Landraces and "Return to Resistance"

Luna: You are correct in assuming that you can grow several varieties of squash together and save seeds from them. The children will tend towards a blending of the traits of both parents. The grandchildren will also be blended, but some might look more like one grandparent or the other, with perhaps traits combined in new ways.

Luna Vehmas wrote:in your book you mentioned that there's a temptation to save seeds from plants that survived a local plague, but then you risk only saving the genetics that are adaptive to that particular problem. Can you elaborate on this? I wasn't sure I understood fully what you were communicating, but it seemed important.

It's messy. Probably would have been better if I had not included a discussion of Return to Resistance in a beginner's guide to landrace gardening. It has caused more questions, and claims that I'm inconsistent, than any other topic.

The basic idea behind Return To Resistance is that the first growing season, you plant into a pest/disease infested field, then only save seeds from plants that struggle to survive. Culling any that are really thriving. Then you allow cross pollination among the survivors, and select for offspring that do well. The premise here is that you are selecting for a whole bunch of genes, of small effect, and that the combination of them is strong. The plants the thrived that first generation might have done so because of only one gene. Single genes are easy for a pest to overcome. The combination of many resistance genes is harder to overcome.

Return to Resistance is geared specifically to crops that can't grow in a pest infested area. Examples might be late blight in tomatoes in the eastern usa, or vine borers in maxima squash in the midwest.

In general, when creating landraces, I advocate very gentle selection for the first 2 or 3 years. Allow the ecosystem to do most of the early selection. And after that, I advocate liberal ongoing selection.

Yes, this is an important point and concept.  Let's say you had been maintaining a pretty nice landrace of some favorite bean or tomato in which, for several years running  and across growing seasons that were petty close to "average" for your local climate, you had been careful about selecting diversity when saving seeds for the next year.  Now a year arrives of extreme drought.....and from what you plant, maybe 20=30% of what sprouted survives to produce seed.  It would be more important in this year to save seed from as many individual plants as possible since the extreme drought will favor those plants with resistance to drought.  As Joseph noted, you might be tempted to save the "best looking beans" that year and discard "the rest".  But "the rest" may still harbor much of the diversity of your original landrace......may in fact harbor good genes to survive a season of extreme saturation.  If you had saved only "the best looking beans" that had survived your drought season and now the following season was extremely wet, you may have lost the genes that would allow any growth of your crop in that wet season.  It's an extreme example but hopefully assists in the thought process.  Extrapolating from this with regard to varieties possessing low genetic diversity.....and I may be wrong with this assessment....you will occasionally notice that for some of the more inbred material from some of the major seed catalogs, you open the catalog to a favorite variety only to find the words "No seed for 2021.....crop failure during seed production in 2020".   It's not that a  diverse landrace can *never* undergo such a catastrophic loss, --- but the probability of this happening to a  landrace versus an inbred variety is much lower.  I hope I have that right!....

Thanks John. I needed that example.

Another option would be to spin off a line of “drought resistant beans” from the best plants in that dry season, and continue growing your original landrace, with all the diversity, from your stored seeds (which you didn’t plant all of, of course!).

I often split my landraces some examples include:

hot peppers vs sweet peppers

sweet corn vs flour corn

fall planted vs spring planted spinach

frost tolerant beans vs main season beans

spring wheat vs winter wheat

They share common traits for adaptation to the general ecosystem, and they have traits that make them unique.

This spring I coddled my tomato plants taking them in and out of the greenhouse when temperatures dipped below freezing and even supplied heat when it wasn't feasible to take them inside.  One bed which I'd applied compost to last fall had several tomato seedlings pop up and remarkably survived freezing temperatures. I'm growing the strongest of those seedlings on and we'll see what happens.

Thank you for the knowledge, teacher Joseph.