Selfing to achieve 4N breeders

[FairyInTheFlowers]

If you don't want to use your 4n equestris var. cyanochilus, I would gladly take any unused pollen!!!

One point I'd like to add to Peter's is that yes, 3n may breed, but the key is to cross one with an even ploidy, 2n or 4n, not another 3n.

[TxRobNLa]

Ironically Rob's 4N equestris poses a problem for me now. Now that I know better. I didn't buy it knowing it was GM - its not advertised as such ( CT or whatever ), but I think knowledge about that fact is implied. Well that deed is now done. I have used it on a 4N hybrid as well as a 2N species, pollination failed on the 2N.

I don't ever remember selling any of the 4n cyanochilus. Maybe I'm completely forgetting. But to date the 4n cyanochilus is the only converted orchid from my program that I have offered for sale and they have been specifically priced to be stud plants.

I can definitely tell you I have never and will never sell any colchicine treated plants without having done a chromosome count and then making sure that plant was correctly labeled. That is something I am obsessive about.

Best, Rob

[TxRobNLa]

ok, orchidsarefun was talking about equestris 'Riverbend'.

'Riverbend' is a tetraploid. It used to be commonly available back in the 90's and then we started seeing less of it around. I have sold keikis off my plant from time to time.

'Riverbend' is case in point of a cultivar that we have no idea how it came about being tetraploid. It's pretty unlikely it was from a colchicine treated batch of seedlings. It's more likely it was one of the chance mutations that just naturally happened.

There was an earlier question asking where all our large tetraploids came from and I'm assuming the question was directed at large white and pink phals. Back when the early breeding was happening with standard whites and pinks, huge volumes of seedlings were being grown out much like the scale we see these days in Taiwan. When you grow out that many seedlings, the chance of getting a natural occurring tetraploid increases significantly because its really just a numbers game. In nature when an unreduced ovule and pollen pair up, you end up with a tetraploid. It does not happen very much, but it does happen. Breeders are usually going to select for the largest flowers with the best form and that is exactly what happened with standard white and pink breeding. What those breeders did not realize is at some point they had start selecting chance/naturally occurring tetraploids and after many years of that kind of selection, we ended up with these tetraploid populations of hybrids. This was not the result of species and hybrids being treated with colchicine.

There are even a few examples of wild populations of tetraploids. All Doritis pulcherrima var. Buyssoniana are tetraploids. You have to assume that at some point in it's past a chance tetraploid happened and then it's progeny survived in the wild.

I'm sure the next question is going to be, then why don't we have triploids out in the wild. I'm sure there have been times in the past when 4n Buyssoniana bred with other 2n pulcherrima. But given most triploids are sterile, those populations probably never survived and for long. Over 1000's of years or more these 2n and 4n populations survived and evolved enough that pulcherrima and Buyssoniana are fairly different more so than just ploidy.

[zxyqu]

Dang Rob... You've got skill. Love talking this stuff with you.
I once argued with an OS member about Buyssoniana being a 4N pulcherimma. He didn't like that argument, but at the time I was only guessing given the size disparities.

[TxRobNLa]

Buyssoniana is one of those inconvenient exceptions. ;-)

One of the reasons many of the really nice dark and full form pulcherrima's have horrible ploidy is they have Buyssoniana in them. As line breeding has happened hybridizers frequently did not differentiate a cross that was only pulcherrima from a cross that had some Buyssoniana in it. Especially if it was not the original cross.

[TxRobNLa]

Here's another fun one....



So this odd bugger is an indigo violacea that was a chance tetraploid out of a batch of diploid seedlings that I purchased. This was not a colchicine treated population. I was lucky that I even ended up with this one given I only had something like 15 seedlings.

It's a great modern example of a naturally occurring tetraploid. This can happen at any time. You just can't plan for it.

[orchidsarefun]

what are the differences in a successful crossing of:

a) a naturally evolved/occurring 4N like Riverbend to a 2N
b) a GM 4N to a 2N ?
I suppose what I am trying to get at is would a) potentially result in a population of 2Ns, 3Ns and 4Ns if the population was in the thousands - like maybe 97% 3N, 2% 2N and 1% 4N ?
and b) only 3Ns or a potential population as in a)

[FairyInTheFlowers]

Dear heavens, you are an extremely lucky man, Rob!!! Just look at those leaves!!!! I would easily be tempted to steal a high quality, diploid indigo violacea. . . I think I would do anything for a tetraploid one!!! LOL, unfortunately the consequences of such actions may not be worth it, but I still want one really bad!

[TxRobNLa]

a) a naturally evolved/occurring 4N like Riverbend to a 2N
b) a GM 4N to a 2N ?
I suppose what I am trying to get at is would a) potentially result in a population of 2Ns, 3Ns and 4Ns if the population was in the thousands - like maybe 97% 3N, 2% 2N and 1% 4N ?
and b) only 3Ns or a potential population as in a)

There is absolutely no difference between the two cases in terms of how they would breed. The genes are not being modified when colchicine treatments are used to produce 4n's. The chromosomes are just being doubled.

I know you disagree with this, but I do think it's important to state that from a science perspective. Creating tetraploids is not considered genetic modification. Any plant that is considered to be GM has literally had genetic material inserted, deleted or changed in it's genome. When we are doubling chromosomes we are not actually working down at the gene level. The genes are exactly the same as when we started.

This was an interesting bit of data I found:

According to the EU regulations (Directive 90/220/CEE of April 23 of 1990), polyploids are not considered genetically modified organisms (GMOs).

[orchidsarefun]

from Wiki ( I bolded ):

"Polyploidization is a mechanism of sympatric speciation because polyploids are usually unable to interbreed with their diploid ancestors.

Polyploidy can be induced in plants and cell cultures by some chemicals: the best known is colchicine, which can result in chromosome doubling, though its use may have other less obvious consequences as well. Oryzalin also will double the existing chromosome content."

Lets say that colchicine does not alter the genes of a plant so its not true GM. It can enhance specific characteristics of a plant ( and that is a crapshoot ). Unfortunately not only "good" things can occur and its subjective as to what is good. Fragrance could be sacrificed for blooms that are 2x the size or for something else that the breeder thinks the 99.99% general public will prefer.
So my point is that if there is any possibility that an "ancestor" can be contaminated, I am not "for" it, as I don't believe there is a practical way back to that that original species/ancestor, even if we think/believe that it is only characteristics that have "enhanced".
Polyploidism occurring through the natural selection process in general populations is 100% OK with me because it is the plant adapting to its environment ( hopefully ), not us adapting the plant to ours.