What is this pattern?

If a disease, will it spread to my newly planted roses - do I need to get rid of this rose?

I do not know what this rose is (has 2inch red multiple petal flowers - I will take photos when it blooms - maybe Dr Huey...)

The one thing about Elina, all she does is bloom and that's all she wants to do is bloom those huge (big as your head) blooms. My favorite HT. Do they get any bigger or better than Elina? I think not. If I get rid of her it will be because something devastating happened. I cannot stand to think about it but if they got RRD, I would be forced to get rid of them. Otherwise, I have bouquets from her all the time and two neighbors, one who is doing a tea and another a brunch this weekend, want bouquets from my Elinas for their tables. That is how big and beautiful her blooms are.

I agree with everything you say about that wonderful rose.

Paul

The latest public domain information I have about PNRSV from the U. of Davis is:
"May 2006 meeting:
"Debora Golino (UC-Davis) (with written report) has been documenting the spread of grapevine leafroll disease in the Napa Valley since 2002. The disease is spreading but slowly. Rose mosaic disease is associated with several viruses, but primarily Prunus necrotic ringspot virus and Apple mosaic virus. After three years, there is no evidence of pollen or seed transmission of these two viruses. Mechanical transmission with mechanical trimmers and root grafting appear to be the major routes of virus transmission."

http://www.lgu.umd.edu/lgu_v2/pages/reportMeet/6824_min.doc.

I sent them an e-mail on 10-8-2007 regarding their mechanical transmission report. I received a reply the same day; and, although it is my understanding that I am not free to reproduce a private e-mail on the web, my intrepretation of that e-mail is that at that time their report stood as presented.

Other rose viruses may be spread by pollen, aphids, and/or nematodes. It is my impression that the symptons may overlap.

See, for example:

http://apsjournals.apsnet.org/doi/abs/10.1094/PDIS-92-4-0508

Also, Blackberry chlorotic ringspot virus (BCRV) has been found in roses, see: http://www.bspp.org.uk/publications/new-disease-reports/ndr.php?id=013005

Also see:
http://www.ars.usda.gov/research/publications/publications.htm?seq_no_115=202249

and

http://www.ars.usda.gov/research/publications/publications.htm?seq_no_115=226990

I will post photos when it blooms.

Actually, while the rose may survive and bloom every year, its a proven fact that an aggressive case of RMV like you have in your plant reduces performance and bloom quantity/quality by about 20%, sometimes more. If you had a virus free specimen, you'd see a noticeable improvement in its performance. But.......if you think its doing well enough, thats all that matters.

My one remaining modern HT never shows the signs. But I know it must be there.

Jeri

Above, it was stated, "One of the most common viruses under the collective name of "Rose Mosaic Virus" (RMV) is PNRSV. This virus is a temperature sensitive virus. In southern climates the risk of transmission is probably small as the virus will probably be mainly in the roots for much of the season. In Northern Virgina I would have some concern about spread."

I'm not sure where that idea comes from. Certainly, virus titer falls in warmer weather, but there is no day of the year that we can't consistently and reliably find virus in leaf tissue from an infected plant, by ELISA. We've never once had a plant test positive in the cool time of the year, then negative in the hot season; if it tests positive once, it will always test positive.

Then, "The latest public domain information I have about PNRSV from the U. of Davis is:
"May 2006 meeting:
"Debora Golino (UC-Davis) (with written report) has been documenting the spread of grapevine leafroll disease in the Napa Valley since 2002. The disease is spreading but slowly. Rose mosaic disease is associated with several viruses, but primarily Prunus necrotic ringspot virus and Apple mosaic virus. After three years, there is no evidence of pollen or seed transmission of these two viruses. Mechanical transmission with mechanical trimmers and root grafting appear to be the major routes of virus transmission.""

Note that this is from the minutes of a meeting, and the minute-taker apparently misheard what Dr. Golino said. If one actually looks up Golino's paper in Acta Horticulturae, she states that they did NOT see spread by mechanical hedging, nor by pollen nor by seed; indeed, that the only form of transmission they've seen is by root grafting of closely-spaced plants in a nursery row. As of this morning (4/30/09) I have an email from FPMS agreeing entirely with this -- to date, they have seen no spread by mechanical hedging at all.

