Selfing to achieve 4N breeders

[FairyInTheFlowers]

Originally Posted by Call_Me_Bob

jsut something to note on that, for hybrids that have questionable parentage, such as George Vasquez or the violacea/bellina things, if you remake them with clean parents. that will be great and we will know exactly what they are made of. however, we also may not have the same hybrid, if indeed the parentage is fuzzy, then using the supposed parents to re-create it wont actually get you the same thing

That's true. It will be interesting to see the "true selves" of some of these hybrids! And then it will also be neat to remake some of them using what we believe was used in the original crosses.

[TxRobNLa]

Could anyone shed some light on how the genes express themselves when you are making an initial cross vs. making a sib cross of the resulting hybrid?

For example, will a Phal Princess Kaiulani that has come about directly from the two parents be nicer than a Princess Kaiulani that has come about by crossing two parent Princess Kaiulani plants? Do genes start to get muddled up after a few sib crossings?

When you are making an initial cross, you have a higher chance of getting a larger range of variety. This can be good or bad as you might just get something better to work with. The advantage of then line breeding and working with sib crosses is you can start to stabilize the characteristics you are looking for by choosing two parents with those attributes.

Supposing orchidsarefun has a point (just to be clear, I'm not taking sides here...this is all hypothetical), what would be the ramifications of leaving the species plants as 2n and converting the resulting hybrids to 4n, then sib crossing those 4n hybrids to make more of the same hybrids instead of going back to the original species plants for each batch?

It can actually be easier to work with diploids until you narrow down the characteristics you are looking for and then move to working with tetraploids. Remember in a diploid you can only have two different genes for a given attribute. With a tetraploids you can potentially have 4 different genes being contributed from 4 parents down the line. In diploids you start to lose some genetic information faster. That can be a good thing depending on what you are trying to accomplish as it can eliminate the chances of some latent characteristic popping back up in a later cross.

[orchidsarefun]

is there such a thing as a "perfect" sampling, i.e. one where you would almost get the entire range of expected/unexpected results for that cross ? I am thinking in terms of numbers - 20,30,40,100 ? Or is it by its nature infinite ? I would have thought with just about everything reduced to stats, that there may be something out there that someone has figured out.
I would much rather grow out 20 seedlings, than 100 !

Secondly - how do you determine which chromosomal characteristics are "hard-coded" and cannot be changed
through selfing ? Or can all chromosomes be changed one way or another ?
For example if you obtain a tetraploid which has a great fragrance, can you enhance or eliminate that fragrance through generations of selfing or do you have to outcross to get a change. Or is it an outcross that will speed things up, but then again also "muddy" things up ?

[gnathaniel]

Originally Posted by TxRobNLa

When you are making an initial cross, you have a higher chance of getting a larger range of variety. This can be good or bad as you might just get something better to work with. The advantage of then line breeding and working with sib crosses is you can start to stabilize the characteristics you are looking for by choosing two parents with those attributes.

Sorry to butt in, but I've always been told that primary hybrids actually display less diversity than can be achieved with line-breeding in the resulting sib population. The rationale is that nuclear genes of F1 primaries are (almost) always exactly 50% contributed by each species parent, while recombination btw parents who are 50/50 of two species results in an intergrade population that can go all the way from 75/25 to 25/75 in percentage of nuclear DNA originating from each constituent species. Basically a Mendel diagram, which of course doesn't account for differences in maternal vs paternal inheritance (plastid DNA is only maternally inherited) and other factors that affect actual expression of genes in a cross. Am I wrong in my understanding of this?

[TxRobNLa]

is there such a thing as a "perfect" sampling, i.e. one where you would almost get the entire range of expected/unexpected results for that cross ? I am thinking in terms of numbers - 20,30,40,100 ? Or is it by its nature infinite ? I would have thought with just about everything reduced to stats, that there may be something out there that someone has figured out.
I would much rather grow out 20 seedlings, than 100 !

This can be an advantage to dealing with diploids, mathematically you have fewer possibilities. So in general you can grow out less plants and get a good sampling. In practice it's not always that simple though. If I'm growing to make selections and want to make sure I'm going to increase my chances of getting that really special plan, then I'm going to go for 100 to 200. The reality is the ideal case is higher than that. But few of us have room to grow in that volume. If I'm just growing to test a cross, then I may only grow out 20 to 40 seedlings.

Secondly - how do you determine which chromosomal characteristics are "hard-coded" and cannot be changed
through selfing ? Or can all chromosomes be changed one way or another ?

Nothing is really hard coded, but there are some characteristics that can be very dominate. Unfortunately there is no simple answer to this and it's completely case by case.

[TxRobNLa]

Sorry to butt in, but I've always been told that primary hybrids actually display less diversity than can be achieved with line-breeding in the resulting sib population. The rationale is that nuclear genes of F1 primaries are (almost) always exactly 50% contributed by each species parent, while recombination btw parents who are 50/50 of two species results in an intergrade population that can go all the way from 75/25 to 25/75 in percentage of nuclear DNA originating from each constituent species. Basically a Mendel diagram, which of course doesn't account for differences in maternal vs paternal inheritance (plastid DNA is only maternally inherited) and other factors that affect actual expression of genes in a cross. Am I wrong in my understanding of this?

If you are focusing on one trait, then yes you are correct. But it usually get's a lot more complicated than that with orchids. All the special cases really mess with the model and there are a lot of special cases.
(The genetics and inheritance dealing with coerulea Phals has turned out to be completely ridiculous.) As you already mentioned the inheritance through the nuclear DNA is only part of the puzzle. So it just depends on what you are trying to accomplish and what your working with. Basic Mendelian inheritance can break down really quickly when you start dealing with different color forms and genetic material from very different orchids.

Your typically going to get a broad range in the f1 generation that represents a mixture from both parents. In the f2 generation, you can use that to pull out latent characteristics that did not come out in the original cross, though this is more applicable in tetraploids or in crosses where one parent has contributed a gene that is blocking what another gene is doing. Or you can also use it to increase the percentage of certain characteristics that you working towards. There are also some differences between selfing and sib crossing on the f2 generation. And yes for a specific characteristic you can use line breeding to increase the range of expression of that individual trait.

[cobalt5]

I stumbled upon this polyploidy discussion from 12 years ago. Very interesting and a real learning experience. You just can’t beat the experience and expertise of great orchid growers!