A whole lot of fruiting perennials spring to mind for me. Particularly when you factor in how many of them are ornamental, shade tolerant, drought tolerant, and/or nitrogen fixers.
Currants are delicious, thornless, very easy to clone, and have a lot of variability in flavor. On top of that, there are a whole bunch of different species that could be crossed in interesting ways, some native to Europe and some to North America.
Gooseberries are closely related, and could use even more breeding attention. They’re even tastier, but unfortunately almost all of them have nasty thorns. Captivator comes close to being thornless – it has small, soft thorns as a baby, and no thorns at all when it’s mature. Gooseberries can be crossed with currants: jostaberry is a thornless gooseberry / black currant cross. So there are tantalizing hints that it’s possible to breed these for thornlessness and maintain deliciousness.
Seaberry has a lot of potential. I think it’s not really there for most people yet, but with a small amount of breeding work, it could be. Right now, they’re very sour and thorny, but I’ve seen at least one person showing a bush they grew from a seed that was thornless and tasted exactly like tangerines. It was a random seed from a batch of 200 seeds they bought online. This is particularly interesting because it’s a nitrogen-fixing bush with a very high fat content. If the taste could be improved and the thorns bred out, this would be a highly desirable crop nutritionally.
Beautyberries are beautiful, native to North America, and I’ve heard they have a very mild flavor, almost tasteless. The flavor is pleasant when it’s concentrated, however. These could be bred for stronger flavor. They’re thornless, and their leaves are a mosquito repellant. A tasty ornamental that repels mosquitoes and doesn’t take up much space or leave a mess? Everyone wants that!
Goumi berry is another nitrogen-fixing bush. There’s not a lot of variability in flavor – most people seem to say all their varieties taste like mildly tart cherries – but they’re supposed to be tasty and productive, and they’re not invasive, unlike their cousins, autumn olive and silverberry.
Prickly pear could be bred to be completely thornless. Right now, the closest it gets to being thornless is to have no giant thorns, but still all the particularly nasty tiny glochids. If this species could be bred to be glochid-free, and still have delicious fruit, wow.
Dragonfruit would benefit immensely from having its thorns bred out and its cold hardiness increased. Right now, only one seedless cultivar exists: Sin Espinas. It apparently has a very good flavor, though it’s not among the very best or among the most cold hardy. Making a lot of crosses with it, including backcrossing to reinforce the thornlessness as needed, may be good way to breed top-notch-flavored and/or more-cold-hardy-than-most thornless cultivars.
Feijoa seems to have a fascinatingly large amount of untapped potential:
Loquats, which are mostly grown as ornamentals, may have just as much untapped potential waiting for someone to breed them seriously.
Chokeberries may, too. I gathered fruit from a local wild tree this year, and the jam I made from the fruits tasted almost exactly like blueberry jam. The fruits are very tart and astringent raw, unpalatably so, but if they can be used to make “blueberry” jam in a place that has hot dry summers and alkaline soil, on a small tree that’s productive and thornless and grows wild in a desert . . . I mean, that’s interesting.
Spicebush is a shade tolerant bush that is native to North America and hardy to zone 4. The whole plant, from berries to leaves to twigs, is edible and tastes somewhat similar to cinnamon and clove, which are large tropical trees. It seems to me that a lot of breeding could be done with it to produce cultivars that taste just as great as the large tropical trees, and can be grown in a small space in a back yard.
Tulips, stocks, cannas, and dahlias are all edible flowers that taste good and have been eaten extensively in the past. They’ve fallen out of fashion to eat in the past century. I say let’s bring them back and start breeding them for flavor again.
The same goes quadruple for roses. They used to be bred for their fruits, as well as their flowers. Rose hips are delicious. Rose petals are delicious, too. Let’s breed better-and-better-flavored thornless roses that make big yummy fruits.
Yucca aloifolia and Yucca baccata are unusual yucca species that make big, tasty, sweet fruit. Super drought tolerant, being desert plants. And yes the tips of the leaves are poky, but you can snip those tips off with scissors without hurting the plant (many people do that with yuccas in landscapes), so that’s a lot easier to deal with than thorns. Both species’ fruits have been prized by indigenous people.
The most common yucca species, Adam’s Needle, is equally edible. Do you want an extremely drought tolerant, perennial, hardy to zone 5 green bell pepper? That’s what their flower petals and immature seed pods taste like.
Che and jujube are drought tolerant fruit trees that could be bred for better thornlessness. Their fruits are tasty and often enjoyed in Asia. There are a few thornless cultivars of each species. Not many, but the fact that there are some shows that it’s possible.
Carob could be bred for greater cold hardiness and longer shelf life of the green pods, which are supposed to taste delicious, so that they could be shipped to people in colder climates.
The same goes for ice cream bean.
Hopniss and hog peanut could be bred for greater flavor and productivity. Both are perennial protein crops that aren’t tree nuts, so they could be very useful nutritionally.
Prairie turnip (Pediomelum esculentum) needs to be grown more often, period. Select it for whatever you want – just grow it, and eat it, and share it. It used to be a very common food for indigenous people, it’s said to be delicious, and it’s now extremely hard to find because of all the habitat destruction to turn wild prairies into farmland. I think it deserves to have its seeds spread everywhere, so that the species can keep thriving and delighting many people.
Pigeon pea would benefit from faster days to maturity, so that it could be grown as an annual in more northern climates. Same goes for moringa. More cold hardiness, so they could be grown as perennials, would be nice, too.
Miracle fruit could use a lot of breeding attention to get a little more cold hardiness into it. Right now, it will die if the temperature hits freezing (32 degrees Fahrenheit). But it’s in the sapote family, so maybe it could be crossed with white sapote, which is said to be delicious and hardy to 24 degrees Fahrenheit. Miracle fruit could also use breeding attention to make the fruit more flavorful and delicious, which might happen if you crossed it with white sapote. This species is particularly worth putting a lot of breeding effort into because the miraculin it contains is unique: we’ve never found it in any other species. Imagine what you could achieve if you crossed it with white sapote, or any other delicious fruits in its family.
Any delicious tropical fruits, in general, would benefit from being landraced in zones they can barely survive in, and handing their seeds over to zones just a wee bit colder. (Obviously bananas and citrus are other examples.) Betcha a few dozen people doing that per species could accomplish a lot in a mere few decades.
