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Author Topic: Polyembryonic seeds  (Read 316 times)

Sven_chinotto

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Polyembryonic seeds
« on: October 10, 2018, 08:18:43 AM »
Question here since the internet is full of biological explanations that for me are chinese...

If a citrus seed is polyembryonic, will it have more than 1 shoots coming out?

I have these "double" seedlings but never really checked why this happened. As far as I now, polyembryonic seeds are 'true' to the parent plant thus, if this results in double shoots from 1 seed, these 'doubles' are in fact also true to the parent plant.

Please enlighten me on this one. :)

Edit: another question: are all seeds from a single plant poly or mono embryonic or does it vary? In that case, the only way to get true seeds is by having them germinate and see if there are multiple 'shoots' (in case my above theory is correct).

Greets
« Last Edit: October 10, 2018, 08:20:27 AM by Sven_chinotto »
Cheerios!

Sven

Ilya11

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Re: Polyembryonic seeds
« Reply #1 on: October 10, 2018, 09:08:51 AM »
If a citrus seed is polyembryonic, will it have more than 1 shoots coming out?
By the definition polyembryonic seed will give more than one seedling.

As far as I now, polyembryonic seeds are 'true' to the parent plant thus, if this results in double shoots from 1 seed, these 'doubles' are in fact also true to the parent plant.
In polyembryonic seeds one of the seedlings could be zygotic, that is not true to the mother plant.

Edit: another question: are all seeds from a single plant poly or mono embryonic or does it vary? In that case, the only way to get true seeds is by having them germinate and see if there are multiple 'shoots' (in case my above theory is correct).
Some varieties are strictly zygotic, giving monoebryonic seeds with seedlings that are not true to type, many others are giving variable number of seedlings per seed.
In practice, if you want to be sure of true to parent selection, you should germinate several seeds, discard monoebryonic ones and select uniformly looking strong seedlings. In most of the cases zygotic plants are weaker and variable in appearance than nucellar, true to the type clones.
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                       Ilya

Sven_chinotto

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Re: Polyembryonic seeds
« Reply #2 on: October 10, 2018, 09:29:51 AM »
Thank you for the reply.

So basically there is no 100% sure way to tell if a seed is true to the parent...

A bit disappointing. :p
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Sven

Ilya11

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Re: Polyembryonic seeds
« Reply #3 on: October 10, 2018, 12:06:28 PM »
It could be easily done by DNA analysis, but this is out of our reach for the moment ;D
Best regards,
                       Ilya

Sven_chinotto

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Re: Polyembryonic seeds
« Reply #4 on: October 11, 2018, 02:16:10 AM »
I should have my DNA tester laying around here somewhere... ;D
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Sven

SoCal2warm

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Re: Polyembryonic seeds
« Reply #5 on: October 11, 2018, 03:24:54 AM »
If a citrus seed is polyembryonic, will it have more than 1 shoots coming out?
Usually, but not always.

By definition, polyembryonic seeds have multiple seedlings sprouting up from the same seed, but usually when the term "polyembryonic" is used it is referring to nucellar seed, meaning the embryo in the seed originated from nucellar tissue and thus did not result from sexual recombination. If it's nucellar, that essentially means it's going to be a genetic clone of its parents, with the same genetic composition.

The seedlings coming out of polyembryonic seeds are usually all nucellar, but in some less common cases one of the seedlings (not uncommonly the weaker one) could be zygotic (meaning that it originated from sexual recombination and was passed down genes coming from the pollen).

Different citrus varieties have different percentage ratios of nucellar to zygotic seed, ranging from all zygotic to virtually all nucellar.


Polyembryony is a good way to spot nucellar seeds, but it's not always completely reliable.

SoCal2warm

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Re: Polyembryonic seeds
« Reply #6 on: October 11, 2018, 03:38:10 AM »
So basically there is no 100% sure way to tell if a seed is true to the parent...

A bit disappointing. :p
This is one of the biggest impediments to breeding.

I would agree that there is no 100% certain way to know (in the absence of genetic analysis), but there are a few strategies that can be used in intentional breeding to be very close to certain (maybe 97% sure). One would be for example if the seedlings display any obvious traits that can easily differentiate them from their seed parent, usually leaf shape.

It's a bit too complicated to get into here, but if you carefully select the varieties, using the right combination, and emasculating the male/female parts of the flowers of the two parents, you can be pretty sure.

And again, with certain citrus varieties you can be pretty sure. Oranges are almost certain to produce all nucellar seeds, while original species citrus like pomelo, citron, many varieties of mandarin, are sure to produce all zygotic seed.
This is very generalized but most of the seeds in lemons and grapefruit will be nucellar, while some will be zygotic.

 

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