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Post by gilbert on Feb 14, 2016 11:35:36 GMT -5
I'm wondering if it is possible or desirable to stabilize a landrace. What I am thinking is a variety that was stable for some given characteristic, but retained enough diversity keep all the advantages of a landrace.
I know Joseph sorts tomatoes by size, but I was wondering if, say, you could have a zucchini landrace where every plant produced fruit that was at least fairly identical, but which still had a lot of diversity to it. Or a landrace of some green where they all grew at the same rate for even cutting.
Would it be possible? Or would all the other diversity get selected out?
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Post by Joseph Lofthouse on Feb 14, 2016 15:09:12 GMT -5
I stabilize my landraces for traits that matter to me... For example, I don't grow hot peppers so that I don't have to worry about my sweet peppers becoming hot peppers. I was grumpy this fall because a lady grew hot peppers in my field after I made sure to impress on her that they were banned from that field. Barring some type of fubar like that, my sweet peppers are always sweet peppers, even if the color, size, and shape are allowed to float. I keep the popcorn separate from the other kinds of corn. I keep the sweet corn separate from other kinds of corn. I don't mind if a small percentage of sweet corn is present in the grain corn, but I don't want any hard kernels in the sweet corn. So when I make a cross between sweet corn, and grain corn, I reselect for only sweet corn, and/or I minimize the amount of sweet genes in the grain corn. But I allow other traits to remain variable... In recent years, I have been selecting my corn for resistance to predation by skunks and coons. That lowers the genetic diversity of the crop, but it increases productivity. Days to maturity of warm weather crops is critically important to me. Squash, tomatoes, peppers, corn, beans, and melons must produce mature seeds for me if they are going to remain in my garden. That trait is very easy to stabilize. I lose a lot of genetic diversity when I stabilize for that trait, but it's a choice that I am more than willing to make. I choose to keep the shape of my zucchini the classic zucchini shape. I allow the color of the skin to vary. I choose to keep the vines short and bushy. I allow the color, shape, and size of the leafs to vary. If I wanted the fruits to be a consistent color, I could select for that trait while allowing other traits to float. Landrace zucchini I am much less tolerant of diversity within the crookneck. Again, I allow the leafs and vines to be diverse, but I stick very closely to crocked necks and yellow skin. Yellow Crookneck With the butternut/moschata squash, I am currently stabilizing on taste and flesh color. I allow other traits to float. I aim to have about 10% of the crop be pumpkins, and the rest to be necked squash. The first trait that I stabilized for was days to maturity. After that was stable for short-season, then I started stabilizing on taste and flesh color. Lofthouse Landrace Moschata, medium. When I find unusual shapes, sizes, or colors of fruits, or leafs, I may pull them out and try to stabilize on a particular trait. I call these sister lines, cause they share a common heritage, but are becoming different from each other. Here's a couple of examples that I am currently working on. Fig-Leaved Moschata Extra long-necked Moschata Extra large-fruited Moschata Sure, I'm losing diversity when I stabilize on one particular trait, but when I grow sister-lines, I am also keeping some of the diversity around that might otherwise be lost.
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Post by gilbert on Feb 14, 2016 17:44:54 GMT -5
OK, that makes sense. I guess how far it can be carried is up to each seed steward.
On a related note, if I only saved seed from a handful of out breeding plants, at which point would inbreeding become a problem? Of course, if I stated out with 8 plants each from a different variety, I would have plenty of diversity for a while. Would it ever drop to the point where I would need to be saving the standard recommendation of 100 or so for outbreeders?
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Post by templeton on Feb 15, 2016 19:37:50 GMT -5
OK, that makes sense. I guess how far it can be carried is up to each seed steward. On a related note, if I only saved seed from a handful of out breeding plants, at which point would inbreeding become a problem? Of course, if I stated out with 8 plants each from a different variety, I would have plenty of diversity for a while. Would it ever drop to the point where I would need to be saving the standard recommendation of 100 or so for outbreeders? I agree that the diversity is high if you use diverse lines as a founder population. How quickly that declines I'm not sure - thereis probably some statistical test you could do to get a number, but as far as i can figure out the 100 plant thing is just a rule of thumb, or perhaps accepted wisdom based on growers' experiences. If space is an issue, you can substitute time for space - save initial hybrids, plant half the f1s next growing season and select, then the year after plant some more F1s along with some of your F2s, and repeat - keep delving back into your founder stock or previous generations to keep the diversity up. Problematic if you have an obligate outcrosser with short seed life On second thoughts, you might need to keep alternate years separate to keep the diversity up, but use these to establish a third line of mixed generations...
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Post by reed on Feb 16, 2016 9:17:50 GMT -5
Since it takes several generations to stabilize a new variety from just a simple two variety cross I think you can drastically reduce the number of individuals needed to prevent genetic depression each season. Especially if you keep the whole or at least most of the resulting grexs (sp?). Even selecting for particular phenotypes as Joseph Lofthouse suggests still keeps a lot of diversity for many generations to come. Crossing many, not just two varieties as I intend to do for example with corn and carrots along with mixing seeds from prior years, I think will pretty much completely eliminate genetic depression. Also with corn since it is so easy to detassel and thereby insure no seed has just one parent I think would help even if you were growing just one variety. For now corn and carrots are the primary crops I'm working on.
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