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Speaking of viruses

This is a discussion on Speaking of viruses within the General Orchid Culture forums, part of the Orchid Culture category; I read in an issue of AOS ORCHIDS magazine a few months ago that testing ...

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    Default Speaking of viruses

    I read in an issue of AOS ORCHIDS magazine a few months ago that testing was being done to see if the brown spotting notoriously found on Sharry Baby and Linda Isler was in fact viral. Does anyone have any updates about this? If the spotting *is* viral, it's not causing the flower color breaks so often associated with virus, so growers have just been living with the spots. Can anyone comment about this?

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    Louis, I am far from a lab guy or scientist or expert on the matter but I can tell you what I know. typically virused seedlings have a very hard time with growth. secondly, most sharry baby come from massed produced clones and are in GH packed with plants. This is great for the spreading of botrytis which I thought was the leaf spotting on many Onc types.

    I personally have owned a few plants with the spotting and have grown out the spotting by constant spraying of physan on new growths and cutting old growths. If it was a virus I would assume it would show up on the growths no matter what you did.

    I would be shocked to find it's a virus whose effects can be stopped by an antibacterial.

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    No, you're absolutely right; an antibacterial would have no effect whatsoever if it was viral. What seems to happen with those types of plants here is that new growth developing over fall and winter is clear of any spots, but then once spring hits and the light and temps intensify, the spots suddenly appear, regardless of our spraying. Other than the spotting, the plants seem fine--healthy as horses in fact--but the spots are a real deterent for people who have never seen them before. I (along with, apparently, the writers of that article) haven't been able to "grow them out" and keep them off, so am wondering whether any headway was being made in the "maybe it's a virus" direction.

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    Mike, I think I totally missed the point of your message ( on my part...). You say you've managed to get rid of the spotting and it stays off once gotten rid of? How often do you spray with physan? If there's something I can do culturally to eliminate those spots on a plant for good, that would be great. Thanks...

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    Quote Originally Posted by lja
    I read in an issue of AOS ORCHIDS magazine a few months ago that testing was being done to see if the brown spotting notoriously found on Sharry Baby and Linda Isler was in fact viral. Does anyone have any updates about this? If the spotting *is* viral, it's not causing the flower color breaks so often associated with virus, so growers have just been living with the spots. Can anyone comment about this?
    I don't subscribe to the magazine any more, so I have no idea. I did read one article on plant disease in the magazine, and it was bad. I think it was on Botrytis.

    I think it's just something fungal. Those spottings are localized at the end of leaves, and viral necrosis tend to be obserbed along the leaf vein. You may want to look at the disease lesion if there is any fruiting body or not.

    We have a serious viral problem at university, and two plants of Mtdm. Issaku Nagata were severely diseased. The foliar symptom was more like ring spots, but not like brown speckes you mentioned here. The part of problem with Mtdm. Issaku Nagata is that one of the parent is Milt. warscewiczii, and according to Moir, it is very susceptible to virus. Don't know which virus they were writing about, though.

    I used to hear about fluoride damage on monocots, but not any more. Don't know what heppened.

    This is not an absolute rule, but when you see color break, the foliar symtopm is very often milder. I think the opposite may hold truth, too.

    But the best thing you can do is to have your sample diagnosed. It will be helpful for others who are wondering about the spots.

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    Thanks, Nob. The fungal explanation seems to have been the assumption for quite a while--the thrust of article was to explore whether that assumption was in fact correct. The plants are definitely not infected with TMV or ORSV, which would typically cause the mosaic ringspots you describe. And, if I remember correctly, the writers of the article were PhD researchers so, without knowing more of their background, I'm taking for granted that they know their field and are justified in publishing--or at least posing the question.

    Quite frankly, I have never seen a mature Sharry Baby from any grower *without* that localised spotting, and it just seems to get worse as the leaf and growth ages.

    Anyway, I was just curious... Thanks for answering.

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    Quote Originally Posted by lja
    the writers of the article were PhD researchers
    I may take a look at it, but there aren't many plant scientists that are familiar with orchids. I tend to trust if they are from Hawaii or Florida, though. Dr. Uchida seems very good in my humble opinion.

