Comparison of different seed preservation techniques?

[Frosti]

Does anyone know of a source (paper/blog/YouTube/etc. ...) that compares different seed preservation techniques?
Common wisdom is of course, that one should ferment the seeds and then thoroughly dry them. But I'd like to see the data that backs up this wisdom. How do the germination rates compare between 4, 7 and 10 days in the water? How much does the gel actually inhibit germination? Does it play a role in the maximum storage time of the seed?
What about the drying process. Does it matter if I let the seeds dry for 30 days?
Maybe some of you have done some experements of your own, if so - please share.

Thinking about starting an experiment in the off-season.
Maybe I'll buy a bunch of supermarket tomatoes and setup a little experiment ...

rgds
Frosti

[Shule]

> How much does the gel actually inhibit germination?

While I've never actually done a study analyzing the numbers or percentages, my general observation when overseeding both is that there isn't much of a difference. Of course, that doesn't mean it's good idea to leave the gel sacks on. There are more reasons than germination rates to be concerned:
* Aesthetics (they won't look like nicely brushed horses if you leave the gel sacks on)
* The ability to have non-sticky seeds that are loose and easily separable
* Disease (there's said to be a greater disease risk if you leave the gel sacks on; that would seem to be possibly true)

> What about the drying process. Does it matter if I let the seeds dry for 30 days?

That probably depends on the conditions, but in my experience, it hasn't mattered a great deal whether I bag them immediately, or leave them on the seed-drying table for months. Again, I don't have the hard data you're looking for, though. I'm just giving my two cents, which you can ignore, if you want.

[bower]

This was discussed at great length at Tville, and I believe a few, scanty mostly not peer reviewed papers were turned up to support various methods including peroxide, acid treatment (the norm of commerce), and fermentation (Carolyn Male's preferred standard), as well as lots of anecdotes of people's experience with unfermented seeds and the various methods.
As Shule pointed out, prevention of seedborne disease is another reason for removing the gel.
But you may be right that drying healthy seeds with their gel might give them greater longevity.

The effect of length of fermentation is an interesting thing to study. Experience says that temperature plays a big role. With warmer temperatures you get a complete ferment sooner. So do monitor and/or control temperature as part of your experiment.

The formation of a cap or "mold mat" is visual confirmation that anaerobic Lactobacilli have become dominant organisms in the process.
Sometimes there isn't a cap, but by looking at the bottom of the jar you can see that the seeds are free and have sunk to the bottom.
So you might also get around the temperature variable by checking for these signs daily and then leaving some samples to ferment for a number of days past the sign of completion.

Since our home fermentations are 'uncontrolled' we are starting with a mixture of whatever microorganisms are on the tomato seeds plus whatever is in the air. Sometimes there are a variety of molds growing on the cap, which don't benefit the process. I believe some of these, or possibly some of the wild yeast types, may be the cause of darkening seeds in ferments, which are sometimes associated with fermenting too long as well. I have thought about inoculating with lactobacillus to try for a cleaner or more controlled ferment but haven't tried it.
I have also noticed that different tomatoes in my own grow have different levels of lactobacillus in/on the fruit and thus ferment at different rates. My yellow tomato line for example is loaded with lactobacillus and makes the fastest and cleanest ferment of all, even though as a plant they are more susceptible to foliage diseases. So you might find that your supermarket tomatoes are not typical of all tomatoes. But for the purpose of a clear result, it would be best to use one variety for the experiments, as using different ones for different treatments might confound the results.

WRT drying time and seed viability, there is an optimal percent moisture in dried tomato seeds, which you can probably find in the literature. Since I don't have means of measuring that, I have forgotten the figure, but this has been studied by industry for all kinds of seeds. It is a small percentage iirc 15% or so. Seeds that are insufficiently dried may turn moldy in the package. OTOH seeds that are over dried lose viability. How well seeds dry in the open air for your experiment will depend on the relative humidity.
In my home, the relative humidity gets very high in summer and into the fall because home heating is off. My air dried seeds might be a bit too damp to pack into plastic before the RH is forced down. So I keep them in paper envelopes until the heat has been on for a couple of weeks. After that though, the RH in the house drops very low during the winter heating season. I had a problem with reduced viability and slower germination, of seeds which were left all winter in paper packages instead of storing for long term in plastic zips. At least, that is my unproven conclusion. I still get up to 100% germination with decade old seeds that were stored in ziplocks at room temperature when their moisture content was, evidently, optimal. So that seemed the obvious cause of having trouble with fresh seeds that weren't stored the same way.

