The findings/interpretation of these researchers is different than Dr. Foucherâs teamâs work in Angers, France. I wonder if maybe these researchers just saw that the same mutation wasnât in R. rugosa and for some reason assumed what R. rugosa had/was âwildâ type. Their paper was a number of years ago now and Dr. Foucher and his team have done more work since.
âRecently, a French rose group conducted KSN genotyping of a wide range of rose cultivars and found that some Damask-related roses (e.g., Damask, Moss, Hybrid musk, and Bourbon roses) and Asian roses (e.g., Hybrid rugosa and Hybrid bracteata roses) are CF but have no mutated allele of KSN from R. chinensis (Araou 2011).â
Iâve heard Dr. Fabrice Foucher present his work on this topic a few times and there are mutations he presented in the rose KSN gene in rugosa, multiflora, R. chinensis, etc. and he compared them and I think expression levels as well. He sequenced the gene in many rose groups and cultivars- rugosa, multflora, chinensis, bourbon, damask, etc. and presented a really nice paper of rose cultivars in France over a century or so and how over time more and more of the newer cultivars switched towards the R. chinensis allele with stronger repeat/continuous bloom. There appears to be a retrotransposon that has landed in the gene to reduce or totally hinder expression. Some alleles have different amounts/sections of the retrotransposon in it. Depending on where this additional DNA landed, how large it is and specific sequence, etc. it can totally inhibit the expression of KSN or reduce it enough to get some stray repeat like in the Damasks and their relatives that inherited the same mutated version of KSN, which is likely the R. fed. allele from my understanding. I should see if Fabrice would be interested in some of the more free flowering R. arkansana to test that species as well.
With continuous/repeat flowering being due in large part to a lack of functional KSN and it being recessive (just one functional copy of KSN seems to compensate fine and lead to one time bloom as we cross repeat blooming roses with one time blooming species), it is interesting to see that when we cross repeat flowering rugosas and polyanthas, rugosas and modern roses with R. chinensis backgrounds, etc. we do get hybrids that repeat bloom, suggesting that when the different alleles are brought together there still is dysfunctional/lack of enough effectively expressed KSN.
I suspect roses like R. rugosa, R. fed., R. arkansana as species where this has been selected in nature and is prominent across the species, they have some secondary genes that govern the expression of repeat/continuous flowering, generally preventing it, to contribute to survival (i.e. juvenile bloom would put a plant at a disadvantage before it is established). For R. chinensis and R. multiflora, it seems like the repeat bloom in these backgrounds is a more recent event out of the wild (i.e. R. odorata, R. gigantea, and R. multiflora) and plants have been perpetuated by horticulturists over the centuries without the selection for those seedlings to have secondary genes to suppress repeat bloom in the juvenile stage or awkwards times in the growing season to bloom and realistically make seeds. If they put too much energy in repeat bloom at a young age or all of the growing season,their neighbors can more easily out compete them in nature. The R. multiflora allele from my understanding from Fabrice is found in some of the early completely multiflora based polyanthas. Again, as they are crossed with R. chinensis background roses, we tend to get strong rebloomers. The alleles of different backgrounds have different regions of the gene that are disrupted helping identify the source of the gene, but ultimately functional KSN synthesis is reduced/doesnât occur. When we cross rugosas with modern roses, we often get greatly delayed expression of free flowering, as is with many of the Explorer roses, but that may be more so these secondary alleles that are in place out of R. rugosa to help the plants carve out a space in nature first to survive before blooming freely.
I suspect there have been many events of transpons messing up the KSN gene across rose species. In order to be expressed, the alleles need to be homozygous recessive and that takes some time for alleles to accumulate and then a limited number of individuals expressing rebloom. When there are individuals that do repeat bloom, I suspect in many situations those plants have a hard time competing. It is especially interesting to see how in R. rugosa, for instance, that a mutated KSN (if we trust Fabrice correctly determined its KSN is mutated) has led to a number of associated alterations for it to be successful/a benefit in the species. R. rugosa can ripen its fruit much more quickly than many other roses (so some of the later flowers can actually lead to ripe fruit) and young seedlings typically have delayed expression of repeat bloom, etc.
It would be fun to sequence the KSN alleles in Above and BeyondTM. It is tetraploid and its mom is a mini that likely has the R. chinensis alleles and contributed 2 copies and its dad is a hybrid of R. virginiana and R. laxa. The R. laxa parent likely has an allele similar to, if not the same as, R. fed. which leads to a little KSN expression from my understanding at times and a bit more stray rebloom versus continuous rebloom. A&B blooms on new wood from the base later in summer and from some side branches if conditions are favorable in mid summer, but then is able to shut down before winter comes and is very hardy. Perhaps if we were able to catalog the different alleles out there and someone would be willing to sequence and check different cultivars or wild collected roses breeders are interested in using, we could use that information more strategically breeding for repeat blooming/continuous flowering roses bringing in different genetic backgrounds and having a clearer understanding of what phenotypes we could expect.
Perhaps that would be too much work, and researchers would prefer to focus on mutating the KSN gene through CRSPR through targeted mutation to really mess up the KSN gene to get no expression and get continuously flowering roses out of any genetic background. That process would probably lead to someone getting a utility patent and prevent us from working with those roses for continued breeding for a couple decadesâŠ