Line Breeding

I’ve seen some discussion here regarding line breeding to “fix” desirable traits. I’ve read that some animal breeders also use this practice without as high a risk of producing undesirable traits that may occur with close inbreeding. I was curious if any of you know whether the practice of line breeding in plants causes inbreeding depression fairly early on or do you see that it takes a fairly large number of generations to induce inbreeding depression. I am a layman and am in the process of reading up on the subject to get a better understanding.

I do know one thing: classes like the Hybrid Teas are now so inbred and have such a limited gene pool that it is very easy to get a lot of weak, unhealthy offspring when you breed within the class.

If you mix widely divergent classes you will often get improved health and vigor like you hadn’t imagined possible.

It is true. Line-breeding HTs always resulted in throw aways for me. I am sure that some breeders will have exceptions but the generalized pattern I witnessed was not a positive one. There are a few rare exceptions in commercial introductions though. For example, Opening Night is one of the best garden red HTs currently available. It is the merging of two lines of Red Planet. Is has excellent vigor and good architecture for an HT. But it really is a major exception and divergent enough of a line-breed to work. I wish I could recall a line breed of two HTs I tried a few years ago. I recall the runty, mildewed seedling en masse but I cannot recall the parents.

To be honest, the only valid reason to directly line-breed HTs is to attain a rare trait so that one can outcross divergently in the following generation. For example, I can see why breeders used to do this with yellows. But there is no real reason now. Now, the focus is on breeding yellows that someone would actually want to keep in their yard, LOL. Its hard to find one that is healthy, hardy, not thorny and in an appropriate shade of yellow. It is no wonder Elina became so popular if one considers what else there was to choose from. So, my advice is to only pursue line breeding in HTs if the quality is rare enough to not be able to attain it from another, more appropriate tangent.

Sorry, I should have listed my last name with my original post.

Thanks guys for your input. I’m not thinking of HTs…I don’t grow any HTs because they can be such a problem. The reason I started looking at this subject is because I have a seedling, (Rugosa #3

From my animal science classes inbreeding for several generations will result in an increase of genetic abnormalities and reduction in fertility. Line breeding (a form of inbreeding) sire to daughter then back to granddaughter, carries fewer risks than sibling x sibling and can go on for several generations before abnormalities are noted. I personally like to use more than one dam of similar type then line breed several generations and cross those lines back to each other.

If I remember correctly some fruit flies have been inbred 150+ generation.

Off the cuff answer based on livestock I would say 3-5 generations before you see a determental effect but that is not to say you will get what you want with this cross. I am curious to see what other will say, I am new to hybridizing roses.

Hi david,

The main emphasis Paul was making re: HT’s is that theyre pretty much inbred to begin with. So the generational stacking is already at play. The majority of modern bush types usually stem from a few originators. Examples: Floradora, Crimson Glory, Eva, Peace, Goldilocks…etc. The list could go on for about 15-20 prime examples. Crimson Glroy, in my opinion, has a type of architecture that can still be seen in its long distant descendants. If anyone here ever sees or grows Vogue then you will understand what I mean.

Rob,

I do not see a specific problem with that. I had Rugosa #3 at one point but it began to “fail to thrive” by no fault of my own. It grew for about 2 months then quickly started breaking down. It was weird. I got some seedlings from it that did the opposite. Unfortunately, theyre sterile but very beaitiful. Theyre tall, thin, very healthy rugosas with orchid pink OGR form. I think it would be helpful to retain these traits and make the line more genetically stable.

Distant Drums has a very rare quality, and it is not the color. The scent is the rare myrr fragrance which I think would be delightful in other roses. Jude the Obscure seedlings produced the same fragrance for me, which makes me think that Cantebury is producing this treat in both roses even if Jude the Obscure itself does not smell mike myrrh. That is the thinh with breeding though. One never knows what latent traits are there waiting to be expressed. If anyone here gets the chance to smell White Licorice, the new DD hybrid from Weeks, you will smell this unusual trait.

David,

Thank you for the information. I understand line breeding better having posted this thread.

Jadae,

Sorry to hear you had such problems with Rugosa #3. I still have it growing in a large pot and it does fine for me. If you ever want plant material please let me know. I could be wrong but I think I’ve seen a difference in leaf sizes between canes on my plant. I could be way off but I have been wondering if some canes are diploid and some are tetraploid.

I strongly agree with you regarding DDs scent. It’s wonderful. That was the reason for me purchasing it this season and secondarily for the color. The rugosa #3 x glauca seedling described here has a very strong unusual (to me) scent that I can’t describe. I’m hoping seedlings from this cross with DD will have very strong scent, repeat bloom and health.

Dd has produced healthy kids and grandkids. Unfortunately none of them looks or smells like dd.

For me when I consider line breeding I do not consider it an option with modern classes of roses. Looking through the parentage they all seem to descend from the same parentage. For example Peace seems to pop up over and over and their are other parents that do the same thing. So for me these classes seem to need new blood. But with species and near species hybrids I think inbreeding could concentrate some of the more garden worthy traits. What I am planning to do with my species crosses is start two lines that have the same set of species as parents and different modern roses and then cross them together. But we will see how this goes. Some one else out there has more experience than me. For modern roses I am using Ralph Moore miniatures, Buck’s roses and some of the Canadian breed roses I think these are some of the more diverse classes in the modern rose groups.

