Friday, June 28, 2013

Size Matters

Tremendous amount of diversity is in
evidence in one generation of corn.
When teaching seed saving, I often rely on allusions to animal reproduction because most of my students have some experience with that and it helps make the point easily. However, one concept that doesn't lend itself well to such conversion is the need for population size in seed saving.

In the inventory that SLOLA has garnered over the last several years, we have enormous variety of seeds, many different beans, some different corn, a ton of squash varieties and so on. This is wonderful and I'm sure we need to consider saving all these varieties locally. But I don't think we can and the reason is population size.

The genetics of open pollinated seeds are very different from hybrid seeds or animals. The seed we call Yugoslavian Red Lettuce is not 'pure' like we think of when we think of genetic purity (like we sit around and contemplate that on a weekly basis). The genes in open pollinated seeds have a certain amount of 'flex' in them. You get the typical Yugoslavian Red Lettuce from the vast majority of your plants, but lurking under those frilly red leaves is a foundation of other genetic code. You don’t see it normally, but every so often a 'one off' pops up. If you are saving seeds for Yugoslavian Red, you don't collect seeds from the one off – if you like the one off, you save seeds of it separately from the Yugo Red and label it Yugo Not Red or Hungarian Red, just something different.

This variability is a great strength for seeds. It allows for adaptation to meet threats from insects or disease – or even drought. Perhaps from a garden full of Yugoslavian Red only a few plants survive the drought, but that's better than none. Or perhaps only one or two don't get the disease, but that's better than losing everything – and this is part of our desire to save these varieties: they survive under less than ideal conditions and they can meet threats to our food security better than any lab-created hybrid – especially GMOs.

However, our seed library – and I would imagine MOST seed libraries – are in danger of compromising this variability in our open pollinated varieties. They are not doing it intentionally, but it might well be happening despite their best intentions. I do believe SLOLA has inadvertently gone down this path somewhat and I hope we can refocus our efforts.

Back in the beginning I asked us to consider saving only seeds of some 150 varieties of vegetables. No more. I did this because I wondered at the time if we could really save seeds for several hundred different varieties for a period of time. I asked several times for folks to list the seeds they wanted saved – the varieties in their gardens they couldn't live without and got very little response. I went along with the flow and we allowed SLOLA's inventory to bulge with varieties from donations and gifts. Now I am convinced we cannot save all these different varieties of seed and we must return to a figure nearer 150 varieties. The reason is population size

The variability shown in open-pollinated seeds means to have a viable representation of all the different traits that make Yugoslavian Red Yugoslavian Red means there must be many plants each year from which the seeds are saved in order to keep that variety as viable as it has been for all these many different generations.

To save seeds from one plant for several years stands to lose some of those unseen genetic traits that make it such a good competitor against insects and disease in our gardens – might even result in a poorer quality lettuce over time. To save seeds and ensure the viability of our varieties over time, we must adopt policies that encourage larger population size of each variety. This might mean limiting our offerings to three lettuces, several tomatoes and so on.

I am going to ask our Best Practices committee for a list of varieties we on which we can focus and narrow our offerings towards those varieties. We still need knowledgeable gardeners create lists of the best varieties for Los Angeles and we must strive to have seeds from many more plants per variety to keep the diverse genetics present.

Here are a few guidelines, followed by simple definitions, towards which we need to work:

Breeding Style
Minimum Populations
Examples (but not complete!)
Severe inbreeders
10
tomatoes, lettuce and regular beans for the most part
Moderate inbreeders
40
all the other night shades, including eggplants and peppers; other bean family members like peas and other beans
Outbreeders in general
80
the cabbage family
Sensitive Outbreeders
200
corn, carrots and onions, these are 'sensitive' to a phenomena called 'inbreeding depression' which causes a severe reduction in plant performance in just a few generations – corn is considered the most sensitive of all
Insensitive Outbreeders
10 to 20
not sensitive to inbreeding depression, specifically Cucurbits, including squashes, cucumbers and melons

Inbreeding is a term applied to plants that will pollinate themselves (male and female flower parts exist in each flower of the plant and can self-pollinate before the flower even opens). Outbreeding apples to plants that must be pollinated by other plants to produce viable seed. These definitions are much simplified for this discussion only. If you like to learn more about this, Carol Deppe's book “Breed Your Own Vegetables” offers one of the most thorough and easily digestible definitions of these terms.

I am not proposing a drastic change. For the library, this means we will be less diligent about the return of seed for some varieties than for others – we are on a learning curve anyway, so we will need to realize there are some varieties that will be lost from our inventory and we will not be concerned with them. Over time, the varieties that are truly SLOLA varieties will change into an inventory we can manage more effectively. Some of this will be through natural attrition. Others will be actively cultivated into predominance by the Best Practices Committee and other active members.

What we need to do most of all is educate members about the minimum populations we are trying to achieve. Remember, it is the collective total of all the seed returned that make minimum population size – so if Megan grows Nutribud Broccoli (one of my favorites) and collects seeds from 6 plants, Linda does the same collecting from 4 plants, Albert collects from 7 plants and I collect from 3 we've met our minimum population of 20. All seed goes together to make the minimum population.

This concept is very important and central to our mission. Thank you for taking the time to read this.  I hope it makes sense to you.  If not, please let me know as I wish this to be clear; it is important to the long-term viability of the seed library and our seeds.

david


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