R. xanthina Lindl X Blue rose,Can you make roses bluer?

Can R. xanthina Lindl flavonoids make roses turn blue?
Can Japan’s APPLAUSE genetically modified delphinidin make roses turn blue?
The following content was not edited by me, but found online
First, let’s understand the synthesis of anthocyanins. The genus Rosa contains four anthocyanins, cyanidin (corresponding to the most common pink to rose color in roses), geranium (fluorescent orange like “Scarlet Queen Elizabeth”), paeoniflorin (purple Rosa), and delphinidin (purple to blue). There is no delphinidin in modern roses

It is generally believed that the conditions for the formation of blue flowers are

  1. Contains delphinidin

  2. High vacuolar pH

  3. Containing flavonoids or flavonoids as co pigments

Fortunately, the ability to synthesize delphinoside obtained through transgenic transformation can be inherited

In the following study, R. xanthina Lindl was confirmed to contain only flavonols and to express strongly in hybridization. The introduction of flavonol synthesis genes from R. xanthina Lindl is clearly the most effective way to increase the concentration of co pigments.

Flavonol, the yellow pigment in R. xanthina Lindl, can act as a co pigment and combine with cyanidin and delphinidin to shift the color towards blue, forming a stable sky blue or even cyan color



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I’m not sure if delphindin is really key to producing truly blue roses, but for anthocyanidin and flavonol to produce the desired blue color, it seems from what I’ve been reading that the presence of metal ions (Fe and/or Mg) might be necessary. This apparently works at a low vacuole pH in flowers like Meconopsis and Corydalis, and without delphinidin (both contain cyanidin instead). The anthocyanidin and flavonol naturally present in some roses might then already have that same potential; it’s possible that ensuring the presence of the necessary metal ions in sufficient quantity, whether by way of some sort of genetic modification or otherwise, could be the final piece of the puzzle:

https://www.researchgate.net/publication/7101963_Ferric_ions_involved_in_the_flower_color_development_of_the_Himalayan_blue_poppy_Meconopsis_grandis

Stefan

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Thank you for your link, which also mentions flavonoid and delphinidin, which require rose experiments. The yellow color of xanthina Lindl is flavonoid, not carotene. The varieties with higher pH values in the table are bluer. On this basis, can adding delphinidin and flavonoid make roses bluer? You can try to cross xanthina Lindl with a blue rose with a higher pH value or a blue rose with a higher delphinidin content. I have never seen an example of xanthina Lindl crossing with a blue rose online, and I would like to know the results

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One of the two studies that I linked to only mentions delphinidin as a contrast to the anthocyanidins that they found responsible for the blue color in Meconopsis and Corydalis. That color is not produced using delphinidin, but cyanidin, which is also the predominant anthocyanidin in roses.

I’m not sure why you mention carotene–carotenoids seem to have nothing to do with the processes under discussion. The ratios of anthocyanidin to flavonol found in the blue flowers that depend on the presence of metal ions (particularly Fe, or iron, in the case of cyanidin, with kaempferol as the flavonol in the case of at least Corydalis) are actually similar to that already found in some of the roses in the study that you cited, as is the vacuolar pH.

Without a process involving a metal ion to form a complex, delphinidin will probably not produce a true blue color no matter what kind or amount of flavonol is present. I suspect that is why the genetically engineered roses that produce delphinidin still appear an unimpressive lavender color, not blue, and are no real improvement over naturally bred lavender or purple roses that contain primarily cyanidin. For the same reason, breeding with Rosa xanthina will likely not produce significant gains, even if you could increase the amount of flavonol in a hybrid by doing so.

Delphinidin happens to be the anthocyanidin that is found in the inflorescences of Hydrangea macrophylla, which are generally pink to reddish in the absence of Al ions. The blue color of Delphinium flowers also depends upon a complex involving dephinidin and Al ions; their vacuolar pH is also acidic.

It seems to me that a better approach would be to find a way to engineer roses with the same pathway that leads to metal ions, particularly Fe (iron), interacting with the anthocyanidins and the flavonols to produce true blue color in other flowers. It isn’t clear that delphinidin is necessary or even helpful for making that happen in roses, especially if they don’t tend to absorb or accumulate Al (aluminum).

