Selfing to achieve 4N breeders

[TxRobNLa]

Variation from Colchicine Treatments

Here is some food for thought to explain the variation from colchicine treatments...

When you think about a diploid cross, there is inherent variation in both the floral and vegetative characteristics of the resulting progeny. If it is hybrid and hybrid vigor comes into play, that variation can be even more extreme. Some may have flowers with great form while some may not. Some of the plants may be larger than others. Some may have different leaf shapes. Larger and smaller roots. This is all normal variation within a diploid cross.

When you colchicine treat protocorms from a diploid cross, some of the seedlings will convert to tetraploids and some will not. The age of the protocorms, the conditions and duration of the treatment, the specific crosses sensitivity to colchicine can all have an effect on the number of 2n and 4n seedlings that result.

Now pair the fact that the cross already had variety in it with the fact that seedlings exhibiting any of those individual characteristics could be 2n or 4n. So here are some examples of how that could and often does play out.

Seedling 1's inherited characteristics:

* small leaves
* bad flower form
* small flower
* converted to tetraploid, all the characteristics above are slightly improved

Seedling 2's inherited characteristics:

* medium size leaves
* good flower form
* medium size flower
* remained diploid

Which one is going to look more like a tetraploid? These two might actually be about the same size and quality. Now let's take it a step further...

Seedling 3's inherited characteristics:

* Hybrid vigor kicked in, larger leaves
* nice full flower form
* above average flower size
* remained diploid

Seedling 3 that is diploid is probably larger with better flower quality than Seedling 1 that is a tetraploid. If you use visual indicators you would think that Seedling 3 was the tetraploid.

Seedling 4's inherited characteristics:

* Hybrid vigor kicked in, larger leaves
* nice full flower form
* above average flower size
* Converted to tetraploid, this one hit the lottery and all the characteristics improved greatly.

Seedling 4 would be that great plant that really stands out. This is the plant that people tend to use as the standard for what happens with colchicine treatment. But as you can see with the other 3 seedlings, you've ended up with a range of characteristics, some are diploid, some are tetraploid, some of the diploids are better than some of the tetraploids.

Now increase the number of variables that can be average, great or bad beyond the example above to give a more realistic example of what might happen in a real cross. Map each of those combinations with the potential to end up with both diploids and tetraploids. Let's say you grew out 40 of them and you get a 50% conversion rate. Good luck visually telling all of the tetraploids from the diploids. Yes a few will stand out and if you were lucky one or two of the converted one's hit the genetic lottery and were great before they were converted. But most of them are in this gray area where visually you just can't tell what they are.

It's really a maddening prospect when you think it through all the way. I can't tell you how many tetraploids I've tossed that represented that Seedling 1 example population. I've got a blood red tetraploid Princess Kaiulani that has some of the crappiest form you will ever see.

Luckily one of it's siblings that also ended up tetraploid is everything I could have wanted... Blood red flower, great form, large flower, smaller compact plant. The plant does not look tetraploid, but it is.

Hopefully this helps everyone better visualize what is going on. I wish I had some photo examples to match up to the example plants. I might work on that for a future presentation.

Best, Rob

[isurus79]

Great info Rob!

I am wondering about species treated with colchicine. Is there typically less batch variability as you described before? What about from sib crosses of small genetic variability highlighting a coerulea flower or another recessive, uncommon trait?

Also, if done correctly, what is typically the 2n to 4n conversion rate when treated with colchicine? What about 4n x 4n?

[orchidsarefun]

was colchicine used as a gout medicine a few years ago ? Maybe not in the USA, but definitely in South Africa. I remember my dad was prescribed it. I will have to check if he still takes it.

[isurus79]

Originally Posted by orchidsarefun

was colchicine used as a gout medicine a few years ago ? Maybe not in the USA, but definitely in South Africa. I remember my dad was prescribed it. I will have to check if he still takes it.

Colchicine for gout

[FairyInTheFlowers]

Wow, thank you for the eye-opening explanation Rob! Now, about this whole guard cell method, how reliable do you think it would be? If I were to take my idea, having one pod in two flasks, treated and untreated, and sending several samples from each flask, do you think it would be relatively easy to pick out tetraploids?

[orchidsarefun]

Originally Posted by isurus79

Great info Rob!

I am wondering about species treated with colchicine. Is there typically less batch variability as you described before? What about from sib crosses of small genetic variability highlighting a coerulea flower or another recessive, uncommon trait?