Then, "Other rose viruses may be spread by pollen, aphids, and/or nematodes. It is my impression that the symptons may overlap."

I am not sure where this concept comes from, but there are no known or documented cases of mosaic-like symptoms, on roses, by any other virus(es). Sure, it could happen, but there are no known cases.

Then, "Also, Blackberry chlorotic ringspot virus (BCRV) has been found in roses, see: http://www.bspp.org.uk/publications/new-disease-reports/ndr.php?id=013005"

Notice that this is a new find of a disease in the UK. Again, I suppose it indicates the vague possibility that something else is going on, but then, there is the vague possibility that the earth will be hit by a giant meteor tomorrow. We have no evidence, nor even any suggestion, that we ought to be in any way concerned here.

1) "Above, it was stated, "One of the most common viruses under the collective name of "Rose Mosaic Virus" (RMV) is PNRSV. This virus is a temperature sensitive virus. In southern climates the risk of transmission is probably small as the virus will probably be mainly in the roots for much of the season. In Northern Virgina I would have some concern about spread."

I'm not sure where that idea comes from. Certainly, virus titer falls in warmer weather, but there is no day of the year that we can't consistently and reliably find virus in leaf tissue from an infected plant, by ELISA. We've never once had a plant test positive in the cool time of the year, then negative in the hot season; if it tests positive once, it will always test positive."
------------------------------------
I am not sure that any discussion is needed as the above author admits: "Certainly, virus titer falls in warmer weather,"

I should have added that in hot weather the lifetime of the virus outside of the plant should be shorter than at lower temperatures.

The latest paper on the temperature dependence that I have found is:

http://www.au.poznan.pl/ptfit/pdf/PP38a/PP38_091-098.pdf

Table 2 on page 94 gives the month dependent data.

For your convience: The average high temperature for Warsaw, Poland is 73.4 F June, 75.2 F July, and 73.4 F August.

I have a posted link on my web page which I feel may be easier to follow:

http://home.roadrunner.com/~kuska/high_temperature_effect_on_pnrsv.htm

Note that this is from the minutes of a meeting, and the minute-taker apparently misheard what Dr. Golino said. If one actually looks up Golino's paper in Acta Horticulturae, she states that they did NOT see spread by mechanical hedging, nor by pollen nor by seed; indeed, that the only form of transmission they've seen is by root grafting of closely-spaced plants in a nursery row. As of this morning (4/30/09) I have an email from FPMS agreeing entirely with this -- to date, they have seen no spread by mechanical hedging at all."

The Acta Hort paper was presented in 1995:

http://flowers.tamu.edu/symposium/acta.htm

In it they state: "This suggests that transmission on cutting implements is not the primary means of virus spread"

Please note the: "not the primary means"

The later paper was presented at a different meeting in May 2006. As stated I e-mailed them in October 1997. I can reproduce what I sent:

"To: Deborah Galino;

Hi,
The latest that I have found from your group is the brief summary given at a May 2006 meeting:
"Debora Golino (UC-Davis) (with written report) has been documenting the spread of grapevine leafroll disease in the Napa Valley since 2002. The disease is spreading but slowly. Rose mosaic disease is associated with several viruses, but primarily Prunus necrotic ringspot virus and Apple mosaic virus. After three years, there is no evidence of pollen or seed transmission of these two viruses. Mechanical transmission with mechanical trimmers and root grafting appear to be the major routes of virus transmission."

http://www.lgu.umd.edu/lgu_v2/pages/reportMeet/6824_min.doc.

Did you use temperature control with the mechanical trimmers experiment, or were the trimming experiments done during the cooler months, or was there actual observed spread during the heat of summer?
Henry Kuska"

------------------------------------------------

In the reply that I received there was no mention of an error.

And the Polish paper has nothing to do with temperatures, nor does it indicate that PNRSV "lives" outside of living tissue at all, let alone for differing amounts of times.

I give up -- it's happening again. You are lying and trying to obfuscate the issue. This is not worth the raised blood pressure. I'm sure you'll answer every one of my points. I would encourage other readers to carefully consider what you say and the literature you cite, and they'll have to come to the conclusion that you don't know what you are talking about. But I will not reply on this thread again.

