Benefits of polyploidy.

[Izzie]

I've taken genetics, so I can follow most of this. However, I am not sure how having more gene copies would benefit the plant.
Can someone explain the reasoning behind this? And how it is done? I find it fascinating, but I'm more familiar with color genetics than this kind.

[Royal]

Polyploidy occurs very rarely by chance. This is how the first few came on the scene a long time ago. Now it is induced by treating developing protocorms with mutagens. Colchicine (sp?) is the most common but others are used, it's usually nasty stuff. They usually prevent cleavage so the normal mitotic doubling occurs in each cell without splitting (or something like that... )

Not all poyploidy is beneficial. Aneuploidy (odd number like 3n) can lead to deformities, and nearly always means sterility. This is a real problem now because there are so many growers doing colchicine treatments but never verifying that conversion took place. You can't just eyeball them and tell they're 4n. If someone breeds with an assumed 4n that is really still 2n, to another verified 4n, the result would be a ton of sterile breeding dead-ends. There are also growers that don't care - they just supply the NOID potted plant market. Grocery stores don't care (or know) if a plant is fertile.

Having more chromosomes can be advantageous, though. If a plant has double (4n) than it can have more contributing alleles for size, substance, color, etc. Often times tetraploids have thicker substance, more saturated colors, or larger flowers. On the flip side, more possible genetic combos means a breeder has to grow out more seedlings to get a good spattering of gene expressions.

Polyploidy isn't always better, but it has opened doors for certain breeding lines. Now we just need to get some good 4n species verified and cloned so breeders won't keep crossing big complex 4n hybrid Phals with a diploid equestris.

[King_of_orchid_growing:)]

Originally Posted by RoyalOrchids

Polyploidy occurs very rarely by chance. This is how the first few came on the scene a long time ago. Now it is induced by treating developing protocorms with mutagens. Colchicine (sp?) is the most common but others are used, it's usually nasty stuff. They usually prevent cleavage so the normal mitotic doubling occurs in each cell without splitting (or something like that... )

Not all poyploidy is beneficial. Aneuploidy (odd number like 3n) can lead to deformities, and nearly always means sterility. This is a real problem now because there are so many growers doing colchicine treatments but never verifying that conversion took place. You can't just eyeball them and tell they're 4n. If someone breeds with an assumed 4n that is really still 2n, to another verified 4n, the result would be a ton of sterile breeding dead-ends. There are also growers that don't care - they just supply the NOID potted plant market. Grocery stores don't care (or know) if a plant is fertile.

Having more chromosomes can be advantageous, though. If a plant has double (4n) than it can have more contributing alleles for size, substance, color, etc. Often times tetraploids have thicker substance, more saturated colors, or larger flowers. On the flip side, more possible genetic combos means a breeder has to grow out more seedlings to get a good spattering of gene expressions.

Polyploidy isn't always better, but it has opened doors for certain breeding lines. Now we just need to get some good 4n species verified and cloned so breeders won't keep crossing big complex 4n hybrid Phals with a diploid equestris.

This does seem to present a bit of a problem for those interested in breeding but don't have labs to facilitate finding out whether the plant they have is a polyploid or not.

Sterility of plants and debiliatating mutations, to me, is a big waste in a great deal of ways.

Is there a service that is provided for those who'd like to find out if their plants are polyploids or not?

[Duane McDowell]

