This is sort of a ‘mystery of life’ question. I guess I’m hoping that someone like Dave can answer this genetically someday:
The rose I’m thinking of is the English Rose Sharifa Asma:
On the surface it has a lot going for it. It is moderately disease resistant (doesn’t defoliate in my climate even without spray). It has an incredible bloom period (I need to note that my rose is planted up against my house w/ a E-SE exposure). It’s one of the first to bloom and goes up to November. And the blooms are quite fragrant. The bush stays about 3 ft in height, but throws up strong canes. The rose sets hips and seeds easily.
However, the seedlings in my experience (and others from what I’ve gathered in the past on this forum), are terrible. They don’t grow, and the germination rate is poor to begin with. Now I understand there may be something faulty with the genetics to prevent good germination, but once germination has occurred, why are the seedlings so poor? I can understand the OP/self pollinated flowers, might be doubling up on detrimentatl/lethal genes, but even outcrosses have this same trouble. I would think, that if the rose is ‘good’ and outcrossed to a ‘good’ rose, that at least a percentage would be also of at least average quality.
That’s a great question Chris. I wonder that too for some of the cultivars I’ve been trying like ‘Carefree Sunshine’. I’ve been leaning towards the idea you proposed about detremental / lethal genes. Perhaps these roses rely on such a perfect balance of various genes and alleles that when they go through meiosis, favorable allele combinations are broken up and very difficult to recover in the progeny. I have one seedling that is relatively nice, but it’s seedlings are generally poor- disease prone, weak… However, last year I was surprised that in one specific cross the seedlings were a lot better and many were much more blackspot resistant than both parents. So these two roses have good combining ability and probably compensate for each other’s genetic weaknesses. Maybe there’s a rose out there that will combine well with this cultivar you are working with.
I’ve been thinking more over the years about the value of inbreeding to weed out some of the deleterious alleles and then use the best inbreds (still somewhat weak probably) to outcross to potentially improve the progeny. I’m always impressed how it has helped the MN mum breeding program. Dr. Ascher started this and good headway has been made. Mums are hexaploid! He worked with another professor who didn’t quite share his passion in this direction and in the early years many of his inbreds were “accidentially” plowed under because most didn’t look so hot. Good thing Dr. Ascher persevered.
A technique that I practice and recommend is to use mixed pollen on difficult mothers.
When I harvest pollen I normally use it “pure” for about a week (outside it is carried in a styrofoam box). When brought in for the day it goes into a refrigerator. After I have used it for about a week the pollen goes into a special container that I have built. It was made from 2 “dollar store” glass/plastic salt and pepper shakers that have the lower half made out of a glass container with what (I assume) would be called a male thread. The upper plasic half contains what I would call a female thread. I removed just the tops (where the holes are) of each plastic half. I expoxed the 2 halves together (top to top) with a fiberglass fine screen between. The result sort of looks like an hourglass with a filter at the narrow junction of the 2 halves. I labled one side as “TOP”. I put all of the old pollen plus some some water absorbing plastic units from aspirin bottles in the side labeled “Top”. I shake the unit, and the now mixed pollen drops into the lower half. I access the mixed pollen by unscrewing the lower glass jar and dipping a small brush ino the jar. The “hourglass” is stored in the refrigerator.
This is sort of a “let nature decide” what will work for a given set of genes. If I then get something that looks like it has potential, I cross it back to the original mother and to other roses of interest.
I also “hope” that although some of the old pollen is dead, that the dead old pollen may be providing chemicals to help override the plants self sterility and/or provide nourishment for the still living pollen.
Have you tried ‘Carefree Sunshine’ with any Old Garden Rose types? I ask, because I have quite a few hips forming on an old found damask (all from ‘Carefree Sunshine’) and I’m hoping that the seedlings won’t be a sickly bunch. Unfortunately, the damask is already somewhat prone to mildew, but is very vigorous in spite of this fault. This is the first year that I’ve used ‘Carefree Sunshine’; but I’ve been impressed with it’s health and almost continuous bloom.
I’ve also got a few hips on ‘Rose de Rescht’ from ‘Carefree Sunshine’. So, I’m hoping maybe ‘Carefree Sunshine’ will combine better with these OGR’s, than what you’ve experienced.
Hi Tom! My biggest disappointment with C.S. seedlings is that they haven’t been very blackspot resistant, even though C.S. has been holding up very well in the Twin Cities, just a little rust. The seedlings seem to be a little weak too. Hopefully your crosses will be different. I crossed C.S. with a lot of different shrubs and species, but haven’t crossed it with damasks or old garden roses.