The viability of seeds from many fruit species declines over time after they are removed from the fruit. What are the best practices to maintain seed viability?

If I mail seeds, or acquire some during my travels, I'd like to keep them as viable as possible - at least for a few weeks. Is this possible with Lychee and Mangosteen seeds?

John

Tropical fruit seed, dont dry them as per vegetable seed, clean all the fruit pulp off to prevent mould. Pack them in new clean plastic zip lok bags with a little bit of just moist peat. Check them after a few days and open the bags to change the air and check moisture/condensation. If possible try to keep the seed bags cool, wrapped in clothes in your suitcase etc.

same here.

I never let citrus seeds dry out.

Either I keep them in fruit (best), or between moist tissues in fridge.
To send them is best in moist tissues in a plastic sack.

I wash them, dry them, treat with fungicide, put them in a ziplock and store them at the bottom of the fridge.
6 or 7 months later they are still good.

Sylvain has the right method. I have stored them months using this method. have great results.

Yes, I agree but take care with the following:

Drying - just remove surface moisture, don't leave to dry out completely for a long time. For some seeds thorough drying improves long-term viability, but not for citrus. On the other hand, leaving surface dampness encourages moulds, so its worth checking every couple of weeks and, if needed, re-wash or throw out any seeds with black moulds starting.

Fridge - never allow to freeze. A few degrees above freezing is ideal.

My fridge has -5 ° C as deepest themperature.

Mold on surface of the citrus seed is no problem at all .. it never does any harm, but help to rot the hull and let the seed sprout.

Not so - Millet (247 BO-)

I agree, -5 ° C will kill the seed.

oh sorry .. a stupid mistake .. I meant + 5 ° C

I also don't agree with the assertion that "Mold on surface of the citrus seed is no problem at all". Actually If mold is not quickly corrected it can cause a BIG problem for citrus seed. - Millet (247 BO-)

well, I put citrus seeds into compost .. all about molds, but the seeds grew all

As I wrote, moldy seed is a big problem for a citrus seed's viability. That is why growers always treat citrus seed with fungicides. - Millet (247 BO-)