R. acicularis and some questions about ploidy

A while back in the cold hardy yellow climber thread, it was mentioned that R. acicularis could be crossed with a diploid and that would yield tetraploid offspring.

I thought this was fairly interesting and started looking into this a little bit. I came a cross a blub on the ARS website. It listed 2 forms of R. acicularis. R. acicularis sayi and R. acicularis acicularis. Sayi is a hexaploid and acicularis is a octoploid.

My first line of thinking was about sayi. Crossing it with a diploid yeild would tetraploid. How sucessful is this? In looking at the offspring on helpmefind.com, there didnt seem to be an abundance of them. Th


I have researched the literature of Rosa acicularis in North America extensively, and I have never seen any scientific evidence that it is an octoploid on this continent. Supposedly the octoploid form grows in the far north, but who originated that statement? No one knows, but it is accepted as fact.

Rosa acicularis sayi (also known as R. bourgeauiana and R. engelmanii) supposedly is a sub-species of Rosa acicularis but that is incorrect. There are many different phenotypes of Rosa acicularis, so it is ridiculous to identify any of them as a sub-species. Taxonomically, Rosa acicularis acicularis is also incorrect. That’s Modern Roses for you; it’s full of mistakes regarding the identification of species and rose cultivar parentages.

Crossing, for example, the diploid rugosa with the hexaploid acicularis is very easy. It’s been done three or four times by Canadian hybridizers, including myself. Resulting cultivars include Robert Erskine’s ‘Carlos Dawn’ and 'Georges Bugnet’s ‘Lac La Nonne’. These are tetraploids and valuable for further breeding. ‘Therese Bugnet’, since it is a diploid likely has Rosa woodsii and not R. acicularis in its parentage.

Yes, there are a lot of “interesting” diploids out there. Perhaps the most valuable to work with are the Rosa multiflora and R. wichuriana species. The former is valuable for increasing floriferousness and the latter for improving disease resistance. No question, both should be crossed with Rosa acicularis to develop relatively hardy tetraploids. These tetraploids can then be used to hybridize with modern roses (or OGR’s for that matter) to develop new types of roses.