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atomfullerene t1_jedsuqu wrote

There are three basic ways to do this.

For long-lived vines, bushes, and trees, it's done by cuttings. You find a rare mutant plant that produces good fruit with no seeds, then take cuttings from it. You root those in soil or graft them on to roots, and you essentially make a bunch of clones of the original. This is how it works for bananas and grapes.

For annual plants, it's done by hybrids. For example, seedless watermelons are made by hybridizing two strains that produce infertile watermelons with few seeds. It's a bit like breeding mules.

Finally, in some circumstances you can get seedless fruit by preventing fruit from being pollenated. This is how pineapples are kept seedless, for example, and it's why Hawaii was a major pineapple producer. There were no native pollinators that would pollenate the fruit, resulting in seed free pineapples.

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CuriousHuman111 OP t1_jeemwn7 wrote

That was really interesting, thanks.

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wildfire393 t1_jeg3nog wrote

The trick they do with seedless watermelons is really neat.

Basically, they have strain A of watermelons that produces seeds. They take it, and make strain B by doubling up every chromosome. The chromosomal composition of B is the same as A, so the resulting plant behaves the same and still produces seeds. You can then make offspring plants with one A parent and one B parent, taking half the chromosomes from each - so it gets, for instance 15/30 from A and 30/60 from B. The resulting plant is still chromosomally equivalent to A and B, but it has an odd number of chromosomes - 45. So when it goes to create sex cells (which grow into seeds), it can't, because those require that the chromosomes be evenly split. So it grows fruit that are identical to A/B, but that don't produce seeds.

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avalon1805 t1_jeflsvl wrote

Wait, pineapples have seeds?! Damn, you just messed my head real good

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atomfullerene t1_jefpoc0 wrote

well, most of them don't, but they would if they were fertilized. It would look like this

Interestingly, pineapples almost never reproduce by seeds. Even in the wild, most of their reproduction is vegetative. Why? Their huge, spiny fruits are adapted for being eaten by the extinct megafauna of South America. Ground sloths, Gomphotheres, etc. When those animals went extinct, pineapples and their relatives lost their usual means of dispersion and had to limp by on occasional lucky seed spread and vegetative growth...until humans started growing them.

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