How can this happen? Dr Eckener???

I was looking at 1st gen. hybrid rugosa on HMF to try and get a feel for how it breeds (in terms of form not ploidy) when put with tetraploid roses such as HT and found a rose called ‘Dr Eckener’. Just wondering if someone can explain this… it’s not making sense to me… ‘Dr Eckener’ (see link) is a 1st gen. hybrid rugosa. Rosa rugosa is a diploid. It’s other parent is a HT called ‘Golden Emblem’. I was readng that most HT are tetraploid but some of the earlier ones are triploid. If ‘GE’ is tetraploid then the most likely outcome of this cross should be triploid offspring right??? ‘Dr Eckener’ is listed as being a tetraploid. I’m a little confused as to how this could have happened. The only things I can come up with is that R. rugosa made a 2n gamete. Even if ‘GE’ was triploid instead of tetraploid then the most likely outcomes would be diploids and triploids wouldn’t it? So where does this tetraploid hybrid rugosa come from?


There are several was to explain this. First, sometimes a breeder will fudge a parentage. Dr. Eckener may actually be a OP seed of a first generation seedling. Breeders simplified the parentage quite often back then. I think they did it because the didn’t want people to know the true parentage.

Second, some diploid plants develop unreduced eggs so they will be 2n instead of 1n. Robin Hood is good for this, several of it’s offspring are tetraploid.

Ahhh… so a 2n gamete IS possible… I will be going back to HMF now and doing an advanced search putting tetraploid in to see if this is an isolated thing…

Hmmmm… it didn’t work… I just get a blank screen with no message saying it found no matches… oh well…

That’s a great point Paul that simplifed pedigrees are probably used. It would sure be great if we could just take things at face value and it was true. It makes me sad too that for the pedigree of Knock Out, for instance, it seems that to make things easier it is just listed as a ‘Carefree Beauty’ seedling and a ‘Razzle Dazzle’ seedling. In our RHA newsletter Bill Radler shared with us the pedigree. It would be a really long list of cultivars with parenthesis and brackets if Modern Roses or others printed the whole thing.

I’m amazed how tender Dr. Eckner is if it really was a first generation rugosa hybrid. Maybe there is something missing in the pedigree like you suggested Paul. From the project Paul Barden and I did looking into the bracteata hybrids it was interesting to find tetraploid offspring from a diploid x triploid cross (‘Out of Yesteryear’ was the triploid). From looking at the pollen from the triploid it looked like it could produce some 2n pollen as some pollen had the diameter expected for all three sets of chromosomes being included. Hmm. Maybe Dr. Eckner has one set of rugosa chromosomes and if the male is triploid, a 2n gamete bringing along all three sets of chromosomes leading to Dr. Eckner being 1/4 rugosa. Just an unfounded speculation.

It’s amazing all the exceptions possible in meiosis with roses and I think the wide hybrids we work with helps to facilitate this. I’m amazed that as I’ve looked carefully and did chromosome counts on out of the ordinary seedlings, finding haploids from tetraploid parents among seedling populations has been possible, triploids from crosses of two tetraploids, 2n and 4n gametes, etc.


Another rose from similar breeding is Rokoko (shrub, Evers/Tantau, 1987) White Hedge (2n hybrid rugosa that is known to throw 2n seedlings)