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I really appreciate your ability to reply to my message. Upon hearing this news, my heart felt like a sinking sensation. I was very sad, and I felt like I had to accept that all my efforts had been wasted. I originally thought I could increase the content of rose flavonoid and delphinidin by hybridization, increase the pH value, and the rose could turn blue. I was suffering a significant blow. Should I stop cultivating blue roses?

Absolutely not! If you enjoy the colors of the “blue” roses that you grow now, then there is no reason to stop, or to stop trying to improve them within the limits of what is possible through conventional breeding, as long as you aren’t expecting to produce a truly blue rose that way. What you have now are really all lavender and purple roses, and you should certainly be able to breed better ones–maybe even bluer lavenders and purples, but I would say that is possibly more likely to happen by chance than by design.

It probably isn’t realistic to think that the vacuolar pH of roses could ever be shifted through breeding to a range where the anthocyanidins would naturally become blue; those of individual cultivars may be higher or lower, but will likely always remain acidic. I don’t think that we have any understanding of the genetics involved in shifting that through breeding, so we don’t know what sort of cross might raise pH higher (if higher pH actually leads to bluer purples, even when it is still acidic).

Even in Chrysanthemum, an additional gene to metabolically modify the anthocyanidin (in its case, delphinidin) was needed to reach a bluer color through copigmentation (I would still say that it is not a pure blue in effect, but more like the lavenderish to purplish “blue” found in Campanula):

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Sincerely thank you for your suggestion. I looked at the xanthina lindl that I had planted for three years and had not yet blossomed.I was disappointed. It took me many ways to obtain the seedlings, and I carefully nurtured them for three years. If it cannot be used to dye blue roses, then using it to crossbreed may only achieve cold resistance and disease resistance, and there is a high probability that future generations cannot repeat flowering. The above hybrid combination I will continue, after all, the materials are available, and perhaps there will be miracles

I am a fan of ordinary blue roses, and I am currently eliminating roses in my garden that have colors other than blue, unless they are resistant to disease or have a strong aroma, and can only remain. A combination of blue and purple can produce blue and purple. I have discovered that the ancestors of blue and purple roses are gray pearls, and they must have a lineage of gray pearls to turn blue. Now my idea is that blue and purple cross each other, and blue and purple cross with strong aroma or disease resistance, Blue-purple and Austin roses cross, and there doesn’t seem to be a blue-purple Austin rose yet, right?

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Solid disease resistance, especially in combination with strong fragrance, is certainly one of the things that is most generally lacking in modern lavender/purple roses. Every effort made towards progress in that direction is laudable, I think. Crossing roses in that color range together can produce more roses of similar coloring, but there is literature from past breeders regarding various other combinations that can and did result in lavender/purple roses. One important article about this came from Edmund LeGrice in 1968, kindly put online by Karl King: Le Grice: Unusual Colors (1968) (you can find more articles on this subject, and others, that Karl has curated here: Rose Breeding Articles)

In the LeGrice article, the point is made that yellow roses bred from Rosa foetida are already a key component of many, if not most, of the classic modern lavender/purple roses.

I think that you should try crossing Rosa xanthina with lavender/purple rosess to see what happens anyway, because we can’t know for certain what will happen, and even if you don’t find that it leads to bluer roses, you might discover something else useful along the way. It will probably not be an easy path, with chromosome number differences, infertility, longer juvenility in at least the earliest hybrid generations, and a slow return to reblooming descendants (likely with a diluted genetic contribution from R. xanthina by the time you do get reblooming seedlings).

I’ve wondered if David Austin had something of a distaste for blue-purple roses, since he never really seems to have gone in that direction with his selections. I’m not entirely sure why, since he fully embraced the warm side of the modern rose color palette, so maybe it was just a personal dislike of the color. Beyond Austin, there already are modern roses with lavender/purple flowers and an old-fashioned flower form. However, the combination of strong disease resistance with good fragrance (along with other good garden rose qualities) has been elusive. Of course, that combination has been fairly elusive in modern roses of all colors.

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“In spring, the leaves of any variety look very healthy. As the temperature rises, I feel very painful in summer. The black spots and falling leaves of roses make them in a bad state, especially the black spots on the leaves, which make them directly bare.”

