Biology is the closest I could find to botany on SE. Grafting can not occur naturally and so if a fruit does not have seeds there is no way it could reproduce in nature.

That logic makes complete sense to me so I am wondering why seedless fruits claim to not be GMO?

Take for example, Satsuma oranges.

Were they somehow crossed like a mule? See here. And then grafted over and over again?

It appears they occur naturally and are then grafted. See here.

So the deeper question is does grafting create a "clone" of the grafted organism?

And deeper yet, what defines genetically modified ( GMO ) from simple genetic variation?

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    $\begingroup$ The production of seedless fruits is quite well described on: en.m.wikipedia.org/wiki/Seedless_fruit $\endgroup$ – tsttst Dec 30 '18 at 7:16
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    $\begingroup$ Pick a question, but most of your issues can be answered by asking what is a GMO, because the answer is nobody can agree. $\endgroup$ – John Jan 2 '19 at 0:17
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    $\begingroup$ @jamesqf ????? Huh?? Not at all. And in fact, such a question best belongs here on Bio.SE $\endgroup$ – theforestecologist Jan 7 '19 at 4:27
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    $\begingroup$ @anongoodnurse (and John) It's not too tricky; but rather it's surrounded by a lot of misinformation. The term "GMO" is strictly applied to genetic modifications due to human-mediated transgenic manipulations. The genetic variation that arises from cross-breeding (even if it's "unnatural" in a cultivation setting) is simply a "natural" result of subsequent normal biological processes. Such crossbred crops do not have their genes modified directly by humans and are therefore considered to simply be "crossbred" and not genetically modified. $\endgroup$ – theforestecologist Jan 7 '19 at 4:39
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    $\begingroup$ @anongoodnurse I think most scientists in the field would agree that it isn't all that conceptually different which is why any furor about GMO safety is a bit silly, the exception being the economic arguments, though there could also be an argument that the speed at which we are able to make changes makes it more likely that those changes will have unintended side effects. $\endgroup$ – Bryan Krause Jan 8 '19 at 19:56

GMO stands for Genetically Modified Organism.

Grafting a plant to a rootstock of another plant is a form of plant husbandry -- a farming technique -- but this isn't changing the DNA code of either of the plants. Sort of like you receiving a donated organ wouldn't be the same as Genetically Modifying you. When a desired trait arises in a plant this is a way to keep reproducing it without having to wait for cuttings or seeds to grow.

There are some plants such as seedless watermelon that are reliably made by crossing two seed species. You take two species of watermelon, Species 1 and Species 2. Both of these are normal -- they make seeds. When you cross them, you get seeds that grow into AB hybrids, seedless watermelons. These AB are infertile, so you have to cross A and B again each year to get more seeds to plant.

Species 2 has twice the number of chromosomes as 1. They are able to cross and make seeds that grow. But when the [1x2] plants grow and try to form seeds, those cells have an odd number of chromosomes. The process of making seeds and pollen -- meiosis -- has a step when half of the chromosomes go into one cell and half in another. Because there is an odd number, the process never finishes and you get no seeds.

to demonstrate how this doesn't work, lets look as a simple example. Species 1 has two chromosomes [A and B]. It has two copies of each chromosome in all of its cells (one from each parent), and just one copy in its sex cells

Species 1 Normal Cells [AA BB] and sex cells [A B]

Now, Species 2 has a different set up. It has twice the chromosome number Its normal cells are [aaaa bbbb] and its sex cells are [aa bb]

this means that when you cross pollen from one with seed from the other, you get [aaA bbB] or [AAa BBb]

When these crosses try to make seeds, its impossible to halve the triplet chromosomes.

True GM technology is used to do things such as, in olives taking the genes that cause oil production to occur, and copying them many times. This gives you more oil production.

Or, in tomatoes -- when you pick a tomato the cells of the skin start expressing a gene that makes the skin soften and break apart. This facilitates seed dispersal. GM deletes that gene, making the fruit bruise less, reducing need for packaging and quadrupling the shelf life.

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    $\begingroup$ The system has flagged you as a new user to me and other list members who help monitor this site. I have noticed quite a few other answers from you which have also been flagged as requiring additional references, so can I point you to the Help on Answering Questions. The reason we ask for supporting references on SE is if you post an answer, how do I or anyone else know it is right? What if someone else disagrees? One may feel: "this is my area" or "I taught this to students for years", but one has to demonstrate one is correct to others. $\endgroup$ – David Dec 30 '18 at 18:13
  • $\begingroup$ This is a very good answer, but, as David stated, sources are usually required for this site. Having said this, it's nice to see such a good, detailed, and correct answer. $\endgroup$ – anongoodnurse Dec 30 '18 at 21:45

Starting with your last question: The USDA (United States Department of Agriculture) defines genetic modification as "heritable improvements [...] by genetic engineering or other more traditional methods". The EU defines GMOs as "an organism, in which the genetic material has been altered in a way that does not occur naturally" using DNA altering techniques.

These are rather legal than biological definitions. For example, the EU Court of Justice has recently ruled that organisms produced by mutagenesis are technically GMOs but do not fall under the GMO legislation.

So, let's look into how seedless fruits are produced:

This can be achieved by making a plant, that is able to grow fruits but fail to produce functional seeds due to unsuccessful meiosis. This is done for bananas and water melons by crossing a diploid with a tetraploid plant, which produces a triploid plant where chromosome pairing during meiosis is unlikely (more on this in the wiki article). For oranges this is done by growing genetic clones together. Since they cannot self-fertilize (and identical clones cannot fertilize each other), they don't develop seeds but still grow fruits.

These techniques don't require any genetic modification by targeted manipulation of the DNA. Crossing two plants with different characteristics is also done in conventional breeding, which is also not classified as GM. However, it would be possible to genetically alter plants to block seed production and produce seedless GMOs. It would probably be a legal dispute whether this change is "heritable" when there are no seeds, so classification might depend on country policies.

The problem with seedless fruits is that you need seeds in order to grow new plants. To produce new seedless water melons you always have to cross the parents again. Plants that are able to reproduce vegetatively (parts of the plant can grow new plants), can be propagated by replanting branches. For plants, where this doesn't work very well, grafting is a solution to improve the process (a well growing plant is used as a root). Vegetative propagation in any case produces genetic clones, as you have pointed out correctly. The propagation method is independent of the technique that first produced the seedless plant and does not decide the GMO or non-GMO classification.

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