While triploids usually have reduced fertility, they are not always entirely sterile. One famous example is Paph. insigne 'Harefield Hall' - a confirmed triploid which is one of the cornerstones of modern Paphiopedilum breeding. There are any number of other triploids and aneuploids in orchids which range between somewhat fertile and very fertile.
One interesting thing about orchids is that there is no endosperm in the seed. In most plant families, this is a great way to keep aneuploids from producing seed - in orchids, it is not. The cool thing about breeding with aneuploid orchids is that their progeny are frequently polyploid.
As for the wisdom/ethics of producing triploids - they are some of the best plants in terms of growing well and producing lots of flowers. Think any complex Paph, Cattleya, Phal, Masdevallia, Oncidium etc. crossed back to a species. They grow fast, bloom early and tend to have excellent vigor. Overall quality tends to be pretty consistent - a high degree of uniformity. From a breeders standpoint, this is an ideal sort of cross to make - lots of satisfied customers.
As far as further breeding goes - there are many lines of breeding that have very limited fertility. The best way to go is to use known parents and/or species plants (for the most part, species plants will be fertile - not always, but for the most part).
Chromosome counting is labor and equipment intensive. I work in a lab studying meiosis and we avoid counting chromosomes whenever we can. There may be some contract labs who can do counting (try: Biomedical Testing Laboratories), but I'm betting it would be really expensive...
In terms of overall benefits of polyploidy in orchids, some can be:
Improved form (broader segments)
Improved size
Improved substance
Intensified colors
Not all polyploids have any or all of these benefits, but the ones that are used as parents generally do. Overall, polyploids tend to be slower growers than diploids - again, this is more of a generalization.

[Royal]

Duane brings up some good points. Generalizations are always dangerous, and there are always exceptions. I have no experience breeding Paphs or Phrags, so I'll defer to Duane there.

Regarding breeding with triploids, yes, it can be done. (In Phals) triploid plants can be fertile as the seed parent. Pollen is almost always sterile. The fact that some will breed is, in my opinion, more of a problem than it is a virtue. This muddies the water even more, and makes the "ploidy issue" even more difficult to sort through for the next generation of growers. I liken orchid breeding to dog breeding - it is our (the breeders') responsibility to not perpetuate genetic problems and deformities.

I do understand that some oddball crosses have been instrumental in breeding some lines. I refuse to believe that these crossed needed to be triploid, they just happened to be. With the information we have now, these crosses could be remade with knonw diploid or tetraploid parents, and possibly open some new doors due to genetic stability. If a triploid paved the way, think of what a tetraploid could do while maintaining fertility in its offspring.

I'm familiar with the protocol for counting chromosomes, but I've not done it. As far as I know, there is not one single lab that will do a count for you. My main beef is that if you have a lab set up to do conversions, you have most of what's required to do the counts to verify the conversions before releasing them.

[King_of_orchid_growing:)]

Originally Posted by RoyalOrchids

I'm familiar with the protocol for counting chromosomes, but I've not done it. As far as I know, there is not one single lab that will do a count for you. My main beef is that if you have a lab set up to do conversions, you have most of what's required to do the counts to verify the conversions before releasing them.

I don't have a real lab per se. It's just a makeshift station for home tissue culture. Is there still a way to do it myself?

It's not a big issue at the moment, because species orchids aren't saturated with polyploid plants (at the moment). But I'm still very well aware of how some species are polyploid plants.

[Royal]

Originally Posted by King_of_orchid_growing:)

This does seem to present a bit of a problem for those interested in breeding but don't have labs to facilitate finding out whether the plant they have is a polyploid or not.

Sterility of plants and debiliatating mutations, to me, is a big waste in a great deal of ways.

Is there a service that is provided for those who'd like to find out if their plants are polyploids or not?

Phillip,

This IS the problem. I don't have a personal grudge against triploids. I have a few and they're beautiful plants. I just can't use them for breeding, which makes them less valuable to me. Breeders that do use them in breeding just make more plants with little value. As an aspiring breeder, vigor and fertility are just as important to me as color or flower size.

Figuring out the ploidy of a specific plant is tricky. There are known 4n lines and known 2n lines. Some 4n species now too. There are some grexes that are riddled with aneuploidy. Sometimes only a particular cultivar has a problem but others are fine. Phal Golden Sands has a 6n cultivar that can be fertile.

There are a few growers doing counts to confirm ploidy. They are usually VERY generous about sharing this information. These lists are the best and sometimes the only source of dependable info.