Thank you for the link to the article you sent. In order to find out some varieties of parents, I have a member of the helpdefine website. I think Foetida is the main factor in the black spots of all roses, and I feel disgusted. His contribution is great, bringing yellow, which can be used as other roses, but without it, I believe that the history of roses also has yellow roses

There is a saying on the internet that:; Foetida’s carotenoids are amaranthine, which is stable in nature and not easily degradable. At the same time, their color is the darkest. Foetida brings the ability to synthesize ROSEYANIN ROSEIN, which is bluish purple in color. Foetida is the beginning of modern “blue” roses. The sweet aroma substance, geraniol, citronellol, is produced by the decomposition of carotenoids. The rich, dark yellow varieties that do not fade are doomed to lack the aroma of Damascus, and the aroma is often sour

Blue Dream, a type of blue purple that does not have the lineage of gray pearls, can also become close to blue under certain conditions. You can try mixing blue dream, a type of blue purple rose with the lineage of gray pearls. However, the reality is cruel. A friend of mine has experimented with these combinations to produce a rose color that is still biased towards the red of blue dream, so he stopped this type of combination, but I don’t think so. Perhaps he hasn’t tried enough

“Xanthia seems to have let me down. When you told me it couldn’t make roses blue, I didn’t want to use it anymore.”. “But why not try? The experiment will only yield results. As mentioned above, I will combine several roses (the bluest rose in the grey pearl lineage, the blue dream of not relying on grey pearls to turn blue, the genetically modified non blue purple rose in Japan, the rose with flavonoids and high ph value), and don’t give up.”. “I must have thought about the chromosome multiples of xanthina combined with roses, but in fact, many triploid roses are fertile, otherwise there is no result when pollen is used as a male parent. It seems unrealistic and difficult to add and change some element data in hybrid roses. I know, but I don’t have laboratory conditions, so I can only sow seeds through pollination.”

There are many blue roses in Japan that are really close to blue, and I have also collected many, but most of them are not resistant to disease and have a weak rise. Regarding disease resistance, I think the most resistant is the Knock Out series. I have collected three types, Rainbow Knock Out, Double Knock Out, and Pink Double Knock Out. “They are all low and hardworking, and I recommend crossbreeding to many flower friends. They say that Knock Out is ugly and unwilling to be used for crossbreeding, but in fact, many resistant and good-looking varieties are their descendants, such as MEIbenbino=(Baby RomanticaX unknown) X Knock Out, which is very resistant to disease. The resistance of MEIbenbino is derived from Knock Out, so non resistant blue-violet varieties should be hybridized with the Knock Out series to obtain disease resistance.”, “I don’t know who the resistance genes of the Knock Out series come from, and I can’t find the specific history. According to the actual cross combinations, their descendants can indeed inherit the ability to resist disease.”. “The resistance of roses in the carpet series should come from Wichuriana. I think this resistance will be diluted in multiple crosses. Of course, I have also collected several carpet series rose varieties.”.

My breeding requirements; Short, hardworking, resistant to disease, with a strong fragrance. The best color is blue purple, and the flower type is like an Austin rose. I can’t wait for the roses to make me faint! I like Fragrant Cloud, which has many fragrant descendants, as well as Rose Pompadour. Wonderful? It has a strong aroma from flower buds to withering, and is not susceptible to external factors. Many varieties of strong aroma are susceptible to external factors, such as weather, temperature, and light.

Can I complain about Austin Rose here?

“His rose varieties are almost not small, and even if they can be potted, they need to be re cut. They cannot bloom many flowers, without the spectacular effect of planting on the ground. The plants are tall and tall.”

The aroma is myrrh and anise. Oh, my god, does Austin himself like this aroma? Many friends and I don’t like this aroma, which is uncomfortable. Moreover, Austin roses can inherit the myrrh aroma, which is a bit bad
The colors are yellow, pink, or rose red, and he will not breed roses of other colors. Even if blue and striped roses are hybridized, they will be eliminated immediately? He is bred according to his own preferences. If you don’t like it, maybe he likes it himself. Indeed, this is also true. It has formed his own breeding style. Everyone likes his rose type and is used by rose breeders all over the world to crossbreed

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While the introduction of Rosa foetida into hybrids generally did not help the problem with blackspot, many roses that have no R. foetida in their background at all are still incredibly susceptible to it, so it really does not deserve to be singled out for blame when it comes to diseased modern roses. Most old garden rose hybrids, even Chinas and tea roses (with rare exceptions), and some species like Rosa moschata are very prone to blackspot in my climate; most of the better ones are able to carry on growing and blooming in spite of it, but that is all. Only a very, very small number have sufficiently minimal symptoms to be considered healthy overall here. Of course, there are other diseases here that can badly affect even those that do resist blackspot well, like cercospora and anthracnose (not to mention rose rosette virus). Thank goodness we have low disease pressure from rose rust or mildew, at least.

