Hi all. I am growing an amazing bright yellow floribunda called ‘Lo and Behold’. (Got it from the (also amazing) Burling Leong at Burlington Roses.) This rose cranks out perfect modern-style spiral-centered flowers so frequently that I have to disbud it to encourage the plant to put on size. I once had the pleasure of meeting Luis Desamero, who discovered this rose as a sport of the mini 'Behold" (He is responsible for spotting and making available to us “Gourmet Popcorn”,a sport of the mini 'Popcorn". Here is my question: While climbing sports and interesting variations in color are not uncommon, I don’t know of any other rose that has sported from mini to standard-sized. What is your experience? Does this happen to other roses you know about? What do you think is the mechanism that causes this to happen? Thanks! Brian
Hi! I find sports extremely interesting since, in simple terms, usually they go from the expressed dominant phenotype to something that’s already inside the DNA of the variety due to a genetic ricombination. Spontaneous mutations, that produce a new alleles that were not in the DNA of the variety, are very rare. Sometimes recessive mutations find the way to “fix” the mutation and go back to the original wild phenotype (I think that’s the case of repeat flowering varieties sporting to once blooming).
The miniaturizing gene is dominant, so I guess it can happen that minis sport to regular sized plants, even though any other example come to my mind. I’m not sure that it is as sesirable as other sports are; minis often have severe health problems, and it’s probably easier to find good floribundas/HT in varieties bred to be that
Sporting larger and smaller isn’t all that uncommon. Peace sported to a miniature (Baby Peace, 1962, 'Baby Peace' Rose ). I’m sure there have been others but not all of them are registered or reported. It’s possible for a rose to sport to whatever genetic traits are behind it, so if there are floribundas, HT’s and climbers behind a mini, those are all fair game for it to express.
I’m thinking of the miniature version of that lovely monster, “Mermaid”, often called “Happenstance” (Talk about apt names!) EVERY single plant of Mermaid that I have ever observed has at least one patch of Happenstance on it. Weird. It’s just the opposite “mini to full-sized” conversion…I haven’t seen this ever yet. Until now. Have you?
Brian
Don’t forget Little Mermaid. Happenstance has very short internodal lengths so it appears compressed, “arthritic”. Little Mermaid is miniaturized so it IS a smaller climber version of Mermaid instead of a “stumpy” shrub.
You’re right, Kim. I forgot about Little Mermaid. And I hadn’t known that Happenstance was one of those short-internode things. So, you are the one to ask: Do you know of any other mini-to-standard-sized sports? Thanks. Brian
Hi Brian, there likely have been others, but none come to mind.
So this is a more complex topic than it can seem.
First, miniaturism and gigantism are a concept of whole plant relativity. Second, partial and general dwarfism and semi-dwarfism are an entirely different concept. these two concepts relate to similar but different hormone systems for growth.
A simple example of gigantism is a species diploid where all plant parts are wholly larger than the ploidy typically should be. We all know what miniaturism is, and how quite dominant it can be. ‘Old Blush’ vs. ‘Madame Falcot’ is an easy example of this. Diploid rugosas bred into HT types by Kordes is a decent bloom size/ploidy gradient example of this.
Miniaturism seems to be there or not, and gigantism seems to be a gradient. Perhaps it is additive or polygenic. We don’t actually know yet genetically. What we do know is that one can get a hybrid tea (ish) from a tri/tetra miniature with few miniature alleles bred into HT. Once that miniaturism disappears, many things were weren’t aware of are possible. We also know the concepts of dwarfism and mini/gigantism stack. ‘New Zealand’ obviously has gigantism and tetraploid with its large part sizes, and semi-dwarfism is apparent in the very tight internode spaces between the leaves. 3 generations bred away from a rose bred from 2 miniatures. There are also tetraploid HT x HT crosses registered as miniflora. How? The likely answers is that they hit a genetic recombination where gigantism was not gained. There are no evident signs of phenotypical miniaturism, yet its a single-flowered 2 to 2.5" bloom with small stature and foliage.
Microminiatures are likely the result of concurrent miniaturism, absence of gigantism, and semi-dwarfing. They have been known to produce larger variants. This could be as simple as a gain of some gigantism from a mutation.
All any of these things take is one allele missing or present. Many are one mutation away from a SURPRISE! moment. And they can be induced a multitude of ways, including just simple intense UV in high elevations. Most of these mutations go un-noticed. How many people would notice a partial semi-dwarfism mutation, in, for example, only the roots? Almost no one. But these things exist. The list of semi-dwarf variants in rice alone could be an entire essay.
There is an alternative mechanism that does not force us to imagine a mutation undoing another mutation.
Ralph Moore (All About Miniature Roses, 1967), raised a useful idea regarding the nature of Miniature Roses:
This brings up yet another often observed phenomenon known as witches’-broom. These dwarf, multibranched growths which occur quite often on conifers and other plants are an abnormal growth formation which may occur almost anywhere on a branch or tree. A number of dwarf ornamental conifers have been propagated originally from such brooms.
http://bulbnrose.x10.mx/Roses/breeding/Moore/MOORE.html
It is known that some instances of “Witches’ Broom” are caused by fungi that produce cytokinins [a class of plant hormones that promote cell division, or cytokinesis, in plant roots and shoots].
On the other hand, some dwarf strains of maize are deficient in one of the gibberellins [a group of plant hormones that stimulate stem elongation, germination, and flowering].
http://bulbnrose.x10.mx/Heredity/AugerGibbsCorn2005.html
Either an excess of cytokinins or a deficiency of gibberellins could result in miniaturization.
