First, a warning: Not infrequently, I come up with what I think is a really good idea for somebody else to work on. This is one of those.
Next, some background: I’ve been using some spare time during winter to become better informed about persimmon varieties, including hybrids and recent releases. This is a result, but I freely admit that I am a total novice so I may be totally wrong for reasons that I don’t yet grasp.
Now the point: It strikes me that the American/Asian hybrid JT-02 / Mikkusu is something very special. It is a direct cross of an American variety (Josephine) with a Japanese non-astringent PCNA (Taishu). So the genotype is half non-astringent. [Unfortunately, the phenotype is still astringent because the Japanese NA trait is recessive.] Moreover, in contrast to other pure PCNA hybrids in Japan (including Taishu itself), JT-02 is very cold hardy. It is also reportedly very tasty.
So I have to ask: Isn’t the obvious next step a back-cross of JT-02 with an Asian PCNA, maybe Taishu itself? Aren’t we one step away from a non-astringent hybrid? As noted in another thread, Taishu reportedly tastes great – it sells individually wrapped in Japan for the rough equivalent of $30 apiece! So back-crossing to Taishu would probably not compromise flavor. And it produces male flowers.
Of course, we’d have to test MANY crosses. In their PCNA breeding, the Japanese test thousands of offspring from each cross before ever selecting one for release. If my math is right, only 5% of the crosses of JT-02 x Taishu would be non-astringent. That’s [3 chances out of 6] x [2 chances out of 5] x [1 chance out of 4] – 50% x 40% x 25% = 5%. Plus we’d want to optimize taste and hardiness. Even so, a cold hardy, good tasting, non-astringent Asian/American hybrid seems within reach.
Reportedly, the Japanese breeding program shifted after 1992 from mainly crosses of PCNA x PCNA to (a) crosses of non-PCNAs with the Chinese PCNA (e.g., PCA x C-PCNA) and (b) crosses of non-PCNAs with both crosses and back-crosses of the Japanese PCNAs (e.g., PCNA x PVNA or PCNA x [PCA x PCNA]). As far as I know, there have been only two subsequent releases, Taiten and Taigetsu, both PCNA x PVNA and classified as PVA. So no reported successes so far with PCNA x PCA, maybe because it takes time to work through two generations.
Finally, based on published reports, there is only one other hybrid that is a cross of an astringent American or American-Asian hybrid with a PCNA: Reportedly, NBT-01-08 is a cross of Nikita’s Gift x Taishu. This could be another good candidate for back-crossing. Obviously I could be missing some cases, and I can’t know anything about work that is not yet published.
Bottom line: Shouldn’t we – and I use the pronoun “we” loosely – be back-crossing the crap out of JT-02 / Mikkusu with Taishu and/or any Japanese PCNAs with pollen?