It’s true that triploid roses can be quite fertile as a general rule, but when working with more distantly related species and ploidy differences at the same time, that rule might not apply quite as well. It’s good to be prepared for some challenges, at least at first, but such challenges can help to build character (in roses and in rose breeders).

There are few fragrant first-generation or second-generation offspring of Knock Out that have been named and introduced. The only one that I have been able to try (Sweet Spirit) failed to possess either Knock Out’s blackspot resistance or lasting fragrance after the spring flush. Maybe that kind of cross just hasn’t been attempted enough times or with enough fragrant parents, but I would caution you to select the healthiest fragrant roses possible to use in such crosses. You can (and should) try something like Fragrant Cloud, of course, if that intrigues you. You’ll never know for sure what might come of it unless you try, but do it with eyes wide open.

I feel about the same as you and your friends do about the “myrrh” fragrance, overall. However, in some roses, when there is an anise note mixing with citrus or other spice notes, I find the combination to be exceptionally pleasant (Fair Bianca comes to mind)–but in most roses the myrrh component does not smell especially good to me. I think that it was probably something of an obsession for Austin. I agree that having a unique “eye” (and nose) helped to make his roses stand out from others, and his breeding and marketing work helped to renew appreciation for diverse flower forms and greater fragrance in garden roses, to the point that the market itself was altered. That said, his plants did not always stay the sizes that his catalogs advertised, at least not in warmer climates than the UK. Some of them do grow well as climbers, and climbers can be an asset even in space-limited modern gardens. They draw the eye upward and can make a small area feel larger, and they can add more romance and drama to a setting than a compact shrub might.

Stefan

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Im glad we can chat again. Perhaps there are some roses of lineage where Rosa Foetida’s lineage record cannot be found. I guess there are still some, almost all roses now. They all have Rosa Foetida’s ancestry, and there is almost no powdery mildew in my garden. The high temperature and exposure to sunlight in summer are the source of all evil. Because of exposure to sunlight and black spots, most roses remain bare, while other diseases are okay. The biggest threat is black spot, which is caused by high temperature and high humidity. The high temperature in summer on my side lasts for a relatively long time, which may reach 40 degrees. It is easy for roses to dehydrate if they need to be watered every day, I have collected some low maintenance roses and I plan to crossbreed them, hoping to select offspring with good resistance to black spot from their offspring and not lose their leaves in summer.

You may be right about the question of rose triploid, but depending on luck, there may be fertile rose individuals.

