VIRUS INFECTION IN ONCOCYCLUS

[Steve Garvie]

I must admit to having developed a fascination for Oncocyclus Irises. I have a modest collection which I am trying to add to. I would have preferred to raise plants from seed but have found it difficult to source seed for a wide range of species and when I do get seed I struggle to germinate it. So almost all of my current collection is derived from rhizome divisions from various commercial sources. Unfortunately the big risk of building a collection in this fashion is the inadvertent introduction of virus.

Whilst I know that viral infection is very bad news in Oncocyclus Irises I have found very little information on how to identify early infection. Colour breaks in flowers, stunted growth/growth deformity and yellow stippling of foliage are all suggested as signs of virus. From what I can gather it would seem that the main players in Oncos are Iris mild mosaic virus (IMMV), Iris severe mosaic virus (ISMV), Cucumber mosaic virus (CMV) and possibly Bearded iris mosaic virus with co-infection between two or more types of these viruses not being uncommon.

I accept that infected plants must be ruthlessly culled to protect “the collection” and that this should be done as early as possible to limit risk. This means trying to identify virus infection when only a few “symptoms” may be present. The stakes are high; on the one hand an entire collection of rare and expensive plants may be in jeopardy, but on the other hand I would hate to destroy a valuable plant without there being compelling evidence that it is virus-infected.

Yellow mosaic streaking/blotching would seem to be the earliest practical signs of infection but I get the impression that some yellow streaking of foliage and mild “mosaic” patterning may occur in response to culture conditions such as cold damp and low light levels.

Does anyone have any images of virus infection in Oncos?
It would be useful to pull together some images as a reference.

I ask this as I have one each of Iris lortetti, mariae, nigricans and petrana which all have some mild yellow streaking/flecks in the foliage. The lortetti flowered last year (normal flower) but the others are not yet large enough to flower. These species are semi-desert plants which do not experience harsh winters. They have had a tough growing season over this last winter due to damp-cold and were temporarily exposed to snow/frost when my greenhouse glazing was “compromised”. I note similar marks on the foliage of flowering plants photographed in previous Oncocyclus threads on the forum so I remain hopeful but have taken the precaution of separating these plants just in case.
I will post some images of these plants over the next few days but would be most grateful for any images or thoughts on virus infection in Oncos.

[Steve Garvie]

Below are some images of the Oncos I’m worried about. This recent growing season has been challenging here due to cold, dampness and low light levels. Weather damage to my greenhouse allowed in snow and cold east winds; it seems to have been the Jordanian/Israeli/Palestinian semi-desert species that have suffered and these are the ones which are showing the foliage changes.

My fear is that the foliage changes represent viral infection rather than weather damage and I would be grateful for opinions and advice.

First up Iris nigricans:



Next Iris petrana




Iris mariae



Finally Iris lorteti

[Yann]

I think it's the mosaic virus, it usually begin by central decoloration and then yellowish border.
The main problem as usual is not the contaminated plants but which one has been in contact of aphids.
Except isolating plants no other solution.

[Steve Garvie]

Thanks Yann.
My Iris mariae has been separated for the last two growing seasons as it failed to thrive from the start.

What do you think about the other three plants?

[Yann]

your nigricans has chlorotic deformations which often are due to virus, do you grow crocuses in the same greenhouse (first source of mosaic virus)?
Sometimes the cold can mark the leaf as on your lorteti. Mr Onco Scheldeman should help you on the diagnostic.
Do you light them a bit?

[Steve Garvie]

Thanks Yann.
I have a few Middle Eastern Crocus (moabiticus, etc) at the opposite end of this greenhouse but I suspect that the source of any mosaic virus is more likely to be other Oncos.

I am thinking about trying supplementary lighting for next winter.

[BULBISSIME]

Steve, I agree, virus is a big issue with onco (and other plants of course) , as well as rot ;-)
First of all, the best way to see if a plant could be infected, is to watch it with backlight, it helps to find the signs.
Then, to destroy or not to destroy... this is the question !
I personaly destroy all of my infected plants... but not if I only have 1 or 2 plants. Then I'll isolate them, trying to get seeds, the only way to recover healthy plants.
attached 2 pictures of badly infected plants... RIP

[Steve Garvie]

Many thanks for your advice Fred.
I am grateful to you for posting images of infected plants.

With regard to my plants I think I will destroy my Iris mariae and nigricans. I will isolate the petrana and lorteti but I would be grateful for your opinion on whether the images of lorteti/petrana suggest early virus infection to you. I will also examine my other plants under backlighting.

Do you know of any sources of Onco species seeds? (I already buy from Oron Peri).

[Yann]

destroying a pot of nigricans, the nightmare 
Steve you can try Jan Jílek, not always easy to get in touch with him but his list is very interesting.

[Steve Garvie]

Thanks Yann.
I regularly get plants from Jan, he has a wide range of Junos but unfortunately very few Oncos.

[GordonT]

Steve, I suspect you may already know about the Aril Society International, and their seed exchange? The exchange is closed now, but I found some of your desired species listed in past offerings. https://arilsociety.org/index.pl?Seed2008

[Steve Garvie]

Thanks for your helpful post Gordon.
It’s certainly worth checking out.

[Steve Garvie]

This is the same Iris lorteti whose leaves are shown in the last 3 images of reply #1 above. The image was taken before the flower had fully opened as I was subsequently away from home.
I can’t see any obvious signs of virus in the flower: what do you think?

[BULBISSIME]

Looks nice indeed ! probleme vith virus is than they can affect leaves, flowers, and are more or less active and visible depending of the growing conditions

[Steve Garvie]

Thanks Fred.
I had always thought that the virus will always show up first in the flower.   

Can an Onco have a virus infection even when the flower does not show signs of infection?