pathogens & hybridizing

General Discussion
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21

To those that are not interested in this side-thread, please skip this post, however, I thought that there were references made to which I needed to respond.

Henry, I am not sure why you referenced Malcolm Manners. He was responding to a statement made by Tom Liggett, “In my view, there is NO way to remove Mosaic (and mayhaps other) virus(es) from plants once they’re infected.” Dr. Manners disagreed with this statement. I agree with Dr. Manners.

In your next website reference

http://home.neo.rr.com/kuska/discussion_of_whether_virus_have.htm

you use various unrelated sources (“eight sections”) to support your ideas. I say unrelated because different host organisms and viruses are referenced that may have nothing to do with one another. Toward the end of the above link (in section 7), you emphasize that, “the possibility of transmission of viral diseases is not completely eliminated.” It appears that this is a reference to an article about the purification of human coagulation factor VIII. As a medical doctor, I can tell you that this has nothing to do with roses and certainly nothing to do with the conjecture that pollen from virus infected roses transmits virus infection to seedlings. Note, I do not disagree with the idea that viruses can be transmitted via pollen. I just don’t think that it happens very often in roses and your line of reasoning is not convincing to me.

You give another link (the link did not work with my computer) in your section 8 that suggests that thermal inactivation of viruses is described using “half-life”. Then you go on to say that "Concentrations that can be described by “half-lives” never go to zero (half of half of half, etc.). I wonder if we are looking at something similar to the distinction between the term “disinfection” and the term “sterilization” concerning bacteria. “Disinfection” means to reduce the bacterial numbers to some arbitrary acceptable number while “sterilization” means to make completely free from live bacteria. It appears (to me) that heat treatment, by itself, is similar to a bacterial disinfection process." Your line of reasoning is just not there for me.

I am not a member of the GRC, however, I was a guest attendee for a commercial rose grower to their meetings for three years. I too, would be interested in a progress report.

In your next post above, you give the example of a relative getting a lung transplant (I am sorry that happened), to compare a high inoculum of virus in a human to a low inoculum in a plant through sap or pollen delivered by an insect. Again, there is a very big gap between these two examples.

In the case of the lung transplant you don’t mention that it was probably the medications used to suppress your relative’s immune system that probably greatly contributed to her having an overwhelming viral re-activation.

Interpretations and extrapolations between major Kingdoms (plants and animals) are interesting but far from having any direct correlation with scientific fact.

Let me give my own interesting side line. I think that it is absolutely amazing that an infant of an untreated HIV infected mother only has about a 30% (or less) chance of becoming infected with HIV. Isn’t that incredible when the birth process involves a very high level of exposure to blood?

Though interesting to me, this is an example of a virus in a human model that cannot be applied to viral transmission through pollen in roses.

Jim Sproul

22

Jim, I am sorry that you are having such difficulty seeing how my documented examples are (were) used. I do not know why you could not see that the diseased lung transplant was being compared to a diseased root systen transplant (“If you bud a modern rose to a virused understock, probably 100 % of the resulting plants will be virused”).

The pollen spread by insect was being compared to a person exposed to a cold virus - sometimes it can be fought off, sometimes it cannot “If an insect delivers a small amount of infected pollen or sap to a healthy rose will it be able to fight off the infection? We cannot answer that in advance; but it now appears that we can tell which roses have fought off a virus attack.”

Regarding Malcolm Manners statement and your statement, I will let each reader decide whether what you stated:

“I think that the reference to “supposedly clean blocks” was made in a discussion of varieties that had been heat treated. They were surprised to see virus infected plants showing up again after they had been indexed at Davis.”

is consistent with what Malcolm Manners posted.

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Paul, the scientific documentation is for those who want to make up their own minds as to what is happening. I realize that it tends to turn off those without a scientific background, but I do not see an easy solution.

The final part sums up the present state of thought as far (as I can determine). I will repeat it here:

"The following quote from a UCDAVIS link concerning their general virus testing program may help show that a “virus free” by a seller may too optimistic:

"While the testing and disease elimination programs are conducted under very exacting conditions, there is no ironclad guarantee that materials released from the program are 100 percent clean, Golino says. “In a simpler world, it would be wonderful if we could say this grape is disease or virus free, or we know it’s healthy,” Golino says. “But the truth is, especially as the technology becomes more complicated, we are finding that there is a lot we don’t know about diseases.” While the goal of a perfectly healthy plant may be a purely “academic” exercise, FPMS can assure its customers that the material has undergone an extensive testing program, Golino says.

