Selfing to achieve 4N breeders

[zxyqu]

I do actually have access now to all the chemicals. it's been a bit difficult, but I got it. Sigma makes you justify what you need and why you need it, so it makes it difficult. Some of the chemicals needed are carcinogens, and kind of nasty, so you have to know what you're doing really.

[isurus79]

Originally Posted by zxyqu

While I understand that it is possible for a 4N plant to shed back to 2N, it is HIGHLY UNLIKELY, and I dont think anyone has actually shown proof of it happening. Maybe I'm wrong, but I think it is just as safe to assume all 2n x 2n =2n as it is to say all 4n x 4n = 4n. Plants are remarkably capable of increased ploidy, but even ploidy seems to be the best when it comes to breeding.

And don't forget that 4n seedling outgrow 2n seedlings at an astonishing pace. Just throw away any stragglers that aren't keeping up and you should be rid of any 2n plants.

[Call_Me_Bob]

Originally Posted by GirlGoneWild

The problem is, I think, that even when you cross two 4n plants, the offspring is not GUARANTEED to be 4n. From what I read, the offspring will sometimes mutate back to 2n (the plant's natural state) as the plant sheds some of the redundant chromosomes.

So even if we do breed two 4n plants together, we'd still have to check the offspring if we want to know for sure.



As for a quick way of sorting into "maybe 4n" and "probably not," I think Rob said on his site that you can take a few cells from the leaf and look at the size of the guard cells. 4n plants will have significantly larger guard cells than their 2n counterparts, so that would give a primary "weeding out" of plants that probably aren't 4n. But then you still need to count chromosomes to be positively SURE. Is this the process you're referring to?

as far as i know a 4n x4n , reverting back to 2n is a rare as a 2nx2n mutating to become a 4n.. maybe someone can confirm this?

Originally Posted by zxyqu

Yes, guard cell measurements are this somewhat quick method of weeding out potential 4N plants for future confirmation via chromosomal counting. You take take cells, you actually just take the leaf "fingerprint" by peeling off clear nail polish, which fills the cell voids and shows you signs of the guard cells.

While I understand that it is possible for a 4N plant to shed back to 2N, it is HIGHLY UNLIKELY, and I dont think anyone has actually shown proof of it happening. Maybe I'm wrong, but I think it is just as safe to assume all 2n x 2n =2n as it is to say all 4n x 4n = 4n. Plants are remarkably capable of increased ploidy, but even ploidy seems to be the best when it comes to breeding.

lol, guess i didnt even have to ask! thanks!!

Originally Posted by isurus79

And don't forget that 4n seedling outgrow 2n seedlings at an astonishing pace. Just throw away any stragglers that aren't keeping up and you should be rid of any 2n plants.

right! the 4n plants will be more vigorous Carrie Raven-Reimen once told me that a certain group of P. schilleriana seedligns were 4n, she said she could tell because the leaves were as thick and stiff as cardboard. so the substance of the plant can be another way we can take guesses. but of course its not positive and i would venture to say that some 2n have thick leaves too, if they are particularly vigorous and the parentage allows for it.

[isurus79]

Originally Posted by Call_Me_Bob

right! the 4n plants will be more vigorous Carrie Raven-Reimen once told me that a certain group of P. schilleriana seedligns were 4n, she said she could tell because the leaves were as thick and stiff as cardboard. so the substance of the plant can be another way we can take guesses. but of course its not positive and i would venture to say that some 2n have thick leaves too, if they are particularly vigorous and the parentage allows for it.

With 4n parents its REALLY obvious! I bought a suspected 4n (colchicine treated) Catt. dowiana rosita seedling from Alan Koch recently and he brought me one (from California to Texas) that is a MONSTER compared to anything I've ever seen at that age!! lol The leaves really are thick and stiff as cardboard! I can't wait to see it bloom in few years.

