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This is a purely theoretical question which has been bugging me for some time now.
As far as I know, most cacti flowers will be able to make fruit only when pollinated by a genetically different plant (i.e. a cutting separated from mother plant will not do). Now suppose I have a flowering cactus which I pollinated with a completely different plant (not mine) and a single fruit was formed. That fruit contains multiple seeds. My question is, do the plants grown from these seeds have exactly the same genotype? Can two specimens grown from two different seeds from the same fruit pollinate each other?

Hope the question makes sense. Cheers!

Of course it make sense.

As far as I know two seedlings from the same seed pod can mate. Teoreticaly siblings (human ones) doesn't have exactly the same DNA. Nor do twins if they are from different ovule. So it should do at cacti aswell as I'm consered.

But then again....I'm no botanist.

Now this is something that interests me too. I've always regardeg seeds from a single pod as being so similar genetically to not being able to pollinate each other but I'm probably wrong. Do any of our experts know the answer?

Steve

The answer is no. While the seeds are certainly closely related, they are not genetically identical.

In recognition of the great similarity of seeds in the same crossing event, orchid growers assign a grex designation to a single cross, but the different plants in the same grex are distinct.

BarryRice wrote:The answer is no. While the seeds are certainly closely related, they are not genetically identical.

In recognition of the great similarity of seeds in the same crossing event, orchid growers assign a grex designation to a single cross, but the different plants in the same grex are distinct.

Distinct enough to successfully pollinate each other?

Ah, so you're talking about a plant that does not self, right. Well, I don't know. Interesting question!

No, seeds from the same cross-pollinated fruit are not genetically identical. They are just like brothers and sisters. I've grown Gymno's from my own fruits like this and the seedlings all differed visually from each other - by number and length of spines, ribs, skin colour, etc.

Even seeds from self-pollination are not identical but much more similar.

I must have phrased my question a bit badly, but my main concern is whether these "brothers and sisters" can pollinate each other. Does anyone have experience with this?

Yes they can but genetic variation is reduced. Its not like insest causing immediate physical issues but after generations it can cause weakening of the genes When compared to cross bread plants.