A couple years ago I acquired PhenoGeno Roses’ yellow HT, Nadia Zerouali. This variety, or at least the specimen I grow, exhibits a specific type of leaf variegation I had never encountered: the first leaves the plants produces in the spring show significant variegation, slowly fading as the spring procedes. It isn’t anything too striking, but gives something to an otherwise quite bland variety.
At first, I thought it could be some weird expression of RMV. However, it didn’t seem quite right for a few reasons:
Nadia Zerouali is a new variety developed in Europe, where clonal rootstocks are really not common. My plant was budded on a seedling Laxa rootstock, as probably were the few mother plants it came from
Apart from the variegation, there were no other symptoms. Specifically, the plant had excellent vigor
I’m not familiar with RMV, but my understanding is that to be inhibited higher temperatures are needed. This variety stopped having variegated leaves with temperatures as low as 15°C. Moreover, I haven’t noticed any variegation in the fall.
I tried germinating a few self set seeds and the same variegation passed on to roughly half of the seedlings. The sample was too limited to have any kind of statistical significance, but out of 5 seedlings 2 showed normal leaves, 2 were variegated (with one appearing more variegated than the other), and one had completely white cotyledons (and therefore passed away).
I tried pollinating The Wegwood Rose with its pollen, and I only got two seeds. Both germinated, but none got big enough to notice any variegation.
Looking at these results, I would guess that it is an incompletely dominant gene, varying from no variegation to albino.
I’m not sure I will try any further hybridization with it, as it gets more blackspot than I was hoping for, and is otherwise quite distant from my goals, but I thought it could be of interest for someone else.
I still have one of the variegated OP seedlings, but is probably too inbred to be even distantly garden worthy.
There are many viruses that could be responsible, not just RMV. However, it could also be genetic, no way to tell without screening for viruses.
I would keep the line going to see if you can amplify the variegation.
Also, the pattern might be expressed in flower petals at some point. I think, for instance, that McGredy’s ‘striped’ roses and their descendants actually have a form of variegation.
It looks and acts like variegation, with no reason to suspect a virus. I had a similar result using ‘Verschuren’, with a few seedlings from a small test cross showing some variegation similar to that of the parent. Sadly, I lost all but one of these (they were a bit weak and disease susceptible, even though the other parent had very high disease resistance), and the healthiest had only slight variegation that it subsequently lost. If I were to try again, I would certainly aim for a much larger number of seeds.
What made me think of a virus in the first place was that, since leaf variegations are rare in roses, I would have expected it to be a huge part of its marketing. I would have expected other people to point out the novelty as well.
A thought I had is that, if it is of viral origin, it may also be transmitted by grafting. I could try next season with some spare cuttings I have around (could grafting a NZ bud on a cutting of some other variety, letting it grow for a while and then letting the rootstock prevail work?)
What I may try is using it both ways and see what happens. If it is a virus, it may (or may not) only be transmitted via seed and not via pollen.
Or, maybe, it is just genetic. That’s the most likely explanation, in my opinion, mostly due to the distribution of its seedlings. I may expect the virus not to be present or visible in all of the seedlings, but the albino one makes me think of some kind of codominance. I know albinos do naturally happen sometimes, but they are quite rare? I have grown about 2000 seeds in my life and this was the only albino I had. What are the odds of being a coincidence?
There are pollen-transmitted viruses, too, but I can pretty well guarantee that this is not that. The pattern seen is common for non-viral variegation. Grafting would certainly be the best test to use if you do feel the need to prove it further, but I think that is unnecessary.
Albino seedlings do happen from time to time, so coincidence is always a possibility.
I apparently spoke too soon about my surviving ‘Verschuren’ seedling losing its variegation. I noticed today that the now rather large plant has a single leaflet with a pretty obvious sector of cream color–I’m not quite sure how I missed seeing it before.
