Yesterday I was doing some chromosome counts on some of the hardy roses Paul Olsen kindly shared to be propagated and distributed to interested people in the US. I learned that these yellow hybrids are all triploids. They are crosses of R. spinnosissima and a yellow rose of some sort.
Yellow Altaica 3x
Butterball 3x
Kilwinning 3x
I went on help me find to learn more about these yellow R. spinn. hybrids and for Kilwinning found this quote:
Elliott & Pittao:
“It was in 1938, when I had recently moved to Moose Range, that Prof. C. F. Patterson mailed me flower buds of Persian Yellow and it was from these that Hazeldean, Yellow Altai, Kilwinning, and others that I discarded are descended”. Percy Wright in correspondence to W. Schowalter 07/17/1976. [Pittao]
Hmm, maybe Percy Wright got something different than buds of 4x Persian Yellow and it was some diploid yellow rose. maybe the R. spinnosissima he used was 2x??? I look forward to counting Hazeldean and learning more to the story. It looks like from most literature that the likely parent of Hazeldean is ‘Harrison’s Yellow’ and I heard that as Percy Wright aged he may have had a more difficult time remembering details. I wonder if Butterball has a similar background to these others. I should look into getting a ‘Harrison’s Yellow’ and doing a chromosome count on it to confirm that it is tetraploid like it is reported to be.
These yellow roses are new to me. For those of you that have worked with these hybrids, how much fertility have you found with them?
Sincerely,
David
David,
Have you or were thinking about checking the ploidy of R15.
If it is a triploid that might explain why it has been so hard to work with.
Hi Paul,
That’s a great idea. Thank you for suggesting it. I have a small plant of it in the greenhouse. I was thinking about going through and collecting some root tips today of more roses and will look at R15. Sometimes if the soil is too wet/dry or other reasons the roses don’t have active tips at the right stage. I just keep coming back until I hopefully find some. I wasn’t thinking about R15 and it is in a different corner of the greenhouse I was going to collect tips from today. Thank you for the great idea.
Sincerely,
David
Hi David,
Peter just emailed me yesterday with his experiance with R15. Here is what he wrote:
"I have tried to use it as a seed parent (it does set hips easily), but the seeds do not germinate well with any treatment I’ve given them (we’re talking about a germination rate of maybe 1-2%), and the seedlings that do emerge do not grow well. It’s probably a lethal self-incompatibility of some sort. I would really love to grow some selfed seedlings because it should be possible to get the same hardiness with repeat blooming–but that has not happened yet. A friend bragged that she could get the seeds to germinate, and she left them in her fridge for about 6 years. She got 5 or 6 seedlings from 150+ seeds, but (so the story goes) her dog killed two of the seedlings and she killed 2 by forgetting to water, and … I don’t know what happened to the other 2, but I’m guessing they failed to thrive and she didn’t want to talk about it.
It might be possible to get a better germination rate from these OP seeds, and a few that would grow, by embryo excision, but my hands are not steady enough for that anymore.
Many of the seedlings in which it is the pollen parent have female fertility problems but their pollen is good. This year a good seedling (which also seems to be female-fertile) appeared. It is a grandchild of R15-01, so its Hazeldean ancestry is down to about 12.5% and I doubt it is significantly hardier than average, but if I can cross it with its sibs and get something good I’ll be happy, and it should be good for zone 5."
So when you said you were looking into the yellow R. spinnosissima hybrids I immediately thought of R15.
Paul
Hi!
could it be, that the pollen of Persian yellow is at least partly only haploid because of an incompatible species crossing?
The other thing: In Debeners “Encyclopedia of Rose Sciences” from 2003 they do write that its simply – not possible – to cross in yellow flower colours via pollen.
The info for “yellow” has to be somewhere in the mother plant, according to them.
I am really amused. One of them tells us not the truth. 
Greetings from Germany,
Arno