I picked up seeds for all the varieties of Allium fistulosum x cepa that I could get my fingers on with the idea of 1) generating a landrace with them and 2) breeding some new walking onion type creatures. As many of you know, walking onions are hybrids of A. fistulosum and A. cepa. But they make top sets instead of seeds because the hybrid is infertile. I'm fairly certain that these grow by seed varieties have twice the number of chromosomes to enable them to regain fertility (they have a pair of chromosomes from both parent species so that the chromosomes can pair up during meiosis, which makes them a new perennial allium species we can help develop for our permies needs).
One thing I'm planning to explore is what happens when these tetraploids are crossed back to their diploid parents. I'm particularly interested in crossing them back to shallots and potato onions just to see what happens. I'm expecting them to become top setting onions like walking onions since they will be triploids...but I have no idea. Maybe they'll retain some fertility and set seeds that carry odd numbers of chromosomes? I'm kind of hoping to find some plants that top set larger bulbils that taste like shallots, but again, no idea. Has anyone played with these?
One thing I didn't know is that if you cut off the individual flowers, not dead head, of an Allium that you will get top sets. What a neat way to make lots of clones fast of a desired Allium.....nice way to share too! My interest in this case will be in doing this to the seedlings I get from my packets of hybrids to see how large their bulbils get and how much variation in that trait there is. Then when I make a landrace from them I'll repeat it to see the same among the individuals so I know which ones I may want to do further breeding crosses with.