The Orchid Garden

symptoms like the mosaic virus?

Question:

Hi, thanks for the information! The problem is that I do not know any places in Finland where they would actually test plants for viruses. Orchids are not a very common hobby in Finland, our society has about 400 members. I have also read the society’s magazines from the last 25 years and they do not mention anything about testing orchids for viruses. And we only have one finnish orchid-book which came out in -69 (if I remember correctly) and I do not think it even mentions the tobacco mosaic virus )  But I am very happy to know that it might not be the mosaic virus after all *phew*!  Thank You!   Miu

Response:

What to do about the false positives of which you speak?

The level of false positives depends primarily on the quality of the antibody being used to probe for the viral antigen, the type of test, and the quality of protocol. The quality of antibody is controlled primarily by the purity of antigen used to produce it, ie how well you have purified the viral antigens from the host antigens. Many plant compounds are strong immune stimulators and will produce an antisera that will react against not only the viral antigens but also against plant tissue (a typical polyclonal antibody is a massive cocktail of thousands of different specificity antibodies against the virus it was produced against as well as any contaminating antigens in the preparation plus antibodies against anything the producing animal has been exposed to in its life). Compounding this would be the sensitivity of the test, ELISA tends to be a very sensitive test because of the amplification effect of the enzyme substrate reaction. I’ve spent half my life designing this type of test for quite an array of viruses, and there are times when a less sensitive test such as immunodiffusion serves the purpose better, an example being a situation where a highly specific antisera is not easy to produce and the antigen is usually present in very high titers – CyMV and ORSV are two good examples. A second approach is to produce a monoclonal antibody (this is done in the laboratory by isolating individual antibody producing cells and immortalizing them by fusing them with a cancerous cell- one cell equals one speciifc antibody). Ideal would be the production of several individual monoclonal antibodies to be blended into a cocktail so that any antigenic variation of a single virus epitope would not present a problem. Sometimes you get lucky as the USDA did and come up with a monoclonal antibody that is "group" specific, that is it is an antibody that is reactive to an epitope that appears to be present on a whole class of viruses. They found one that appears to work for all potyviruses, and this monoclonal is used to screen for potyvirus infection in general, so a single test can be for many viruses. You can also create cocktails of several specific monoclonals to create single screen assays for several viruses. Is there only one type of test, the ELISA, available outside of using indicator plants?

No, as stated, for those viruses that tend to be present in large quantities immunodiffusion is probably a more desirable choice of assay, and there is a tremendous host of other types of assays that can be employed, but ELISA is most common. BTW, using indicator plants is not as easy as it sounds until you gain experience. The inoculation of the plant has to be cause sufficient wounding of the leaf (I use carborundum powder) to cause infection, but be gentle enough not to produce wound lesions and bruising that can be confused or coverup virus symptoms. Secondly, indicator plants have to be sensitive to the virus. A good example is Bean Yellow Mosaiv Virus, a serious concern for orchid growers. Most commercial bean strains have ben selected for resisitance, so you need to get a strain that has been maintained purposely for sensitivity, and that also has been indexed for bean Common Mosaic virus, which if present would interfere with the sensitivity to bean yellow. I had tho beg my seed stock from a Cornell research station. It is my understanding that ELISA tests for both TMV-O and ORSV?  Is CyMV a synonym for one of these two?

TMV-O and ORSV are synonymous, CyMV is a separate entity. Are there other *known* viruses that may affect orchids for which we have no tests at all?

By definition, no. If they are known ,they were detected by some means. Hoever, there may not be any routine tests available commercially. Are there *any* that have symptoms we can SEE and distinguish from correctable issues our orchids may be facing?

After testing many thousands of plants, I’ve concluded that most of what people think is virus infection based on foliar symptoms is fungus, and most virus infection is asymptomatic. There are some very clear cut flower symptoms with certain types of plants that can be identified, but this is the exception. What is the difference between single well and double well ELISA?  WHAT does ELISA stand for anyway?

ELISA is enzyme linked immunosorbent assay, a test that can be configured many different ways but essentially uses an antibody that has been conjugated to an enzyme to detect an antigen that has been immobilized on a surface, or conversely it can be used to detect antibodies to a known antigen. Its sensitivity derives from the amplification created by reacting the enzyme with its substrate. It is usually run in a 96 well microplate and single versus double well simply means whether the particualar sample was run once or in duplicate. I put a lot of question marks in the above.  I guess my biggest question is: how do you weed out the false positives?

Use a reliable laboratory. that have professional immunologists on staff. The best is probably AgDia, next would be well equiped labs using AgDia reagents (I have no connection with them). And for your reading pleasure I offer a rhetorical question:  What can be done about OVH-G, better known as the "G"rower’s strain of "O"rchid "V"irus "H"ysteria?