Looking forward to see how your experiments go!

[Frosti]

Great input guys, thanks!

@Bower, I've noticed that sweeter tomatoes ferment way faster than mild or tart tomatoes. Maybe the yellow tomatoes simply have a higher sugar content and less acid, which leads to a better medium for certain microorganisms that then ferment the seeds faster?

I'll update this thread if and when there is anything to report regarding my little experiment.

[bower]

@Frosti the yellow ones are ironically more tangy than other lines I'm growing, but they are also sweet. It would be cool to figure out why some ferment differently than others. There's certainly a lot of variation. Makes perfect sense that sugar/acid could be a factor too.
I conjectured that it is microbial community in this case, because the yellow fruit ferments rapidly become milky and the seeds also fall to the bottom often before there is any cap formed. Maybe they even have a different dominant lacto species endophyte?
I have certainly seen big differences between different fruit varieties.
Another factor that I forgot about is the absolute maturity of the fruit. Much slower for anything slightly less ripe. Maybe maturity stage is also difficult to judge and compare, as well, since some varieties mature differently ie rot or self ferment very readily at maturity, while others do not.....
Just possibly those yellow ones ferment quickly because they are softer and less meaty than the others?
So many mysteries!

[Paulf]

@Frosti I think studies have indicated that all tomatoes have nearly identical pH so that the acid content is the same, but the difference in flavor is the sugar content rather than more or less acid.

My experience is all using the fermentation process. Riper fruit ferments faster, heat increases fermentation and needs less time to complete the cycle. And most importantly in my experience, the longer seeds are in the fermentation process, the lower the germination rate. There is an optimum time to allow fermentation to take place. Too little time will allow diseases to be present, too much fermentation and viability suffers. The time is measured in days not hours so there is wiggle room.

[Tomatina]

I always spread the seeds on a papertowel and let them dry like this for a couple of days - till it is all dry.
Germinationrate is great and it is super easy. I store them like that & just rip off the seeds I need.
Just for the swap here I dried some on a non sticky surface, but I didn' like it that much, cause the dryingprocess is slower.
I never tried fermenting the seeds so far, but I'll probably do it for the next swap. Bigger amounts of seeds are just easier to handle like that, I suppose.

[Frosti]

There is an optimum time to allow fermentation to take place. Too little time will allow diseases to be present, too much fermentation and viability suffers. The time is measured in days not hours so there is wiggle room.

That matches my current understanding. I always try to keep the fermentation process as short as possible, but long enough to actually separate the seeds from the gel sacks.
Do you guys believe an overly long fermentation process outright kills the seeds (if so, what exactly kills them) or does it only have a detrimental effect on the time the seeds can survive dormancy?

[Tomatina]

I think they will eventually start sprouting, if you ferment them for too long.
And if this sprouting process started, there is no way back.
That and the work with fermenting them always kept me from trying it.

I take the seeds from the first fruits and I always got healthy plants. If the plants would show any signs of disease I wouldn't take seeds from it.

[Cole_Robbie]

I have always used oxiclean.

My mother's attempts at saving tomato seeds without fermentation or oxidation, just spreading them on a plate, all ended in a bunch of nasty black mold. I think in the late summer, my climate is very humid, so seeds spread out to dry with gel still on them will just mold instead of drying. I would need a dehumidifier to do it that way, and the oxiclean is easier.

[zeuspaul]

Another vote for oxiclean. I don't have the patients to baby sit the seeds through the fermentation process. With oxiclean I am one and done within an hour or so. Then I place them into a bowl to dry. After a few days I rub them with my fingers to separate them.

