Do heirloom varieties taken to a new location adapt or stay the same?

Before I started reading this site I'd always heard and believed that if you took an heirloom plant variety to a new location and saved seeds from the best plants, it would adapt over time and five years or so later you'd have a new variety, similar to the original in appearance and taste but better suited to thrive in your climate.

However, a lot of people on here seem to think that heirlooms are incredibly inbred and thus incapable of adapting, and that you'll continue to get the same results year after year unless you introduce new genetics. Implying that either the best plants were the best by random environmental factors and chance, or that saving the best does as much harm through further inbreeding as it does good (contrary to the common wisdom that saving from eight plants is enough for most vegetables).

Also, I've seen seed companies online that apparently have been growing an heirloom from some location other than their own and selling the seeds for years, so they must also subscribe to that theory, or at least they'd have you believe it.

Not having done the long term experiment, I'd like to hear thoughts on this, maybe from someone who has and can say for sure. Or somebody else's theorizing at least, lol. They should adapt even if they are somewhat inbred, because epigenetics or something, right, right? Or if you've got a strong argument that they don't, well that's fine too.

L. Tims wrote:
However, a lot of people on here seem to think that heirlooms are incredibly inbred and thus incapable of adapting, and that you'll continue to get the same results year after year unless you introduce new genetics.

Not having done the long term experiment, I'd like to hear thoughts on this, maybe from someone who has and can say for sure. Or somebody else's theorizing at least, lol. They should adapt even if they are somewhat inbred, because epigenetics or something, right, right? Or if you've got a strong argument that they don't, well that's fine too.

Just MHO, FWIW and YMMV...

Some plants like beans are already quite inbred since they are naturally self-pollinating.  Others like maize are out-crossing and likely are less inbred.  In both cases where they are heirlooms, adaptation to a new environment will likely occur over time.  Generally speaking, the out-crosser will come with more genetic diversity naturally as a consequence of the cross-pollination and may adapt sooner to a new environment.  You may have genetic diversity in a handful of heirloom beans, but if they were derived from a single seed, then they will be pretty genetically homogeneous (more 'clonal').  Either way, "new genetics" will enter your operation by default, even if you stick with the same seeds and do not experience wind-blown pollen blowing in from neighboring beans or maize.  This is because mutation (in addition to the epigentics to which you referred) naturally occurs in the genomes of all organisms with each generation, to a greater or lesser extent.  It generally takes longer to see genetic gains/improvement via this mechanism of 'new genetics' as compared to crossing with (a) something either more naturally genetically diverse, or (b) crossing with something that might not be so diverse, but is at least different in its genetic background or history from the heirlooms you brought with you.  Most publicly-offered seed from seedbanks will, by practice, tend to give out seed that has genetic diversity *within* the seedlot so that the recipient can make faster gains or improvement for their own location.  All of this said, for *some* types of crops and seed sources, you might find a pretty severe initial 'bottleneck effect':  If you brought heirloom seed from a family farm in, say, Maine to a new abode in Tuscon, AZ, the climate shift for those genetics *may* be such that you see high mortality in the first few seasons of production and, in later seasons, gains thereafter as the best 'new genetics' that survive the new conditions begin to establish your new seed cache.  You may in fact observe a shift in flavor, size, and other attributes of the plant, but generally it will be close enough to the original to still warrant retaining the original variety name.

It depends on the a number of factors:

The species involved

The history of the variety and where you got it from

Genetic diversity

Epigenetics

So tomatoes as an example:

Most heirloom tomatoes are inbreeding varieties of an inbreeding species. That said there are exceptions and there are even species tomatoes that obligately out breed. So you might find an heirloom tomato with exserted stigmas that does a modest amount of outbreeding. You might also find that if you got an old variety like Cherokee Purple tomato from 10 different true sources that they would all be slightly different. Thats because even highly inbred species and varieties are subject to mutation rates, occasional outbreeding, and change. Tomatoes may also be subject to some epigenetic change. So if you grow in a harsh climate your strain of something highly inbred might show some significant adaptation over a few years. These adaptations are heritable as long as the stresses that induced them keep recurring. You the gardener might also get better at growing it after a few years. You the gardener by selecting the best plants might accidentally save seed from a hybrid and reselect a better tomato. Some so called varieties might actually be land races and if so will have naturally greater variation from some sources or if multiple sources are aggregated together as some sources may maintain variation and others cull it out in favor of a preferred type.