Sweet Spirit has a better resistance to disease than other roses. It is not as resistant as Knock Out. There are definitely a few roses with strong resistance and strong fragrance, and even fewer roses with strong resistance and beautiful fragrance. There are few perfect roses, and there are not many strong fragrance roses with online beauty on the adr list. Perhaps strong fragrance will bring more diseases, and I will also use the roses on the adr list to hybridize. After all, the awards they have won are not for nothing. After all, adr is not the strongest award for disease resistance. Disease resistance still depends on Knock Out. I will try to cross all roses with Knock Out. It seems unlikely that two parents who are not disease resistant will have disease resistant children.
Unexpectedly, our thoughts are the same. For aromatic end products, sometimes it makes people feel smelly and nauseous, with the aroma of fennel and end products. It can be said to be a series, but it can be considered as two flavors. Fennel is still acceptable. According to Fair Bianca’s information, it is a pure strong final medicine. Some people also say that mixed final medicine can make it smell good. I prefer the sweet aroma of cinnamon, clove, musk, bee honey, In Austin, I only selected a few varieties (HERITAGE, Abraham Darby, Wedgwood, JUDE THE OBSCURE, Geoff Hamilton) with relatively low final aroma as the maternal hybridization selection. Although some varieties are not final aroma, they may carry final aroma genes that can be displayed in future generations. Hybridizing other strong aroma varieties may dilute the final aroma, but I do not want to use roses with final aroma to hybridize, According to my friend, the fragrance of the final drug can easily be passed on to future generations in hybridization. Even my individual friend insists on not using Austin roses. He feels that there is pollution from the fragrance of the final drug, but I am okay. I think beautiful looks are the most important. In order to obtain and quickly obtain the rose shape of Austin, I have to use Austin roses. Austin roses are his own idea, his own idea of breeding roses, "We think there are shortcomings, but maybe he doesn’t think so. I think his rose history lacks a dwarfing process. There is no hybrid miniature rose, which is not suitable for family potted plants. He hasn’t said it is suitable for potted plants. He has already passed away, but the company is still there. It seems that no good varieties have been listed in recent years. I still very like Austin’s flower patterns, which are popular with many people and can be easily obtained through hybridization.This is inherited from Duchesse de Montebello, and there is no inheritance of the aroma of Duchesse de Montebello. Unfortunately, he has taken a wrong direction, mixing the rose varieties with the fragrance of the final drug, polluting all his rose varieties
Rosa moschata What I would like to recommend is (Marie Pavie, Aunt Mary’s). They are a combination of Rosa multiflora (honey aroma) and Rosa moschata (musk aroma). They smell good. I like their rose aroma. It seems that Rosa moschata is one of the sources of strong fragrance. Do you know who the parents of Marie Pavie and Aunt Mary’s are? There is no detailed introduction online. Blush Noisette and Jaune Desprez also have a strong aroma, but they are too tall and have other shortcomings. I don’t think they are suitable for hybridization. The rose plants I want have always been short

It sounds like Sweet Spirit has much worse blackspot resistance for me than it does for you. However, in addition to overall climate and other site differences, there may be more blackspot strains in my garden. I do have quite a collection.

Breeding for habit and disease resistance in roses does not always, or even often, follow a straight or predictable path. Roses with relatively poor disease resistance do sometimes lead to ones with better disease resistance. Small-growing roses can frequently produce large-growing seedlings, and vice versa. Limiting your parent selections strictly to only those varieties that look much like the rose you are trying to breed (particularly in terms of plant size) might be overly limiting. Even tall ramblers can produce compact, everblooming shrub seedlings; for instance, ‘Sweetime’ originated from a cross between ‘Blush Noisette’ and Gourmet Popcorn. However, if growing space is a problem, then it may be necessary to constrain the sizes of the parents you choose to work with anyway. If disease pressure is too high and you don’t use fungicides, some varieties might be very challenging to cultivate for use in crosses.

Not all Austin roses have a background containing genes for the myrrh (fennel/anise) fragrance, of course, and they are not a genetically cohesive group. Abraham Darby is a purely modern rose in its makeup with no contribution from the ‘Constance Spry’ background (with its myrrh fragrance coming from ‘Belle Isis’, not ‘Duchesse de Montebello’). Some roses with ‘Constance Spry’ in their background do not have any obvious myrrh fragrance, like Jude the Obscure. It could be that when it is diluted or modified sufficiently, it adds complexity to a fragrance without actually being identifiable itself.

The backgrounds of both ‘Marie Pavie’ and Aunt Margy’s are unrecorded, although ‘Marie Pavie’ is usually speculated to be a seedling of a Noisette (maybe ‘Blush Noisette’; it’s worth mentioning that ‘Blush Noisette’ is healthier than ‘Marie Pavie’ in my experience). Aunt Margy’s is pretty clearly from a hybrid multiflora background, but because it is a “found rose,” its discoverer could not have known its actual parentage. Here, ‘Marie Pavie’ is not resistant to blackspot at all, making it difficult to grow; Aunt Margy’s is significantly healthier (though not absolutely perfect). Aunt Margy’s has grown fairly tall for me, for what it’s worth, although I’m sure that it would stay small with more pruning. Besides Rosa moschata and Rosa multiflora, other species of section Synstylae are also useful for contributing heavy flowering and often sweet or musk-like fragrance traits to their hybrids.

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I’m not afraid to say that Pink Double Knock Out and Double Knock Out roses have shown poor growth and disease resistance in my area, which many people don’t believe. However, the reality is that Rainbow Knock Out is completely not sick in my area, very diligent in flowering, and blooms 365 days. Who doesn’t want to cultivate more black spot resistant roses?

