Selfing to achieve 4N breeders
 

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.

Since some of the offspring of the selfing may mutate back to diploid and I wouldn't know it, I run the risk of breeding another diploid with a tetraploid and ending up with a sterile triploid. 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.

Thanks for your help, friends! :bowing

There is no guarantee of getting a tetraploid through selfing and then colchicine treating the protocorns. However, any 4N x 4N cross should always yield 4N barring anything weird. If you can access 4N plants, and you're sure they are tetraploid!, then that is the better way to move forward. Otherwise, you have to colchicine treat a diploid cross, screen them for 4N conversion through chromosome counting, and then make the cross of interest with another 4N.

Both are not easy, but if 4N plants are available as parents, it's the best way.

To best answer your questions, you should make the cross between 2 known diploid plants, and colchicine the protocorns. Or, use two known 4N plants, with which merely need to be grown out.

Hmmm...that's not what I was reading online...I read in several places that when two different plants are used to reproduce, the resulting progeny are still diploid, because they retain one set of genes from each parent. However, when "selfing" occurs, for some reason the resulting progeny retain the redundant chromosomes, resulting in 4N offspring.

I inferred this first through a post on OrchidVault, where Rob himself said that he could "self" a phal to get a 4N plant. There was no mention of using colchicine. The tone of the statement implied the selfing process in itself would result in 4N plants. I can't remember the exact quote, but it was something like, "If it turns out to be diploid, selfing it should solve that."

Anyway, that's when I started digging and found other sites that backed up this statement that a "selfed" plant's progeny retains (for the most part) the redundant genes.

I spent quite a bit of time digging around, because it didn't seem to me that "selfing" a diploid would result in a tetraploid, but rather more diploids. Unless I really misinterpreted what I read, though, it seems it is the case.

Hmmm...hope some others join in to clarify. Now I'm really confused. LOL I did post a thread in Rob's forum, so hopefully he himself will pop in to answer, too! Perhaps I misinterpreted everything I was reading. It's all very scientific...:confused: hehee...

What I said is generally pretty accurate. A selling of a 2n plant can yield a 4n plant, but you would use colchicine to induce polyploidy. There are probably very rare instances of polyploidy occurring naturally as it seems some species can be naturally 4n, but it is just that; rare.
Without knowing the context, but knowing Rob, I'd guess he was interested in making a cross, and since he loves 4n plants (really needed when making coerulea crosses), he found a diploid he liked and was going to make it a 4n through the process I described, as you can make a diploid plant 4n without a cross involved (this is general, as you can also isolate meristematic tissue and colchicine that to yield potential 4n meristems, but that's more difficult).
Hope that helps. If you've got a cross in mind, go for it. There are labs that treat the corns for you, but you still have to get stuff counted to confirm 4n status. I'm working on that last part myself. It's tricky.

I don't think that selfing of a 2n plant will result in a higher number of 4n plants, though I could be wrong as I am not an expert in this field. Getting lucking lucky with a 4n plant from 2n parents is very rare, which is why people use colchicine treatment or known 4n plants to increase the odds of getting 4n progeny.

Like you, I am also collecting 4n plants whenever possible and I find that certain breeders are using 4n parents or colchicine treated plants to get larger crops of 4n plants. I think it might be easier to buy from these growers than to hope for 2n parent(s) to give you 4n plants. I know that H&R Nurseries and Gold Country are doing this a lot for Cattleyas, though I'm not sure which type of orchids you are looking to get 4n plants for.

Also, please report back here on this thread if you hear anything from "Rob." Who is Rob BTW? lol I'm curious!

Howdy
unless there is something terrible unstable, selfing should not give you 4n.

Do you have the link to the article(s)?

The rest of your logic seems on track. Best advice already given above = cross your 2n x 2n and cochicine or orzalin treat the protocorms -- (orzalin is safer for the chemist, and more likely to work than the older cochicine stuff) ; or go the 4n x 4n route.

4n sometimes occur in nature when reduction does not take place for some reason, but there are lots to have to come together, like the ovum in the same quandry of not reducing.

But 4n has been found in wild cattleyas in the past.

Take care
have fun
looking forward to the link, should you have them

Rex
aka POLKA

Simply stated, crossing 2 diploids gives you diploids, and selfing a diploid gives you diploids. There is absolutely no difference. In both cases there can be rare occurences of tetraploids from special circumstances, emphasis on the 'rare'. Any sources to the contrary are just plain wrong. If tetraploids were commonly produced from selfing then selfing a tetraploid ought to give you a octoploids, etc. and every conceivable ploidy would be rather common up to the point where a single cell couldn't even contain the necessary chromosomes. Is this where American 'science' education is leading us?

I'm looking for phals and/or vandas. Ah, well...

LOL! Rob is the owner of Sapphire Dragon Orchids. He is a genius and has done some groundbreaking work in breeding primarily coerulea phals and hybrids. His orchids are absolutely GORGEOUS, and he's a huge fan of using 4N plants. He's got a database on his site of "confirmed ploidity" for various exceptional phals, and it's nice because then the rest of us mere mortals can reference it when we are looking for stud plants.

Hehee...I see what you're saying about how if this were true, selfing a tetraploid would result in an octoploid..I was wondering about that too. The article I was reading seemed to say that in cases of crossed tetraploids, the plants dropped extra, unneeded sets of chromosomes.

I wish I could remember which sites I was on when I read all this. I was reading pdf's from scientific journals and my head was spinning at the time.

Obviously I misinterpreted what I was reading, from the overwhelming number of people who are saying that diploids x diploids=diploids.

And this actually makes total sense to me, and is what I would have expected, which is why when I read Rob's comment about selfing the plant to get a tetraploid I was a bit confused and went on an unsupervised internet research rampage (clearly not always a good idea...LOL)

Don't worry...it's not where "American Science" is leading us...it's just what happens to a gal when she reads something confusing and goes off to try and figure it out on her own, using the most reliable tool out there, of course...the internet. :biggrin:

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.

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." ;)

Thanks so much to everyone who helped clarify this for me! I should have just come here in the first place. Next time I will!
:bowing

Ill just say i agree with everyone above 2n x 2n + 2n unless a rare oddity occurs.


as for working with phalaenopsis, i know there are a good amount of know 4n cultivars of some species and many more hybrids. it shouldnt be too hard to find 4n hybrids, finding certain species that are 4n would prove to be more difficult, but other species should be relatively easy to find. goodluck!

ps. where in pennsylvania are you? im in the harrisburg area

Well, hello, fellow Pennsylvanian! :waving

I'm a bit west of Allentown. :biggrin: I went to college in Annville, though, which isn't too far from you!

Anyway, yeah, I've figured out where I went awry now.

As far as finding 4N stud plants...Rob has a list of plants with known ploidity started on his site. It's mostly hybrids, though, so if I wanted to veer way off into the novelty phals arena, that would be a good way to go. I'm more looking to create primary crosses, though. It's going to be a pain in the tush to find many 4N species plants, I think.

I was just on eBay looking at a GORGEOUS amabilis that I suspect is 4N (from the multiple spikes and full flowers) but when I asked the seller if he knew the ploidity of the plant, I got back "Sorry, we don't know."

Bummer.

I just don't want to accidentally cross a diploid with a tetraploid and end up with a triploid. Although I suppose that isn't the WORST thing in the world...some famous and very successful plants are triploid, but ideally I'd want to make something that could potentially be desirable for further breeding.

Oh, who am I kidding? I should just go out and buy a microscope and learn how to visualize chromosomes. We all know that's where this is heading...
:biggrin: