Viruses and orchid collections

[escualida]

I do care about viruses, a lot. I test all my plants as soon as I get them and if they come out positive I let the seller know. Some sellers are good about refunds and exchanges some are really not.

[NYCorchidman]

A few words on phals from Taiwan.

It is a misconception that all or almost all phals from Taiwan are virused.
Taiwan is a world leader in breeding and distributing phals and yes, like anyone else, they had (and have) some virus issues, but it's not like old days when people didn't know better.

They (at least the well known large ones like Taisuco) do quality control to the best they can.

Being one of the main distributor of phals, they have been wrongly blamed and rumored to be virused phals producer. Simply not true!

Enough said I guess.

[quiltergal]

So after doing a bit of research online I found several scientific papers on orchid viruses. There are 30 different identified viruses that can infect orchids. Testing typically is done for ORSV, CymMV, and CMV...... 3 out of 30. As I said before there are new viruses that have popped up within the last 5 years that scientists are still trying to identify taxonomically. I don't know if there is a specific test for these yet. PhCSV (Phalaeonopsis Chlorotic Spot virus) is related to INSV (Impatiens Necrotic Spot virus), but is not the same. PhCSV also has the nickname "Taiwan Virus", rightly or wrongly.

Camille you probably know the answer to this question since you studied plant viruses. When a study states that the virus is non-persistent does that mean it is not systemic but localized instead?

[zxyqu]

As a virologist, I would guess that non-persistent viruses are viruses the plant can naturally cure itself (think human influenza infection, which is generally cleared, whereas HIV is a persistent virus that is never cleared). If there are 30 now, there will probably be 60 in 10 years and even more later. I'm sure we are also unable to capture latent plant viruses (assuming such exists: think varicella zoster the cause of both chicken pox and later on, shingles.).

[quiltergal]

Thanks Jarad! Do you know if it is even possible for a virus to be localized rather than systemic? Some of the stuff I have read says that PhCSV is a localized virus. If that is the case I'm getting out my razor blades! That doesn't really make sense to me though because it spreads so quickly.

[zxyqu]

I'm really bad on plant viruses and plant anatomy in general, but yet I can say it could be possible. For example, human flu virus is generally highly localized to the lung, as that is the only site with the enzymes needed to release and allow spread. I can easily envision a similar situation in plants. I also see no issue in cutting off infected parts as a preventative, provided you treat the wound and plant aseptically.

[camille1585]

In plants, "non persistent" (vs semi persistent or persistent) refers only to how the virus interacts with its insect vectors, ie, how long they are vectors. Non persistent means its a virus that simply becomes attached to the stylet of a feeding aphid (for instance) when it feeds on or simply probes an infected plant, and when the aphid goes to feed on another plant it can inoculate the virus. But non persistent viruses are lost very quickly once the insect moves off the infected plant (within minutes to a few hours).

Semi-persistent viruses are just that, an insect moving off an infected plant will lose the virus within hours or a few days. These viruses usually have particles that are localized in the foregut of the insect.

Persistent viruses go through the gut of the insect then pass into the hemolymph (insect blood) and then in to the glands that make saliva. As saliva is injected into the plant when feeding, contamination happens. Persistent means that the insect is contaminated for life. Even worse, the virus can be passed down to the offspring. Some of these viruses actually replicate in the insect, making it a plant and insect virus. In fact, some plant viruses are suspected of being of insect origin, and a few mutations made them plant viruses as well.



Yes, it is possible for a virus to be localized. I don't know the specifics of it, but if a plant can mount a successful defense against the virus, it will prevent it from spreading to other parts of the plant. But that I don't know much about, since I'm not a virologist. I know about the transmission types because I work with insects.

[quiltergal]

Thank you Jared and Camille!!

I emailed Critter Creek about what they can actually test for. I may send them a few samples just because my scientific curiosity has been peaked.

[NYCorchidman]

So called "Taiwan Virus" that causes strange cloud rings or yellow ( or very light green) spots to appear on the leaves on phals, is not very well studied yet.
It is thought that this particular virus is possibly localized where symptoms are shown, although this is not 100% confirmed and still being studied.

Terri- You can try testing affected leaf and unaffected leaf of the same plant and see what the test results turn out to be. I would love to know!
Also, there are very likely more than 30 viruses that affect orchids. 30 of them have been discovered. More will or may be "newly discovered" in the future.
I believe Critter Creek mainly tests for 3 (the ones you mentioned) but two of them, CymMV and ORSV, because these are most common and do the most damage to orchid industry. When both CymMV and ORSV infect an orchid, the symptoms are quite severe.

Also, virus can spread very fast within the plant. It makes numerous copies of itself with cells of a plant, then spread between cells via connecting holes called plasmodesmata, or released into water or food channel, which can spread even faster.
It depends on the type of virus, plant type&health, environmental cue I think.


Camille- Thanks for the info you shared. I learned non-persistent viruses as the ones that disappear when insects molt. I guess it is wrong.

[Brooke]

Critter Creek can test for more viruses than the normal ones if requested and of course for more money.

Brooke