I am not sure where this concept comes from, but there are no known or documented cases of mosaic-like symptoms, on roses, by any other virus(es). Sure, it could happen, but there are no known cases. "
------------------------
My reply: Here is a literature abstract:
Title: Roses: virus and virus-like diseases.
Author: Lisa-V
Published in: Colture-Protette. 1998, 27: 5 Supplement, 35-38; 14 ref.
Language of article: Italian
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."

Please note the number of rose viruses that are included under the term "rose mosaic". i.e. other viruses give mosaic symptons.

Notice that this is a new find of a disease in the UK. Again, I suppose it indicates the vague possibility that something else is going on, but then, there is the vague possibility that the earth will be hit by a giant meteor tomorrow. We have no evidence, nor even any suggestion, that we ought to be in any way concerned here."
----------------------

My reply In the U.K.????? the virus was found in roses in the U.S.

See:

http://apsjournals.apsnet.org/doi/abs/10.1094/PDIS-91-4-0463C

Every mail order bareroot grafted rose from Jackson & Perkins - season 2005-2006. Has the virus. Every single one of them.

*** That doesn't surprise me in the least.
If you look at the way roses have (for decades) been produced in the U.S., the only surprise should be the appearance of a rose that was NOT virused.
Every year, as the rootstock was cut down, those trimmings were used to grow more rootstock.
Obviously, if one was virused, eventually ALL were virused.

I know that by that time J&P was fully aware of that problem.
Perhaps (giving them the benefit of the doubt) they were even making a (second) attempt to deal with it.
But it takes a long time to turn this ship around.

If Malcolm now estimates that the U.S. industry has moved from just about 100% infected to about 70% infected (Malcolm, was that your estimate?) then things have improved by 30% in just a decade or so.
That's actually pretty fast, considering the scope of the problem.

Jeri

Title: Association of a previously undescribed filamentous virus with yellow mosaic disease of rose

Authors: B. E. LOCKHART (1), N. E. Olszewski (1)
(1) University of Minnesota, St. Paul, MN 55108, USA

Published in: Phytopathology 96, issue 6, page S70, 2006.

Abstract: "Yellow mosaic is an apparently unrecorded disease of rose (Rosa spp.) that was identified in New York and Minnesota in 2004¨C2005, Symptoms of the disease consist of yellow to bright yellow sectoring and mosaic on leaves.
Necrotic ringspots on stems, similar to those described for rose streak disease, were also observed on one cultivar. Filamentous virions 800 ¡Á 12 nm in size were observed by transmission electron microscopy in negatively-stained
partially-purified leaf tissue extracts form symptomatic, but not asymptomatic plants. The nucleotide sequence of a 1.7 kb fragment of the 3¡ä terminus of the viral genome was determined. Nucleotide and amino acid sequence comparisons revealed no close similarity to any previously described viruses.
The virus associated with yellow mosaic of rose was named provisionally Rose yellow mosaic virus (RoYMV).

------------------------------------------
A 2008 international meeting lists this paper:

Author: Ben Lockhart
Title: "Identification and partial characterization of five new viruses of roses in the U.S.A."

http://www.plantenvirologie.nl/ISVDOP12/program.htm

I do not have a copy of the abstract.

*** I'd say Bob was a dolt. And a fibber.
Or they just hired him yesterday.

In his last job, maybe he flipped hamburger patties for Mickey D.

Jeri

Among other things, they studied the PNRSV ElISA readings on the hybrid tea rose Anna.

They tested the leaves on an infected mother plant 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

-----------------------------
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 %.
------------------------------

There is one confusing factor in these numbers, relative to drawing temperature conclusions. On page 523 they state that Anna was grown in a greenhouse. No statement was made on the temperature control in the greenhouse. Later they state that cuttings were grown in a heated greenhouse, minimal temperature 25 deg C. Whether this was the same greenhouse or not is not known, but still nothing is given about possible air conditioning use in the summer.

http://apsjournals.apsnet.org/doi/pdfplus/10.1094/PHYTO.2000.90.5.522

I do think most of the main commercial growers are working hard to get RMV out of their stock. I'd actually thought that by now they were mostly clean, certainly I don't see it much on new roses like I used to. If I'm not mistaken, J&P was clean, and then got RMV again when they acquired someone else (I forgot who) that was all infected with RMV.

