Simple methods for embryo rescue?

[billw]

Usually embryo rescue is required due to endosperm failure. The embryo cannot grow without the nutrients that would normally be provided by the endosperm. So, I don't see how you could pull it off in soil. Normally, the embryo is cultured on a nutrient rich medium that substitutes for the endosperm.

[gilbert]

Thanks for all the discussion everyone!

I'm mostly interested in squash hybrids, which should be fairly easy to work with.

[philagardener]

A complication may be that all your embryos are literally in one basket - staging when to harvest the developing fruit may be a bit tricky at first, but days after pollination should be a way to standardize. Good luck and keep us posted!

[walt]

Days after pollination may not be a constant, due to temperature etc.  
But it is often true that the embryo is good for several days.  Generally, one wants to let the embryo grow naturally as long as possible, then rescue it.  But the embryo might have been recuable over a few days.  Depends on the cross.


billw.  What you said above is generally true.  One exxception I know of is Zea x Tripsicum hybrids.  Sometimes the embro grows well enough, but the endosperm starts breaking down.  By the time the embryo is mature enough, the endosperm is gone.  By sdetting the embryo upright in sterile soil and keeping it from drying out, the light on the upper embryo can feed what is pretty much a tiny plant, though it is indeed an embryo.
I learned that studying the history of Zea x Tripsicum.  This was the first way to do it, other than just make the cross thousands of time and hope.  Today, standard embryo rescue is done for the cross since it gives a higher % success.

[reed]

Do I understand this right? Your talking about growing the new plant before an actual seed even forms? So first you have to know that a pollination has occurred but the seed either won't mature or will be deficient in some way if it does?

[philagardener]

Yes, essentially growing out the young hybrid embryo to get around genetic incompatibilities that would interfere with seed development on the mother plant.

You wouldn't use the technique for crosses that can mature seed (easier to let the plant do it!); there are often clues that fertilization has taken place (like when flower doesn't immediately drop like a failed pollination, or ovary tissue that starts to swell) that suggest when the effort is worth trying.

[walt]

Embryo rescue is typically only done after the natural seed formation fails.  Then one watches and tries to find out when it fails.  Then one decides whether one really wants that hybrid that bad, 'cause it really is extra trouble.  But often it is worth the trouble.
With all the history of embryo rescue, one doesn't usually have to do testcrosses to know if embryo rescue is necessary, and if so, how.  That is what google is for.