Hybridizing Dahlias

Bessie · 2023-09-14T03:43:02+00:00

Krista to discover if seeds are growing in the seed pod, after there are no remaining anthers on the pod, gently squeeze the pods between your thumb and fing...

SteveM

@Bessie "#p17491 a hard green center is the opposite of an open center Dahlias.

Green centers can be environmental or genetic. The "genetic green-center" is a result of too high of a petal count. When the petal count is too high the center is green even when the bloom is open because there are more florets waiting to open. This type of green center could be considered the opposite of a "genetic open-centered" dahlia. With an open-centered dahlia the bloom does not have enough florets to fill the center when the bloom is fully mature. Green centers and open centers can be be caused by environmental factors (daylength or temperature) and jn these cases would not be considered opposites.
To guestimate the results of your hypothetical cross we need to have an understanding of the genetics involved. Is petal count on dahlias the result of a single loci involving only one gene and it's alleles or is the petal count determined by two or more genes. Also, I am pretty sure the single row of ray florets is a dominant gene but this doesn't explain partially-double blooms like the first bloom (left) in your cross. Is there a partially-dominate allele on the "petal count gene" or are we dealing with additional genes. This is all simplified and speculation on my part.
So, if I had to guess the results of your hypothetical cross I would guess almost all of the seedlings would have open centers and a few would be fully double. However, if you were trying to get a breeding line the seedlings would not be good genetic candidates.

Teddahlia

Yes, in dahlias many traits are multi genic meaning that two or more sets of genes influence that trait. How do you deal with that in your breeding? Persistence. Keep trying for better flowers and why they are better is a bit irrelevant. I still put up my shackles when I see the word "dominant " in dahlia breeding. The substitution of "more prevalent" is a better choice of words. Perhaps fully double is caused by a gene that doubles the one row of florets. And anther separate gene doubles that one. One more double and we have a fully double flower. That would be a multigenic trait.

SteveM

I use "dominant" in the true, genetic sense. Even with an octoploid it is sometimes helpful to know which allele of a particular single gene is the dominant allele. For example, if I have a dahlia with a long pedigree of fully-double blooms and cross it with a single dahlia with a long pedigree of single parents the resulting seedlings will not be 50% singles and 50% fully-doubles. Or not even mostly semi-doubles. They will be almost all singles with a few semi-doubles and even fewer fully-doubles. Knowing the dominant genes can be helpful but is not necessary to know when breeding octoploid dahlias. It is very helpful when breeding diploids.

Teddahlia

"It is very helpful when breeding diploids." And with octoploid dahlias no one really knows.. We only guess that there are some genes more dominant than others. Enough unfounded conjecture on my side. I do not believe we will be getting real answers to our questions soon.
M SC lav blend. Most all flowers look crappy because of the heat . Cool the next several days.

SteveM

Looking pretty blue on my monitor. Does the ADS have color chips to cover the "blues"?

Teddahlia

SteveM It ain't blue. Sometime, someplace there will be a blue dahlia. Not pure blue but a "just barely blue" that will cause controversy as to whether it is "blue enough". This one ain't it.

Bessie

@SteveM I'm curious what stem length you cut in your wholesale Dahlia sales. Does it depend on the variety or type of Dahlia? Does it vary by time of the season?
Any other sellers of Dahlia fresh flowers are welcome to chime in!

SteveM

Bessie Most all stems I sell are between 16" - 24". I sell to a broker who sells almost exclusively to wedding designers and florists. Through the years most florists were taught to believe that the stem length of a rose equated to a better quality rose. So, many florists used to believe (maybe still do) that longer stems = better quality = higher price, also for dahlias.
However, the tallest dahlias seldom make the best cut flowers. I cut the very tall dahlias at knee height and throw away the excess stem length. Otherwise, the tall dahlias cost too much in labor (staking and spraying).
The ideal plant height (for my purposes) is between 4-5 feet. The best dahlia I am growing this year (for 5 months of continuous production) is Hollyhill Lilibet. She grows about 4.5 - 5 feet under shade cloth and it is easy to get 24" stems (strong stems) all season.

Teddahlia

I like this one.

Bessie

Bessie of all the seeds I attempted to start in July, only one seed sprouted a few days ago, Sweet Nathalie.
A very poor test, since at this point it looks like most of the seeds I attempted to start appeared to be under developed.

Bessie

@SteveM has many times said he picks the best stock for making cuttings for next years plants. As I see blooms on the same plant vacillate between open center and closed center, clockface and 45 degree facing, I wonder "Would it be prudent to use the best blooms for hybridizing?" Is there possibly a genetic difference between blooms on the same plant?

If there's a spontaneous sport within a plant, would it follow that there is the same mechanisms working on growth features like number of petals, open centered, and bloom facing? I'm putting aside the cultural aspects for this discussion.

SteveM

Bessie I wonder "Would it be prudent to use the best blooms for hybridizing?" Is there possibly a genetic difference between blooms on the same plant?

L.A.T.E. is an old variety that used to be my "go to' cut variety for peach colored cut. Every year about 10% of the plants would go open-centered for no apparent reason. I used it as a seed parent because it was a very productive plant with long stems. L.A.T.E. produced many nice seedlings, in an array of colors, but the seedlings (most of them) inherited the same propensity to randomly produce a percentage of open-centered plants. I decided to discontinue L.A.T.E. and all of its seedlings because I didn't want that trait in my cut dahlia genetics. I think there are some varieties that can produce very nice blooms but have hidden traits that make them undesirable as seed/pollen parents.

Teddahlia

Margaret picks nice flowers for pollen but probably more because nice healthy flowers make more pollen. When she used Pam Howden for breeding our stock was not the best but the pollen worked well. We will never grow Pam Howden again as it is not vigorous enough for further breeding.
m c or sc seedling

Teddahlia

Sounds like a transposon, the famous jumping gene.

SteveM

That makes sense. I have also had that trait in the old Maarn variety. Random plants (entire plants) would go open-centered for no apparent environmental reason and they remained open-centered all season. One year I marked, and dug, two of the clumps that had gone open-centered. I planted those tubers and every one of them had normal, perfectly-formed blooms the next season. Jumping genes could be the explanation. Without knowing the cause, I just decided not to use any variety with that trait in a breeding line.

SteveM

Interestingly, both L.A.T.E. and Maarn are varieties from which I have been able to isolate pink sports.

MissyWeitzel

I have possibly a stupid question. When a dahlia seed pod is half closed like this, can it still be pollinated or produce pollen that can pollinate other flowers?

Bessie

MissyWeitzel I would think it's definitely able to accept pollen and produce a seed for every sigma that exists. It may be past the pollen making stage. If more stigmas emerge, then more pollen would likely appear. I find the stigmas shrink/shrivel after pollination takes place.

Teddahlia

Marked one to keep a second year. About 3 inches in diameter.

calico20hill

Teddahlia I don't just "like" this one...I love it! Would love to grow it!

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