Selection at seedling Stage

I haven’t worked with very many big populations of seedlings, so I’ve usually let all but the sickliest seedlings grow to maturity (if they will).

However, I was just reading this old article and found Griffith Buck’s perspective on seedling selection very interesting:

NOTES ON SEEDLING SELECTION - Dr. Griffith J. Buck

“Along with the increase in hardiness with maturity comes such other maturity traits as tolerance or resistance to disease, foliage fragrance, plant habit and type of inflorescence.”

I’ve certainly seen disease resistance change with maturity, but I hadn’t really given much consideration to the idea that cold-hardiness and other traits might also take time to be fully expressed. Makes me rethink my “let nature take its course” attitude.

Can anyone think of any other traits that would require maturity to properly evaluate?

Interesting. It was probably a mistake for me to line out all of my first year seedlings this year. They’re having to deal with a moderately cold winter with little snow cover. And their crown depth is not nearly as deep as when planting a #1 bare root rose.

I have two baby seedlings of Cal Poly x fedtschenkoana (thanks, Kim) that have really nice fragrant foliage…it would be cool if that somehow intensified as he mentions it might.

I don’t think this is the same as plant habit, but I’ve seen plant vigor really take off in the third year. This is particularly true of seedlings with a high degree of R.arkansana in them and seedlings of My Hero which is not a vigor plant itself.

That reminds me of the phrase my Masters Advisor would use a lot- Market Limiting Trait. He is a potato breeder. The idea basically is to know your priority of traits that are important to you and then basically select in that order. One has to have the size of plants needed and conditions to confidently select for the presence of the desired trait. Potatoes can be raised and managed a little easier in some instances than other crops. Seedlings can be raised for a generation in the greenhouse in small containers. Multiple small tubers are harvested. One can take each of the tubers of a clone and put them in different trials for evaluation and cross reference them. For instance, if the goal is late blight resistant chipping potatoes, one would plant some tubers of each clone in a field you will innoculate with late blight and another field you will keep clean in order to harvest tubers for more propagation and to survey for potato chip quality after typical storage conditions. What you have then is the data right away for late blight resistance the first field year and chipping. You can then throw out (or eat) all the tubers from your increase field that did not have enough resistance. There are more than enough good chipping susceptible varieties. This way you narrow down your population quickly for the true market limiting traits (first resistance and then chipping) in an efficient way. The resistant potatoes are chipped and hopefully there are some that have both traits. It is harder to breed for resistance than chipping quality typically. Traditionally potato breeders would plant the tubers just in one field. They would walk the fields and save 1% of the “pretty” looking tuber genotypes. They may chip a tuber or two that winter. The next year they will plant out more of the advanced selections, etc. and move down the process. How “pretty” a tuber looks from a single hill isn’t all that consistent later on when it is grown in slightly different soil types and fertility levels. In a study with potatoes someone put leading potato cultivars in seedling fields and tested how often breeders selected them. If I remember right it was sadly very low.

That was a lot of potato talk, but there are/have been similarities with roses. Saving only the 1% or so of the roses with attractive flowers at a young seedling stage to move forward and then hope there is good plant habit, health, etc. may not be the most efficient use of those resources that led to all those seedlings being generated. Floral qualities change as the plant matures and and then is taken from a greenhouse or under lights and then is grown outside.

For many of the market limiting traits now in roses, it takes more resources to screen for them as the plant needs to have some size to them, like what Dr. Buck described. Years ago there was more opportunity for selecting the prettiest flowers and having average plants and expecting people to spray preventatively for disease.

Bill Radler and others have made great progress with disease resistance and raising relatively small populations that they can truly assess and manage. I remember in Herb Swim’s book his discussion of not raising more than 10,000 seedlings a year because beyond that he couldn’t truly assess them. His colleagues were raising 100,000+ seedlings.

