RobLaffin said:Maurice,
I'd be very interested to hear your thoughts on the work JG is doing on unusual ploidys as set forth here:
http://www.heavenlygardens.com...
Rob
RobLaffin said:I'd be very interested to hear your thoughts on the work JG is doing on unusual ploidys as set forth here:
http://www.heavenlygardens.com...
RobLaffin said:Thanks very much, Maurice, for taking the time to lay all that out.
I have to assume that FCM must offer some advantage of traditional chromosome counting - easier or faster?
If one had a plant and was unsure of its ploidy and wanted to know, then a FCM test might indicate ploidy, but the reliability of that determination would be subject to question unless the tester A) followed the specific protocols you quoted above, or B) confirmed through chromosome counting. Is that fair?
If tet conversions have some tendency to throw odd ploidys, that would provide at least one explanation for the fertility problems users of conversions sometimes report. I assume these problems be avoided by waiting for the next generation?
RobLaffin said:So FCM, by measuring DNA, which bears some, but not a perfect/constant, relationship to chromosome count, offers a reasonable guess of chromosome count, and this is of some value because FCM is easier and faster than the most accurate method, which is counting chromosomes.
The trade-off is ease for accuracy.
When you say:
"If all 11 sets aligned as two pairs then tetraploids would be equally as fertile as diploids (more or less) and there would be no problems as long as they always aligned in that pattern. But they don't and there is nothing to make them do so in new tetraploids"
does that mean there is something that would make them align properly in OLD tetraploids?
And if so, would that just be from careful selection of the most fertile conversions, or is there some tendency for them to 'learn' to align better over time (successive generations)?
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?
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?
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?
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?
Is that a likely reason for the pod infertility?
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?
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?
RobLaffin said:Thanks very much, Maurice. No, you hadn't answered previously, but I figured I had just worn out my welcome with so many questions. I was therefore happily surprised to see your thoughtful and detailed response. I think I understand all you've said, although my nonscientific brain may take a while to fully digest it all.
So, when you say (I have yet to figure out how to make the block quotes everyone else uses):
admmad said: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.
roblaffin said:what that means is, in the original cross of cultivar A x cultivar B, when that fails, it does not necessarily mean cultivar A is pod infertile; it could just as well mean that the female identifier of cultivar A and the male identifier of cultivar B are so similar [identical?] that cultivar A's incompatibility system rejected the cross. But cultivar B x cultivar A might work because then it's cultivar B's female identifier checking against cultivar A's male identifier and those are not necessarily a match even though A's female and B's male were, so the cross is allowed?
But in the scenario you describe, even if it were two large flowered UFs being crossed, doing the cross 'backwards' might work if the apparent pod infertility were actually just an incompatibility issue between identifiers in one direction.
As always, thanks very much for your in depth explanation in a way I can understand.