Has anyone tried Rainbow Sorbet, Love and Peace, The McCartney Rose (the hybrid tea) or Fragrant Plum as seed parents?
Also, does anyone know how Love and Peace holds up to blackspot and mildew? I am wondering if it is any better than Peace (which is a martyr to blackspot and somewhat susceptible to mildew).
Any help would be appreciated!
Love and Peace has race specific black spot resistance. Vance Whitaker reported on that at last years American Society for Horticultural Sciences meetings and the abstract is in HortScience. Vance just successfully defended his Ph.D. last week!! He is a good friend and I am thrilled at all the work he has accomplished during his MS and Ph.D. with black spot resistance. During his MS he characterized different races for forms of black spot and in his Ph.D. took roses with different race specificity and crossed them and looked at segregation of resistance in the offspring and characterized additional resistance genes. What this means for Love and Peace in the end is that if you have the Race C form he has you are in good shape and there is one allele copy in L&P so half of the offspring get it. If you have other races in your garden that overtake L&P you have a problem.
Thank you David. I would love to read Vance’s writings!
David, maybe you can help me with my understanding of blackspot resistance. If I were to cross Love and Peace with a blackspot resistant rose that has race specific resistance to a different strain of blackspot (let’s say Baby Love), are the two resistance genes cumulative? I am assuming there are always exceptions to the rule, but I am trying to get a general idea.
I have not had much success with getting blackspot resistance in my roses. For example, on several occasions I have crossed blackspot free roses in my garden with each other only to get blackspot disasters. One example were my crosses of Carefree Sunshine with Basye Legacy. Both are completely blackspot resistant in my garden but not one of the resulting seedlings had any resistance to blackspot. I have also used Knockout (not extensively) and have yet to get a completely blackspot resistant rose.
Fragrant Plum is fertile, but most of its seeds will develop on the outside. McCartney Rose is very fertile too.
Great questions and point Shane. I have been disappointed with the resistance of Carefree Sunshine offspring too.
It is easiest to think of resistance in the two major forms- race specific (sometimes called vertical resistance) and non-race specific (sometimes called horizontal). Race specific is typically all or nothing. It is like a locked door in the rose. Unless the fungus has the right key, it cannot get in. These locks are typically single gene and from Vance’s work and the limited numbers of examples in roses out there, most roses with this have just once allele copy. So, there is segregation in the offspring for if they get the lock or not. Baby Love has a lock that has been pretty effective as most black spot forms out there do not have the key. However, some do and it has been compromized. When a pathogen that has the key unlocks Baby Love it falls apart from black spot fast. As more and more offspring from Baby Love are released, the black spot with the appropriate key will continue to spread and enjoy the feast across rose gardens. Vance found in his MS research that races of black spot are pretty widespead and geography is not that predictive of what is where. He proposed that black spot may just be so variable since it is spread via sales of roses with some infection and they get transported across the country pretty easily.
There is also horizontal resistance, which is thought to be more durable. It is due to typically multiple genes each having an effect to limit black spot development and reproduction. Plants get infected, but limit its growth. If weather isn’t too conducive, plants with high resistance typically hold up pretty well and look okay during the season. Segregation of resistance among ‘Applejack’ offspring points to AJ having this as well as what is generally known about ‘New Dawn’ and some other roses like ‘Carefree Beauty’.
THere of course are grey areas in between and some exceptions.
One approach is to build strong horizontal resistance by crossing above average parents for resistance and selecting those with even higher horizontal resistance. I suspect when we cross above average roses like ‘Applejack’ and Carefree Beauty with less resistant, but colorful, etc. roses we generally dilute the horizontal resistance. BIll Radler did a great job generation after generation building the horizontal resistance in Knock Out.
Another approach is to stack multiple kinds of locked doors in the rose so a pathogen would have to have a bigger key ring to unlock all the doors to get in. If we would be able to combine race C lock with whatever different lock is in Baby Love (gene needs more characterization, but seems like a simple single gene resistance), would we have a black spot race or form able to overcome it? If not now, how long until one does???
Perhaps a good approach may be to try to combine both forms of resistances. Perhaps we can stack race specific resistances to get multiple locks and then if they are unlocked hopefully have good underlying horizontal resistance underneath to still have useful resistance. It takes a lot of effort and tools, especially trying to combine other traits with resistance.
