Title: INHERITANCE IN TRI PLOID HYBRIDS OF ROSA
Author: LATA P
Author Address 23 SALISBURY RD, LONDON E7, UK.
Published in: Environmental and Experimental Botany, volumn 23, pages 85-92, (1983).
Abstract: " Crosses between a diploid, Rosa rugosa typica and a tetraploid, R. spinosissima pimpinellifolia resulted in 20 triploid seedlings. The characters of these hybrid plants with regard to the habit of growth, stem armature and foliage closely resembled those of R. s. pimpinellifolia while certain other features were intermediate in nature. The hybrids produced soft pink flowers, unlike their parents which had carmine-red and yellow-flowers, respectively. Fruit set was abundant in parents and absent in the hybrids; moderate flowering was observed during every flowering season. Detailed scanning electron microscopic studies of the pollen grains of the triploid hybrids revealed that the malformed and mainly shrunken pollen grains of hybrids also had a poorly developed exine pattern relative to that of the parents. A comparison of the cytological characters was also made between the above mentioned diploid and triploid plants and 3 ancient Rugosa roses. The latter group consisted of diploids and a triploid which have been cultivated for more than 55 yr."
I’ve done a very similar cross; only difference – the spinosissima I used was white (not yellow). It’s interesting to see these results, since I’ve only assumed that the offspring are triploid.
I agree that the seedlings resemble the spinosissima more in some features but are intermediate in most. Also, most have soft pink flowers, although at least one has completely white flowers. I would differ in saying that the flowering has been fairly heavy (though not remontant) every year. Fruit set is definitely absent.
This may be a blessing, since this hybrid is so vigorous. I see a potential for it to be a weed. ;o)
I have three analogous crosses maturing two hips each, right now: rugosa X spinosissima (double white), rugosa X ‘Hazeldean’, and rugosa x davidii. I expect that these will give triploids also.
The link below shows rugosa X spinosissima
In the late 1940’s, Percy Wright crossed ‘Hansa’ with ‘Hazeldean’ ('Harison’s Yellow x Rosa spinosisima altaica) and grew many seedlings. He described this cross as “unhappy,” since most of the seedlings didn’t grow well. However, a few were okay. One selection he named ‘Musician’ (because of its changing tones of colours) and it was registered in 1953. Even though it only blooms once, it is an outstanding Rosa rugosa hybrid. On a mature shrub, the combination of light yellow, pink and red flowers blooming at the same time is a stunning sight. The shrub is slow to sucker and as a result this was probably the reason the cultivar never got into the nursery trade.
Several years ago, I developed one seedling of ‘Hansa’ x ‘Suzanne’. While the flowers were poor (single, small white), the shrub had healthy and attractive foliage. Unbelievably thorny though. I’ve repeated the cross to see if I can obtain better flowers.
I have no doubt there is potential in developing Rosa rugosa/R. spinosissima cultivars. But it appears it takes a lot of effort to develop acceptable selections.