The one grower exception that I'm seeing is from a surprising number of Austin roses with RMV, at least 5 different varieties that we brought in this year have the tell-tale signs. I told them about it and sent photos as proof, and they assure me that they're tracking down the culprits.

Thanks for the clear information Malcolm!

Incidentally, it's been my experience that Malcolm has done more to help us get virus-free roses than any other single person. I knew about his work in this area around 20 years ago when I lived in Florida, way ahead of just about everyone. His expertise should not be treated casually, to say the least.

--Ron

See the post by David Zlesak in the following thread:

http://www.rosehybridizers.org/forum/message.php?topid=8947&rc=3&ui=1261935478

*** Not completely, but they were quite a way along in the process when Armstrong Roses went tennies up,
and were acquired by J&P's parent company. (I think back then, it was the perfume outfit.)
This is what I was told by the folks here in Somis. Keith Zary and, back then, John Walden.
(In case that name doesn't ring a bell, John hybridized that Disneyland rose, and quite a few others.)

They went along for a few years, keeping the collections separate, and sold the Armstrong roses under that label.
But then there was ANOTHER takeover. (I think the one where Harry & David bought them out.)
After that, all of the roses were dumped into one bunch for production, and the whole effort to clean the stock was lost.

Now, of course, J&P has been absorbed by yet another group (associated with "Wayward" Gardens?).
I doubt you'll ever again see a major effort to clean up old cultivars.

Jeri

I am surprised to hear that Elina doesn't flourish there. It is enormously vigorous and productive here in Asheville, where our average summer high is 82-83, same as yours. Our Sept.-Oct. are degrees cooler than yours, but the old gal keeps booming along. Our summer nights are a little warmer than yours, but quite cool by Eastern standards.

Tobacco streak ilarvirus was found by R. H. Converse and A. B. Bartlett naturally infecting roses in the U.S. (in 4 locations). They published a paper in Plant Disease Reporter, volumn 63, pages 441-444, (1979). They studied 21 wild rose plants from 17 Oregon, U.S.A. locations. 5 plants out of the 20 that were tested by agar-gel diffusion (1 plant was not tested) were found to have tobacco streak virus (often the "ilar" is dropped). The positive testing plants came from 4 of the 17 sites (2 positive out of 2 tested from one site; 1 out of 1 tested from another site; 1 out of 3 from another; and 1 out of 1 from another)."

The following is what appeared in a Google Scientific search:

"Occurrence of viruses in some wild Rubus and Rosa species in Oregon
RH Converse, AB Bartlett - Plant Disease Reporter (USA), 1979 - fao.org
... Personal Authors, Converse, RH; Bartlett, AB. Publication Date, (Jun 1979). AGRIS
Subj. ... Availability number, 7919311. Serial Title, Plant Disease Reporter (USA). ...
Cited by 10 - Related articles - Cached - Web Search - Library Search"

As you can see, it has been cited by 10 studies during the years that Google has abstracts for.
----------------------------------------
Another related point, some feel that viruses were not found in roses until the 1920s when grafting started.

See the link below:

One Elina shows the watermark-type virus pattern every spring and occasionally later. It is on Dr. Huey and is 8-10 years old. The other, on multiflora, has never shown visible symptoms. It is two years younger, but became the larger plant probably in its second year and is now much bigger. It blooms, I'd say, three times as much.

The plants are about 12' apart in about the same sun but are in different soil, the symptomatic plant in heavier silt loam where some Dr. Huey plants have done well. Both plants have severe winter damage every year, but the symptomatic plant slightly moreso.

The symptomatic plant hasn't declined much (yet), but it hasn't improved with age either. It performs OK for the spot it's in, where there wouldn't be room for the Big Momma. The latter would grow from 3" stumps to 8' x 5' in a season except I take 12-18" deadheads later on.

My soil is pH 6.7 and seems fine for Dr. Huey.

