I've been reading a bit about ploidy in Liliums lately and am interested to find out more. I have a few questions that I hope some of the members here might be able to help with.

Firstly, how do you go about determining ploidy? Besides doing a chromosome count (which part of the plant would you sample to do this, by the way), what things do you look out for that suggest it's a triploid or tetraploid?

I know tetraploids are supposed to be larger and more resilient than diploids, but I'm not sure how that would apply to distinguishing them if you don't have a diploid and tetraploid version of the same cultivar. I've also read that the majority of LA, LO and OA crosses are triploids.

Secondly, is there any kind of reference list to indicate what ploidy cultivars are? I know some have been entered into the database here, but it seems like it is quite hard to find out what ploidy cultivars are, especially since you can't necessarily assume they're mostly diploid any more. Otherwise, could people please list the cultivars they know the ploidy for (especially Asiatics, since those are the ones I'm most likely to get)?

Thanks.

Some ploidy information can be found here.
https://www.rhs.org.uk/plants/...
Crosses that have most potential to be successful (pod parent X pollen parent)
Diploid to diploid
Tetraploid to tetraploid
Triploid to tetraploid (less seed produced, but can be successful)

Apparently the stomata (tiny 'breathing' pores found abundantly on the reverse side of leaves) of tetraploid lilies are significantly larger than those of diploids. In theory, if you found yourself a good quality botanical hand lens, like the one here (not promoting this site or brand, just using it as an example because I'm not sure how familiar readers are with them!): https://www.pilbarageology.com...
you could examine your lilies and see if you can note a difference.

Of course that means you need to have a few confirmed diploids and tetraploids already, to compare... and it doesn't help you make a judgement before buying a particular cultivar if you can't find a ploidy reference for it. I admit, when I tried looking I didn't have any confirmed tetraploids and I just squinted at a bunch of my seedlings then gave up because diploid stomata really are so damned small! I should really try examining a few tetraploid leaves next summer so I can see for myself if the stomata are indeed any bigger. Or if my eyesight has improved.

Thanks Tracey and Della. Didn't realise that the RHS Lily Register mentioned the ploidy where known. I've realised it's incomplete, though, since I've found a paper that lists the ploidy of a few more cultivars:

http://www.liliumbreeding.nl/L...

I will have to see if I can get a lens for looking at the stomata. Very few of the plants I have or am hoping to get have their ploidy clearly stated, so I'm going on assumptions in most cases. Will be a bit of a challenge. As I result, I'm making a list where I can find out the ploidy (from different sources, such as papers, the lily register, these forums, etc.). It's in the early stages, but hopefully it will be useful.

So I've compiled as much of a list as I can for now and have published it from Google Docs:

PDF:
https://docs.google.com/spread...

XLXS (Microsoft Excel):
https://docs.google.com/spread...

It will automatically update as I make changes to it.

If anyone has any corrections, additions, etc. please let me know and I'll try to keep it updated.

You've been busy. I just wish I could read it - I lost my key before I activated microsoft office! (Something to do with despising microsoft maybe )

Try now, Della. I've updated the post and added a link to a PDF version as well.

Cool, can read it now. That's quite a list!

Thanks, Della. Just added a couple more after I found in this paper:

https://www.researchgate.net/p...

The paper is also well worth a read, since it shows that using triploids in hybridising is not as simple as crossing with a tetraploid. After reading it and other documents (plus the invaluable posts here) on polyploidy, I reached the following conclusions:

2n X 2n = 2n (3n on very rare occasions)
2n X 3n = Typically nothing (since triploids are almost always pollen sterile)
2n X 4n = Mainly 3n (sometimes small numbers of 2n and 4n)
3n X 2n = Typically nothing unless pollen parent matches pod parent’s dominant chromosomes (see below), in which case small numbers of 2n and occasionally 3n, 4n or aneuploids.
3n X 3n = Typically nothing
3n X 4n = Small to moderate numbers of 3n and 4n
4n X 2n = Mainly 3n (sometimes small numbers of 2n and 4n)
4n X 3n = Typically nothing
4n X 4n = Moderate numbers of 4n

For triploids (the key in the paper is Table 3):

L/A (3n) X A, L/A (4n) or O/A (4n) -> should produce some seed
L/A (3n) X L -> won't work
L/O (3n) X L, L/T (4n) or L/A (4n) -> should produce some seed
L/O (3n) X O -> won't work
O/T (3n) X O, O/T (4n) or O/A (4n) -> should produce some seed
O/T (3n) X T -> won't work
O/A (3n) X A, O/A (4n) or L/A (4n) -> should produce some seed
O/A (3n) X O -> won't work

For those working with triploids, the paper is well worth the read.