Here, in Australia, we have a polyantha called ‘Alice Amos’. I grow it here and it is quite nice and healthy. It does not go fully dormant when the weather is hot (here) and it retains most of its foliage and has a very good bill of health. I have two OP seedlings from my plant of ‘Alice Amos’ and they do not experience summer dormancy nor do they lose their foliage.
‘Alice Amos’ is from a seedling (pollen) crossed with ‘Tip-Top’ (aka ‘Baby Doll’) (seed) and ‘Tip-Top’ is from ‘Trier’ x Rosa foetida. Kim has mentioned to me that Rosa foetida has been implicated, by LeGrice, in the development of good purples and this seems to be true in one of my seedlings ( 'Amity' Rose ) as the purple is different to other purples in that it does not blue and seems to have a different luminous quality compared to other purples such as that from ‘Ebb Tide’ etc. When the weather really hots up the purple seems to lean more towards pink. However, what is interesting to me is the reports of excellent health of ‘Tip-Top’ and what I am seeing here health-wise in these seedlings. ‘Tip-Top’ seems to have a clean bill of health on HMF and I can’t fault ‘Alice Amos’ much (she does lose a few leaves in Summer but not many), and I certainly can’t fault my own ‘Alice Amos’ seedlings much yet. It seems that foetida’s short lived foliage tendancies are not present in this mix. I am wondering more and more whether there is much more to the link between black spot and foetida than we first thought and that maybe by choosing a different rose to start with yellows could be made that don’t have these spotty habits???
Lammerts (1947) listed ‘Tip-Top’ and some other Polyantha roses derived from Rosa foetida. The problem, thus far, is that however healthy these varieties may be, they are not the deepest yellows. If we only need Foetida’s carotene to enrich to perfume, these Polys would be useful. But to get the deeper color we might try crossing to a yellow Tea, for instance.
‘Mevr. Nathalie Nypels’ is not at all yellow, but nicely fragrant. I once raised a seedling from it (I forget the pollen parent) that had pale yellow or ivory petals. It was also very fragrant. I didn’t have a yellow Tea handy at that time.
‘Tip-Top’ or other Foetida-derived Poly might be crossed with one of the better yellow Floribundas or HTs (e.g., Allgold, Henry Fonda).
It is also peculiar to note that even when tetraploid R. foetida bicolor is used as the pollen parent, the offspring seem to come up shy one septet of chromosomes.
BTW: I got Macoboy’s Ultimate Rose Book through Interlibrary Loan. The passage I needed was the discussion under ‘Miss Edith Cavell’, not in a separate section.
Is that when crossed with diploids or other tets or does it not seem to matter? I’m thinking that something like ‘Tip Top’ put back to foetida might help with the yellow saturation issues. I was thinking a yellow Tea might wash the colour out even more.
Foetida contributes increased carotene production (and more complex forms of carotene) as well as the lack of a carotene-cleaving enzyme that starts the conversion of carotene to perfume.
Yellow teas are not so deeply pigmented as Foetida, but they do lack the carotene-cleaving enzyme. An alternative would be one of the deep yellow Tea-Noisettes. They inherit the lack of carotene-cleaving from the Teas, along with a more complex carotene from the Musk/Noisette side of the family.
The loss of 7 chromosomes when Rosa foetida is used as pollen parent seems to occur whether the seed parent is diploid or tetraploid. ‘Lady Penzance’, however, seems to have received 14 chromosomes from R. foetida.
That makes sense. It does make me wonderwhy , however, if Teas lack carotene-cleaving enzymes why they seem to resist forming deep yellows so tenaciously? Don mentioned something interesting many years ago that ‘Fortune’s Double Yellow’ might be an alternative non-foetida source of yellow.
The depth of color in yellow roses is due to at least four factors.
Type of carotenes produced in the plastids
Size of plastids
Number of plastids per cell
Presence/absence of carotene-cleaving enzyme
Carotenes vary from colorless to light yellow to deep yellow (various shades) to orange to scarlet (lycopene). Tea roses alone may have simpler carotenes than musks and noisettes, but the latter burn off their carotenes as perfume. Tea-Noisettes keep the more complex carotenes intact, providing a deeper yellow than the “pure” Teas can manage. ‘Fortune’s Double Yellow’ does have more complex carotenes than Teas in general, which could lead to deeper yellows … if both the size and number of plastids is high. I don’t have a microscope to look at the plastids, so I’m waiting for further information.
‘Marechal Niel’ is reportedly more deeply colored when grown at high temperatures. I’ve only grown it once, in a mild climate. It was pale yellow but richly fragrant. ‘Diamond Jubilee’, a seedling of MN, is not sweetly scented in hot weather. I’ll have to remember to sniff it next time I see it in mild weather.
The behavior of MN suggests that the carotene-cleaving enzyme is inactive (or less active) at high temperatures.
There are a few Teas with Fortune’s Double Yellow color such as Clementina Carbonieri from which I got full yellow non paling triploids with HT pollen?
I forgot to mention two other possible contributors to yellow:
Harborne (1976) noted that Quercitin 7- and 4’-glucosides contribute to the deep yellow of Rosa foetida.
Smith, et al. (2000) “Although the quercetin yellow faded rapidly on exposure to UV radiation, the colour of luteolin darkened. This was due to the formation of a photoproduct absorbing maximally at 450 nm.”
I can’t say for sure that luteolin is responsible, but I have noticed that ‘Cl. Devoniensis’ sometimes yellows as the petals begin to fade. It’s not a particularly attractive shade. In fact, it reminds me of the immortal words of Frank Zappa: “Watch out where the huskies go, and don’t you eat that yellow snow.”
But if this yellowing tendency were combined with carotene and quercitin yellows, it might improve the lasting quality of the color.