Viewing post #2465192 by plasko20

admmad said:@blue23rose
In my opinion you should take the pentaploid, hexaploid and other "unusual" ploidies with a grain of salt.
Flow cytometers are very useful equipment. But there are published protocols for how to use them to determine the ploidy of plant cells. When the protocols are not used or not followed properly, incorrect ploidies can be reported. This has happened often enough by researchers (in published research) that there have been published reports about the errors and the need to follow correct procedures.
A pentaploid daylily would be expected to have very very low fertility when it is crossed with a tetraploid. A hexaploid daylily would be expected to have very very low fertility when it is crossed with a tetraploid.
A daylily that is very fertile with tetraploids is likely to be a tetraploid rather than a pentaploid or hexaploid. Unusual cases can sometimes (rarely) occur. For example, most crosses of triploid daylilies with tetraploid daylilies are not very fertile but some triploid cultivars may have reasonable fertility with tetraploids. The triploid 'Europa' is not very fertile with tetraploids but one triploid that Arisumi examined was reasonably fertile with tetraploids.
One of the necessary procedures when one finds unusual ploidies using flow cytometry is to double check the results by examining the plant's chromosomes with a microscope and counting them. This has not been done with any of the "unusual" ploidies. It really needs to be done.

It may be faster just to use qPCR of a marker gene, next to verified diploids and tetraploids to quantitate copy-number differences of certain genes that are known there are only 1-copy per haploid genome. Microscopic karyotyping is a lot slower and more difficult to do (at least for mammalian cells).
However, as discussed above, in many cases it is thought that the pentaploid plants may actually be chimeras of hexaploid and tetraploid, meaning they have the potential to create triploid and diploid pollen within the same plant. So would be very fertile indeed. In theory.