So some heirlooms even of tomato might have more variation then others and thus be able to adapt and others will not. If the variation you need isnt there the result will be dissapointing. If you have two varieties though, and you cross them, the resulting cross will have a lot more variation for at least 6 years and more of an ability to adapt. However, if you do not choose at least one of those varieties carefully for good traits for your location, the result may still be disappointing. If the variation you need isn't in a population but it is available somewhere, buy a seed packet of whatever variety has the trait ofbinterest and cross it into the population. YouTube has how to videos to show how.  

Contrast corn:

Corn is always a natural outbreeder. It is normally always going to be more heterogeneous than domestic tomatoes. Though some of the same general truths apply. I just got a seed packet of Gaspe flint corn from Sherck seeds in the mail. It contains 100 seeds, for variety preservation I should have ordered two packets at least. So by ordering only one if I preserve it my population will suffer some founder effect. John got his population from four different sources and found some differences between them. Why? Undoubtedly because Gaspe was originally a land race and the four different sources probably subjected their source seed to different selection pressures and different levels of selection both intentional and unintentional. By purchasing only 100 seeds from John my population already has a selective force. Founder effect. I think John mentions somewhere selecting for larger ears. If he does that and I select exclusively for earliest ripe ears our populations should diverge over twenty years or so. If then recompared I bet mine would be earlier and have much smaller ears than John's. John has a special page for his composites where he explains his influences in creating them.

https://www.sherckseeds.com/seeds/grains/corn/gaspe-flint-corn/

https://www.sherckseeds.com/seeds/grains/corn/gaspe-flint-corn-alsf-strain/

https://www.sherckseeds.com/seeds/composite-mixtures/

If you bought seed for an heirloom corn from Native Seed Search such as Pima 60 day you would be buying a true historic landrace corn.

https://shop.nativeseeds.org/collections/corn-flour-flint/products/zl152

If instead you got a heirloom flint corn from a subsidiary of Monsanto you might get an more uniform version of something that was once a landrace.

Because both were corn they would probably both have some variability and you could apply selection pressure to either.

However, let's say you wanted an huge amount of variability? A couple of folks I know on the homegrown goodness forum Walt and Mike crossed Gaspe Flint and Pima 60 day corns in the hope that they would have very different genetic basis for earliness in the two. They are still working on it but the principle is sound even landraces diverge if separated by enough time and space.

How much variation is there in a landrace? It depends on a lot of factors. You could start a population with hundreds of varieties of corn or tomato which is often given as an impressive figure for a modern landrace. However strong selective forces may prevent most of those from contributing much to the resulting population. Plants that do better will almost certainly contribute more seed and pollen to the population. So for any finite population eventually those high performers will contribute more genes. If you cross just two extremely different inbred varieties the resulting variation will be very landrace like. Not all landraces will contain the variation you need.

My personal strategy is often to found my own population from several sources. My tomatillos which are outbreeding are from two landraces, a breeders grex, and three or so varieties. Some of the sources are local and some far away. My tomatillos are doing fine, I've saved seed, they volunteer readily, and the original packets have more seed in them if I can find space for an even larger patch I will plant more. If I find a cool variety of tomatillo I will buy a packet and add it to the population. If possible get some local seed and some from sources with harsher climates than your own.