Education. Although misinformation tends to spread much more efficiently than information in the electronic age. Electron microscopy was also mentioned in another post. It sounds like the perfect solution, just use a powerful electron microscope and physically look for the viruses. Problem is, until you have actually had the experience of doing this, you do not realize how much it can literally be like looking for a needle in a haystack. Most of those electronmicrographs you see with piles of virus particles are of preparations where the virus has been extracted and purified and concentrated by ultracentrifugation before being put on the grid. I recently reviewed 21 plants from a friend’s collection that she had tested by critter creek laboratory for virus.  Only one had tested positive (a Phal seedling for CyMV) and it was impossible to tell from looking at it that it was infected with anything.  It looked as healthy and was growing as strongly as the other 20 plants.  No one would have picked it out of the line up as the sick one.  She wanted to throw it and a dozen or so other plants that had been setting near this one away and all I could think to do was tell her to slow down, take several deep breaths and learn more about orchid virus before reacting to it.  I wish I could do more but, alas, I got that darn three pointed fool’s hat stuck on my head again. (Will I ever learn?)

I once gave a talk where I spread out 40 bags with large sections of Phal leaves in them, and asked the audience to come up and pick out the positive leaves. They were from a run of several hundred plants that had just been tested, and all the leaves were immaculate, and all 40 were positive for either CyMV or ORSV. – Hide quoted text — Show quoted text – have a good weekend, y’all. It is not possible to tell if a plant is virused simply by looking at it. Markings considered characteristic of viruses may be from environmental effects, genetics, insects or mites, physical damage, and so forth. On the other side of the coin, plants that are asymptomatic may also be infected. The only true way to tell is to have the plant tested. There are a number of labs that will be more than happy to charge you to have your plants tested, which is expensive and will tell you only one thing: whether or not that plant was infected at the time of testing, and that it was or was not infected by the viruses for which it was tested, which may or may not be helpful. I’ve also been informed by a PhD in plant pathology that orchids tend to have a strong ELISA response whether they are infected or not (reads: you may get a false positive). Another option is to use an indicator plant. Buy the seeds, wait until they grow, and then expose them to juices from the suspect plant. If the indicator plant displays virus symptoms, then the host plant was infected. Again, just a snapshot for the viruses tested at the time. Cheers, -AJHicks Chandler, AZ

Response:

How much does an Elisa test cost for an orchid?? I had one of mine tested about 4 years ago and I don’t remember it being very expensive at all..      

        Sorry, I don’t have current prices. Anyone have a Critter Creek ad from the AOS?         But look at it this way. At $3 per plant (the price as of 1995), one plant is nothing. For two viruses, it’s $6. Not too bad.         Let’s try one shelf: 10 plants. Let’s try a bench: 100 plants. Try the whole greenhouse: 1000 plants.         If this still strikes you as being cheap, please get out your checkbook, make checks payable to "The Ed and Larry Beer Fund," and mail to… oh, never mind. Didn’t work last time, won’t work now.         Once again, it’s a snapshot of that plant’s health at the time of testing. Next year, if you want to do the same again, it’s become quite an investment.         Plus, CC tests for the two biggies; I’m not sure if they test for other, lesser viruses.         Viruses should be a concern primarily for larger growers. Take pains not to transmit viruses, and you’ll be good to go. A cavalier attitude or an ineffective disinfection solution can lead to the infection of tens or hundreds of plants at a commercial flower facility- very costly. Aunt Martha with her windowsill of supermarket phalaenopsis doesn’t need to submit each new accession for virus testing.         -AJHicks         Chandler, AZ

Response:

which is expensive and will tell you only one thing: How much does an Elisa test cost for an orchid?? I had one of mine tested about 4 years ago and I don’t remember it being very expensive at all..

Response:

What to do about the false positives of which you speak?

        Ya got me. Is there only one type of test, the ELISA, available outside of using indicator plants?

        No; a scanning electron microscope will tell you if a virus is present. However, it is prohibitively expensive. Plus, you’d have to have a competent virologist tell you what they are. It is my understanding that ELISA tests for both TMV-O and ORSV?

        ELISA is specific for the virus being tested at the time. You can test for one, and then the other. That sort of thing. Is CyMV a synonym for one of these two?

        Cymbidium mosaic potexvirus is also known as CymMV. Odontoglossum ringspot tobamovirus (ORSV) is also known as tobacco mosaic virus – orchid strain, so TMV-O and ORSV are identical. Are there other *known* viruses that may affect orchids for which we have no tests at all?

