Seedling/genetics question

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mntlover
Posts: 283
Joined: Sat Dec 29, 2018 7:11 pm

Seedling/genetics question

Post: # 72479Post mntlover
Tue Dec 08, 2020 4:29 pm

I have seeds germinated from the Rugosa I asked about recently, looks like David Thompson. (Obviously much like Jen's Mini, from pictures on HMF)
Anyway, the rose growing across the path from it was Rosa Glauca (rubrifolia, however you spell that).
One of the seedlings is all purple, stems,leaves and all. I realize it may not stay this purple, but it got me to wondering about that cross, if that is what it is.
So I looked up Carmenata, which is an attention getter in person I must say. But the cross was opposite (with a different Rugosa), ending up with a tetraploid.
But what do you end up with reversing the cross, if that is what I have, assuming the Rugosa hybrid is a diploid?
If I understood correctly when I asked about Maidens Blush there is a big difference in using as seed parent vs. using as pollen parent. Wouldn't that be true in this case?

Also, if that ends up being the case, and it grows well, what do you think it would be useful for in breeding? What would you try if you were going to work with it?
Thanks for any thoughts!
Duane

MidAtlas
Posts: 77
Joined: Mon Jan 28, 2013 8:49 pm

Re: Seedling/genetics question

Post: # 72484Post MidAtlas
Wed Dec 09, 2020 2:32 pm

Hi Duane,

Due to the odd meiosis in Rosa sect. Caninae, there would be a difference in the expected ploidy depending on whether R. glauca was the seed or pollen parent. In this case, assuming that your R. rugosa hybrid seed parent is a diploid, then the offspring resulting from pollination by R. glauca would most likely be diploid as well. It's hard to say how fertile the hybrid might be.

Here is an example of a hybrid with a similar background: https://www.helpmefind.com/rose/l.php?l=2.80966

I think that it would be important to evaluate the plant's qualities and its fertility, along with your own goals, before making any breeding plans for it. It could even be a nice ornamental on its own.

Stefan

mntlover
Posts: 283
Joined: Sat Dec 29, 2018 7:11 pm

Re: Seedling/genetics question

Post: # 72491Post mntlover
Wed Dec 09, 2020 11:46 pm

Thanks for that. Interesting to see other results similar. It will also be interesting to see what fertility ends up like. I don't have any plans for it. Although I am exploring options for cold hardiness and disease resistance.I was wondering if combining Rugosa with other species before crossing with moderns would be a way of avoiding infertility issues at that point.
Duane

MidAtlas
Posts: 77
Joined: Mon Jan 28, 2013 8:49 pm

Re: Seedling/genetics question

Post: # 72496Post MidAtlas
Fri Dec 11, 2020 8:54 pm

I'd guess that fertility is more likely than not to be poor given the distant relationship between the two species, but you never know! If the seed parent is already a fertile hybrid, that adds some uncertainty to the equation; maybe it will actually increase the chances of your seedling being fertile, since straight R. rugosa doesn't always make fertile hybrids directly. The R. glauca-derived foliage color could be diluted in the next generation unless you happen to cross it with another hybrid of that species, or it is somehow able to self-pollinate (assuming R. glauca-derived foliage color is a goal). I also wonder how R. glauca chromosomes behave in terms of preferential pairing with one another in hybrids, especially if there is only one pollen-derived set present. You might just watch this one carefully for open-pollinated hips and sow any seeds to see how the offspring look and behave. If a further generation can be produced via self-pollination, and preferential pairing can take place, that might help sort out some genetic incongruities even while retaining R. glauca influence on foliage color. That's a few stacked "ifs," of course.

I wonder if a cross between R. rugosa and some more closely-related species from Sect. Rosa (Cinnamomeae) might not be the best bridge to crossing with more distantly-related taxa, and maybe negating a few of its less desirable qualities, without losing much fertility in the middle. Even though the pure species seems to frequently have trouble producing fertile offspring from wide crosses, I think there may be a few exceptions, and of course examples of what interesting things can happen in spite of the low initial fertility (like the allotetraploid offspring of 'Max Graf' in the Kordesii Group).

jbergeson
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Joined: Thu Dec 15, 2011 11:54 pm

Re: Seedling/genetics question

Post: # 72497Post jbergeson
Fri Dec 11, 2020 11:26 pm

Another rose to look at is "Ruglauca." I got some fertility out of that, I think. Not full rugosa fertility. I may have posted seedling pics on the forum here if you search it for that. (use google: "site:rosebreeders.org ruglauca").

The first hurdle to jump for your seedling will be if it has good vigor...some rugosa seedlings just wilt up and die at a young age for no apparent reason.

mntlover
Posts: 283
Joined: Sat Dec 29, 2018 7:11 pm

Re: Seedling/genetics question

Post: # 72498Post mntlover
Sat Dec 12, 2020 3:24 pm

What a beautiful rose Ruglauca is! I noticed it may be a self of the species cross. Interesting.
Now I wonder, what if (perhaps after selfing one of these) you cross two seedlings: like Ruglauca with another cross like these.
Would using a seedling like Ruglauca work with one these work to get preferential pairing, or would it be better to select both seedlings that showed desired traits (purple foliage for instance)?
I have noticed seedlings descended from Rugosa will show Rugosa foliage in some offspring very strongly even when parent may not show it much (I have had that with seedlings from Therese Bugnet and Martin Frobisher. Hansa seedlings were not a surprise.)
And, yes I have Rugosa seedlings die anywhere from just after germination till they are small growing seedlings. I even had some forming beautiful little bushes, but suddenly when the branches grow to a certain length the end wilts and begins to die. I pruned branches off but next branches did the same thing. I wasn't sure if it could outgrow that. I don't know if it did or not, left it behind in the move. I can't remember if that was only crosses with Rugosa (wide cross) or I might have had that with Spin crosses also.
Great job on that rose Rob, it's a beauty!
Duane

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