Does virus testing really identify viruses

[nhman]

Don - I order my test strips direct from Agdia. They have a good website for information about the products and an 800 line for ordering. Although it IS an additional expense, it has been one that I have always done in an attempt to "protect" my collection.
I don't know about the % of false positives or negatives. I will have to re-read their website to see if they list that information or email them for the info if not listed.
ANY test in ANY species (Man, dog, orchids) should have a false positive and false negative (Specificity and Sensativity) aspect. So.....excellent points. Thanks!

[Cookiemonster]

nhman- thank you for the heads up about haiku maui, i was thinking to order from them on/off, but its good to know they stand behind their product and are willing to take it back!

I think the key issue is, if there is not enough of that virus hanging around in the tissue which is being tested it might come up as a false negative. I dont know much about false positives. Im thinking about sending some of mine to Critter Creek Labs and seeing how they do- most vendors do NOT test and simply say it is not cost effective and tests are inaccurate. Is that a way for them to slip off the hook on this issue- Until there is something to eliminate this virus, this issue will never resolve itself.

I was talking to unhappykat last night about some of the older classic cattleyas and how many are indeed virused- how would it be possible to recreate the plant without the virus? We discussing selfing, finding the parent plants, ect.

[nhman]

This is indeed a problem with the "Classic" Catts. Especially those that were used during the "Hey Day" of the orchid corsages - so essentially all of the great and classic plants - were probably infected through the lack of bio-security that was used at the time.
They just didn't know any better. Remember, it was only relatively recently (1800's) that Dr. Lister (I believe) suggested that a surgeon should wash their hands between surgeries to reduce infections.
And it wasn't until the mid 1980's that the CDC finally figured out that the HIV virus was a blood borne infection!
So we learn all the time.
Now IF we could find some of the classics that repeatedly tested negative for viruses, that would serve as the "link" to recreate a supply of them.
Likewise, reproducing the original crosses - IF we could find the original parents - would also be a thought.
Nothing that I know of that exists or is even being considered to treat orchid viruses......

[camille1585]

I think the % of false positives and negatives probably depends a lot on the types of viruses being tested.
For example, I know that in the case of potato, the antigens produced by plants infected with Potato Leaf Roll Virus are also produced in unifected plants that are under stress. So it is possible to get a positive result for the virus just because the plant was stressed. However people are aware of that and additional tests can be done to make sure it's not a false positive.

Then for an onion virus there is the opposite problem. In experiments, the scientists know which plants are infected, but the ELISA is coming up negative for many of them, simply because the quantity of virus is too small. They are trying to improve the accuracy of the test in regards to this virus, but each solution they come up with brings up new problems (the antibody binds to stuff its not supposed to bind to leading to false positives).

All in all, virus detection is complicated business!

[orchids3]

Hi
Thanks for starting this thread. Paticuar thanks to Andrew & Camille for their educated answers. Now - if you look at the Agdia website Agdia, Inc. Plant Virus, Disease, and GMO Test Kits you will see that a strip is sold or orchids which will test for CymMV and ORSV viruses. These are the most common in orchid collections. If your look at the Agdia product list you will find that there are many other viruses not covered by the "Orchid" test strips which "may" not be detected by the test strip sold for orchids. I believe the only sure way is to submit a sample of suspect plants to a good lab. The Agdia system is a good one and should be used but if you are a plant hybridizer or commercial grower it would be to your best interest to go one step further and screen valuable "stud" and Meristem candidates in qualified labs. Good vendors will refund your money for infected plants. We could ask that all shipped plants be tested - but we can expect to pay for the service. For the rest of us who suspect a virused plant it is often cheaper to just throw the plant away and get another one however not only should a virused plant be thrown away but the area should be steralized and all surrounding plants thrown away. It is just best to be very careful what you introduce into your collections and be always vigilant.

[Cookiemonster]

nhman- it is truly tragic that most are indeed infected. I have heard about the cut flower industry and how one blade was used on hundreds if not thousands of plants at time!!! Like you said the concept of virus never really came up till later after all the damage has been done
Now would both of the parents have to be virus free or only one?

Camille thank you for the insight- I think the onion example is amazing! They know its there but because there isnt enough virus there it comes out falsely negative! I had a friend who tested a plant that LOOKED incredibly sick/virused and it came out falsely negative - we both were in shock she got it tested again with a different part of the plant and turned up positive for 2 viruses.

I think testing is critical- camille do you know anything about finding a cure to virus- that is something I would love to know more about.

[camille1585]

Originally Posted by Cookiemonster

I think testing is critical- camille do you know anything about finding a cure to virus- that is something I would love to know more about.

I don't really know what is going on in terms of research on cures for plant viruses. The problem is that plant 'immune' systems are so vastly different from those of animals. For now, the only "anti-virus" is genetically engineered plants, which work in a way similar to vaccines. This 'vaccine' is aimed at only 1 virus. A gene encoding the virus coat protein is added to the plant. The plant recognizes that this piece of virus should not be there, and then silences the gene expression. When the real virus does come into the plant, the plant already recognizes the coat protein of the virus, and blocks it. I think that's how it works, this was only briefly discussed in lectures.

Plants also have a nifty way of defending themselves as soon as they detect RNA viruses. This is called RNA interference. The plant recognizes double stranded RNA of virus replication as being foreign, and then degrades it with enzymes and destroys it. Apparently this also works with DNA viruses too, but the trigger is different.
The problem is that viruses are smart little boogers: They have evolved ways to suppress the plant's gene silencing. If that's the case, the plant is the loser, and the virus takes over. Once the virus is in and replicating, there's nothing the plant can do. And nothing anyone can do for that matter, except destroy the plant.

As for cures, I can look it up later if you'd like, to see if anything is happening in that direction. Hope this was clear enough, I tried to make it understandable!

[nhman]

Again, thanks to all for the education and information on plant viruses!
I've always believed that a day is not complete without learning something,so today was a really great day.

[MuscleGirl'sHobby]

This thread had been very informative for me. Thanks to all who have contributed!

[Grandma M]

Originally Posted by MuscleGirl'sHobby

This thread had been very informative for me. Thanks to all who have contributed!

Does anyone know of a source for less than 25 strips. I would like to try them but don't want to invest that much, if it's possible to buy less?

Marilyn