I'm CymMV Positive

[Bloomin_Aussie]

Hmmm interesting... they don't attribute virus infections with insects. I wonder if there was a scientific basis to that?

If that is the case there is no reason you could not keep happy virused plants in a collection as long as you were careful about handling and proximity to other plants.

That begs the question though... where did CyMV come from? Is it just a mutated form of another plant virus (eg. TMV) that was intruduced to orchids by mixed handling with other infected plant types?

Also, do plants have no immunity to viruses? I mean we get a cold and after a week or so we feel better. OK so Europeans have been exposed to this particular virus for ages and have built up immunities but does this not occur in plants?

[Jerry Delaney]

I honestly don't know Dan. I know that it seems logical that an insect might transmit virus from plant to plant, but with the more common orchid viruses I am not aware of any controlled study that definitely proves that is the case. However, my knowledge is years out of date and nearly all my experience is with mammalian viruses.
As to keeping known virused plants in your collection, I imagine that might be a lot like playing Russian roulette with three chambers loaded!! I mean even in the best of conditions, one may shoot themselves in the foot, but one need not take aim first!!
As to where CyMV originated? Probably anybodys guess. I'm not aware of it occurring in nature. I know some think that if they allow smoking in the greenhouse that the plants may become infected, but to my limited knowledge it has never been shown that an orchid can be infected with "type" TMV. It is probably a mutated form of the virus.
I am not aware of any "resistant" orchid plants but having said that, I am also not aware of any proven virus infections in Paphs. I have seen orchid plants that showed NO signs of infection produce flowers exhibiting massive color break. On the other hand, I have seen plants that looked like they had every known virus in the book (and maybe some that were not!) produce perfect blooms year after year.
Go figure!!!!

[lambelkip]

Jerry, CymMV is a Potexvirus, so it's possible that it mutated from Potato Virus X. ORSV is a strain of Tobacco Mosaic Virus, and can infect plants other than orchids. Both occur in nature. Insects can transmit the virus, but this is a very rare occurance due to the very small amount of infected material being transfered. It is much more easily transmitted by having overcrowded greenhouses, where plants are repeatedly exposed to infected material. There are some species of orchids which are completely immune, due to the fact that the virus has no place to attach to their cells.

Dan, the human immune system works in a much different way. plants do not have white blood cells to destroy the virus, and do not create antibodies to allow white blood cells to attach to the virus. The plant can't "feel better" in a week, since it has no way to destroy the virus. With plants rubbing up against each other, or having insects chewing on multiple plants, you have more chances for the virus to spread, and those chances eventually add up to a certainty.

[Bloomin_Aussie]

Thanks for the info guys. Kip, you've answered in one short post what I could not find after weeks of searching on the web.

All the books I've read say just to destroy infected plants but they never give a reason why (other than the virus could spread). Call me a control freak but I don't like taking an action without knowing the reasoning behind it.

[orchids3]

I have read that nurseries in England actually burned Tobacco in greenhouses as a method of insect control.
(In the earlier days of orchid cultivation.)
No one smokes in my greenhouse except maybe a chance guest - but am wondering if it is possible to actually infect plants with Tobacco Mosaic virus in this way? Is it the smoke or could it be that a virus might be transmitted by the hands? Could it be that some of our modern viruses were mutations of virus that was introduced in this way?
Curious to know if anyone knows anything about this.

[Jerry Delaney]

It is much more easily transmitted by having overcrowded greenhouses, where plants are repeatedly exposed to infected material. There are some species of orchids which are completely immune, due to the fact that the virus has no place to attach to their cells.

Thanks for the explanation Kip. So, is that the case with Paphs that there are no receptor sites for the virus to attach to? I have heard some claim that all Paphs are infected with another virus which makes them resistant but I could never quite buy that. I do know that interference takes place in mammals, but I am not aware of the occurrence in plants. I agree totally that the main transmission in orchids is via mechanical damage usually due to overcrowding and use of contaminated cutting instruments. I have seen pictures of Hausermann's Orchids in Chicago where there is a huge pile of virused plants. They destroyed literally thousands of plants most of which were being grown in large pots set rim to rim (huh, just like mine) for the cut flower market. The same cutting instrument was used all day without being decontaminated.

Is it the smoke or could it be that a virus might be transmitted by the hands? Could it be that some of our modern viruses were mutations of virus that was introduced in this way?
Curious to know if anyone knows anything about this.

Kip can probably give you a better answer, but no, I doubt it is the smoke. The hands are another matter. As far as modern viruses being mutations, this "swine flu" that is currently making the rounds is a good example. The mutation rate in some viruses can be quite high and others, quite rare.

[Florida_guy_26]

Ok, health 101- here is how things work in animal cells, A virus infects a healthy animal cell, that cell releases chemicals called interferon as it is attacked and succumbs to infection. The viral cell usually injects RNA into the nucleus of the animal cell and the RNA tells the DNA in the cell to make new virus cells. As the Interferon reacts with other animal cells it bonds and forms a protective coat on the other animal cells so they become resistant. There are also antibodies which disable the movement of viruses and bacteria and then white blood cells to eat the immobilized bacteria or virus. There are no known protective or immune cells in plants which would explain them getting viruses. I hope this helps for anyone who wants to know how the process works.

[Gin]

Thanks Fl. Guy that answered something I wondered about regarding bird viruses such as polyoma .. Gin

[MuscleGirl'sHobby]

Thanks for the great info everyone. It helps to understand a bit more about how these viruses operate.

My testing continues... My new tests arrived yesterday and I tested 25 plants today. A couple plants I was sure would be positive are not... and my lovely Phal. Sogo Grape 'Fireball' tested positive for both CymMV and ORSV. It has not a mark on it. The plant and flowers are immaculate! It is the only plant to show ORSV, and it's one of my plants that has a location pretty much to itself. I'm fearing this means it came to me with both viruses, but I'll slowly get around to testing the rest of my plants.

I've separated out everyone who tested negative. Still, I'm a bit apprehensive about calling a couple of them OK. I don't like the spots I see, but I suppose I'll treat with physan, and be ultra careful and see what happens.

FedEx says my greenhouse will be here Monday... then goes the work of putting it together. My aquarium for the smaller guys is nearing completion. I'll post pics for both the aquarium and the greenhouse in a separate thread as they're finished.

[Jerry Delaney]

I would not be too quick to pronounce the suspects that tested negative, Nichole. I am sure the tests today are much more sensitive than years ago, but being an ELISA test means that there is a minimum threshold level of virus that must be present to give a positive. I have seen plants that tested positive and then a year later tested negative.