- 2019, November 6th at 21:15 #25635The Peony Societywebmaster@the-peony-societyTopics: 27Replies: 9
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[Read the full article: Fertile shrub hybrids: diploids or tetraploids?]
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- 2019, November 8th at 18:23 #25690TheresaParticipant@theresaTopics: 0Replies: 3
These were just Bill’s unfinished thoughts from years ago, but they are a good topic to think about in hybridizing. Bill was trying to create a simple picture in his mind about how lutea hybrids breed in order to pursue a goal: up-facing flowers. Diploids should have created a relatively simple model giving us, perhaps, a simple double recessive goal, but this was not what he was observing in his garden. Tetraploidy complicates things greatly, especially if a trait were to be recessive and unseen except in progeny. How do you select for what you can’t see? There is also the matter of multiple possible chromosomes added or lost, and perhaps not nice neat full sets in going from wide diploid crosses to tetraploids.
Hopefully, when it comes to lutea hybrids, the trait is additive, that is, you are able to see improvement by degrees in your plants. Your first generation hang from one (or more) gene from lutea, and how far down they hang depends on the gene(s) from the suffruticosa parent. The next generation get more or less the same, but doubled. As we go down the line the plants can lose damaging redundancies and regain fertility, but what of our upward facing yellow? You select the most upright plants each generation, but aren’t quite able to get the flowers fully upright. There could be gene linkage that keeps the trait of yellow with the trait to hang. It is something that can be eliminated with enough crosses until that magic crossover occurs that will break the link. What if the trait of yellow is also additive? To get a nice strong yellow in an upright tetraploid, would we need four copies of each gene? Is our best course of action to self that special plant and/or sib the progeny?
Bill had some success in his pursuit, but fate intervened and the plant died from both our gardens being flooded, though at different times. His plant was not selfed, nor the offspring sibbed, but by ordinary selection. Maybe someone else already has an upright yellow and fulfilled Bill’s dream. If not, good luck to all of us still trying!0
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