I know that not everyone is a horticulturalist. Allow me to explain why this is dumb. It is true that for a crop like tomatoes, you might just grow any old mongrel seed, and that the tomatoes will still produce... even if yields are off 30% or 40%. Monocropping in that case is about increasing yields, not making the impossible possible.

This is simply not true with most orchard tree crops (or grapes, or about half the sorts of food crops you've enjoyed all your life). An apple, for instance isn't just a monocrop of closely related sibling plants... each Fuji or Pink Lady apple you've eaten is a genetic clone of any other of that type. They are literally cloned through grafting (and sometimes rooted cuttings). If we want to get really technical, each tree is technically a chimera, with only the crown being Pink Lady, the low trunk and roots will be something like M.111 (another variety that you don't eat it's fruit). Hell, sometimes there's even a third type in the middle of the two called an "interstock". What would happen if you didn't clone apple varieties? You wouldn't eat apples anymore. Every apple tree would produce its own kind of fruit, some might be just as good as Fuji or Yellow Delicious or any of the others you're familiar with. But there'd only ever be one tree of that. Apples do not grow true to seed. Some would be little golf-ball-sized crab apples. Others would be completely tasteless. Or dry and pithy. Or nasty-looking things that always split while growing. Maybe farmers would still grow them as feed for hogs (but productivity is also a genetic trait, and you've just struck a death-blow against having a large number of highly productive trees). Maybe they'd be grown to make alcohol (more applejack or cider than apfelwein I'd think).

But apples as a desert fruit would be gone.

And it's like this for many, many crops. Hell, even something like wheat... you can complain about monocropping, but these new varieties that they use actually resist diseases better (not to mention prevented who knows how many famines through increased yield). This is the argument of someone who whines about GMO crops and shops at Whole foods, a certain political type whose preferred policies seem designed to just make food more expensive and scarce.

>Another example is the Cavendish banana.

There are plenty of banana cultivars... few of them of the sort that people in the developed world enjoy. It's the same problem as all of the other. But for Cavendish (and a tiny handful of other varieties), you'd have no bananas at all.

You bring up apples and other orchard fruits. Yes, in production you want things like uniformity and yield. But from a long term survival standpoint, you want some diversity, such as through preservation of heritage varieties or allowing some seeds to grow and selecting from them. Otherwise, you end up with a very short list of possible options when faced with new diseases. You need some genetic pool to select resistant rootstock from. It also prevents things like genetic and epigenetic adaptations to the environment (see progressive cold hardening). Of course the economics of it discourages farmers from selecting currently inferior varieties for crops. But perhaps a biosecurity program could fill that gap.

You don't get to have that. It's just not an option. All these polyploidals do not work like that. You can have uniformity (which people want anyway), or you can have fruit that's so bad no one wants to bother growing it. There's no middle ground.