I have been (mostly) a lurker here for some time now reading and learning as much as I can. I am also an avid breeder of animals and am well versed in rabbit coat colour genetics and am learning poultry genetics in terms of feather colour, feather type, comb type, skin colour etc inheritance patterns. In each of these breeders will often speak of particular genes and have a good understanding of their dominance etc. Reading this forum I have not noticed any/much discussion of particular genes and was wondering if this information is known? For example is miniaturisation in roses due to the presence of a dwarfing gene and if so what is it’s dominance compared to standard growth genes? Is it’s inheritance Mendelian an so predicable? Is red due to a particular gene and if so what is the order of dominance? e.g. is red more dominant than white which is more dominant than yellow etc? How are pink roses formed? Is it due to incomplete dominance etc. These are just hypothetical questions not based on ANY fact at all but none-the-less I am curious as to what we actually know about the effect of specific genes and how they are expressed and inherited. I have more than 50 different varieties of roses growing and am looking at them as possible crossing candidates and so this kind of information would be useful. E.g. I have Altissimo, which is a single climbing rose. It formed OP hips for me this year so it got me thinking, is single flowered a specific genetic gene and if so what would happen if you crossed it with a double red flowered rose? What would happen if I put a hybrid tea such as peace over a polyantha such as The Fairy? So many questions…
Here is a partial list of the primary inheritance(s) of some of the key traits. It isn’t always as simple as what is listed, so that is why I say primary. Hope it is helpful.
Black spot resistance
Powdery Mildew resistance
Double flowers (degree of doubleness)
Flower color- flavanoids and carotenoids
Flowering under low irradiance
Prickles (degree of prickles)
Good question Simon. David, thank you for the summation.
Thanks for the replies and the excellent link.
By quantitative I am assuming you mean these are the polygenic genes or those that exhibit some kind of dose effect (i.e. incomplete or co-dominance etc)? So there are red roses and then there are RED roses… And then to add to the equation polyploidy will add further modifying genes.
This information is exactly what I was thinking about.
Am I also to understand that flower colour then is also based on a a small range of base colours like white and red and then the range we see between that is due to the pressence of certain modifying genes that affect the level of expression?
Exactly, the two papers by Dubois in that link above from Henry really help to bring that point home. There are a couple other papers on anthocyanin inheritance including that one by Marshall and Cullicut.
One thing that I’ve found and reported on in the newsletter and highlight in the book chapter on rose breeding I wrote is the strong effect of vacuole pH in the petal. Roses that tend to blue with age tend to have an increase in vacuole pH in the petal cells. With the same primary rose anthocyanin (cyanin) we can get pinks, red, and purple and what they appear as is strongly affected by pH. We can select for roses that have a stable lower pH (more truer red), higher pH (more purple), or transition from low to high to get roses like Distant Drums. Just pulverize a consistent amount of petals in distilled water and test pH and compare for yourself. That’s what I did from inspiration from an article demonstrating that the purpling over time of the cut red rose ‘Mercedes’ is primarily petal pH spiking. I report the pH’s of some various cultivars and seedlings of mine in the RHA article. In addition, carefully selecting for pelargonidin or peonin to get colors of interest is a smart approach as well. It may be hard to determine for sure how much and of what anthocyanin one has, but in general looking for the characteristic shades of each one and guessing may be good enough.
For yellow, I just try to think of it as quantitative as well hoping to select those that are more at the extreme of a deeper yellow. It’s been hard though. I think of anthocyanin and carotenoid pigments as separate beasts and that they just end up later both contributing to the overall color effect of the flower. Anthocyanins are water soluble and in the vacuole and carotenoids are fat soluble an in plastids. Anthocyanins tend to be in the cells of the upper layer or two of the petal surface only, while carotenoids tend to be found throughout the petals cells.
