Hello, so I have only been doing this for 2 seasons on a small scale, however the disease I have seen in my babies has shocked me! Now you may say the parents are too blame, however some of the parent plants I have are very healthy.
Do some of them shake of disease in their second years?
How many actually healthy plants do you get out of 10?
The one benefit I feel is that I have limited space and it will help me cull aggressively. Maybe I am too harsh, however I view foliage in a garden very highly and I want roses to be a part of that.
Iāve grown out the odd seedling or two before, but this year was my first real effort at something larger. Twas all OP seed, from my stable of parents Iāve collected over the last couple decades. I have 15 seedlings at the end of Season One, from scores of seedlings.
I only kept one of the seedlings that didnāt bloom, simply because it remained spotless, otherwise āI donāt have the space right nowā ruled the day. All five of the OP Abraham Darby I kept were spotty, but the twenty or so that didnāt make it to flowering were worse!
I AM looking forward to Season Two; the cast assembled seem willing and I have thoughtsā¦
In my experience, yes, some do out grow juvenile disease issues. MANY donāt. Usually, those with very vigorous root systems are rather healthy with few, if any, disease issues. Those with less vigorous roots seem to be much more susceptible to my main two issuesā¦rust and mildew. If I see either on a seedling (or other rose) Iāll increase the water as water stress can cause even highly resistant types to contract both fungi. I make rather āout thereā type crosses (floribunda, Tea, mini X species and species hybrids) and many which germinate are rather disease prone. Of those which germinate, the ones with strong root systems are healthy.
Itās impossible to generalize about ratios because the numbers vary so much with every cross, not to mention the type of disease and amount of pressure that you experience under your own conditions. Itās safe to say that the vast majority of my rose seedlings are pretty unhealthy in my climate, but then, the overwhelming majority of roses are pretty unhealthy in my climate to begin with. Since blackspot is the main problem here (rose rosette disease is a big deal, too, but thatās a horse of a very different color), trial by fireāi.e. setting plants outside once they are readyāis the only way to gauge each seedlingās level of natural disease resistance. Occasionally some of them will improve in health after a season or two, but more seedlings tend to start out looking promising and then go downhill. The majority of my seedlings crumble quickly and never really recover. Compared to breeding for most other traits with simpler inheritance and/or less variable influencing factors, breeding for disease resistance seems to take significantly more time and patience and either a much greater tolerance of disappointment or the ability to balance low expectations with high hopes. However, the information that you learn and the experience that you gain from your failures can be incredibly valuable as you progress with your work, so nothing really needs to goes to waste if you pay close attention and treat everything that happens as a learning opportunity.
The vast majority of seedlings show their true nature right from the start. Occasionally, a mildew or blackspot prone seedling will improve in its ability to resist infection, but a diseased seedling will never transition into being disease free. Itās best to be ruthless in discarding seedlings that demonstrate disease susceptibility right from the start.
Do highly disease resistant parents produce disease prone offspring? Yes, absolutely! You can choose two of the most disease resistant parents and mate them, and you will still have to cull the seedlings to find a few good ones. Selecting really good, disease resistant parents is no guarantee that youāll get healthy offspring.
How many seedlings do you need to grow to find a healthy plant? When I was actively working on rose breeding (1999 - 2010) I typically grew 500-2000 seedlings each year. It depended on the cross, but I would say that on average, one plant in 100 turned out to be worth keeping for its disease resistance properties. There would likely be half a dozen more that came close to the required level of disease resistance, but ultimately did not have sufficient health to merit keeping. Commercial growers would more likely say that they grow 20,000 seedlings a year and end up keeping five plants from that lot.
Since you are probably primarily interested in the seedlings of Portland roses, I have summarized some aspects. From many years of breeding with Portland roses, 5 seedlings have emerged so far that have been convincing in terms of disease resistance right from the start. However, 4 of these are from 2023, so they are still very young seedlings. It therefore remains to be seen whether they will survive the coming winter with possible late frosts and how they will develop further. So far, they have not yet flowered. This year, at any rate, they have defied the capricious weather and have so far remained completely free of fungi and other pests. I have never experienced this in such numbers of Portland seedlings before.
However, I have hardly noticed any improvement in the resistance of the other Portland seedlings, which were much more susceptible. As soon as the conditions were right again, the attack returned. From what resources should they ultimately mobilize their power if they have to experience a certain degree of weakening again and again? Sometimes the factors that trigger the disorder lies just in the microclimatic conditions. In another place, things might look very different.
In response to Roseusā comments about working with Portland types: I have used a few in breeding many years ago, and two produced very healthy offspring when either selfed, or crossed with non-China (modern rose) types: āIndigoā and āMarbreeā. Sadly, I no longer have āMarbreeā, because if I did, I might use it again. I donāt use āIndigoā anymore because in my garden, it suckers badly and thatās not a trait I want to deal with.