Also, if done correctly, what is typically the 2n to 4n conversion rate when treated with colchicine? What about 4n x 4n?

if species are the "building blocks" of evolution, imho I don't like the idea of artificial genetic manipulation of them. Its not like we have an unlimited supply of them in the wild and I like them just the way they are

[FairyInTheFlowers]

Originally Posted by orchidsarefun

if species are the "building blocks" of evolution, imho I don't like the idea of artificial genetic manipulation of them. Its not like we have an unlimited supply of them in the wild and I like them just the way they are

First of all, most of the modern, high quality species we see nowadays are nothing like the species you see in the wild, and a good percentage of them have small amounts of other species in their background. Secondly, the main reason we are trying to do this with Phalaenopsis is because there are so many hybrids out there that are 4n, so converting the Phals that aren't 4n -the species and novelties- will totally broaden our breeding palettes. Also, treating a batch of seeds to make them 4n won't effect the mother plant, so you will always have those 2n species around. Personally, since I will need to get several each of the 2n species in order to do sib crosses to get the seed to convert, I will probably still keep the original 2n species. This will be a great help in breeding, as if some awesome and revolutionary 2n hybrid or species cultivar comes along, I will still have 2n to breed with that I can then convert when they are flasked.

Edit: I definitely think this should be made a sticky. Lots of good information here, and I have a feeling there will be more to come.

[TxRobNLa]

if species are the "building blocks" of evolution, imho I don't like the idea of artificial genetic manipulation of them. Its not like we have an unlimited supply of them in the wild and I like them just the way they are

This is actually on of the reasons I will not release any colchicine treated plants that have not been counted. I don't want to risk further screwing up the cultivated species population. At least if species and primaries are properly marked as 2n or 4n, then it reduces the chances of people making triploid crosses.

I am wondering about species treated with colchicine. Is there typically less batch variability as you described before? What about from sib crosses of small genetic variability highlighting a coerulea flower or another recessive, uncommon trait?

The less genetic variability the less extreme the differences will be. You'll still end up with some 4n's that are at the less desirable end of the spectrum and look like 2n's. I colchicine treated some of my pulcherrima line breeding and most of the 4n's were no different than then diploids. There have only been a very few that were really an improvement over the diploids. I noticed the same thing with my equestris var cyanochilus line breeding.

Also, if done correctly, what is typically the 2n to 4n conversion rate when treated with colchicine?

It's really a balance. The conversion percentage is actually lower when you are getting the treatment at the right point where your not doing lots of damage. You can start getting as low as 50% conversion. When you start increasing the amounts and treatment time, you end up with a higher percentage mostly because the ones that don't convert correctly die. But you end up with a higher percentage of converted plants that are stunted/shocked from the treatment and they don't grow as well. In the old days growers over treated and that is what lead to the myth that all colchicine treated orchids had poor vigor.

[orchidsarefun]

Interesting article which I came across again

A Brief Look at Polyploidy

but this is what I specifically remembered from the article and makes me not want to give up on those aneuploid orchids - ie offbeat breeding

"Over the years, however, certain plants in the aneuploid or uneven polyploid levels (triploids, pentaploids, etc.) have become known as good parents as a result of the success of their progeny. Sometimes outstanding plants are obtained from these matings, but usually the resulting aneuploid plants are irregular growers and often the seeds are few. For commercial establishments who grow large blocks of seedlings, this type of breeding is not practical. "Off-beat" breeding offers tremendous interest for the hobbyist, however. The hobbyist can't use many plants, and if he drops all his pods for the year, he has lost nothing. This opens up an infinite vista for attempts where the high percentage of failures will keep the hobby in line. The value to this type of breeding is that occasionally very fine varieties arise, and secondly, often the progeny that do arise are strange aneuploids themselves and sometimes breedable."

[TxRobNLa]

Every once in a while you end up with some special cases. P. Golden Sands 'Canary' is one of those special triploids that leaves 3 sets of chromosomes in most of the ovules, so when it's crossed with a diploid the majority of the resulting progeny are 4n. Golden Sands 'Canary' is the only triploid phal that we know this happens in.

The vast majority of the time breeding with triploids and aneuploids just results in more and more breeding road blocks until the plants are mostly sterile. Red phal hybridizers suffered many set backs and dead ends because of ploidy problems. Even today we have some amazing reds that unfortunately are triploids and there is no way to further advance those lines of breeding.

So you have to think long and hard if your willing to take that risk or just spend some upfront time investing in plants with even ploidy. It usually pays off in the long run.