MR12 shows about a gazillion variants, and 2 natural hybrids. It shows only 4x and 6x ploidies, although I had read previously that R. acicularis exists in an 8x form. The natural hybrids include one with R. rugosa, from Japan (no ploidy given) and one with R. macrophylla (R. persetosa Rolfe, and several other names), apparently diploid and known since 1895.
Peter
I had read that R.accicularis usually is 4x in Eurasia and 6x in North America, and that 8x is rarely if ever found.
Here is a previous thread regarding R.acicularis.
Link: www.rosehybridizers.org/forum/message.php?topid=11227#11405
I have several small seedlings of ‘Hansa’ x Rosa moyesii ‘Geranium’. There is not much evi- dence of Rosa rugosa in the foliage. Cold hardiness has yet to be determined, because the seedlings haven’t gone through a winter outdoors. I’m trying to obtain Rugosas with a true red colour and not purple-red, and this may be the way to do it.
In the 1940’s or 50’s, the Canada Department of Agriculture tested ‘George Will’ (and ‘Wasagaming’) for ploidy and they were determinted to be diploids. ‘Will Alderman’ was not tested and hasn’t yet, so we don’t know what its ploidy is.
The link shows Will Alderman’s pollen:
http://picasaweb.google.com/HAKuska/MicroscopePictures02/photo#5110827175560994658
It looks like it is a diploid. That surprised me for in hybridizing I feel that it behaves like a triploid.
Link: picasaweb.google.com/HAKuska/MicroscopePictures02/photo#5110827175560994658
I checked up on Lady Duncan and it used to grow in San Jose Rose Garden and may be extinct. If this is true it’s a shame. I mailed with “Jedmar” that states:
“There is an old reference from 1937 which states a ploidy of 42 for ‘Lady Duncan’, which is unusual if the parentage is correct. On the other hand, the reference is actually quite reliable.”
Henry: Thanx for the info - I do not know how to interpret the microscope pictures - but I trust you 
Too bad about Will Alderman, for a second I thought the it was exactly what I was looking for: A tetraploid Rugosa. The reason for my search is that my little windy Denmark needs rose hedges made of other roses than just R. Rugosa, but the R. Rugosa foliage is perfect as a windbreak in Denmark - So some breeding is needed to get some bigger variety in bloom.
Cheers