The problem of these hybridizations is multiple.
First of all the size of the pollen and the shape and size of the receptors. This is the first step before genetic problems.
But for those who recall children’s games where you have to put the square shapes in the square holes, the balls in the round shapes… we see that with a slight difference in size, our child managed to make a triangle fit into a square.
It is the same for pollen.
Then if the fertilization this product, and it is viable (because many seedlings will lack food reserves, others will be albino…etc).
The last step will be genetics. Because if a pair of chromosomes is missing, the hybrid will live but will be sterile. The doubling of the genetic material makes it possible to make the hybrids fertile. This is what has been done for cereals, for example Titical, but also for hybrid wheat, which today finds a number of chromosomes disproportionate to the original varieties.