[MissS]

I use both fermentation and oxiclean and both of them seem to work quite well. I do prefer fermentation because that is what Carolyn taught me. Now on to drying which to me is the very most important part. Drying a few days will result in seeds that germinate fairly well for the first 6 months. They then deteriorate rather quickly. Seeds dried for 10 days to 2 weeks or beyond if it is humid will keep well for years to come. I have seed that is 10 years old and germinates as if it were dried this year. Moisture in a seed reduces it's viability. To save seed well dry, dry and then dry some more.

[Frosti]

I have always used oxiclean.

My mother's attempts at saving tomato seeds without fermentation or oxidation, just spreading them on a plate, all ended in a bunch of nasty black mold. I think in the late summer, my climate is very humid, so seeds spread out to dry with gel still on them will just mold instead of drying. I would need a dehumidifier to do it that way, and the oxiclean is easier.

Yeah, I think the gel sacks would only dry up fast enough in the summer, so I'll probably not try that right now.

I'll add oxidation to the experiment.

[MissTee]

I’ve only fermented seeds. I have found the ideal length of fermentation to be three days here.

In cataloguing my seed inventory this week I noticed quite a few orange/yellow variety seeds are dark or even black. All the other coloured tomato seeds look the same - a pale beige colour.

Wonder how the colour of the seed affects germination? And if the dark ones are even viable anymore? Will have to do some germination tests on those.

[GoDawgs]

I ferment mine and it takes at most three days. For drying, I spread them out on a piece of wax paper on top of a paper plate, writing the start date and variety on the plate as I'm usually doing more than one variety. They dry 2-3 weeks before I put them in coin envelopes that go into ziplock bags. It seems to work well.

Can someone briefly explain the oxiclean method?

[zeuspaul]

I use oxiclean but I don't know if it is "the method". I squish a ripe tomato into a sieve. Then under running water I press and work the pulp until I have mostly seeds. Then I sprinkle some oxiclean on the seeds and massage with my fingers. Then rinse and then dry in a small ceramic bowl.

[Cole_Robbie]

I ferment mine and it takes at most three days. For drying, I spread them out on a piece of wax paper on top of a paper plate, writing the start date and variety on the plate as I'm usually doing more than one variety. They dry 2-3 weeks before I put them in coin envelopes that go into ziplock bags. It seems to work well.

Can someone briefly explain the oxiclean method?

https://www.theunconventionaltomato.com ... ing-seeds/

[GoDawgs]

I ferment mine and it takes at most three days. For drying, I spread them out on a piece of wax paper on top of a paper plate, writing the start date and variety on the plate as I'm usually doing more than one variety. They dry 2-3 weeks before I put them in coin envelopes that go into ziplock bags. It seems to work well.

Can someone briefly explain the oxiclean method?

https://www.theunconventionaltomato.com ... ing-seeds/

Hmmm, I can't get the site to come up. It just spins around trying to load.

Edited to add: It might be a glitch in the link. I googled "the unconventional tomato" and got to their site just fine. Thanks for posting about it.

[Frosti]

Just a quick update: The experiment is under way. I used about 1.2kg of an F1 cocktail tomato called "Brioso", which amounted to about 3000 seeds. After thoroughly mixing all of the seeds, I created 10 batches of 300 seeds each. I added about half again the volume of the seeds in water to each batch.

The batches are: 0d Oxi, 0d no cleaning, 0d rough manual cleaning, 1d, 2d, 3d, 4d, 6d, 7d, and 14d.

I'll let them dry for about 14 days each. The first 4 are already drying.

In case you're wondering ... this is what 3000 seeds look like:

5395CF72-1C3D-469B-94E8-700207DE340C.jpeg

[AZGardener]

I ferment my tomato seeds. After the rinsing step I spread them on coffee filters on top of paper plates for drying.
I also write the names on the filter if I'm doing several varieties at once.
I've found they dry faster than putting on a paper plate alone. I live in a dry climate and it takes about a week
for them to be dry enough to store. I also move them around on the filter over the drying time so all parts of
the seed is dry.
I've tried oxyclean a time or two and it seems to work well but I didn't have exact measurements or instructions
on how to do it correctly.

Thanks for the link, good information.