<< I think that finding someone who has done research into the specifics of “which gene does what” would be helpful in this quest. >>
I have no evidence that such research exists yet.
<< The Russians, though, clearly have a vested interest and a history of attempting to improve cold hardiness and fruit size concurrently.>
Right but all the Ukrainian (not Russian) work has been with astringent varieties, Asian and American. Only the Japanese and Korean work focuses on non-astringents.
<< Is it known what mechanism in DV or Hachiya causes astringency, and are they actually different genetics? If they are the same genes and we know they could be suppressed with certainty, then the quest is worthwhile. >>
IDK. It seems that the mechanisms are different (maybe merely different tannins) because CO2 / alcohol treatment works in Asian PCAs but not in Americans.
I think a key question is whether the genes occupy the same spots on their respective chromosomes. So then is a hybrid either-or or both-and?
<< I wonder if it would make sense to attempt crossing the Chinese LTTS with JT-02? If you have a higher probability of a dominant non-astringent gene being transferred that could then be bred with DV, would that make the odds drastically reduced and allow for selecting a better tasting seedling instead of hoping for a few that have the one trait you are attempting to replicate? >>
When and if LTTS is available, I’m sure lots of growers would try crosses of LTTS with desirable varieties that would be improved by the removal of astringency. I have no idea whether LTTS produces male flowers. No doubt the crosses would be easier with Asian PCA Kakis than with Virgniana.
<< Would having a DV as the male or female be beneficial in either scenario in a series of back-crossing? >>
Almost all Asian PCNAs are female. Given that PCNA is recessive, that would be an insurmountable problem – all crosses would require a dominant astringent male – except that there are male flowers on a few PCNAs. So the few PCNAs that bear male flowers are very important. Taishu, which has been the pollen donor in most modern crosse, is monoecious. I believe that the same is true of some of the Goshos, which were used extensively in earlier work. Fuyu and Jiro produce some male flowers sometimes, but not routinely; so they have been used occasionally.
<< I’m mostly rambling but just trying to get some thoughts down before they disappear. I don’t have enough background in biology to figure this stuff out, just enough knowledge to get myself in trouble. >>
No worries. I’m only a step ahead.