If I did a wide cross between two rather unpalatable Ipomoea species, would there be any chance of less bitter offspring?
All the hardy Ipomoea species seem to be of dubious palatability. And I could plant thousands of seeds, but there is no reason to be certain there would be much genetic variability; for all I know, all commercial seed sources come from the same wild population.
A wide cross would give me certainty of variability; but would there be any reason to expect better results than either parent?
Post by Joseph Lofthouse on Apr 8, 2018 0:31:22 GMT -5
You could go the Luther Burbank route. Plant thousands of seeds, and select for the one least bitter.
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I suspect if a person could grow and adequately observe thousands of anything they would likely find variations. The only wild Ipomoea I am familiar with is pandurata and in just six individuals that I was able to find there was variation. One of the six kind of climbed a little in that it twisted around stuff like a pole bean only not that extremely and the others just grew up through and leaned or sprawled on top. Other big variation is one made lots of seeds, the others none.
I didn't try to harvest any roots and I didn't taste the leaves, I'll do at least the second of those this year.
This will just be a more long-winded version of the answers already given. The question here is whether or not your starting germplasm is heterozygous for the gene(s) that control bitterness. If it is controlled by a single gene, then if your source material is homozygous, it doesn't matter if the gene is dominant or recessive; in either case, you're stuffed. But, is it likely that your starting materials are homozygous or that bitterness is controlled by a single gene? Probably not. Wild collections tend to be more heterozygous than domesticated varieties. Polyploids tend to be more heterozygous than diploids. And, while I have no idea about the genetics of bitterness in Ipomoea, in every plant that I work with, bitterness is a polygenetic trait that that typically arises from more than one compound. So, I think that your chances of getting useful variability in bitterness are excellent.
Of course, it is also possible that you will get a lot of variability in the levels of bitter compounds that all exceed the threshold of your sense of taste. This is a problem with wild potatoes, for example - the level of glycoalkaloids can vary by an order of magnitude and yet still taste the same once you get past a certain point.