Why can’t one take a seed from a Comice pear and use it to grow a Comice pear tree that produces quality pears?
In: Biology
I’m not sure this is exactly the same reason for Comice pears, but it should be similar for all supermarket fruits:
Imagine you had a wild pear with a gene that determines seed size. Two copies of a gene work together to determine the size of pears, and each copy can either tell the pear to make big or small seeds. The gene for big seeds happens to be dominant, meaning that if it is present alongside a gene for small seeds, the small seed gene is ignored. So far so good? Now imagine that the small seeds can’t actually be used to grow new pears, because for instance they aren’t mature enough or are easily digested/decomposed (think seedless watermelons). This means that in nature, small seeds are selected *against*.
Humans come along and like the qualities of the pear with small seeds, but we couldn’t just breed small-seeded pears with each other, so instead, we take big-seeded pears with one copy of the small seed gene, and breed those together. What you get after breeding these pears 100 times is about 25 pears with two big-seed genes, 50 with one big and one small, and 25 with two small-seed genes. The first 25 are discarded, the next 50 are saved for future breeding, the last 25 are what you see in the supermarket!
You can! Pear trees don’t grow true from seeds, meaning the characteristics of the pear you harvested the seeds from aren’t likely to show up in the tree you grow from those seeds. However, if you grow a lot of trees from one particular type of seed, you’ll probably get a few such trees. Then you can use the rest of the “failed” seedlings as rootstock.
In order to grow the type of pear tree you want every time, you have to use cuttings/buds from live pear trees, rather than seeds. This is the same as with most berries.
The Problem is, that for the flower to become a pear it needs to be fertilized.
But you can not control how your flower are going to be fertilized.
So in the end you don’t know what genes are in your seed because it could have beend fertilized a different variety of peas.
And even if you are sure that is the same variety you want to make sure that the peas you harvest will be the same again.
For this reason pears (and apples and some other plants) are cloned because that is the only way to make sure that you geht the exact same fruits from every tree.
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