In addition to pH there are other factors like metal ions that interact with color pigments to express the color that we see. Light of course is important in some cultivars for expression like Double Delight. There are also genes governing petal surface anthocyanin expression to give us dramatic bicolor flowers. I’m not sure how that is inherited, perhaps it is somewhat recessive or controlled by a limited number of genes.
I think these general principles are nice to guide us, but they are only a snapshot of the deeper, more complete truth of what is going on. For instance, if color was just quantitative, we would expect to see a wider range of color in wild pink species from white to a nice red. Perhaps some genes just become fixed over time and things stabilized out at pink???
I’m excited you are thinking so much about genetics and want to take advantage of the knowledge already present to guide your work. It’s nice to just try things for fun and see what unexpected surprises come up, but it’s also very nice to take advantage and use what others have learned and can benefit and streamline our work as well.
Thanks for the excellent reply David. I haven’t read through all the articles listed by Henry yet but will eventually get through them… I’m a high school science teacher and my specialisation at university was biology so I took genetics and biochem so I guess this is how I approach all my breeding projects. I have to use my degree for something otherwise I’ll forget it Kids tend to glaze over when you start talking about biochem and genetics to them LOL.
Isn’t it the pH of the petals that caused the blue rose project to fail? They had no trouble introducing the transgene but its expression was still not blue because of the pH of the petals so the pigment was acting like an acid/base indicator. One of the tasks I did with the kids in my science classes this year was to extract the pigment(s) from flowers by steeping the flowers in hot distilled water. Then I said to them ok, let’s see if the extracted pigments work like an indicator and they did… In neutral distilled water they were generally a bluey/green, with added HCl they became redish, and with added NaOH they became green - I found it funny that even white flowers showed this effect… I got bored with the old purple cabbage lab so got them to try lots of different things… rose petals were one that also showed ths same effect which, to me, demonstrated that the pigment of a rose could very easily be affected by the pH of it’s internal environment.
Carotenoids are photosynthetic pigments that you can clearly see when you extract chlorophyll from green leaves and then separate them with ordinary paper chromatography but I thought petals were non-photosynthetic so I wonder why there would be carotenoids in the petals… maybe an adaptation to advertise the pressence of the flowers to pollinators shrugs.
In snap dragons pink is due to the incomplete dominance of the red gene over the white gene resulting in an intermediate expression in heterozygotes… maybe there is some homology in the rose genes that give a similar result.
So is there any basic colour inheritance patterns? What are the base colours? Red White and yellow? Is there and order of dominance in the colours?
Most of the roses that I am working with are tetraploids, so the degree of dominance vs. recessive for a particular color is guesswork at best!
Pink is definitely the more common color that you will see. But, as you have probably seen, there are many shades of pink with differences in saturation of color and blend combinations with other colors - so that the range in colors is pretty incredible. Very light pink and very light yellow seem to be very common also. These will appear white in any but the coolest temperatures. True, pure white is not as common but it seems somewhat dominant (at least when combined with other colors, it tends to lighten the other colors).
Orange and red are fairly strong also in inheritence, but a bit less so than those above. Yellow seems to be the most rare, especially the dark yellow color.
As mentioned above, purples tend to produce pinks probably due to pH differences between the parents. It seems that inheritance for the proper pH (more alkaline) to show good purple is probably recessive.
Most of my seedlings and modern roses used in my breeding program each likely has genes coding for most of the above colors, which is why you can find any of these colors in certain populations of seedlings.
It seems also that there are different zones on the petals (both on the upper and lower surfaces) that have specific traits that can independently behave as either dominant of recessive to other traits. This has been seen in the hulthemia hybrids. I plan to write a short article about that for the RHA in the next few months.
“Most of the roses that I am working with are tetraploids, so the degree of dominance vs. recessive for a particular color is guesswork at best!”
You know, I awoke this morning thinking exactly the same thing… How do you work out an order of dominance when there could be 4 copies of every gene instead of just two… and they could all be different!
lol we are all such plant nerds. I love it I wake up with random plant ideas, too.