Teddahlia This is very nerdy and full of questions you may have already answered elsewhere. I apologize if that’s the case.
It is surprising to me that there are any white dahlias at all given the number of chromosomes involved. The mutation(s) must be strongly dominant? Is it known whether the genetics affect the mechanisms behind the synthesis itself - ie. can’t produce a certain compound(s) - or alter the conditions in which the synthesis occurs?
Enzymatic reactions are very sensitive and highly specialized. Is that also why dahlia color expression varies so greatly depending on environmental factors (soil pH, ultraviolet radiation, temperature, etc.). Is anthocyanin synthesis, or its interruption, an origin of varietal sports? Which may also be why some are so hard to capture? I know you’ve mentioned irradiated seed being rumored to have been used, but what about on a plant itself? Has anyone ever tried growing under controlled manipulation to get a sport?
https://en.m.wikipedia.org/wiki/Anthocyanin