“We can describe a series of protocols to which our materials have been subjected,” Golino says. “We can guarantee that those tests have been conducted, that the results have been negative and that we are selling something that is certified.” "

Http://fpms.ucdavis.edu/cafarmarticle.html

This is stated in a slightly different form in their rose virus page:

http://www.goldcoastrose.org/pdf/clean-stock.pdf



"Q How is “virus tested” different from “virus free?” What is “clean stock?”

A Many rose catalogs and books refer to “virus free” roses. The science of plant virology has shown in recent years that most horticultural plants have cryptic viruses in them, the function and importance of which are not known. As more sophisticated virus testing techniques have been developed, many “virus-free” programs discovered that their stock was not as free of virus as thought. FPMS uses the term “virus tested” or “specific virus tested,” meaning

tested for the specific viruses that are known to cause rose mosaic disease. Worldwide, plant material that has been tested for and found free of the viruses known to cause disease symptoms is refered to as “clean stock.”"

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A very recent report of a simularity between the plant and animal kingdom and their reaction to virus infections:

http://www.nih.gov/news/pr/may2005/niaid-19.htm

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Henry, I would love to debate this topic with you further, but will refrain. I would only like to clarify that my comments that you listed above were entirely consistent with my agreeing with Dr. Manner’s statement.

I do believe that it is possible for virus to appear in heat treated indexed blocks. Even though the plant material after heat treatment tests negative before it is put into an indexed block, it is possible that some of the plants were in fact not clean. In most lab tests that I can think of, there is always a possibility for false negatives (meaning that although the test result was negative, that the patient really is positive for the condition, or in the case of a rose testing negative for mosiac, that it really did have some mosaic present) and false positives (meaning that the test result was really supposed to be negative, but the result showed positive).

With that in mind, certainly it would be possible to find virus infection in “clean” blocks.

But, I do disagree with the statement that Tom Liggett made when he said that, “… there is NO way to remove Mosaic (and mayhaps other) virus(es) from plants once they’re infected.”

I believe that it is possible to remove viruses by heat treatment.

Please let me know if that doesn’t make sense to you.

Jim Sproul

26

Again, I will let each reader decide whether what Dr. Manners said that U.C. Davis told him is consistent with what you said you learned at the meetings.

Jim, regarding your statement: “I believe that it is possible to remove viruses by heat treatment.” as a scientist, I am not interested in “beliefs” (without documentation). I feel that the comments of the director of the U.C. Davis program (Dr. Golino) are consistent with my literature search.

It now “appears” (to me) that a combination of heat treatment and / or antiviral drug and tissue culture may “outrun” the virus. Notice I say “may” because this is a new field and there simply is too much that apparently is not yet understood/known to make definite statements. Please review what Dr. Golino has stated.

We are not talking about false negatives in the the general sense, we are talking about the possibility that there exists (after treatment) a concentration of virus below the sensitivity limits of present day technology.

Can you say anything about the possibility of viral fragments of thermal deactivated virus reassembling?

27

It is so hot out so I have to take frequent breaks; thus, I have a little more computer time.

The following is an example of a potential problem from heat treatment only, - having the fragraments recombine to form mutants (which of course could be either milder, the same, or more virulent than the original virus).

Title: The variability of hop latent viroid as induced upon heat treatment.

Authors: Matousek, Jaroslav; Patzak, Josef; Orctova, Lidmila; Schubert, Joerg; Vrba, Lukas; Steger, Gerhard; Riesner, Detlev.

Authors affiliation: Department of Molecular Genetics, Institute of Plant Molecular Biology Czech Academy of Sciences, Ceske Budjovice, Czech Rep.

Published in: Virology (2001), volumn 287(2), pages 349-358.

Abstract: “Heat treatment of hop plants infected by hop latent viroid (HLVd) reduces viroid levels. Here it was investigated whether such heat treatment leads to the accumulation of sequence variability in HLVd. We obsd. a negligible level of mutated variants in HLVd under std. cultivation conditions. In contrast, the heat treatment of hop led to HLVd degrdn. and, simultaneously, to a significant increase in sequence variations, as judged from temp. gradient-gel electrophoresis anal. and cDNA library screening by DNA heteroduplex anal. Thirty-one cDNA clones (9.8%) were identified as deviating forms. Sequencing showed mostly the presence of quadruple and triple mutants, suggesting an accumulation of mutations in HLVd during successive replication cycles. Sixty-nine percent of base changes were localized in the left half and 31% in the right half of the secondary structure proposed for this viroid. No mutations were found in the central part of the upper conserved region. A “hot spot” region was identified in a domain known as a “pathogenicity domain” in the group representative, potato spindle tuber viroid. Most mutations are predicted to destabilize HLVd secondary structure. All mutated cDNAs, however, were infectious and evolved into complex progeny populations contg. mol. variants maintained at low levels.”