A full 2000 paper by Pethybridge et.al can be read in the link below. Note that they feel that "plant intertwining" is a contributer.

In a 2005 paper they changed the virus name from PNRSV to the closely related Apple Mosaic virus (ApMV). The abstract of this paper is at http://www.cababstractsplus.org/abstracts/Abstract.aspx?AcNo=20053143821

I have the full 2005 paper. Of interest is their efficiency of virus spread contributions (Table 4, page 141):

Pruning using scalpel blades contaminated after pruning virus-infected plants - 11%

Pruning using scalpel blades contaminated by dipping scalpel blades in inoculum -35%

Shoot contact simulated by fan - 60%

Shoot contact simulated by agitation - 23%

Root contact - 0%

Root grafting - 20%

----------------------------------------

Based on this investigation I feel that shoot contact (branches of nearby roses rubbing against each other) should be investigated. Of course, because I feel that PNRSV is a temperature sensitive virus, I feel that a northern University would provide the most unambigious results.

I feel that it is a matter of experience outweighing the virtues of sitting down and scouring the Web for any paper that might possibly support speculations on the spread of assorted viruses in woody plants, roses or otherwise. Dr. Manner is the authority on viruses in roses and for all practical purposes, it is his knowledge that should be viewed as the most constructive in guiding the average rose gardener through this touchy subject.

Paul Barden

*** ABSOLUTELY!

Jeri

This is the last comment I will issue on this matter.

Respectfully,
Paul B.

Jeri

I have received a communication (10/16/2007) from Deborah Golino that Davis had an experiment that was underway for 2 years (at that time) but had 1 or 2 more years to go concerning root-to-root grafting. She told me that I would be informed as to how the experiment turns out.

I suggest that the reader read the comments of the first author in Paul's addendum. Then please read the comment about that information at this site:
http://groups.google.com/group/rec.gardens.roses/msg/149feb9699983308?q=g:thl1339858437d&dq=&hl=en&lr=&ie=UTF-8&safe=off

I have investigated the "situation" concerning the 2 statements and prepared a web page on my findings:

http://home.roadrunner.com/~kuska/discussion_of_whether_virus_have.htm

Since then I have documented that there is published research that the detected PNRSV virus concentration in roses is season dependent (and even could not be detected in any of the leaves on September 1 in a 2000 well known study) and that similar variations of PNRSV in peach have been attributed to the temperature "This drop coincides with an increase in summer temperature and attenuates foliation symptoms caused by PNRSV."

In addition to lower concentration papers, there is a published U.S study that reports that Tobacco Ringspot Virus (see my post above about what viruses are part of the collective name "Rose Mosaic Virus") from infected Iowa roses has a temperature dependence to its ability to infect indicator plants. They do not present their data in a table but instead use a continuous line graph with dots indicating their actual data points(their Figure 5a). The graph is a smooth curve with 9 data points located right on the line (no obvious scatter to the fitted line). To convert their small graph into number results in approximate values - these are my approximations:

At 75.2 degrees F - leasons per leaf, about 161.
At 82.4 degrees F - leasons per leaf, about 158.
At 89.6 degrees F - leasons per leaf, about 152.
At 96.8 degrees F - leasons per leaf, about 148.
At 104 degrees F - leasons per leaf, about 141.

Please note this is not a concentration effect as the same collected sap was used ("For TIP studies, 0.2 ml of undiluted sap were placed in thin-walled test tubes (15 X 30 mm), heated 10 min, cooled immediately, and assayed on five cowpea plants." and that this amount of effect was noted after only 10 minutes at the stated temperature exposure. The graph continues until no lesions were observed at slightly less than 147 degrees F.

One could say: but there is only a 2 % decrease in infectivity from 75 deg to 97 degrees is this within experimental error?. My reply is that this observed effect is from a smooth fitted curve with the data points on the curve. To me the interesting question is: if that much infectivity was lost after only 10 minutes exposure, how much would be lost after time periods of hours/days/weeks?

They also studied the longevity of infectibility in vitro and obtained a smooth curve which went to zero at 72 hours (the study was done at a temperature of 77 degrees F). These results are complicated by their use of a mixture (1:2 sap/0.01 M phosphate buffer).