I suspect that over time it has been easier to find / select for race specific resistance in our seedlings- they are the super clean ones. When different races come to our garden or our roses go to others gardens, it is typical for them to fall apart in the presence of another race from which we selected the resistance under.
This is a lot of rambling. You can read about Vance’s major gene characterization work in last July’s abstracts in HortScience for the annual ASHS meetings. His MS work is in print characterizing the black spot pathogen (one on storage in Acta Hort issue 751), and then he has another article in Plant Breeding for his race characterization work and then one in the Journal of the American Society for Horticultural Science on DNA fingerprinting of the fungus (Diplocarpon rosae). His Ph.D. papers are coming out. His literature review has been printed in the recent issue of Plant Breeding Reviews.
Sincerely,
David
I have used both McCartney and Fragrant Plum.
In my garden, McCartney developed HUGE hips and tons of seeds with fantastic germination. I had a very high percentage of very fragrant seedlings from McCartney that appeared to be independent of whether I used a fragrant pollen parent or not. Disease resistance however seemed to be almost the reverse…as in, very dependent on the pollen parent. A down side (in my view), a tendency toward pink (again, independent of pollen parent) seemed very prevalent in the seedlings. I used it for 3 years before we moved and I have not yet added it back in to the new garden, but likely will at some point (particularly now as I am thinking about it and writing this review on it…LOL).
As for Fragrant Plum…lots of seeds…so-so germination for me. It did have a tendency to pass on excellent foliage, almost without fail…and I got some really nice overall seedlings from it. However, I found that I was getting better germination results and seedlings from Shocking Blue and dropped use of Fragrant Plum altogether. On a side note, I also seemed to get better germination results from Blue Nile (and massive hips). I am still trying to get Blue Nile again in the garden…just can’t beat the number of seeds and germination I got from it. Sooooo…in this case, for breeding…I wouldn’t say the whole (Fragrant Plum) is greater than the sum of at least some of its parts (Shocking Blue and Blue Nile)
question- how is ebb tide for mother or father use?. i know its being used but
did not hear much about the results. thanks patrick.
I think when it comes to the twosome that ‘Ebb Tide’ and ‘Midnight Blue’ make up…‘Midnight Blue’ is the one I hear about the most from other breeders. Although, I do not have personal experience with either.
I have one (MB) on it’s way now from Heirloom and I am hoping to give it a try myself since I have a particular fondness for trying most roses in the mauve/purple spectrum in breeding. LOL
David, thank you so much for taking the time to explain! What you said makes a lot of sense. I have used Carefree Beauty in the past, and have gotten a lot of seedlings that are not blackspot free, but highly resistant. In contrast, my Bayse Legacy hybrids are all or nothing (mostly nothing). I am working with a lot of second and third generation Basye Legacy hybrids this year, so it will be interesting to see if the blackspot resistance reappears in future generations. Pretty Lady seems to be another that is all or nothing. I suspect its resistance is race specific.
Patrick and Michelle, Ebb Tide forms hips very easily. Last year was my first year working with it and I made the mistake of moving the plant which killed it before the seeds had ripened. I have heard elsewhere that is works as a seed parent.
Midnight Blue has been hit or miss for me. Two years ago I got a lot of viable seeds that germinated well. This year, only about 5% germinated. I think a lot has to do with the maturity of the plant (2 years ago I had mature plants in the ground, last year I used a newly bought plant in a pot because I moved).
Michelle, Shocking Blue is at the same nursery as Fragrant Plum. I may try that. Thanks for the information!
As a follow up to this, I have discovered that Love and Peace has NO blackspot resistance in my area (Eastern PA). I guess I have the other blackspot strains that David mentioned.
Shocking Blue has been successful for me, too. It is hard to find breeders in this color range that do not suck. It only has one con, which is that it likes to pass on stems that look funky when they go dormant. But I think it would come out in f2 easily.
Love and Peace defoliates completely here. I think it is a piece of garbage.
Jadae, what do you mean by “look funky when they go dormant”? As you probably know…SB is a favorite of mine and I haven’t really noticed a particular trait that is not particularly desirable AND prevalent in the offspring. HOWEVER, I may be looking at different traits than you. 
On a side note, I currently have a ‘Shocking Blue’ x ‘Dancing Flame’ mauve seedling in the same color range that I used heavily this year in breeding (mostly with stripes). So…interested to see what comes from that.
The stems marr during the winter. That is what I mean.