In the course of divergent evolution, species can modify their own chromosomes with various rearrangements. A gene located on chromosome A in one species may be found on chromosome B of another. Erlanson (1936) discussed this phenomenon in ‘Orleans Rose’:
The occurrence of rings of four [chromosomes] in the rose “Orleans”, therefore, shows that it is a structural hybrid as well as a hybrid in the general sense. The low frequency of quadrivalent formation in this plant is due to the smallness of the exchanged segments, since chiasma-formation is fortuitous and random.
http://bulbnrose.x10.mx/Roses/Rose_Pictures/O/orleans.htm
In such a case, a hybrid may inherit one copy of a gene from each parent: one on chromosome A, one on chromosome B. Nothing weird about that. But when this plant is self-pollinated, ordinary Mendelian reassortment requires that about 1 out of 4 offspring will not receive this hypothetical gene on chromosome A, and 1 out of 4 will not get it on chromosome B. And of course, 1 out of 4 will receive this gene on both copies of chromosome A, and 1 out of 4 will get it on both copies of chromosome B.
Assuming that this hypothetical gene is involved in the production of either a cytokinin or a gibberellin, we should allow for some lethality. When the normal balance of growth factors is disrupted, the numbers are not likely to work out neatly. For example, what happens when a pollen tube carries two copies of a gene related to production of a cytokinin or of a gibberellin?
Moore raised self-seedlings from ‘Old Blush’ China. Or so he claimed. Some doubters have suggested that the seedlings resulted from stray pollen. Maybe, but these Minis keep turning up wherever ‘Old Blush’ is found. And there are some apparent duplications. Moore’s ‘Mr. Bluebird’ is strikingly similar to Rosa indica purpurea Andrews.
The purple variety is said to have been first imported from China about the year 1810, to the gardens of Lord Milford, under the appellation of the Blue Rose; and as such many of them were sold at a guinea each, although the plant had not then flowered: such is the fascinating force of novelty, which even in embryo has the power to charm. This rose of expectation, when its blooms unfolded, no heavenly blue disclosed, but a red purple, which as it faded off became much paler, less brilliant, but of a bluer or colder purple, which gives to the fresh opened blossoms a very different appearance contrasted with those retiring; and although the blue’s celestial tint is wanting, it is nevertheless a graceful and very abundant flowering Rose.
http://bulbnrose.x10.mx/Roses/Rose_Pictures/Rosa/R_indicapurpAndr.html
The description fits ‘Mr. Bluebird’ very nicely.
Moore continued:
Another grew into a dense free blooming plant with flowers almost duplicating Pink Joy (which is a self seedling of Oakington Ruby). Cuttings of this plant were difficult to root. Still another one of these seedlings grew not over 8 inches high and bore soft pink double flowers resembling Peggy Grant. Cuttings of this were also difficult to root.
The only seedling of the lot to be introduced was one which has slightly larger foliage and lavender-blue (or magenta) colored semi-double flowers. This selection, Mr. Bluebird, grows readily from cuttings and has proven quite cold hardy. Some seed hips are produced, carrying up to five seeds, but germination is very poor. However, among its self seedlings have been several growing not more than 6- to 8-inches tall with miniature leaves and tiny double flowers usually not more than one-half to one-inch in size. Petals are usually very narrow (lance shaped). No seeds have been observed on any of these seedlings but some pollen is produced.
I mention the above because of the apparent segregation of “rootability”.
And for the record, dwarfs have been raised from the second generation of other hybrids, such as Burbank’s hybrid walnut, ‘Paradox’ [Juglan Hindsii x J. regia]
In the same row, as already intimated, there will be bush-like walnuts from six to eighteen inches in height side by side with trees that have shot up to eighteen or twenty feet; all of the same age and grown from seeds gathered from a single tree. This rate of growth continues throughout life, and the fraternity of dwarfs and giants has been a puzzle to layman and botanist alike.
"These second generation hybrids vary as much also in regard to foliage and general characteristics of form and development as in size. Some resemble the California walnut, others the Persian ancestor, and there are scores of variations, the manner of growth of some of which—notably those that trail their limbs along the ground like a gourd or squash—bears scant resemblance to that of any walnut.
http://bulbnrose.x10.mx/Heredity/Burbank/BurbankWalnuts/BurbankWalnut1914.html
It is worth noting that ‘Little Mermaid’ and ‘Happenstance’ originated as root-sports, as did ‘New Dawn’ and ‘Mordelahanty’.
Risley (1959) presented evidence of rose roots that do not get the full complement of chromosomes.
“N.H. #5425 (Skinner’s Rambler x Yellow Pinocchio). A sterile triploid with 21 chromosomes. Only 33% of the cells examined had all 21: 4 had 20, 7 had 19, 6 had 18 and 3 had only 17.”
It may be that a shoot derived from a root would be different from other shoots growing from branches.
http://bulbnrose.x10.mx/Roses/breeding/RisleySatellites1959/RisleySatellites1959.html
Yeah, “missing puzzle pieces” is definitely something to consider. I saw a study recently that had a list with species where there expectation did not quite match tested reality.
Hi Karl K.! This really is interesting. I had no idea that root cells could be so genetically varied. Could this be a way to unlock the compatibility of a very promising rose, say, a “sterile” triploid or some other chromosomal oddball we have long ago given up on as a possible parent? Has anyone deliberately attempted rose root cuttings, even, as I think of it, exposing a segment of root to light and air as a kind of layering, (by means of a hole in the soil) in order to stimulate shoot growth originating from the root tissue?