The article is:

Title: Isolation of Tobacco Ringspot Virus from Rose

Authors: G.L McDaniel, G. J. Buck (I assume that almost everyone on this forum is familar with Buck's croses), and R.E. Ford

Published in Phytopathology, volumn 61, pages 45- 49, (1971).

From my training, I would expect that the probability of infection of a rose occurring would depend on both the concentration of the virus in the sap AND on the infectivity of the sap due to the temperature that it was exposed to.

Sandy

patricia

I have warned that this may not be meaningful as the assumption that the roundup would not leave the treated plant, pass through the soil, and then be absorbed by the neighboring plant is not supported by recent research. See my 2007 post:

http://www.rosehybridizers.org/forum/message.php?topid=13673#13673

In 2007 I informed Deborah Golino of this problem.

I have also had Elisa testing done on virused roses at various times of the year here. Outside temperatures had absolutely no bearing on how my roses tested. We get below freezing here several times during the winter in North Central Florida, and we can get above 100 degrees in the summer. The rest of the year we have all sorts of variant temperatures. I have never had any of that influence a test result.

I'd hate to see people panic and start yanking roses out that are still giving them pleasure, virused or not.

Sandy

patricia

You're right, it is an interesting topic.

Wow, 600 roses! How do you keep up with all of them? If I'm fortunate enough to buy some land in the near future, I may wake up some morning and realize that I have 600 roses too.

Sandy

'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 pictures (Figure 2, page 158) of infected leaves are also interesting (especially C).

Or maybe, the Elinas we have are just crappy ones.

--Ron

http://www.nature.com/icb/journal/v8/n2/pdf/icb19319a.pdf

The title for my last post should have been Rose Wilt - virus-like disease of unknown aetiology

I may have used brackets or quotes, maybe that is why the title was cut off.

http://www.ars.org/About_Roses/disease_mosaic_virus.html

http://www.ars.org/About_Roses/disease_mosaic_effects.html

He used to have some at another site, but I cannot find then now.

Dr. Kuska
http://home.roadrunner.com/~kuska/

It's quite possible that the virus is more active or more destructive in cooler weather, and that's why our plants are such dogs (no offense to dogs out there!). I do like the flowers, so maybe I'll try to find a clean one to try sometime. In a way, I'm glad this thread came up, I've never seen anyone else's Elina, just heard about them (and then only about the flowers), so I had no idea it was ever a vigorous plant.

--Ron

I'd ask, before ordering, if the stock was TESTED virus-free.

Jeri

Also, one has to consider the area of the poster. In "some" areas 70-80% may be unacceptable. The statement is clearly a relative statement to other hybrid teas in that area.

I see on another thread Kate in Kansas recommending Elina as a no-spray rose for that area.

When I said she only defoliates 70% in my climate, this is opposed to other HTs defoliating two or three times over.

A major difference (to me) is that the old paper stated that the sample size was 10 clean plants.

In designing an experiment one normally calculates the number of samples required to obtain a result (in this case detection of diseased plants due to spread) so that the results of the experiment have a stated confidence level (95% is the common confidence level for non critical occurances). The link below takes you to an equation to use for "Detection of the presence of a disease (outbreak investigations, herd diagnosis, and certification of freedom from pathogens)". Please note, I have reported another set of statistical calculations in a previous thread. Those calculations gave higher number of plants required than the equations in this post. The earlier equation was useful for determing the experimental value of the % spread. The present equation determines the number required to detect the presence of a disease.

The equation is n=(log (1-C))/(log(1-P))

C is the Confidence Level desired (normally .95 is utilized) and P is the proporation of the sample that have the condition of interest (in our case 0.01 to detect 1% spread).

To detect this low rate of spread (1%), 298 plants would be required.

If the rate of spread was 4%, 74 plants would be needed to observe any presence of disease.

If the rate of spread was 10%, 28 plants would be required.

If the rate of spread was 30%, 8 plants would be needed.

If we make the assumption that studying 10 plants for 3 years is the same as studying 30 plants for one year, we see that this experiment was suitable for detecting any virus spread if the rate of spread was around 10% or higher.

