Cass Bernstein Posted on Sat, Aug 16, 2008 some cpmments that did not get enough attention. At least from me.
----I wonder how many of you have read Guns, Germs & Steel? The messages concerning domesticated plants are pretty clear. (1) Domesticated species spread by latitude because a common latitude is where the climate zones exist for optimal growth. IOW, a rose well-adapted to latitude 32 is not going to be optimal in latitude 50. So breeding using species adapted to the target latitude makes a lot of sense for basic survivability. (2) The actual number of domesticated species compared to their close relatives is very, very small. That’s because the actual number suitable for domestic use is really rather limited. I wonder if using species that have proven successful in the past is the most likely avenue to success. Wide species crosses may produce interesting results, but in the long run, I have my doubts how useful those novelties will be - Lens’s R. multibracteata x stellata being a case in point.
Another question I’ve never seen addressed satisfactorily is why hybridizers spend little time selecting from within a species. One of the many lessons of Walter Lewis’s doctoral thesis from…1959?.. is the remarkable range of variation within a species. We know this intuitively, and it was used in hardy roses breeding in the USA (Hansen) and in Canada. I see little mention of it otherwise. I appreciate the practical difficulties in doing this, but I suspect it is often overlooked. Botanical garden material is already self-limited – where seedlings are usually selfs. And some species are clearly more uniform (i.e. from a more limited geographic area, perhaps even isolated) than others. But species like R. californica are dazzlingly, shockingly diverse, from foliage surface to armature to size. When I hear someone say they’ve used R. californica for breeding, my immediate question is: which one?
My last point is that, in light of all this, it wouldn’t surprise me if the major breakthrough in terms of disease resistance comes not from novel crosses but from genetic engineering by inserting the genes of species immune to certain fungal complaints (as R. laevigata is) into a modern cultivar, to create a super breeder. —
There are a few research about the last point with people such as the german Debener team looking for dominant monogenic resistance. I said him that if there were one such gene long ago it would be spoted and introgressed. And when generalized it will be broken down unintentionally selecting a new desease strain.
About Laevigata that superb species with leathery glossy desease free foliage I know one specimen that growing in a shady if airy place is miserably mildewing every year.
Another point of yours: …why hybridizers spend little time selecting from within a species…
Excellent remark I share. When breeding for frost resistance selecting species individuals from the coldest area seems obvious and not so much done.
Considering desease resistance there are a lot of difficulties in testing. I do not think someone can say he has collected all and every strain of a given funghus. Maintaining them in a laboratory appears not to be easy.
Even testing is difficult. I.e. I red somewhere that lab tested rugosa leaves are not as desease resitant as they are in gardens. I would like we had “plant introduction” clones banks with known resistance such as many plant breeders use.
Selecting decorative sp features was done at the very beginnings. There was then a “market” for species novelties with many “grandiflora” or “duplex” forms some whose botanical authenticity may be doubtfull.
Domestication is a quite different applied to ornamentals than to food crops.