Question on inheritance of the color white

Is there are rule of thumb for white roses? Is the white color generally dominant, recessive or variable?

Admittedly, I am not a big fan of white roses, but will be using one as a parent next year. Any feedback would be helpful.

Thanks!!

It is recessive generally, but color may be better approached as a quantitative trait as suggested by a past research article by De Vries and colleagues. Anthocyanins (pinks, reds, and purples) and flavanoids (yellows and some oranges) are additive in their expression. This means that there are multiple genes controlling the intensity of color by effecting the pigments in different ways (genes effecting pH, efficiency of pathway, quantity of precurser molecules…). Red x white generally gives shades of pink. White x white should generally give white or very light colors. There probably are some exceptions. What traits are you using the white parent for? I’m thinking of using ‘Morden Snowbeauty’ more because is has had very good cane hardiness. I’m thinking of getting away from white as well and thinking about what richly colored disease resistant roses I can cross it with.

Good Luck,

David

I believe Griffith Buck wrote abt white in discussing his own work developing hardy roses. That was 20 yr ago or so. He noted that he got an awful lot of them and suggested suppressor genes, as well as recessive for color.

Not to bore you too much but my observation in doing crosses of various shades of pink is, as already noted in another reply, quantitative in general. So 2 med pink give a wider range of colors in offspring. Suppose you have tetraploid and 2/4 genes for “red” color. In self or equivalent crosses you’ll get a small fraction White (ideally 1/16), a small fraction red (1/16) a lot of middling pink and some more and less intense.

However, white may be absence of a color gene at each of several steps and not just the quantity of one step that makes the cyanidin or whatever is “red”. So in some lines there may be half whites and half good pinks in a cross if there are a lot of genes missing, or there may be almost none if the two parents complement each other’s defects.

I once wrote an article about sweetpeas where this was first studied. In that case crosses of two whites could give a colored flower cause each white was absence of a different step in a path.

With roses, I haven’t crossed white on white to see. But very likely a white missing an early step in the pigment path would be so pale and insipid, lacking what’s called copigment, that it would get thrown out. If you look at the commercial whites, they have a kind of glow that’s likely to be material absorbing UV light and just lacking the last step to make it into a pink pigment. They also usually have some pink or yellow underlay. And in certain seasons it comes out stronger. That suggests some genes are there but may be temperature sensitive, or needing high sugar levels or whatever. Hence the idea of suppressors.

When people first started doing recombinant gene transfer in petunias, they discovered a remarkable thing. Putting in a color gene didn’t make the color darker, it suppressed it entirely. A new path for gene regulation was discovered because of those studies. Sometimes you can get too much of a good thing. Hence we have all sorts of strange complexities in hybrids and that’s how we get some of the more striking color shades in roses.

My personal favorite from my own crosses is one I call Silver Sunrise. It was Rise N Shine pollen onto New Dawn. It is a 3 ft tall, thorny like Wichuriana, disease-resistant mini which is almost stark white in some weather, yellow at the base in other seasons and more toward a New Dawn pink other times. The name reflects both parentage and color. Scarcely drops its leaves at 0 F, needs trimming only to shape the bush. But it’s sterile as near as I can determine.

David and lawrence, your posts are fascinating and very informative. Thank you so much.

btw, lawrence, it is pretty tough to bore me with genetics especially when it comes to plants.=).