Of course it does not address what the affect of temperature would be on similar experiments if done in cooler climates.

----------------------

In summary:

Thus, my interpretation of this paper regarding spread is that in the temperature conditions of Florida this experiment is ruling out rates of spread of about 10% or higher (with a 95% confidence level).

--------------------------------------------------
The abstract is probably too technical for the average rose grower, but the introduction contains the following that may get the main point across better:

"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:
"We find that siRNA-mediated RNA silencing is temperature dependent in three dicot species, thus inefficient siRNA generation at low temperature is probably a universal feature of higher plants."

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).

"We do a bio assay of these plants by grafting a bud onto an indicator variety and growing it for two years to make sure symptoms do not show up," says Mike Cunningham, rose program manager at Foundation Plant Services. Cunningham made his remarks to rose experts from around the world as they toured highlights of California's floriculture industry following the recent Fourth International Symposium on Rose Research and Cultivation held in Santa Barbara, California, United States."

Authors: Matic, S; Sanchez-Navarro, JA; Mandic, B; Myrta, A; and Pallas, V.

Published in: JOURNAL OF PLANT PATHOLOGY, volumn 90 (1), pages 137-141, (2008).

Abstract: "The presence of Prunus necrotic ringspot virus (PNRSV), Prune dwarf virus (PDV) and Apple mosaic virus (ApMV) was monitored throughout 2005 in stone fruit trees by ELISA and tissue printing hybridization. The highest detection rate for all three viruses was obtained in winter with both techniques. Detection was reliable also in spring and early summer, except for ApMV. However, neither technique was able to identify successfully all infected samples in one season. Overall, ELISA was more successful for PNRSV and PDV detection and tissue-printing hybridization for ApMV."

http://roseexchange.biz/roseexchange/discus/messages/2/10563.html?1219547808

http://www.apsnet.org/phyto/PDFS/1978/Phyto68n07_1005.PDF

In 2007 Golino et.al. at U.C. Davis published a paper on this subject. The abstract is at: http://www.actahort.org/books/751/751_26.htm

In the full paper, the following is stated (page 29-30): "Field Spread in Scion Cultivars
To test further for the occurrence of virus spread trials were conducted on over 300 plants each of three scion cultivars, ‘Double Delight’, ‘Iceberg’, and ‘Queen
Elizabeth’. Rooted cuttings were planted approximately 30 cm apart in rows in the field, grown for one year and alternate plants were graft-inoculated as described above with one of three virus accessions: 1) ROS98.36, 2) ROS98.27, and 3) ROS70.7, which were 1) a source of PNRSV that caused bright yellow chlorosis in the spring; 2) a source of ApMV, and 3) a source of a naturally-occurring mixed infection of ApMV and PNRSV, respectively. Plants were pruned yearly using shears that were cleaned between each plant by dipping in 10% bleach solution. Bushes were observed for symptoms periodically and ELISA tested for PNRSV and ApMV in the spring for two years. All non-inoculated plants that tested positive were re-sampled and tested to confirm the result."

In the conclusion section (page 221) the following was stated: "In scion varieties, transmission rates two years postinoculation ranged from 0 to 25% depending on virus and cultivar. ‘Queen Elizabeth’ had the lowest percent infection of all the varieties at an average 5% for all three viruses; ‘Iceberg’ had the highest for a scion cultivar at 13% average for the viruses (Table 4).
These differences correlate with the cultivars’ relative root vigor. It is possible that a larger, more vigorous root system would increase the chance of forming a root graft with an adjacent plant. R. multiflora has a more vigorous root system than all three scion cultivars tested and within the scions, Iceberg is more vigorous than ‘Queen Elizabeth’ and ‘Double Delight’."
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I do not understand why someone would make the April 29 statement. Especially since on April 30, 2009 the same writer states: "If one actually looks up Golino's paper in Acta Horticulturae......."

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Please also note that not all types of mechanical transmission were ruled out in the 2007 paper since the observed rate of spread was higher in the unpruned bushes than in the pruned bushes. In another PNRSV infected plant, hops, this is attributed, in part, to the branches of neighboring plants rubbing against each other. Golino et.al. acknowledge this as they state (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."