For anyone wanting to learn more about this breeding technique, it's called backcrossing[1]. It's also used for agricultural crops, but requires many generations.
Simple, yet effective. I've heard it said modern fruits are relatively tasteless compared to their older counterparts because they are bred for size and hardiness. I wonder if these can be backcrossed as well to produce more flavorful fruits with similar sizes
I imagine soil quality and time of harvest also play a decent part in taste. All other factors being equal picking a green tomato isn’t going to be as good as letting it ripen on the vine naturally.
Terroir is the term for this. It's variation in flavour isn't as great as varietal/strain based differences. But yes it does have some impact most commonly taken advantage of in wine production.
Fresh they taste almost like sweet corn, I got to try a few American chestnuts last year, they are sweeter (but smaller) than the chinese chestnuts. My landlord boils the chinese one and eats them like mashed potatos, I roast them in oven or air fry them. To me they are like bread from the trees.
The English ones are starchy I guess? These are common to see in grocery stores when in season.
Also handling changes how sweet they get, some say they must be chilled in fridge for some days to get starches to convert to sugar. For me the Americans are perfect no matter the treatment. Chinese chestnuts I'm fighting getting to them fast enough before any mold grows, processing them immediately to kill chestnut weevil (I use a sous vide and let them sit at whatever temp the rutgers publication suggested to kill potential eggs) then I dry and fridge them for a few days before putting them in oven/airfryer. It sounds like a pain in the ass but it's a lot easier and less foul than the year I gathered and processed gingko seeds (which smells like dogshit) or even black walnuts which will stain your hands for over a week if you don't know to wear gloves.
Another protip: Don't plant a chestnut tree near a swimming pool. Those spines are sharp enough to pop a bicycle tire and the catkins smell like a callery pear when it's dumping pollen which is pretty gross.
Dude I have just the recipe for you. Come on down to Chile and ask for puré de castañas. The really oppressed Chilean women make it the best, it's highly unique, I actually thought I could eat a chestnut because I used to eat this dish, kept biting into absolute bitterness. But bitter isn't bad, now that I'm addicted to something bitter (an undisclosed stimulant) I prefer bitterness to sweetness, but not everyone can be an addict, the addiction doesn't always take. Too bitter. Just like the American Chestnut didn't always take. Too bitter.
Love the bitterness. And in the dish there's a trace bitterness natural to the chestnut left in the puré, which involves sweetening chestnuts and also some I think crema Chantillí or leche condensada not sure which.
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Let me add that in my unique Chileanized upbringing, as an American, a Chilean woman, in this unique case not oppressed, explained to me why I couldn't eat a cactus fruit, what's it called, tuna (no relation to fish in absolutely any way). So typically, she explained, gringos bite it wrong. They think you gotta bite it till your jaw closes, your teeth meet up again after that long goodbye when you put the fruit in your mouth. No, you gotta close your teeth less, not chew, no no, and she explained it to me in plain Spanish in a way I, a Chileanized American, a gringo, a gringuito (and in fact there was a movie about a Chileanized American called El Gringuito in the late 90's in Chile, huge hit), how to eat the native fruit. But I was a kid. This partial chewing made it good to eat, I can vouch. They would never tell you to only chew partially of politeness. But I can. I'm passing that on, to eat tuna fruit, work on your bite, don't bite all the way, like almost. Because it has a lot of seeds, very hard seeds, you see, so biting it all the way hurts, so you hate it.
For an example, the red delicious apple. 75% of the Washington state's apples in the 1980s. It was bred for color and shelf life and, in the process, they bred out the taste. In 2000, a congressional bailout was approved for the growers that had lost $760 million dollars over a 3 year period due to the now-worthless apples.
The hard thing with taste is that it's usually the sum of many quantitative traits, each one being governed by several genes which can be located on different chromosomes, as seen in tomato[1]. Transferring enough of them into the modern genome through backcross would probably require a crazy amount of generations... or a crazy amount of luck :)
You would need to map the relevant loci and then use a speed congenic selection strategy. Done in mice easily. Mapping the loci modulating traits like disease resistance or taste is the hard part.
[1] https://en.wikipedia.org/wiki/Backcrossing