[orchidsarefun]

Phal Orchid World is a good example of what I am trying to convey. This is a proven 3N ( yet its growth and flowers are unbelievable, I say this from experience ).
It has registered offspring of 22 per OrchidWiz.
17 as seed parent and 5 as pollen parent. I did a quick check and none of the offspring have any registered offspring.
I will definitely attempt to breed with it again. First time failed. But it would REALLY help if I could determine chromosome count at replate stage, and I could either scrap or continue.

[TxRobNLa]

I'm not aware of a 4n X 4n ever resulting in any 2n's. This is probably an as common as a lightning strike scenario if it even happens at all.

There are a lot of misconceptions and bad information regarding visually determining ploidy floating around. Dr. Stock and I spent a dedicated amount of time testing out some of those common beliefs and we found many of them were incorrect. Here are a couple...

Be careful with guard cell measurements. The important thing to remember is the measurement is a relative measurement not an absolute measurement. Average guard cell sizes can be different within different populations of the same grex. So you can only compare the guard cells of two different orchids that are from the same cross with any reliability.

Size and vigor of plants from a colchicine treated population. You can have very fast growing and large diploids coming out of a colchicine treated population. Some of the tetraploids will be very vigorous, some will not. If the colchicine treatment is done correctly, the tetraploids are more likely to be fast growers. If it’s done incorrectly, the tetraploids can be really poor growers. Some of the tetraploids will not display any significant increase in the size of the foliage and/or flowers. There are of course some cases when it’s obvious without a doubt that one of them is a tetraploid. We’ve seen some really surprising things from counts on colchicine treated populations.

Increased size in a diploid population does not mean the plant is a tetraploid. We’ve seen a lot of cases recently where people have been calling diploids a tetraploid because there were a few seedlings that were much larger than the others. I’ve counted some of these “tetraploids” and they usually turn out to be diploids. It is a rare occurrence to have a tetraploid out of a batch of diploid seedlings. Violacea hybrids are really bad about this because some of the diploid seedlings will exhibit rounder/thicker leaves than their siblings and still be diploids.

[FairyInTheFlowers]

Holy smokes!! A lot has happened here since I last checked!!! That is good to know that there is a way to potentially tell a 4n from 2n in a colchicine treated batch. I have a seedling of Penang Girl 'Ching Ruey' x John Ewing 'KFO' from Patrick that has a *CT on the label. After looking at his PDF list, I noticed that this is one of the crosses that he (or someone else) treated with colchicine, and I'm feeling that the plant I have is a tetraploid. I have several other similar sized seedlings of similar breeding (Penang Girl 'Chin Yeo' x Kung's Princes 'Lena'), and the PG x JE has ridiculously thick leaves and roots, and it just looks superbly robust in general. So maybe an effecient system can be set up to pick out tetraploids when treating a definite diploid cross. What I would do is make a diploid cross, and then have some seedlings that are treated, and then some that aren't treated. A person would then be able to check for extra vigour of seedlings and larger proportions compared to those that are untreated. Combined with the guard cells, I think we could pick out 4n's with a high amount of confidence.

[Call_Me_Bob]

that would take alot of space though, to grow and get that many seedlings...

[FairyInTheFlowers]

Originally Posted by Call_Me_Bob

that would take alot of space though, to grow and get that many seedlings...

I don't think so. Orchideya has 40 some seedlings in a very small space. So having maybe 30 treated seedlings and 15 untreated seedlings would provide enough diversity to pick out a couple of the largest, most robust plants. Then a person could also keep several treated plants they are unsure of and either do a guard cell check, or if they are really unsure but the flowers are spectacular, they could do a chromosome count.

[orchidsarefun]

Your John Ewing is interesting in that its offspring has no registered offspring ( like Orchid World ) - so its indicative of a ploidy issue. BUT MAYBE the colchicine has "corrected" this. The experiment is definitely worthwhile.

Someone needs to invent a test at replate stage.......is this even possible ? this is when the crapaploids can be discarded.