I have found scientific support for the no reblooming gene hypothesis.
In a periodic (Science et Vie avril 2006 pp134-135) that aims at popularizing scientific findings I found the following infos:
Three scientific teams from Germany, Japan and Sweden (Max Plank Institute, Kyoto University, Umea University) published :
(My digest) For all flowering plants flowers are initiated by a photoperiod regulated gene in the leaves called FT that send an FT protein to the apex where it has to combine with FD protein from FD gene. For once flowering plants production of FD protein is delayed untill enough vernalisation is registered.
My comments: It is now obvious that continuous flowering vars do not have a gene ad hoc but rather do have undelayed flowering as they do not need vernalisation.
FT and FD genes being quantitatively species specific. Interspecific hybrids flowering control breakdown and eventually reappearance in further generations are not at all unlikely.
Apologies if I’m not 100% sure I’m following you, Pierre. I gather the point is that there is not a “reblooming” gene per se, but rather a gene (or combination thereof) which supresses FD production and hence prevents the default norm of blooming?
If so, it strikes me that complete loss of a gene (and its potential effect) in progeny is a greater likelihood than maintaining a “rebloom” gene would be. Such would be favorable to greater likelyhood of hybrids maintaining rebloom, no?
Supressing the production of FD in some hybrids might even result in never-blooming hybrids I suppose…
Am I totally off the mark?
I wrote: “For all flowering plants flowers are initiated by a photoperiod regulated gene in the leaves called FT that send an FT protein to the apex where it has to combine with FD protein from FD gene. For once flowering plants production of FD protein is delayed untill enough vernalisation is registered.”
There is no supression of genes nor nonexpression of.
If leaves delivered FT protein (long known as ‘florigene’) and apex has FD protein available then flowering is initiated.
If FD protein is not available, FT alone is not effective. It is somehow stored untill FD is delivered. As it is for fruit trees.
Sorry Pierre. I hadn’t read the original post very carefully. Thanks for the clarification.
I suppose then the question is, what mechanism(s) delays expression of the FD gene, prevents the production of FD protein, or otherwise inhibits the activity of FD protein in once-bloomers in the absence of adequate vernalization?
Whether said mechanism is related to a third gene or not, it does appear to dominate in F1 crosses with rebloomers – i.e. crosses with plants sans-mechanism.
Interesting study. I would love to know what the control mechanism behind the need for vernalization in once-bloomers is. As i understand it, in seeds, germination is commonly permitted through a simple breaking-down or washing-out of an inhibiting protein. The default for a seed, without the controls, would be to just sprout. The default for a plant would apparently be to bloom.
(So what’s up with the seedlings that never bloom??)
Thank you, Pierre.
One: It sounds like there could be a variance in the amount of FT (florigene) produced which would affect flowering rate in the presence of FD? It would partially explain, perhaps, the difference between continous flowering (i.e. 'blooming machines) and those that are simply remontant?
Two: In many roses, if hip formation is allowed and or deheading not done, it can affect flowering. How is hip presence affecting the FD/FT system?
Photoperiodic optimum is different for monsoon asians species than it is for full sun flowering seasons ones.
Same for vernalisation that is different for coast dwelling rugosa or wichurayana that i.e. require little or no cold stratification to germinate seeds.
Each species and eventually some forms from widespread species has its own adaptations.
Mixing them led to control break down and flowering recurence.
Early chinese vars possible history will never be the same: as the mutated everblooming gene hypothesis fails one has to consider a more diverse ancestry for a quite diverse group of vars.
Here is a citation from very interesting:
The history and legacy of the China Rose by Howard Higson
you can find at Quarryhill Botanical Garden site:
"The Zhongguo Huajing (China Floral Encyclopedia) specifically indicates widespread rose culture in the 4th and 5th centuries AD. By the Song Dynasty (960 to 1279 AD), references exist to