The genetic lines and fragrance of roses are unknown. Two tall parents may produce short children, while two strong fragrant parents may produce children without fragrance. These are all questions of probability. I think in fact, tall parents tend to produce tall children, while two strong fragrant parents tend to produce strong fragrant children. I have a friend who crossbred Rose Pompadour and Yves Piaget to produce strong fragrant offspring,I will plan to cross two strong fragrant varieties with each other, or cross strong fragrant varieties with disease-resistant varieties. For example, some rose varieties will easily produce very fragrant offspring. Abraham Darby’s offspring have many fruit aroma children, and Eyes for You are also prone to produce fragrant offspring of fragrant musk. You are right, perhaps Abraham Darby and JUDE THE OBSCURE contain a relatively small proportion of Austin myrrh ancestry, Therefore, they are not purely final drugs, making people prefer them. Abraham Darby’s fruit aroma may come from Aloha. Some people say that Aloha’s fruit aroma is produced by the combination of musk and tea, and the combination of musk and tea produces a fruit flavor
I think Marie Pavie and Blush Noisette are very similar in some places. The shape, color, and aroma of the flowers are also very similar, and they can spread far away. This may be due to Moschata.Another amazing thing about Marie Pavie is its cold resistance. Who brought this ability to her? I don’t think the plant shape of Blush Noisette is very suitable for crossbreeding with modern roses. I don’t want them to have exaggerated offspring with plant types like octopus. Of course, I don’t rule out that they have short and compact offspring. Aunt Mary’s, I think it’s a pity that he only has pollen in early spring, and generally there is no pollen and no fruit. I like their sweet and musky aroma very much. If possible, I will let Marie Pavie Hybridizing with Aunt Mary’s in the hope of producing a strong fragrance that surpasses my parents. Aunt Mary’s has no descendants online, Marie Pavie has descendants online, but they are not very outstanding. They do not have genetically strong fragrance, and Ghislaine de Felimondel does not have strong and attractive descendants. I originally wanted to buy, but vine and light fragrance have led me to not want to buy. Are there any short roses with strong musk fragrance recommended?
I also collect offspring of strong fragrance. Can the offspring of moschata without musk aroma be called the offspring of moschata? I don’t think so. Some people have said that moschata’s musk aroma is a fragrance enhancer and catalyst, and roses with moschata’s ancestry will be more fragrant. In online examples, moschata hybrid Abraham Darby, moschata hybrid Graham Thomas, is a strong cinnamon aroma, and (cinnamon aroma, honey aroma, musk aroma) is the best aroma in roses

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Delphinidin is no guaranty of blue coloring. When present, it still needs co-pigments, and often some metal ions. The old double daylily Hemerocallis ‘Kwanzo’ contains delphinidin, but it has taken decades of effort to get some markings that really look blue (so I’ve read).
I have some absrtacts by a Japanese chemist, Yasuda, who had some interesting observations that might be helpful.
http://bulbnrose.x10.mx/KKing/RosePigments/YasudaExpression.html
http://bulbnrose.x10.mx/KKing/RosePigments/YasudaInsoluble.html
Coincidentally, Sweet Peas have been pushed forward by addition of another species, the yellow and red Lathyrus belinensis. The hybrid, Lathyrus x hammettii, has added shades of blue not formerly seen. Also some reverse bicolors.
https://www.drkeithhammett.co.nz/everything-sweetpea/

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Karl, that was my take on delphinidin (and cyanidin) as well–and since there seem to be suitable co-pigments present in roses already (unless there is something about the specific molecular structures of their flavonols that makes them less effective), I suspect that a lack of suitable metal ions might be the main reason that roses fail to achieve a really blue color.