Adam,

I like your choice of Moore’s miniatures and Buck roses. I know less about Canadian bred roses. What you, Paul and Jadae write about the problems using modern classes of roses make a lot of sense as does your thoughts on using species/near species hybrids.

I’m hoping that the (rugosa #3 x R. glauca) x unknown seedling might be useful in developing a line to work with. Hopefully the cross with DD will bring something nice to work with in that line as well. A second line that I’m thinking of is using a L83 seedling I have that may be a dwarf. I’ll wait to see if it blooms next season and if so I’ll start using it to develop a potential second line. This is all really plans/thoughts right now and I really appreciate all the advice and discussion.

Hey Dave,

Heirlooms produced a mimic bred from Distant Drums called Distant Thunder. Weeks produced White Licorice, which has the identical scent (to me) of DD. I think its possible but DD itself is such a pain to work with. Personally, I’d use Jude the Obscure. It has proven to me that it can make that scent. I have no idea what would produce that color though. I imagine it requires both yellow and red-purple pigments.

You can see in this photo that this seedling of DD has picked up the architecture of DD, but the scale is smaller and the leaves are different. The flowers are also different. They look smaller with more apricot tones.

I have no idea what the other parent is. John Clements was really random in his choices but often used anything bushy, moody and fragrant. That seemed to be his preference. I would not doubt if it was from some English rose or English rose hybrid.

He also made The Impressionist, which could be a good choice if you like breeding out blackspot, LOL :slight_smile:

I used to grow a whitish (or very pale pink?) Austin rose that smelled almost exactly like ‘Distant Drums’. I want to say it was named something like “Fair Bianca” maybe???

Fair Bianca does have a strong myrrh fragrance.

I like Moore’s roses that are not heavily induced with Little Darling. I think Little Darling was great for its time but is otherwise awful. But a lot of his work is very, very diverse. His legacy leaves a lot to work with.

I checked out this book from the 1930s written by Horace Mc

Farland. The Uni of Idaho library is a 4 story dump but it has a lot of old relics hiding up on the top floors. I LOL’d when I passed by the potater breeding books, haha. The rose book has a photo of Pernet in it. The man that brought us a new world of color was very, very simple. His clothes were dumpy and extremely loose. His hat was very wide-brimmed. He had a long mustache and some very small spectacles. I squinted to see his face, which you can tell he hides. I could see why he was a rare photo opportunity – he looks very introverted and mentally intense, yet he also looks extremely gentle. 60% of the roses described in the book were of relation to Pernet’s work. Its easy to forget that Peace is multiple works of Pernet in one rose. This man has definitely left his mark, and there is a lot of good that came from his legacy, but it has also left a lot of convergent breeding lines. Personally, I think the goal is to retain the positive qualities of Pernet’s work onto new prospects that are far more divergent in nature.

The last time this book was checked out was 1994. Excuse my bitterness but it amazes me that anyone from here could read then. All 4 stories of books are usually strolled among by 3 or so people. Its a shame that a book as rare and historic as this will go to waste on no one. Oh well.

I am curious as to what we will look like to future rose breeders from 2085? I was extremely shy and reluctant when I was a youth about talking about horticulture to anyone but society members or my closest friends. It was not exactly the most masculine pursuit, haha. Now, it is fun to shock people :slight_smile:

ps. I swear this relates to line breeding, lol. Think in terms of time and how both rose genetics and those harnessing them converge and diverge… :slight_smile:

“I was extremely shy and reluctant when I was a youth about talking about horticulture to anyone but society members or my closest friends. It was not exactly the most masculine pursuit, haha. Now, it is fun to shock people”

When I try to discuss rose breeding with my friends their eyes glaze over and then roll back in their heads. lol

Yeah, I gave up eons ago. I have one buddy that knows genetics. He seems to appreciate that I understand his lingo too. Wheat breeding confises me still but I like to hear about anything hort. related, so its all cool.

Reading through the posts on this topic I get the idea that Line Breeding has little to offer in modern rose breeding. In the hope of stimulating further discussion on this topic I put forward some thoughts of mine.

For me anything that can shorten the time required to acheive the “ultimate aim” in breeding is highly desirable.

When you are 65 and starting on the breeding journey then you realise how precious each season is, so I may have a different perspective to many others.

Having said that there are some things that influence my attitude to breeding roses.

First of all we have access to allmost the entire worlds genetics and contrary to popular opinion I think there is enormous diversity within this population. Also we have a very extensive research base to work with to select the parents we use. This is is a huge advantage and should be exploited.

I have seen reports of research done with rats. In this program they were deliberately inbred for many generations with all selection being for those traits that inbreeding usually causes to degenerate. After multiple generations they actually produced a line of SUPER rats that showed no trace of the expected weakness and infertility.

