In a inbreeding line loosing alleles that are not selected for is quite easy. To the point it is this strategy main difficulty. The more so with outbreeding plants. In corn this has been overcome to a degree. The rarer the allele the easier it is eliminated.
Then there is another fact. Most gene’s parts are silent. In human genome about 80% gene parts are apparently useless. With a tetraploid’s large genome the silent part amount is probably quite large. And with crossing over there is the possibility that gene parts are send to silence while others are expressed anew. From recent views and/or findings somatic and meiotic crossing over is much much more frequent than earlier thought. To the point it is with sanitary problems the best explanation of clonal propagated plants.
I was talking about roses of specific lines such as the modern hybrid teas, floribundas, etc,. That is a very good explanation. Bull’s eye. I’ve always find news of sudden reemergence of traits very interesting. Joan, didn’t you have a Baby Love seedling that was distinctly mossy? I had a pic of it, but I haven’t used my hpphoto account for a long time. The parents themselves weren’t mossy, although they were probably decended from Ralph Moore’s work with mini mosses.
Although not pertaining to roses, I have heard that an African Americans couple produced a Caucasian baby (as in blonde hair, blue eyes, fair skin) even when the Caucasian ancestor was several generations away. DNA results disproved that they were albinos, a product of an infidelity, or anything else of that nature.
My Gourmet Popcorn set several OP hips this year so Im going to try them out just for curiousity (inspired by this thread). If they are not self X self then they are most likely OP with The Fairy or Orange Triumph. At any rate, it will be interesting to see if any are self X self and how they turn out. That is if they actually germinate.
I think everyone is doing a great job explaining how inbreeding/selfing and selection can cause lines of roses to lose certain traits (like once blooming).
It sounds like you are intrigued by something else in addition to it, and that seems to be how recessive traits can vanish for a few generations and then reappear.
I think maybe Joan or Pierre can explain this in a more elegant way, but I’m going to give a mechanistic treatment a try…
If a trait (mousy or m) is recessive, then all copies in that creature must be mm for the trait to show. any dominant allele will hide it (Mm).
cross mm with MM,
all offspring Mm and the trait(but not the allele) has vanished.
Continue to cross with MM and you’ll not see mm, just more MM and Mm.
If you start crossing the population of MM and Mm randomly, then rarely a mm will reappear as if from no where.
If you start a line with MM, then m is lost from that line.
I have grown thousands of open pollinated seedlings. The appearance of the vast majority were highly suggestive of them being the result of self pollination. Mr. Ralph Moore was of the belief that it is the rare OP seedling that is a cross with something else.
It is totally varietyy dependent. If you have hips on i.e. The Fairy it is allways from foreign pollen. Same for many vars that never produce hips without a compatible pollen source and an efficient pollinator…
I’ve had mixed results on selfing hybrid teas. For me the best seed set was by crossing with another plant of the same variety. I cover the seed parent as I would normally do to prevent any other pollen entering by mistake. Hope this works for you. My goal on selfing is to produce extra strong disease resistance…ha ha ha…we shall see what happens.
“Mr. Ralph Moore was of the belief that it is the rare OP seedling that is a cross with something else.”
Exactly. Case in point: I am 100% certain that Moore’s ‘Mr. Bluebird’ which is listed as ‘Old Blush’ X self is in fact a hybrid involving one of the “blue” multiflora Ramblers. Ralph had both ‘Velichenblau’ and ‘Violette’ at his nursery and I suspect one of these contributed its genes in this case.
Almost all the new cv of corn are made with diploïd inbred lines (because more than 2x lines are too difficult to “purify”).
The parent lines are self crossed for 7 generations to obtain pure lines. Which means homozygous lines for all the “working” alleles so let’s say you get a FF line for the father line and a mm line for the mother line.
After 7 generations of selfing, the plant and the corn ears are very small with often only a few kernels (because of the repeated inbreeding) but it doesn’t matter. When you cross the mother homozygous line with the father homozygous line, you have the heterosis effect which gives a very nice, healthy and predictable plant because only the selected traits will express thanks to the pure lines.
It would be interesting (but quiet long) to try the same procedures with roses…
I liked these old posts a person could find with a search. Since the change they never come up. What a shame, so interesting, and told of the struggles to understand and overcome the problems of rose hybridizing.