"Selfing" to achieve 4N breeders?

[OrchidAddict]

I am in the beginning stages of developing a breeding program (meaning the planning stage, really), and as I collect plants to be eventual breeders, I am wondering how to deal with the issue of ploidity.

I've read that 4N plants generally produce better results than diploids, and that tetraploid plants can be achieved by "selfing" the original diploid.

So, say I want to turn my diploid species plant into a tetraploid to make it a stronger specimen for breeding, with the desired result being hybridizing with another 4N plant to achieve 4N offspring. So I decide to "self" it to achieve the desired 4N offspring to use for hybridizing.

Since some of the offspring of the selfing may mutate back to diploid and I wouldn't know it, I would potentially run the risk of hybridizing diploid offspring with tetraploid offspring and ending up with a sterile triploid as my end result. I definitely don't want that.

So would it make more sense to cross the two intended plants first, then self the offspring of the cross to get 4N (since the offspring would be the desired plant and would be sold as the end product) rather than selfing each parent and then crossing the (hopefully) 4N offspring?

I hope I'm making sense here. I'm not sure I'm explaining this properly. Basically I want to know this: If I want to create a tetraploid hybrid with plant A and plant B (which are diploid currently), should I self A and B first to create the 4N parents, then cross those? Or should I create a diploid hybrid from the two parents and then self the hybrid to get the final 4N result?

I'm really not looking for a debate on the pros and cons of tetraploids here...I'm more looking for an answer on the best way to go about achieving tetraploid offspring.

Anyone still with me? LOL

Okay, I look forward to hearing what you all have to say! Thanks as always, friends!

[panam]

I imagine Amey will look at this and make sense better than most, and come up with a simple solution. Can't wait to see what it is!

[pavel]

I'll be interested to hear Amey's take on the matter. Magnus may be able to cast some light on the subject as well.

Hmm, I don't see that selfing would result in 4N with any greater frequency (perhaps orchids are different than other organisms?). I would expect that the vast majority of the offspring would still be 2N. Thought I heard/read somewhere that there are artificial means (whether chemical or radiation) which can greatly increase the odds of a 4N, but not simple selfing.

[OrchidAddict]

Ahhh...okay. I know what's up. Apparently I misinterpreted what I read on someone's site, and then I went off on an unsupervised internet research rampage (not always the best idea...LOL!)

I was on a site where someone had said he had a diploid parent but that "selfing" it should fix the problem. He didn't mention treating it for ploidity anywhere in the process, and I inferred by the way he'd said it that the process of selfing resulted in a tetraploid plant. I was completely confused by this, so I went off in search of other documentation to back up the idea that selfing results in tetraploids, and I thought I'd found a few sources which corroborated this.

I must have misinterpreted what I was reading in my frenzy of excitement over the simplicity of creating a tetraploid species plant!

Apparently, what's logical is indeed true in this case: diploid x diploid = diploid. Makes sense.

Anyway, I was mostly curious because my Vanda coerulea (a species plant) is in spike, and I was wondering if I should go ahead and pollinate the designated recipient now (another species plant), or if I should "self" the coerulea and the pod parent to make them better before doing so. My choice is obvious now: just cross the two plants. I don't have the time or the resources to devote to attempting to induce 4N offspring, then checking each resulting plant to verify ploidity.

It seems like the search for tetraploid stud plants would be a journey "down the rabbit hole" unless you are buying from known sources who can verify their plants' ploidity (or unless you are willing to devote a lot of time and energy into treating all of your own crosses for ploidity, then checking each resulting plant).

I am mostly interested in doing primary crosses at the moment, and I don't think there's anyone out there just taking species plants and pumping up the chromosomes for the heck of it.

If there is, perhaps it's better that I don't know about it. Otherwise I'd be tempted to trade out my huge collection of species plants for "better models."

[raybark]

In reality, the tetraploid would be the "mutation", and the chemical treatment of cultures is intended to do just that.

A naturally-occurring, doubling mutation certainly can occur - that's where the connection between plant vigor, flower quality and ploidy came from in the first place - but it's a lot rarer than if that is "forced".

[Halloamey]

Ahhh...okay. I know what's up. Apparently I misinterpreted what I read on someone's site, and then I went off on an unsupervised internet research rampage (not always the best idea...LOL!)

Good that you did some research yourself The only way to generate polyploids would be the use of mitosis spindle fibre inhibiting chemicals like colchicine, or oryzalin. First you will have to generate callus, treat it with say oryzalin, then there are two possibilities, you let the callus regenerate into plantlets and then check the ploidy of the plantlet by flow cytometry, or you already analyse the treated cells by flow cytometry, select the polyploid cells and then allow these cells to form callus and finally regenerate into plantlets, which you can be sure are polyploids. In any scenario you need a dedicated lab, to do all these procedures.

Assuming one does all this your original question, is also something that has fascinated me for a long time. How would the results vary if say we made a tetraploid primary hybrid say Cattlianthe chocolate drop (G. aurantiaca x C. guttata) either 1) By using tetraploid parent species that will produce a tetraploid offspring, or 2) Select a good diploid Cattlianthe chocolate drop and then make it polyploid by oryzalin treatment. I am sure we will see some variation, just not what
From a practical point of view and a long time frame, it will be much better to make polyploid stud plants, then you could generate all kind of hybrids with those without needing to do the tedious steps of callus culture and colchicine/oryzalin treatments everytime. But on the other hand it will take you very long time to generate say a 3rd generation hybrid Like Cattlianthe Burgundy Delight which is a hybrid of Cattlianthe chocolate drop x Cattleya mini purple (Cattleya walkeriana x Cattleya pumila), first 5 years to generate the polyploid parental species, another 5 years to raise the polyploid chocolate drop and minipurple to flowering size, and then cross them and raise the progeny to blooming size so another 5 years, so that would be 15 years in total (a very optimistic estimate) on the other hand if you have already a good diploid Cattlianthe Burgundy Delight you could go with the oryzalin treatment of its callus and in 5 years have a polyploid Cattlianthe Burgundy Delight. Its all perspective and time frame oriented.
As of your last remark, as soon as I am done with my PhD. and am back to India and seriously into orchids, i will have my own lab and pump out those polyploid stud species plants and recreate the primary hybrids with them.

[Roy]

Anyway, I was mostly curious because my Vanda coerulea (a species plant) is in spike, and I was wondering if I should go ahead and pollinate the designated recipient now (another species plant), or if I should "self" the coerulea and the pod parent to make them better before doing so. My choice is obvious now: just cross the two plants. I don't have the time or the resources to devote to attempting to induce 4N offspring, then checking each resulting plant to verify ploidity.

It seems like the search for tetraploid stud plants would be a journey "down the rabbit hole" unless you are buying from known sources who can verify their plants' ploidity (or unless you are willing to devote a lot of time and energy into treating all of your own crosses for ploidity, then checking each resulting plant).

I am mostly interested in doing primary crosses at the moment, and I don't think there's anyone out there just taking species plants and pumping up the chromosomes for the heck of it.

If there is, perhaps it's better that I don't know about it. Otherwise I'd be tempted to trade out my huge collection of species plants for "better models."

There are nurseries adjusting the ploidy of species, make no mistake. Depending on what species you grow is whether or not "better models" are actually available. The easiest to grow & popularity of the species generally determines this.
I will say that some of these "improved" species are in some cases, questionable on their accuracy also.

[catttan]

Thanks Amey. We can always depend on you.