Although itās not a Portland, I consider āSuzanneā to be of similar general character, and my limited use of āSuzanneā in breeding suggests that it has a LOT to offer. I still have one seedling from a cross with āApricot Twistā that I like: '124-10-02' Rose
It has demonstrated total resistance to all disease, and it repeats better than either parent (!!!). Itās only flaw, as far as Iām concerned, is that it has very pale yellow coloring that fades on day one to an off white. But it does demonstrate that crosses of yellow/peach roses with āSuzanneā have the ability to preserve some of the yellow pigmentation. I suspect that if I were to use that seedling with a strongly pigmented yellow/peach variety, it might deliver much better coloring and still retain some of 'Suzanneās best qualities. I bet it might produce some interesting offspring if it were crossed with Henry Marshallās J-5!
Thank you all for your answers, itās humbling how disease prone roses are, I have not seen it as badly in any other species, but I guess no other species (tulips?) has been bred as extensively as roses. I will be using my repeat flowering spinosissma (Paula vapelle and Mon amie Claire) which have been very disease resistant to make smaller plants, so even if they are not healthy I can fit more plants in the space i have. My objectives have rapidly changed. My first aim is to continue in the same journey but focusing on health and form firstā¦
On a side note, I canāt get Marbree in the UK (I have indigo and itās very healthy and fertile) however I recently managed to get some hips of a Marbree locally. Obviously they donāt grow true, however I may be lucky in getting some healthy plants with spotting on the flowers
Iāve grown open pollinated seeds of āMarbreeā and about half of them have some degree of spotting on the blooms, but most have very subtle markings. The real problem with Marbree X self seedlings is that they are impossible to propagate by cuttings; they flatly refuse to produce roots. (in my experience)
Marbree is going to depend a lot on local conditions (donāt think it applies too much to the UK where OP is from though, donāt seem to have the same overlaps), Iāve had the plant 3 times (so far, insanity letās go) and it doesnāt like holding is foliage (blackspot, total defoliation) and then eventually limps to death (but it repeats really well and 2/3rds of blooms will go to seed). Seedlings from it have also failed hereā¦was just using centifolia/gallica derivatives (ie Helga Brauer and 1st gens from it) in an attempt to approximate something like Crested Damask (just wanted to see if the resultant seedlings have more cresting than itās parent similar to how Crested Damask looks like it has more than Crested Jewelā¦being able to repeat similar results would have been useful information, but none of the seedlings lasted more than a few months post germination).
I suspect Marbree would not fair well in Eastern parts of the USA, just because a lot of what is reported to do poorly there also does poorly here, just seems to be a lot of overlap.
-side note- this post also demonstrates what some others above have said about local conditions and local disease pressuresā¦results vary based on so many factors.
Based on that, I would probably expect to kill āMarbreeā fairly quickly here. āIndigoā is quite possibly the healthiest Portland/Damask Perpetual by most accounts, but it canāt withstand the blackspot pressure here in Maryland (USA) and I watched it die just like your āMarbreeā did, almost word for word. As wonderful as the class can be in more friendly rose climates, Portlands are extremely difficult to keep alive (much less happy) in my area.
I find indigo and Jacques Cartier (as itās called in the UK) are very healthy where I live. Less so the other Portlandās. De Rescht has been terrible this year! EDIT: I have also found Amanda pattenotte to be incredibly healthy. However I donāt think it sets hips
Hi James. Iāve only a handfull years of experience, but Iāve one that may be of interest. Iāve made some crossings with multiflora ramblers and musk roses. I had 200+ seedlings that year. The mother gets mildew every year on young shoots in summer. Because I had that many seedlings I felt comfortable in selecting rigorously. I had a heavy powdery mildew infestation that year in my greenhouse. Every single seedling that had but a small infection I culled. I also selected on vigour. This year of the 30 seedlings I kept not a single one got powdery mildew. Theyāre all over 6 ft tall. They do get some blackspot and some get elsinoĆ« (or cercospora), but no PM. This year late in summer we had much PM. But my seedlings are ironclad. Iām very pleased with that outcome and it strengthens me in my belief that having a great many seedlings of one cross and the luxury to select realy hard will give you better offspring.
I also noticed that PM is most common with my young seedlings (that and damp-off). In my experience other diseases come but later in the year, once theyāre planted out, mostly blackspot.
Just a thought, as you mentioned damp off: I lost seedlings the first few years to damp off, even though I tried to be meticulous about my water volume when adding.
After reading on here, and starting to add perlite on the surface (as well as a bit more mixed in the seedling mix) I have never had damp off again. You might want to give it a try if you are still having issues with it off and on.
Duane
donāt think they will care about seeds though!