruners, branches touching, pollen spread by insects, seed transfer) would be decreased. Thus, until spread research is done in northern climates, I recommend that basic precautions be utilized to prevent/minimize the possibility of above ground spread. -------------------------------------------------------------------------------------------------------------------- Other points of interest Is this behavior limited to PNRSV? A 2005 paper ( that cited Paper 1) studied Apple Mosaic Virus (ApMV) in hazelnuts. (ApMV is one of the viruses grouped under the term Rose Mosaic Virus when found in roses). Of particular interest is the following quote (page 157): "ApMV, the member of ilarvirus group, is a labile virus, concentration of which can be negatively affected by high temperatures (Matthews 1991, Zotto and Nome 1999), and whose disease symptoms are masked at such temperatures (Aramburu and Rovira 1998)." --------------------------------------------------------------------------------------------------------------------- The field of RNA silencing has advanced rapidly. The following link is to a paper that applies mathematics to the observed mosaic leaf infection patterns: http://www.biomedcentral.com/1752-0509/2/105 .The title is: "RNA silencing can explain chlorotic infection patterns on plant leaves" --------------------------------------------------------------------------------------------------------------------- One of the easiest ways to catch up in a new (to the reader) field is to read recent Ph.D. Theses in the field. Each thesis normally has an historical section at the beginning which covers the pertinent literature with much more detail than is allowed in a published, reviewed paper. This link will download a 2005 thesis titled:"Antiviral RNA silencing and viral counter defense in plants" I should warn you that it is a long download and took me 4 or 5 tries as my server kept timing out. The thesis also discusses why when a plant is infected by more than one virus the effect is more than the simple additive effect expected. Over the years there have been some comments in rose forums that people have observed that behavior. One example is at: http://www.uk.gardenweb.com/forums/load/roses/msg071057108109.html?16 "When you get severe virus symptoms more than one virus is found from analysis. Most virus strains are not obvious and little debilitating if alone. Combined they are very much deleterious." --------------------------------------------------------------------------------------------------------------------- The concept of cold weather affecting rose mosaic was around even before I started my literature search. The following is a 1988 document from the University of Illinois:http://web.aces.uiuc.edu/vista/pdf_pubs/632.pdf The following quotes are of particular interest (to me): "Usually, the higher temperatures and drier conditions of summer inhibit virus or virus like activity in the plant. As a result, rose plants that had symptoms of infection in the spring commonly resume normal or near-normal growth in summer. With a return of cooler temperatures in autumn, symptoms often reappear, depending on the variety of rose, the strain of the virus or other agent, and environmental conditions." AND "Studies show, however, that the concentration of the virus varies and that the virus is usually not uniformly distributed within the plant." ------------------------------------------------------------------------------------------------------------------------------------ The behavior of the Rose Mosaic Virus "group" with temperature also appears in other State University type fact sheets: "Cool temperatures tend to favor virus multiplication and disease development within the rose plant.", see the University Of Arkansas fact sheet. AND The University Of Illinois has a web page about rose viruses: http://hyg.ipm.illinois.edu/pastpest/200113f.html Of particular interest is the following: "The heat of summer inhibits virus activity." ----------------------------------------------------------------------------------------------------------------------------------------- The following recently posted University of California Cooperative Extension article recommends the following precautions against above ground spread: A University of California Davis -Ventura County link on rose Virus"In the meantime, you need to remember that viruses can be transmitted by pruning and cutting shears. Virus-infected plants should be pruned last and/or have their flowers harvested last. To be extra cautious, wipe your cutting shears with alcohol (rubbing alcohol is good) or a 10 percent bleach solution between plants." (In case you are not familiar with the Cooperative Extension program, the following was stated: "Extension is the other part of our name, Extension, indicates what we do. We extend research-based information from the University of California, other universities, and federal agencies, as well as our own local applied research." ------------------------------------------------------------------------------------------------------------------------------------------------------------------------ Is the pruning and cutting shears warning relevant to PNRSV in roses? There used to be a statement: "But the viruses which cause rose mosaic are quite fragile. Much like HIV in humans, they die almost the instant they leave the host plant." Possibly this statement may be correct in very hot climates, but recent research from Poland reported that the room temperature stability of three different PNRSV isolates from 3 different roses were 6 hours, 10 hours, and 10 hours. ---------------------------------------------------------------------------------------------------------------------------------------------- Other related links:
Go to Can North American rose hybridizers safely use pollen from PNRSV infected roses? Go to When was rose mosaic virus first observed? Go to Comments about rose mosaic virus returning to heat treated plants Go to Information
about Rose Rosette Disease (virus)
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