Re: hybridizing for white.
I have an unproven theory on how to increase the odds of getting a white flower from a cross. If a Dahlia has been a stable sport to white ( e.g. White Onesta), then it's genetic color code becomes dominant, or to use computer jargon, the color is "null". I think my white waterlily 23061 may have had the pollen parent of White Onesta. Another example: The Alloway Candy plant I have is almost white ( not quite a full sport to pure white), and I observed several of its seedlings were pure white. As I listen to @Teddahlia say how rare it is to breed white Dahlias, I came up with a possible explanation of how I could have so many white seedlings.