So, if diploid pollen (as in from a tetraploid rose) has a competitive advantage, as has been shown to be the case, and pollen from a triploid rose can be expected to be a mix of diploid and haploid pollen, then it stands to reason that reciprocal crosses between triploids can be expected to show, on average, a greater influence from the pollen parent. Right?
I’m not good with the terminology. The ovules, or whatever, should also be a mix of diploid and haploid, right? That is, if you smeared uniformly diploid pollen (as in from a tetraploid rose) onto a triploid rose, very loosely half of the resultant seedlings should be tetraploid and half should be triploid. (Assuming there isn’t any competition amongst ovules in the way pollen grains must compete.) They would carry either 50% or 33% of the seed parent’s genes.
If you used that same triploid rose as a pollen parent onto another triploid, and for the sake of argument all of the pollen grains that got lucky were the diploid ones, then the resultant seedlings would carry either 50% or 66% of that rose’s genes.
I’m thinking in this case specifically of Prairie Joy, which has so many nice characteristics, but has an annoyingly low percentage of repeat-blooming offspring. I suspect that with crosses between Prairie Joy and a fully remontant modern rose, you would see a higher percentage of reblooming seedlings when using Prairie Joy as the seed parent.
I haven’t carried out any reciprocal crosses with PJ to test this theory, but I know I have a lot of seedlings of PJ x All A Twitter that have fairly uniform characteristics and have not shown juvenile remontancy. This year I’ll do the reverse cross and we’ll see if there is a greater percentage of juvenile remontancy.
I remember someone on this forum (Johannes or Jinksy?) talking about using a micro-mesh screen to separate out PJ’s haploid pollen.
I think you are right as best we know about triploids. But I suspect that it’s complicated by linkage disequilibrium. Things tend to hang together so 66 % from one parent or the other may not show up that prominently in all cases. My example is Rainbow KO which seems to do fine on tetraploids, and I know in some instances the offspring are highly fertile, not likely triploids themselves. But many of the plants don’t resemble RKO a lot while others clearly do. I don’t think it is simple blending inheritance of most traits.
From a few crosses last year onto Dr Huey I got a few seeds and had 4 that made it past germination. Two of those look very much like Dr H, one looks strikingly like RKO, but no flowering this first season and the 4th is much like RKO, again no flowers. My interpretation is that I probably have 4 triploids but two are weighted by Dr H, the other 2 by RKO. However, as discussed in the newsletter, it takes only 1 copy of the once-flowering gene to over-ride up to 4 of the repeat-blooming version. Once I have blooms, I can look for whether seeds are produced, whether those are fertile and whether some repeat-bloomers show up.
This production of Rainbow Hueys is not a fluke. I pollinated over 100 Dr H. flowers with RKO this year and have more than 10 hips, hopefully more than 10 seeds. Maybe a disease-resistant rootstock lies ahead?
More likely a disease ridden, once-flowering shrub.
Thanks, Larry. I’ll have to check if I get any reciprocal crosses with Prairie Joy this season, and grow them side-by-side for a comparison.
Fertile triploids are fun, because you can use them on either diploids or tetraploids and there should be something that lines up. I don’t let ploidy mismatches stop me from trying any crosses, though.
Looking over my 2012 seedlings, I made a mental note to use RKO more next year. Good vigor and health. Reports of leafspot defoliation in the Twin Cities give me pause. I don’t have leafspot here on RKO or William Baffin, so I have no way of testing seedlings for susceptibility.
I have a sorta nice Prairie Joy x RKO (or vice versa) that has lots of well-formed blossoms that fade to a tannish color (and never drop, similar to RKO). Floriferous. Very fertile, it seems, so I think I’ll grow out some OP hips. I’ll have to check the direction of that cross.
This year my only RKO seedlings, about three, were from a mixture of pollen from Smoothie and Henry Hudson. All are blooming young, and two seem to be Henry Hudson seedlings because they have a sort of pure, blush pink that doesn’t have the tannish, yellow undertones I would normally expect from RKO. One is double in a rugosa-type of way, while neither have rugose foliage. It’s exciting because both are fully remontant, but should be hardier than RKO. I’d like to repeat this cross.
RKO definitely has its good and bad points. I’ve found that in crosses, the petal-holding trait is not unreasonably strong. In selfs it is, making some really tacky looking bushes.
I’ve also found that the red color in some crosses is phenomenally intense, for instance with Golden Monica or Golden Slippers.
RKO rarely gives yellow without red, but it does in 1-2 % of selfs. So I keep hoping that it will work the same in crosses.
Kim may be right about the large majority of Dr. Huey x RKO. But I only want 1, and if it’s a rootstock I don’t really care about flowering cycle, more about thorns and winter hardiness, ease of rooting and general vigor.