Daylilies forum→Teach me about ploidy in daylilies......

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Name: Maurice
Grey County, Ontario (Zone 4b)
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admmad
Oct 23, 2019 10:23 AM CST
Suppose you are working on to hybridize a daylily with a rare trait that is recessive. If the parents of the cross contain these recessive gene, then the probability of you getting an offspring that contains only recessive genes from both parent is 25% for a dip but only 2.7% for a tet.


Unfortunately tetraploid genetics are much more complicated (messier) than a simple 1/36 (rounded to 2.78%) probability of getting a recessive aaaa from a cross of AAaa x AAaa.

That particular situation is only likely to apply some of the time to some tetraploid cultivars. It applies in specific circumstances related to how the chromosomes in each set of four align.
In the tetraploid daylilies that Arisumi worked with most chromosomes aligned as sets of two. Presumably some aligned as sets of four but the exact situations would vary with each set of the chromosomes (11 sets - one set for each of the 11 chromosomes) each cultivar and each seedling. In certain cases, called fixed heterozygosity, it is possible that a cross of AAaa x AAaa will produce only AAaa offspring.

In reality there is unlikely to be any simple way to predict the frequencies of various genotypes in the seedlings of a cross even if we know the parental genotypes. That is because each of the eleven sets of chromosomes in a tetraploid may act in a different way (how they align is independent of how any other set aligns) and each cultivar can align the same sets of chromosomes differently from other cultivars.

If anyone is interested in the complex details see pages 149 to 165 in the book Cytogenetics in Plant Breeding by J. Sybenga 1992.

Maurice
[Last edited by admmad - Oct 23, 2019 11:14 AM (+)]
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Name: Karen
Southeast PA (Zone 6b)
Celebrating Gardening: 2015
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kousa
Oct 24, 2019 8:12 AM CST
@admmad Thanks, Maurice! From what you wrote above, it is even harder than the theoretical 2.8% probability to achieve a complete recessive set of genes in the offspring of some tet daylilies but hopefully not impossible for some. Can you help me clarify some confusion? Is the toothy edge on tet daylilies a genetic anomaly that comes about as a result of chemical forcing? Second, are there any other genus of plants out there that have both dips and tets like daylilies?
Name: Maurice
Grey County, Ontario (Zone 4b)
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admmad
Oct 24, 2019 9:55 AM CST
kousa said: Thanks, Maurice!

You are welcome.
Is the toothy edge on tet daylilies a genetic anomaly that comes about as a result of chemical forcing?

I do not think that the teeth/fringing on the edges are related to chemical forcing. The suggestion many years ago, I think first made by Stamile, is that the petal edge effects are related to ruffled edges. If so, then they are presumably related to genetic effects that possibly change the number of cells at the edges or their sizes or shapes or some combination of those possibilities. I expect that the initial stages of similar effects are present but perhaps not easily noticeable in diploids because they are very small and have not been as intensely selected in the past (fewer hybridizers than tetraploids).

Second, are there any other genus of plants out there that have both dips and tets like daylilies?

Yes, both for natural species and for ornamental plants. Irises are one. Roses are another. Peonies yet another. It is not unusual for a genus of plants to have both naturally occurring diploid and tetraploid species. Sometimes the diploids and tetraploids are different species in the same genus and sometimes they are found in the same species.

Maurice
[Last edited by admmad - Oct 24, 2019 9:57 AM (+)]
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Name: Paul
Utah (Zone 5b)
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Paul2032
Oct 24, 2019 12:13 PM CST
Some Hostas also....
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Name: Mike
Hazel Crest, IL (Zone 5b)
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Hazelcrestmikeb
Oct 24, 2019 9:34 PM CST
Karen the Jaru link didn't work.
Didn't know that about ED Murray that I got from Teresa this spring. Read and learn. Thanks As always Maurice.
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Name: Karen
Southeast PA (Zone 6b)
Celebrating Gardening: 2015
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kousa
Oct 25, 2019 5:38 AM CST
Hazelcrestmikeb said:Karen the Jaru link didn't work.
Didn't know that about ED Murray that I got from Teresa this spring. Read and learn. Thanks As always Maurice.


I am sorry Mike but it appears they took down the slide show from the website. I have a copy in PDF. If you are interested, I can send you the file to your email. Please message me your email address.
Name: Dave
Southern wisconsin (Zone 5b)
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Nhra_20
Oct 25, 2019 10:08 PM CST
Lilium, AKA true lilies, have diploid, triploid, and tetraploid. Same thing with them in that triploids are usually sterile. But once in a while an unreduced gamete comes through in a triploid. There is a naturally occurring lilium species that is triploid. None that were naturally a tetra though.

Colchicine was a popular method of inducing polyploidy in attempts to get tetras. But that came with I'll side effects with the user. I believe the most common method now is using surflan out another type of pre-emmergent herbicide. Some have formulated a method with some success of using diploid plants and nitrous oxide to get a plant to breed like a tetra, along with exposing a plant to extreme heat.

Polyploidy is a result of the cells in a plant multiplying, but not splitting like they would naturally. Some people treat the bulb or rhizome/root of a plant, sometimes a seed can be induced, but that generally has a much higher fatality rate as seeds and seedlings can be tender.
Name: Barb
Quincy, FL (Zone 8b)
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Dragonkeep
Nov 2, 2019 9:36 PM CST
[quote="Nhra_20"] Some have formulated a method with some success of using diploid plants and nitrous oxide to get a plant to breed like a tetra, along with exposing a plant to extreme heat. "

Does extreme heat mean Florida heat? Or do you bake the thing?

Barb


“Because we all share this planet earth, we have to learn to live in harmony and peace with each other and with nature. This is not just a dream, but a necessity.”
― Dalai Lama
Name: Maurice
Grey County, Ontario (Zone 4b)
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admmad
Nov 3, 2019 5:01 AM CST
High temperature shocks at the right time can be used in some plant species. The temperatures used may be as high as 100 to 106F.
Maurice
Name: Maurice
Grey County, Ontario (Zone 4b)
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admmad
Nov 3, 2019 5:13 AM CST
The catch in trying to use unreduced gametes (2n) is that the diploid will also produce normal gametes (n). The diploid is crossed with a tetraploid in the hope of producing tetraploids from the 2n pollen. However, depending on whether high temperatures had any effect and produced any 2n gametes (pollen for example) the amount of that pollen may be quite small while the rest of the pollen is normal. Normal pollen can produce triploids when used in crosses with tetraploids. It does not happen often but then it may happen as often or perhaps even more often than 2n pollen is produced and is successful in crosses. Any seedlings produced may be rare tetraploids from 2n pollen or triploids from n pollen or a mixture.
Maurice

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