I try to plant out all saved seedlings the first year (even late May) and just see how they do for health and hardiness and hope they grow to some decent size before fall. Due to limited resources I toss about 50% of the seedlings in the house before planting out because of them being slower or runtier growers. I love your discussion Joe about the challenge of selecting for hardiness with young plants. With limited resources I feel like I just need to plant them out, but wish I could grow the up more before their first winter. Kathy Zuzek and others raise seedlings in gallon pots for a season before planting out and that probably helps a lot to get them off to a strong start and have a more true reflection of the seedling’s hardiness performance.

Ive never had foliage fragrance, most notably in Rose rubiginosa x Baby Love and [Dortmund x (Shadow Dancer x Carefree Marvel)], until at least year 2. That passage is totally true to my experience.

I’d never breed en masse, even if I had the space, money and resources, because I’m not looking for the holy grail, and I dont think its really a useful idea “to find” because most breeding really doesnt work that way.

I had wondered about such too in the past. I’ve never grown enough to need to physically cull (or rather, never taken enough care that nature didn’t do some culling for me) but I’ve often thought that, if some of my purchased plants require a year or two to settle in before showing their muster, then why do we judge the developing seedling so quickly? Obviously, it’s a numbers game, and if you are growing tons of seedlings, then the odds favor the strong seedling will ultimately be stronger than the struggling seedling, and struggling seedlings would be the first to cull.

On the other hand, I recall, with regards to some annuals, instructions to cull the early germinators as they would generally have less interesting traits than the later germinators, so perhaps something similarly latent could lie in slower developing seedlings… (??) I remember one small batch of near species crosses a decade ago that seemed to have better plants from the very late germinators. (Not enough seedlings to have any statistical merit to that observation, I only had four plants ultimately.) Might late developers too offer something different?

Only because I’m a softy and hate to part with any of my babies I usually keep mine at least 2 or 3 years before I’m finally convinced that they’re awful and have to go, lol. Some of them do improve but realistically, not many in my experience. I keep track of how diseased they’ve been as well as growth vigor and bloom production and only a handful get better with maturity. If I’ve marked it as not too good the first season it usually doesn’t prove me wrong.

So funny I was thinking on exactly this same subject this morning. But I rationalized that the reason that the health of the 2nd and third yr seedlings improved (often dramatically) was that they became somewhat to very colonized by the beneficial flora that assists disease resistance. Almost all of my older (3-4 yrs and older) acclimated shrubs are very resistant to most mildew (except in deep shade), any serious case of rust (unless the roots are decimated by gophers), and almost all blackspot. This past yr. I placed a couple of yearling seedlings with rust and blackspot among my seedlings, and did get the resultant big time outbreaks. And then it got humid and I regretted having done that. Although the seedlings rusted and spotted, the in ground mature shrubs shrugged off any level of outbreak. Only Lavaglut and Europeana (the latter not very well established) had minor blackspot. So this morning I was outside watering all shrubs, seedlings, and yearlings with a new innoculation of beneficials.

Good points Jackie. I hadn’t thought much about the beneficials, but they are surely contributing something. With rust and mildew being minor issues in this climate outside perhaps I’m lucky. This winter I planted a flat of germinated seeds below a mildewed plant under lights. What a disaster that is. If they survive to summer I will test them outdoors. They’re from crosses where I’ve never seen mildew.

I do a fairly heavy cull most seasons to eliminate singles, colors I dislike, scrawny plants, just to get the numbers down to something reasonable. They have to learn to live with “cold” winters with only some inches of leaves for protection at the end of first summer for most of them. Only a few rare or special ones get to stay in refrigeration over winter. Usually a majority do survive the 1st winter, but a lot go down in the 2nd after their neighbors outgrow them and diseases attack. Still there are too many for the allotted space.

