Virus positive plants, Agdia Immunostrip.

[Leafmite]

Interestingly, for human/animal viruses, if the 'reactive' test shows a positive, the next step is to look at a sample under an electron microscope to confirm or clear. As I understand it, other factors can cause false positives in humans and animals (not the fault of the test) so the only way to be absolutely certain of virus infection is to find the virus with an electron microscope. How similar is this for plants?

[DavidCampen]

Originally Posted by Leafmite

Interestingly, for human/animal viruses, if the 'reactive' test shows a positive, the next step is to look at a sample under an electron microscope to confirm or clear. As I understand it, other factors can cause false positives in humans and animals (not the fault of the test) so the only way to be absolutely certain of virus infection is to find the virus with an electron microscope. How similar is this for plants?

Only in a research laboratory would EM be used as a confirmatory test. When a medical test for virus in humans is performed EM is _not_ used for confirmation.

These immunoreactive tests are very specific, I would expect that a false positive that is not due to operator error is only due to the presence of a very similar virus.

[Leafmite]

Interesting to learn that the electron microscope is not used in the health field for virus detection. I had always thought that it was as it is the only way to truly confirm or clear in certain cases. Good to know.
In one of our advanced labs, we got to see and hear how one works. Very neat piece of equipment. With so much happening in the field of nano technology, I don't think we are too far from an easier and cheaper way to detect viruses. I have also heard of research being done to give plants immunity to some of the more common viruses.
I do find it appalling that we do not have stringent laws against selling infected plants. Virus, fungus and bacterial cause great production/financial loss in agriculture. With certain diseases able to infect many hosts and their ability to mutate, it bewilders me that we aren't more careful.

[DavidCampen]

The Agdia Immunostrips use gold nanoparticles to produce the colored lines. See page 6 here:
http://scholar.lib.vt.edu/theses/ava...tion_Final.pdf

[DavidCampen]

Continuing with my testing, I have tested about 40 plants and about 6 have been positive for ORSV or/and CymMV. The virused plants have come from several different vendors.

One that tested positive today for ORSV I just got last week so I will be contacting the vendor. He is actually more than just a vendor, he is a breeder and this plant is a clone of one of his awarded hybrids.

[orchidsarefun]

2 questions
1) as these appear to come in large batch lots, what is the average shelf life of each lot ?
2) if a plant tests positive, what is the general reaction of vendors to you pointing this out ? Do they even care ? Are plants replaced ?

[DavidCampen]

You can also buy the Immunostrip tests in lots of 5 as well as 25. The lot that I got last week has a "Use by" date of Nov. 2013.

The first several plants that I found that tested positive for virus had been in my collection for many months to over a year, long enough to have acquired the infection while in my care (though I strongly believe that that is not the case) so I just trashed the plants without informing the vendor. Yesterday I tested an expensive clone of an awarded plant that I had just received from the breeder and it tested positive for ORSV; I sent him an email about this last night and I am waiting for a response.

Irregardless of how the vendors respond, I will test all of my plants and eliminate any virused plants from my collection.

[orchidsarefun]

I just trashed one last week, it always grew one leaf and then lost an old one. Looked terrible, leaves becoming all mottled when about 3 inches long. Maybe it was atypical for a virus.
I must admit to being apprehensive about testing, and will have to decide either way. Buying from vendors consequently becomes a huge issue.
However
- is reusing a scissors for example on one plant to another, the only way to transmit the virus ?
- I have read that harvesting green pods will prevent transmission to seedlings. Is this true ? What about naturally dehisced pods where seed is sterilised ?
- is there a fail-safe way or "tips" to know if a plant is likely to be infected - just be examining it visually ?

[DavidCampen]

My understanding is that infection occurs when sap from an infected plant enters an open wound on another plant. This could be from a cutting instrument or from sap on your hands or work surface or possibly from commingling of roots or possibly via sucking insects.

Of the 6 infected plants that I have found so far, 2 of them I selected for testing specifically because they looked unhealthy and lacking in vigor. None of the 6 plants had the classic chlorotic rings or mossaic patterns.

I don't understand your comment that
"I must admit to being apprehensive about testing, ... . Buying from vendors consequently becomes a huge issue."
If you don't want to confront the vendors then just trash the plants and if too many plants from a vendor arrive virused then stop buying from that vendor.

[orchidsarefun]

well - how would you suggest you increase your collection/breeding stock ? Its a bit of hit/miss if you have to purchase first and then toss, not to mention the potential considerable $ waste.
I am apprehensive because it could be that I have a lot of virused plants !