How much genetic variation do you need? Depends on your goals and needs. If you grow an heirloom tomato does it produce enough tomatoes for your needs? If your needs change can you go buy a new tomato seed packet? If you are a prepper part of the answer to that question might be to buy six packets of tomato seed two each of three varieties and freeze one of each packet in a tightly sealed container in your freezer. Grow the other three and make sure you chose the right three. Choose one for flavor, one for productivity, and one for disease resistance for this, modern hybrids are fine. I don't follow this advice. Because unfrozen tomato seeds can last a long time and I am almost certain to grow tomatoes again before they go bad and I believe that if we may someday need to garden we should do it now even though we don't need to. So unless an natural disaster cuts you off from access to a store for a couple years you are going to be able to change your mind about your needs and buy a new packet of tomato seeds as long as someone is raising tomato seeds and selling packets and has a trait available that satisfies your new need such as resistance to a new tomato disease or more productivity or you just discover a new tomato flavor that's really good and you want to grow that new kind.

My experience leads me to believe that growing genetically diverse crops is the quickest and easiest strategy for selecting for local adaptability.

If I grow a variety that is uniform, stable, and distinct (inbred), then the genetic blueprint is essentially fixed.  There might be subtle changes in how the variety looks or grows, but it remains essential the same variety with perhaps a slow drift towards being better suited to local conditions. And sometimes there might be (inadvertent and/or unnoticed) cross pollination which can open up possibilities for local adaptation.

When I grow a crop that is highly genetically diverse, I observe quick and dramatic drift towards local adaptation. The first year, I typically observe intense selection against types that are completely unsuited for my garden. Often times I see first-year failure rates of 50% - 100%. The second year, most of the survivors produce adequately, and there are few that fail completely. I think of the third year as the magical year for local adaptation. That seems to be when things have really come together and can thrive.

Some species, such as tomatoes, have come to us as highly bottlenecked and inbred. Their ability to undergo local adaptation seems very limited. Other species, such as okra seem to live more on the wild side, and thus the possibilities for local adaptation are much greater. When I grow domestic tomatoes, any variety is more or less the same as any other variety, with a few choices in flavor, fruit size, shape, or color, and a few variations in leaf shape. When I grow wild tomatoes, there are tremendous variations in many different traits. The domestic tomatoes are inbreeding, which tends towards a rapid shedding of diversity, and thus the potential for local adaptability. The wild tomatoes are 100% out-crossing, which tends towards the conservation of diversity, and confers huge potential for local adaptation.

A common internet meme is that tomatoes don't suffer inbreeding depression, but when we make hybrids using heirloom parents, the hybrids on average tend towards being 50% more productive, and 10% earlier. Which goes a long ways towards explaining why hybrid tomatoes are so popular.

Besides epigenetic factors, there might be other factors in play regarding local adaptation... For example: The farmer learns what the variety needs, and provides for those needs better. The local pollinators figure out how to interact better with the crop. The local microbes establish relationships with the crop and leave propagules for next growing season.

Spent a lot if time on my reply and not sure if I clearly stated something Joseph said.

If you are spending the time and energy to try to adapt a crop to your climate, starting with more genetic diversity, such as that created by making or buying a hybrid, is a very much better place to start then with a single variety even one that is a bit land race like. Particularly a wide hybrid will generate enormous variation in the F2 generation. Though even a commercial tomato hybrid like Sungold F1 is going to become locally adapted much much faster as a dehybridization project then will say trying to breed within the variation in Cherokee Purple.

Even with John Shercks four strain gaspe flint corn- I'm not going to stop there, I am going to grow it next to Lofthouse high carotene flint, Lofthouse Neandercorn, a Mandan flint (if it's still viable), and a flint called nuetta that's traditionally used as a sweet corn. The resulting flint population will have a huge genetic base. If I then want say a blue flint that's as fast as Gaspe I can breed for it.

What I see too often is people trying essentially to start a breeding project with a variety that does not have the variation necessary for their goals.

A local seed saver spent perhaps 20 years seed saving a local strain of Tomatillo. I was impressed by it until I found a non-local Tomatillo a year later that was much shorter season. If your founding population doesn't have the traits you need, but the traits are out there, you need to cross in those traits if you want them.