On the subject of short roses with strong musk fragrance, it’s probably a relatively short list; I can’t think of any I’ve grown with that particular scent other than maybe ‘Marie Pavie’ itself (and I suppose ‘Marie Daly’, which is said to be healthier, would also, but the one I purchased turned out to be a mislabeled ‘Marie Pavie’ instead). I have not yet grown correctly-named plants of ‘Mignonette’ or ‘Paquerette’, but some descriptions suggest that they could also have a musk scent. There are small roses that have other strong fragrances, depending on how short they need to be for you. Some of the poly-teas like ‘Clotilde Soupert’, ‘Perle d’Or’, and ‘Etoile de Mai’ come to mind, and in general the combination of tea rose background with close descendants of Rosa multiflora seems to produce a fair number of well-scented smaller roses. If you have a paid membership on HelpMeFind, you could do an advanced search to combine low-growing roses and strong or moderate fragrance. Doing that, I see more roses that I’m not personally familiar with. However, if you have the space, I think that you could obtain useful numbers of compact or low-growing roses at least by using a rose of that size as one parent, even if the other parent grows larger. It is not necessary to use only compact roses to generate more compact roses, and you might be surprised to find out that some offspring will be much larger than their parents if you do. Control over height seems to be fairly complex, and you can probably learn as much by looking at the heights of any known offspring as you can by simply considering the parent’s own height.

I don’t feel that ‘Marie Pavie’ is exceptionally cold-hardy relative to similar roses in terms of cane hardiness, but it may very well have enough R. multiflora in its background to confer better hardiness than noisette roses typically have. In very cold areas, because ‘Marie Pavie’ is low-growing but vigorous, it can recover quickly to flowering size after freezing back. That is a virtue in such climates where fewer repeat blooming roses survive with much living growth above the ground in spring (they also often have shorter growing seasons, so faster flower cycles and lower growth are a useful combination there).

You are well read up, Eric, on much of the literature I took as dogma several years ago, but I personally would caution against too many of the generalizations you will find. The genome of the modern rose is ridiculously complex, and inevitably the roses worthy of introduction are the exceptions to the rule. (I believe it is in neighborhood of 1 out of 10,000 seedling that currently are deemed worthy of introduction in the best breeding programs.)
I had loved the idea of working with descendants of Marthe Carron (e.g. Bonica) but decided it would never give me anything but scentless, blush and white roses – coraborated by the experiences of others. The exceptional (and under-promoted) Ivor’s rose (Flamenco Rosita) has been an example of the rare exception.
The English rose form was never difficult to create. It was merely rejected for over a half century as it was not in fashion, and countless low-centered cup-shaped seedling ended up in the compost bins of history as breeders strived for the high-centered teas of the show benches that drove sales.
I would certainly encourage you to look at Kordes roses, and go directly to their German site. I feel they do give fairly objective evaluations. Many of their roses may get huge in warmer areas and are generally slow to realize their reblooming potential, but I am a huge fan.
As for Rainbow K.O., I found it could get pm, and personally thought it was a ratty-looking mess. I think it’s parent (rebranded as Coral K.O.) might have better potential, but I cannot speak from personal experience.

Regarding metal ions, Yasuda specifically mentioned iron and calcium as components of the blue spherules.
I forgot to provide the link:
http://bulbnrose.x10.mx/KKing/RosePigments/YasudaBluingRoses.html
http://bulbnrose.x10.mx/KKing/RosePigments/YasudaBrown1988.html
The Musk scent could turn up in some of the Dwarf Polyanthas because some Noisettes and Tea-Noisettes were pollen parents of many of the earliest offspring of the Japanese R. multiflora.
Several years back I tried to sort out the various introductions and distributions of the Multiflora/Polyantha/Thyrsiflora gang.
https://bulbnrose.x10.mx/Roses/breeding/SisleyPolyantha1876/SisleyPolyantha1876.html
The Thyrsiflora type refers to the distinctive arrangement of the flowers. I saw this form often along the highways of Tennessee, but usually in places where I could not park and take pictures. But the trait does pop up in the far removed ‘Popcorn’.
popcorn0

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I’m really distressed about the need for metal ions to make roses blue

A bit off topic, but I wish the entities that invested immense amounts of money and time into creating a “blue” rose, had instead pursued a way to engineer perfect Blackspot immunity into the genus, rather than chasing after novelty.

Agreed, Paul, but we all know they stood a far greater chance of mining gold from a true, visible oddity than a real improvement. For the most part, they did their homework, at least in marketing. Initially, Applause was only available in Japan, where the appreciation for Human manipulation of Nature would be sufficiently appreciated to generate the $35 PER STEM introductory price. I honestly doubt a rose which would significantly resist fungal issues would have sold for anywhere near that amount.

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