        Probably. The VIDE plant virus reference says there are about a dozen that infect orchids. Two are definitely malicious (CymMV and ORSV), others are pretty nasty (ask any pleurothallis grower who had their collection extirpated by bean yellow mosaic virus), and there are almost certainly more that just lurk. These lurkers may be harmless to the host species, but might bring another genus to its knees if it cross-infects (thanks to vectors, such as aphids). Are there *any* that have symptoms we can SEE and distinguish from correctable issues our orchids may be facing?

        There are certainly some types of symptoms that are typical of different viruses, but the correlation is not absolute. Square one: back to testing. What is the difference between single well and double well ELISA?  WHAT does ELISA stand for anyway?

http://www.m.ehime-u.ac.jp/~yasuhito/Elisa.html         ELISA = Enzyme-Linked Immunosorbent Assay. There’s more than enough stuff on this to knock you out on the web. I put a lot of question marks in the above.  I guess my biggest question is: how do you weed out the false positives?

        Good question. Your best bet would be to double-check positive results with an indicator plant. (Will I ever learn?)

        Not if you keep asking us, Al. have a good weekend, y’all.                    

        Thanks, but I have other plans.         -AJHicks         Chandler, AZ

Response:

Hi, does anyone know if something else (too much or too little water, low humidity etc.) cause symptoms on the leaves of orchids that would be like the symptoms one can see when the plants is infected with the tobacco mosaic virus?  In this case I have one Slc and one Lc that have the same sort of marks on their leaves.  Thank you!    Miu

Response:

does anyone know if something else (too much or too little water, low humidity etc.) cause symptoms on the leaves of orchids that would be like the symptoms one can see when the plants is infected with the tobacco mosaic virus?

        It is not possible to tell if a plant is virused simply by looking at it. Markings considered characteristic of viruses may be from environmental effects, genetics, insects or mites, physical damage, and so forth. On the other side of the coin, plants that are asymptomatic may also be infected.         The only true way to tell is to have the plant tested. There are a number of labs that will be more than happy to charge you to have your plants tested, which is expensive and will tell you only one thing: whether or not that plant was infected at the time of testing, and that it was or was not infected by the viruses for which it was tested, which may or may not be helpful. I’ve also been informed by a PhD in plant pathology that orchids tend to have a strong ELISA response whether they are infected or not (reads: you may get a false positive).         Another option is to use an indicator plant. Buy the seeds, wait until they grow, and then expose them to juices from the suspect plant. If the indicator plant displays virus symptoms, then the host plant was infected. Again, just a snapshot for the viruses tested at the time.         Cheers,         -AJHicks         Chandler, AZ

Response:

What to do about the false positives of which you speak?  Is there only one type of test, the ELISA, available outside of using indicator plants?  It is my understanding that ELISA tests for both TMV-O and ORSV?  Is CyMV a synonym for one of these two?  Are there other *known* viruses that may affect orchids for which we have no tests at all?  Are there *any* that have symptoms we can SEE and distinguish from correctable issues our orchids may be facing? What is the difference between single well and double well ELISA?  WHAT does ELISA stand for anyway? I put a lot of question marks in the above.  I guess my biggest question is: how do you weed out the false positives? And for your reading pleasure I offer a rhetorical question:  What can be done about OVH-G, better known as the "G"rower’s strain of "O"rchid "V"irus "H"ysteria? I recently reviewed 21 plants from a friend’s collection that she had tested by critter creek laboratory for virus.  Only one had tested positive (a Phal seedling for CyMV) and it was impossible to tell from looking at it that it was infected with anything.  It looked as healthy and was growing as strongly as the other 20 plants.  No one would have picked it out of the line up as the sick one.  She wanted to throw it and a dozen or so other plants that had been setting near this one away and all I could think to do was tell her to slow down, take several deep breaths and learn more about orchid virus before reacting to it.  I wish I could do more but, alas, I got that darn three pointed fool’s hat stuck on my head again. (Will I ever learn?) have a good weekend, y’all.

– Hide quoted text — Show quoted text – It is not possible to tell if a plant is virused simply by looking at it. Markings considered characteristic of viruses may be from environmental effects, genetics, insects or mites, physical damage, and so forth. On the other side of the coin, plants that are asymptomatic may also be infected. The only true way to tell is to have the plant tested. There are a number of labs that will be more than happy to charge you to have your plants tested, which is expensive and will tell you only one thing: whether or not that plant was infected at the time of testing, and that it was or was not infected by the viruses for which it was tested, which may or may not be helpful. I’ve also been informed by a PhD in plant pathology that orchids tend to have a strong ELISA response whether they are infected or not (reads: you may get a false positive). Another option is to use an indicator plant. Buy the seeds, wait until they grow, and then expose them to juices from the suspect plant. If the indicator plant displays virus symptoms, then the host plant was infected. Again, just a snapshot for the viruses tested at the time. Cheers, -AJHicks Chandler, AZ

Response:

Filed under: Cymbidium Orchids

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