I understand that you can cut off a branch of s tree and stick it to another tree to get fruit of the original one. But then why don’t you get that exact fruit if you plant seeds of it? But then, there’s other plants where you get the exact same fruit that you ate if you plant it.
In: Biology
Ok, a bit late to the party, but I do not agree that it has to do with self-pollination, since such plants can still accept pollen from outside. And even accepting own pollen doesn’t guarantee anything on its own. It all comes down to genetics and the fact that not all genes manifest. Think about yourself, you surely have some traits your parents don’t have, because you inherited them from your grandparents or even more distant ancestors. When you breed two plants together, even if they are identical, their off-spring can be diverse and manifest “new” traits. It’s the same mechanism.
So, to make the results more predictable, we started to select plants for traits we want. In this way, the population gets less and less diverse with each round as more and more traits get eliminated. Eventually all plants are identical and their off-spring is the same. Hence, we have a new variety (we do the same with dog breeds for example). Now, this process is costly and takes time. So sometimes it is not the best option. Many fruit trees can be grafted (and you have to wait several years to get seeds from a new tree, so selective breeding is a very long endavour), strawberries can be cloned with runners, hop plants can proliferate in a similar fashion. In these cases it’s enough to have one plant with desirable traits, so they do not have to be true to seed.
It is worth noting that selective breeding often makes plants weaker, since some positive traits are not easily seen (for example resistance to a particular parasite) and can get eliminated along the others. Also, if all plants are identical, any disease or conditions killing one plant will surely kill all of them. That’s why nature tends towards diversity.
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