Having said all this, in light of disease resistance (only), the seedling that STARTS off disease resistant usually remains disease resistant and even improves its resillience as it ages. My top priority is disease resistance, followed closely by own-root vigour, and so I often find myself pulling out seedlings by just a few months of age because you just know they are going to be duds and I will cull many without seeing a flower. 6 months after they germinate I might have less than 10% of seedlings left before planting them in the ground in autumn. When they go into the ground I often find they have a dramatic transformation. Next season I am going to try an experiment and sow seeds directly into soil in raised beds on the ground with shade-cloth on the ground under the soil to stop beetle larvae (borers) coming up and feeding on the roots and a cage over them to stop the larger above ground critters. I just don’t think potting mix gives them a good start to life.

I don’t think decent potting mixes inhibit any performance criteria. I’ve consistently seen that a healthy seedling always has a vigorous, vital root system under it. Unhealthy ones don’t. Their roots are always inferior in vigor and mass compared to the healthy ones. Decent potting soil would probably provide a greater potential for a weaker root system to perform better than soil, providing the potting soil is in a properly drained pot, protected from extremes in temps of both direction, and not permitted to excessively dry out. I’d LOVE to be able to plant them out in the ground. It ain’t happening on a 24% slope, even without critters to eat them top to bottom!

the seedling that STARTS off disease resistant usually remains disease resistant and even improves its resillience as it ages. My top priority is disease resistance, followed closely by own-root vigour, and so I often find myself pulling out seedlings by just a few months of age because you just know they are going to be duds and I will cull many without seeing a flower.

I am in the same frame of mind, alot of my seedlinds may not even see one month after being transplanted into tubes, regardless of the cross. I think vigour is such an important traite, its responible for a lot of the health issues, growth flushes between blooming and its ability to recover from minor disease problems.

I’m not terribly surprised that this is the case. In annuals, such as corn (maize), there is a distinct juvenile phase and an adult phase. And there are definitely characters that are expressed in one phase that are not expressed in the other. DIMBOA is a compound that maize seedlings make that is effective against European Corn Borer. It is only produced in the juvenile phase, not in the adult phase. Leaf waxes also change in the 2 phases, with the waxes being present in the juvenile phase but not in the adult phase. There are also differences in the root system and probably a whole whack of other traits that we just have never noticed.

I’ve never thought about distinct juvenile and adult phases in roses before, but from a developmental standpoint I suppose that it would make sense.

Liz

Probably for the continuous blooming roses there is less of a juvenile phase, but for sure the once blooming shrubs do. Much like apples, they have to get a certain amount of wood established before they make enough of the florigen to initiate inflorescences. I don’t know if grafting would actually speed up the blooming process but there’s likely some interaction of host and scion because the florigen definitely is mobile. And something that blocks GA-3 may help too.

I just transplanted a Toprose x Baby Love into real soil. It germinated back in June, but it stayed a very clean. multi-branched ball shape (4" x 4") until about a month ago, in December, which is when it decided to shoot up a 9" basal with a fully double primrose/chlorophyl yellow bloom, which had absolute rain resistance. Sometimes these seedlings hover in seedling stage. It is weird. It has obvious vigor, especially when I saw its root system, but it just sort of stayed in stasis for 5 months.

Real soil

As opposed to soilless media :] which is what seedlings are germinated in. ie. no sand/clay/silt.

Thanks for all the great observations and input!

I totally agree that a healthy seedling is more desirable. I guess it’s just a matter of not being to hasty to throw seedlings out when you DON’T actually have a bunch of healthy ones from the same cross to keep. ;0)

Oh and on the matter of foliage scent, I’ve also generally noticed it more strongly expressed in the mature plant but as an exception…

I do remember my bracteata X (rugosa x palustris) seedlings having a fairly strong sweet foliage scent every time I brushed against them or watered the foliage. This was when they were still very small in pots indoors. I’ll have to check them to say for sure, but I think this foliage scent has actually gone away as those plants have matured and are growing outdoors.

Perhaps the foliage scent was more preceptable due to the softer texture of foliage grown indoors versus the harder foliage developed outdoors?

Good possibility Kim - I also wonder if maybe the still dry air indoors allowed the volatile scent glands to accumulate more stuff than they do now outdoors.