clockworkhawkins said:thank so much for this information. I've learned so much
my final two questions.
are there pictures of this hexaploid?
what is the reason for loss of fertility?
You are welcome.
There is a black & white photo of the flower in Arisumi's article. The article is CYTOLOGICAL, HISTOLOGICAL, AND MORPHOLOGICAL EVIDENCE FOR A COLCHICINE-INDUCED HEXAPLOID HEMEROCALLIS By Toru Arisumi and L. C. Frazier and is in the Daylily Journal archives. I do not have information on which issue.
In diploids each chromosome of the chromosome pairs has only one choice for pairing at meiosis. So they pair symmetrically at meiosis and there are 11 sets in daylilies. In tetraploids each chromosome has a number of possibilities when it comes to pairing/aligning. One set of four can align as a quadruplet or it can align as a triplet with one "unpaired" or it can align as two pairs. When the chromosomes separate, singles can be lost completely and quadruplets may separate as three and one rather than two and two. Each set of four does this independently of how the other sets align. The end result is that in diploids basically 100% of the gametes have a balanced chromosome set of one chromosome for each of the 11 sets - they have 11 chromosomes. In tetraploids the gametes do not necessarily have 22 chromosomes and even when the number is 22 it may not be two of each of the 11 sets. Unbalanced gametes are not necessarily viable and the seeds created by viable unbalanced gametes are not necessarily viable. The situation in triploids is much worse in terms of balanced chromosome sets in gametes. In hexaploids the alignments would be more variable and the viable gametes fewer.
Some research evidence also suggests that there are other factors that affect the fertility of tetraploids and higher polyploids. I don't know if there is any scientific consensus on what those other factors are and they may vary in different species.
It is known that one can modify the fertility of new tetraploids by selection. If one only breeds from those tetraploids that produce the most seeds then one can fairly quickly increase the fertility of the tetraploid population. Unfortunately that is not happening in the daylily tetraploid population and even if it was, since there are newly converted tetraploids being continuously created, it might not be effective.
