It seems like everyone is crossing different species of stone fruits these days, so I was wondering if anyone had tried European plums (which are hexaploid) with any of the diploid plums (Asian or American) or any of the other diploid species, like apricots, cherries, or peaches. The offspring would be tetraploid, 3/4 European plum and 1/4 other species.
I suspect the resulting tetraploids would have fertility problems, as the chromosomes wouldn’t line up perfectly during meiosis, but 4 is an even number, so they might be able to reproduce. Tart cherries are tetraploid, and they set fruit fine.
It seems like a crazy idea, but crosses like this have been done between hexaploid and diploid blueberries to get fertile tetraploids, so there is a precedent.
The number of chromosome doubling that strawberries are subjected to is mind blowing.
When it comes to crossing chromosome counts can be overcome. Tart Chery can still back cross with both parents. European plums like tart cherry’s arose from a natural cross the tetraploid sloe and the cherryplum. Cherryplums have been crossed with Japanese plums before. Sloes have been crossed and recrossed to produce various bullace plums. Assuming chromosome doubling does not have to be preformed first issue is the widely different bloom times. One could keep a Japanese plum in cold storage till euro plums blossom or you could store pollen at -25c till the partner tree blooms. Does not seem to feasible for the back hard orchardist.
Pollen storage seems like the easy part, as it can be done in an ordinary freezer.
https://ucanr.edu/repositoryfiles/ca707p12-71852.pdf