Colored hypocotyl - Do they act as marker for successful transfer of pollinators genomes

[Roseus]

Hello everyone!
Since the beginning of my breeding work, the darker colored hypocotyls which freshly emerged from the soil caught my special attention. In my further observation, the seedlings mostly proved to be particularly remarkable with a clearer hybrid character. For the seedling with green hypocotyl you need some more time to identify the real hybrid if it is one.

Only a few months ago, I stumbled across the following post by Warren from 2014:

@Warren

Don (would be possible to use coloration of the freshly germinated hypocotyl as a marker in roses) I use this every year as a means of determining whether or not a cross has worked for me. Certain pollinators I use, produce seedlings with dark coloured hypocotyl, this ensures me that the part of pollinators genome has been transferred accross to the seedling. It is the first thing I want to see as it breaks through the soil.

Interestingly, Warren’s statement confirms my own observations.

For many of us, the seedling season is here or just around the corner. I am now curious to find out how you deal with this topic. Is the color of the hypocotyl also a special selection trait for you or are you without this preference and inspect and select all seedlings equally.

Thanks for your time and feedback!

[RikuHelin]

I find this interesting - if comprehend it right - germinated seedlings from an already crossed rose created by a Quebec hybridizer (Andre) caught my attention.

The second example is one of my crosses -both photos today.

The seed leaves (proto-leaves not 2nd true leaves) of Andre’s cross were dark and underside burgundy coloured. Thought latter odd and dismissed it as a random occurrence.

I would assume from extrapolating the “Warren”excerpt above in the first already existing cross that l should see a “clear pale white green” cotyledon stem - a bit unclear as to being coloured distinct (red- brown).

The second is “first ever cross” this year of a rugosa hybrid with a “maybe found damask” and has a stem with a stronger distinct colour.

Species in other pots for the most part clear pale white - green.

[Roseus]

Hi RikuHelin,
thank you very much for your interest in this exciting topic. Your photos show exactly the meant difference between the hypocotyls, you call it “cotyledon stem”. The degree of coloration can of course vary. Maybe the attention of this little detail can be a helpful assistance in one or the other case.

[RikuHelin]

I agree it maybe a useful “qualitative test or indicator” of a cross.

Something that has been lacking in my crossing vocabulary (tools).

May avoid twiddling my thumbs for 6 months or two years while the seedling grows to provide physical proof. Since l tend to once bloomers, its all the more useful.