    Quote Originally Posted by lja
    Quite frankly, I have never seen a mature Sharry Baby from any grower *without* that localised spotting, and it just seems to get worse as the leaf and growth ages.
    I received Onc. Sharry Baby 'Red Fantasy' (or something) from Hawaii lately, and this one does not have those spottings in question. On a similar note, I have read that there is a virus called Colmanara rhabdovirus. In (plant) virology, the virus is named after the first host recorded (and characterized).

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    I received Onc. Sharry Baby 'Red Fantasy' (or something) from Hawaii lately, and this one does not have those spottings in question.
    That would fit (and I should have been more specific--sorry). The hypothesis was that certain SB clones, among them 'Sweet Fragrance' (if I remember correctly), were virused with this pathogen from the outset, thus bringing up the possibility that every Sweet Fragrance clone in existence carries the virus at this point, and every Sweet Fragrance clone will exhibit the spotting.

    I'll have to look up the article and post the names of the researchers--maybe you've heard of them.

    Thanks again--I'm really curious about this one.

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    Default I found the article.

    It's in the Jan. 2004 issue of ORCHIDS, entitled "What causes those spots?" and the article focuses on Onc. Sharry Baby 'Sweet Fragrance'.

    Writers of the article are:

    Mani Skaria, PhD, Prof. and plant pathologist at Texas A&M

    Yin-Tung Wang, PhD, Prof. floriculture and plant physiology, Texas A&M

    Larry Barnes, PhD, Prof. plant pathology and Director of the Texas Plant Disease Diagnostic Laboratory.

    This is a pertinent quote from the article:

    "There is no sign of a fungus or bacterium present in any of the leaf cross-sections examined under the microscope, with or with or without fluorescence. This was also true even after incubation of lesions for four days at room temperature of 77 F."

    The article ends by saying, "Some viruses produce symptoms only at optimum conditions for the virus. We will continue our search for a possible cause, starting with leaf-mineral analysis and some preliminary virus diagnosis."

    So I was just wondering if anyone has heard about any further developments concerning this--whether virus was, in fact, the cause of the spotting since, according to these folks, the cause is apparently not bacterial or fungal.

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    Quote Originally Posted by lja
    "There is no sign of a fungus or bacterium present in any of the leaf cross-sections examined under the microscope, with or with or without fluorescence. This was also true even after incubation of lesions for four days at room temperature of 77 F."
    Little skeptical here. Nothing showed up? And why four days? They saw something after 5 days? I have done something similar for Hemerocallis diseases, and even non-patheogenic ones showed up.

    Quote Originally Posted by lja
    The article ends by saying, "Some viruses produce symptoms only at optimum conditions for the virus. We will continue our search for a possible cause, starting with leaf-mineral analysis and some preliminary virus diagnosis."
    Ok, this is one of the "what happened???" articles. I remember a similar one that was on carnivorous orchid (a Spiranthes relative) from South America (Peru?). Nobody really knows what happened. I know somebody who went to Texas A&M for her Ph. D in Plant Path, so I can ask her, but the best thing is to ask them directly.



    Quote Originally Posted by lja
    So I was just wondering if anyone has heard about any further developments concerning this--whether virus was, in fact, the cause of the spotting since, according to these folks, the cause is apparently not bacterial or fungal.
    Not necessarily. I think that is their best "guess." Scientists do not present evidence that the event A is NOT the event B. We present an evidence that the event A may be actually the event B. In other words, there is always a possibility that it can be either. Or it can be neither bacteria, fungi, or viruses.

    One example: For a longest time, the cause of commercial Poinsettia branching was unknown. The branching trait is something you do not see in the wild population, and whenever a new cultivar is created by breeding, it is grafted to trasmit the trait. It wasn't fungal, bacterial, and viral. But people still thought it was possibly viral because of transmission. I thought it may be caused by mycoplasma-like organisms (or Phytoplasma) simply because it causes excessive branching of Yoshino cherry. And.......I happened to be correct this time.

    Also if it is viral, you may not see that on every one of Onc. Sharry Baby 'Sweet Fragrance.' Yes, if you propagate virused plants by TC, there is a chance to dessiminate more. However, an excessive propagation have lead to elimination of virus at least in strawberry. There is a possibility that their hypothesis may be correct. However, this is something that can be argued either way.

    But whatever it is, the symptoms do not look like viral ones that I am more or less familiar.

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