Any Hexaploids available......?

[MrCym]

I have to laugh when people tell me orchid gossip. I get told that all of a sudden, there's people looking for hexaploids. If they really did any research, they'd realize we freely admit that although we're not too nervous, the whole exercise could be a disappointment. For the most part we are using our Oryzalin-created hexaploids to intensify warmth-tolerant (WT) character in Cym hybrids. It is a worthy project but necessarily, one must caution, still unproven as of December 2024!!

The math is interesting:

Take a 60% genetically WT 4n and cross it with a 100% WT diploid and you'll get progeny that can be expected to be 80% WT influenced. Take a 60% genetically WT 6n and cross it with a 100% WT diploid and you end up with progeny that is also 80% WT influenced! However the key difference for future development is that one is a putative sterile triploid while the other is almost certainly going to be a fully fertile tetraploid.

Now we are also using a couple of non-WT hexaploids with regular diploids to dabble in some interesting new tetraploid avenues. Maybe people hunting for hexaploids should search for quality diploids first. There's mighty lean pickings among extant diploid breeders today apart from various species and even quality species are hard to source.

[Australis2]

Take a 60% genetically WT 4n and cross it with a 100% WT diploid and you'll get progeny that can be expected to be 80% WT influenced. Take a 60% genetically WT 6n and cross it with a 100% WT diploid and you end up with progeny that is also 80% WT influenced! However the key difference for future development is that one is a putative sterile triploid while the other is almost certainly going to be a fully fertile tetraploid.

Sorry, but both of these examples are incorrect.

For the triploid example (4n x 2n), the progeny will be two-thirds of the 4n parent and one-third of the 2n parent. This means that its WT makeup will be (0.6)*(2/3) + (1/3), or ~73% WT.

For the tetraploid example (6n x 2n), the progeny will be three-quarters of the 4n parent and one-quarter of the 2n parent. This means that its WT makeup will be (0.6)*(3/4) + (1/4), or 70% WT.

Obviously the 6n x 2n cross is still the more useful and only slightly less WT than the 4n x 2n cross, but they are not actually the same.

[MrCym]

You are correct. Hated Math.

Main point, the 6n X 2n combination will be invaluable for warmth-tolerant on-breeding. More areas of the world are warm than cold..... Russia has never been a serious market for me!

[jjurlina]

Maths aside surely the key is developing a breeding line.

[MrCym]

Correct and we're a generation or more ahead of any competitor in this line of Cymbidium!