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The Colour of Roses

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The Colour of Roses

Post by OzRose on 15th October 2010, 18:02

I'm hoping someone tell me how colour is determined in roses . Does one colour have dominance over others ?
It's been intersting reading through rose pedigrees and seeing how many white roses have a lot of colour in their background.

cheers. Rosalie
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OzRose

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Re: The Colour of Roses

Post by The Lazy Rosarian on 16th October 2010, 08:22

Rosalie, I hope you plenty of time for reading the answer to your question, as I reckon Simon might have a short novel in the way of an answer, he is our genius of genetics Thumbsup
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Re: The Colour of Roses

Post by Admin on 5th December 2010, 20:59

Sorry to disappoint... I'm still trying to work it out too... Iknow that white can mask a lot of colours and a white rose can breed like a coloured rose but not all whites act the same way. I know stripes appear to be dominant but there is something not entirely straight forward going on there too. It's not as easy as saying one colour is dominant to another etc as there are top colous, base colours, under petal colour, over petal colour, picotee colours, and a hundred other patterns. It seems like colour is zonally controlled (like a white eye or a hulthemia blotch), and to top it off the internal chemsitry can affect the expression of the colour as can the structure of the petal.... so... unfortunately I don't think it is that easy and if it is... I still haven't cottoned on... all I know is that I get pinks... a lot Wink

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Re: The Colour of Roses

Post by AdamE on 14th December 2010, 20:01

Here's what I know about color. They say color in roses is made up of anything between 20 to 100 genes.

So the basic level of dominance is Pink and Yellow** are dominate to all other colors. Then dark red. And white is recessive to all colors.

Some points on indivudual colors:

Mauve seems to be a mix of colors.

You have two main types of red coloring. Pelargonidin coloring (orange) recessive to cyanidin pigment (red) [the pelargonidin can show through the red. Red roses has the dominant cyanin gene in at least two of the four chromsomes] pelargonidin genes have also been linked to weaker seedlings. The one pigment above also causes certain old red roses to blue and burn with age.

While Yellow color may be co dominate. A lot of the times it is mixed in with say pink so you don't see pure yellow. Secondly it can be turned into perfume in many roses any crosses with European roses like gallicas will eliminate most of the yellow coloring by causing the pigment to change into fragrance. lastly the yellow color is affected by the pathway. Some yellows like Austrain Cooper hav a full pigment pathways and other yellows have only a partial pathway. this is a totally different set of genes than that for the yellow pigment.

The same pigments that are responsible for lavenders are the same pigments involved in browns, tans or russet colored roses the proportions are the only difference. Also it seems that the yellow roses are some how related to the mauves.

White roses come in two types one is recessive to all other colors and apparently this is the most common type found in modern roses. But in some species their is a separate gene that instead of coding for pigments it prevents any pigments from forming. Apparently this is dominate, but I do not know an example.

Stripes are dominate. It is not clear whether it is a gene or a virus at the moment that causes it. But simply put when you have stripes you see one color as the ground usually the dominate color gene wise red and then another recessive color as the striped part say white stripes.

Spots seem to be dominate.
Hulthemia seems to be dominate

Different eyes and patterns I do not know yet.

Genetically speaking in modern roses (tetraploids) you are looking at something like this for a single rose

4 genes for the underside of the petal (two copies from each parent)
4 genes for the upperside of the petals "....."
4 genes for the eyezone "..."
+ any assessory genes for color (Hulthemia Blotch, spots, stripes, carotene pathway for yellow roses, fragrange genes could also affect color, even petal thinkness genes)

When you do the math that is a lot of possible combination's. Helps to explain the wide range of colors in roses however.

I hope this was helpful. Still trying to learn a lot of the genetics part myself.




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Re: The Colour of Roses

Post by AdamE on 14th December 2010, 20:33

OZrose sorry for the late reply. I do not look at the forum as much as I should. Some other thoughts about color.

When crossing roses from totally different species backgrounds some interesting things appear. Some of these genes in question probably have different purposes than color but when crossed with other roses the color is what is affected.

Example 1: there are certain photropic genes. mostly arising in the R. chinese class of species. Most roses fade with age but this gene causes the pigments to change and get darker when exposed to sunlight.

Example 2: the species R. foliosa native to north america in the wild it has only two color forms some form of pink or white. Yet when crossed with other roses these roses can for some unknown reason take on a deep purple shade. I do not think this is a gene for pigment but something that effects the pigment that is present.

Example 3: Certain roses have higher PH or lower PH than average. This is certainly regulated by some short of gene or genes and this can effect the coloring that is present.

Example 4. R. rugosa when it makes hybrids with other species a lot of times you see a purplish cast to the petals in these hybrids. Again I do not think this is a pigment but some sort of assesory gene. However an interesting thing happens when crossed with R. nitda that purple cast is eliminated for some reason.

Example 5. The R. spinossima class has a way of creating some very unusual freckled patterns when mixed with certain classes of roses. Their are several examples of R. spinossima crossed with R. foetida and none of these at least that I know of have these patterns but other crosses involving modern roses and r. rubignosa seem to inherit these patterns. Also pure spinossima never seem to have the patterns. The spinossima that have these patterns seem to be all spinossima crossed with something else.

The point I am trying to make is that we do not know all of the genetics of roses yet. Their is still plenty to learn. Also as we experiment with some of the species or bring together two independent lines of breeding together we may find new head scratchers to ponder.

Also sorry for my spelling errors I am sure there are plenty.

AdamE

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