I suggest that now is the time to do the long shots. Pollinate your fast ripening diploids (such as rugosas) with tetraploid pollen. Most of these will probably not take and those that do will probably be sterile triploids. But, look at how important New Dawn turned to be!
Rugosas are odd. I’ve had more success using tetraploid pollen on Hansa, re: number of seeds, germination rate, than from diploid pollen.
What about using r. banksiae normalis with a tetraploid. Does it make a decent parent? I"m really new to this. You said that those that take will probably be sterile triploids. I had thought that this was a certainty. What else could they be? I have read that some triploids that produce alot of pollen sometimes make good pollen parents. So what would be the resulting ploidy of a tetra x tri?(if it took, if they germinated if, if, if) I can’t get any more specific information.
Thanks,
Julie