@RobLaffin Did I answer your last two questions from your last post somewhere else? Otherwise I seem somehow to have missed them, if so I am sorry and if you let me know I will post answers here. I am posting answers here.
if someone were to do a careful study of [some sufficiently large number of] hybridized, tet daylilies using both FCM and chromosome counts and found there was no indication that the relationship between DNA measurement and chromosome count would fail, can they from that point forward reasonably rely on FCM alone?
Assuming that the methods used to do the FCM accounted for all the possible known problems associated with using FCM for ploidy conclusions and that those same methods were used in future FCM studies then yes from that point forward one could reasonably rely on FCM alone. That does not mean that the FCM analyses might not fail in the future for some unknown new reason but those should be rare. However, I would add that it would always be wise/prudent to confirm any very unusual biologically unorthodox ploidy findings based on FCM with chromosome counts. The ploidy results based on FCM being suggested recently for daylilies are extremely biologically unorthodox.
Such a study would have to find that the maximum amount of DNA in any diploid never ranged up to a value that overlapped with the lowest amount of DNA in triploids; that the maximum amount of DNA in any triploid never ranged up to a value that overlapped with the minimum amount of DNA in any tetraploid and so on. Such studies would need to be done on substantial numbers of diploids triploids and tetraploids. That would currently be very difficult as there would not be enough known verified triploids. The daylilies chosen to be studied would have to be a random sample of all possible daylily genotypes. That would mean that registered cultivars would not be a good choice as they are a selected sample. The size of the random samples would probably need to be quite large but that depends on the shape of the DNA amount distribution. Below are just three examples of possible distributions. The important parts are the tails of the distributions.
Is there any reason to think a tet intro that traces its lineage back to H. Altissima (e.g.) would have the same relationship between DNA measurement and chromosome count as a tet intro that traces back to H. Sempervirens?
No there is not. Different species in the same genus (Hemerocallis) with the same chromosome number can have different amounts of DNA.
Or does the fact that modern tet intros trace their lines back to a number of different original species mean they cannot be relied upon to all behave in a substantially similar way re: reliability of relationship b/w FCM and chromosome count?
Yes. Different daylily cultivars, both tet and dip, cannot be relied upon to have the same amount of DNA even when the chromosome counts are the same.
When a tet is discovered to be pollen fertile but pod sterile (or vice versa) does that mean that the pollen gametes have the normal complement of 22 chromosomes, but the egg gametes are likely to have fewer, or more than 22?
No.
It would usually mean that the cultivar had a genetic variant that affected female fertility but not male fertility (female sterile). There are also genetic variants that affect male fertility but not female fertility (male sterile) and probably genetic variants that affect both male and female fertility.
Is that a likely reason for the pod infertility?
It is a possible reason but with our current level of knowledge about daylilies not the most likely reason.
If so, what would be the best way to 'fix' that through hybridizing? Look for a sib that is pod fertile and breed to that, trying to pick up pod fertility while keeping the genes limited to this particular cross? Or just breed to some other, unrelated tet known to be pod fertile and go with the most fertile kids?
True pod fertility is probably quite difficult to show in daylilies because daylilies have an incompatability system that prevents self-pollinations from working. This is not present in all daylily cultivars, but probably is present in the majority. The system has not been studied well but Stout did make some preliminary observations. Basically (with many assumptions and generalizations) the pod parent will carry certain female identifiers and certain male identifiers and the pollen parent will carry certain female identifiers and certain male identifiers. In a cross where the female and male identifiers are the same the cross will fail to produce viable seed. That means that a cross of cultivar A x cultivar B may suggest that cultivar A is pod sterile (because it is known that cultivar B is male fertile from other crosses) but in fact the cross of cultivar A x cultivar C succeeds indicating that cultivar A is not pod sterile. Actually the cross of cultivar B x cultivar A may succeed. That is because in the cross of A x B it is the A female identifiers that are combined with the male B identifiers but in the cross of B x A it is the B female identifiers that are combined with the A male identifiers.
It's curious, because large-flowered UFs are often very difficult as pod parents, and I am wondering what it might be, genetically, that might help explain that and point the way to correcting it. Also, there are some large-flowered UFs that are Pod Very Difficult, but sometimes success can be had by making crosses in cooler weather. Would this mean there might be wrong # of chromosomes in the eggs, but this is somehow ameliorated by cooler weather? Could that be? Or is it more likely that you just lucked out and got a flower where the eggs did have the correct # of chromosomes?
Older, larger flowered UFs may be difficult as pod parents because they may be fewer generations removed from crosses with the original triploid daylilies. If that is the case the lower fertility may be due to unbalanced chromosome numbers (complements).That has been speculation in the past but as far as I know there has never been a check of the ploidy of pod-sterile large flower UFs. Another speculation has been that the pistils are too long for the pollen tubes to successfully grow down in time. I strongly doubt that the length of the pistil of any daylily cultivar is too long and affects fertility. On the other hand, high temperatures are known to affect fertility as is high humidity. Both reduce ferility in most plant species and that would include daylilies.