To me this shows that intense selection is the key to making real progress in any breeding program and this can only be acheived by using the greatest no. of plants we can handle.

To me the first thing we must consider is what our aims really are.

Are we breeders aiming to produce a specific rose from known parentage with a clear idea of what we expect or are we hybridizers whose first aim is to produce a plant with a diverse genetic base(which will give our plant Hybrid Vigour) and then select a desirable plant from what results we get?

As all new roses are the result of selection by the breeder based on what is considered to be personally desirable, the most important thing is the size of the selection base and the variability within that group.

It is generally accepted that diversity is desirable and will give greater advances but I dont agree with this concept. In my opinion ,if a large % of the selection base are obvious culls then they are actually a waste of space and time. We would be better off if all the plants were “similar” so that selection pressure would be extreme and we would be selecting really superior plants for the next generation.

This is where I feel line breeding,inbreeding or even continuous deliberate selfing has a part to play in producing future roses. We could "magnify"the features of any rose by multiple generations of “line breeding”,selecting the "best"of each generation to move on with. Then when we are “satisfied” with the result of this process we can introduce a complete outcross desighned to introduce the features considered most needed.

While this would probably be a true hybrid step, the diversity that comes from hybridizing would be an advantage at this time , as it is likely to produce plants that “look” like the line bred parent that we have aimed for, with the vigour that comes from hybrids.

I think that the increased selection pressure which comes from the “similarity” of all the plants used would shorten the time needed to acheive any aim. By comparison the diversity of hybridizing by its very nature will produce a large % of auto. culls and since the no of seeds we produce each year is relatively fixed by our time or space these culls waste precious facilities.

This is the real case for line breeding but it is critical to select superior plants to start with or the time you hope to save would be lost in the first few generations by the extra culls similar to the “waste” in Hybrids.

Just my thoughts, I am open all comments or critiques

Russ

I want to add one more detail to this discussion.

I specifically mentioned line breeding in Hybrid Teas, noting that as the genetics of this group has been whittled down to a very limited set and that breeding HT X HT over and over is just stirring the pot. I believe that is a bad idea at this stage of development of garden shrubs.

That said, I don’t think line breeding is a bad thing, as long as you are working with some original ideas/materials. For example, Kim Rupert has created several very unique R. fedtschenkoana hybrids in recent years. I believe it would be quite worthwhile to breed some of these selections with each other, perhaps over several generations, in order to distill some of the traits you want to develop. When working with such unique, original plants I think you stand to gain quite a bit by marrying siblings and related crosses without worrying too much about accumulating negatives. I have seen evidence that hybrid vigor persists for generations with some species and near species crosses.

Case in point: I have several R. pisocarpa hybrids from a variety of seed parents that I will spend a few years crossing with each other. Same goes for a project I already have underway working with R. foliolosa and R. arkansana.

I think that it is worth noting that there is not anything specifically wrong with working with HTs. Its really easy to create a line of inclusion/exclusion when giving a social value basis for what one works with. It is epsecially tricky because we are hard-wired to do just that. What I do think is valuable from all of the above information is to look at everything from a distant, whole perspective, as well as what has occured in breeding over time. When that is done then it is easier to see if what one is doing is what they think should be done.

So, I want to go back to the original question. We have been thoroughly implicit without attempting to address this is an explicit way–

“I was curious if any of you know whether the practice of line breeding in plants causes inbreeding depression fairly early on or do you see that it takes a fairly large number of generations to induce inbreeding depression.”

I think that the answer has been implied in many ways. The basic implication is that HTs are a long line of both inbreeding and linebreeding because they are mostly a culmination of the same original nodes. It is also implied that specific traits have been fixed. What we do know collectively is that HT x HT often results in mostly weak seedlings even if the parents are not weak. HT x HT is usually a numbers game primarily due to this factor. Is this from inbreeding depression or the practice of selecting specific traits over vigor? It would be hard to know because the practice of using root stock has obscured this. When I do get a seedling that is not species-related that is immensely vigorous, I take note. It is rare. How many generations of line breeding vigrous non-species x vigour non-species would it take to impress this genetically? I have no clue and it could be random. Would it be quicker if each was as distantly related as possible? I dont know. Lastly, would vigor be increased if one were to outcross in between linebreeds? I am guessing so but I do not know.

These questions remind me of the difference between King’s Ransom and Constance. The former is several lines of the latter combined. KR is a very non-vigorous HT that is very linear. Constance is very rangey and vigorous. They are both yellow HTs. I chose King’s Ransom because it is the last of the HTs where the Pernet characteristics become lost – ie. the lime colored foliage, the nodding necks, the curved thorns, the thin stems, etc. KR is basically 60 year goal. They refined the growth, increased the repeat bloom, doubled the bloom form and got the yellow to retain better. However, I have a feeling that Constance would do fine on its own roots. King’s Ransom is barely decent when grafted. I doubt it would be all that great on its own roots.

What makes the original question even more tricky is that not all rose species interact in the same fashion. We have all seen genetic breakdown as well as complete incompatibility. Its definitely frustrating. This factor further muddles any clear patterns.

So, the original question would probably require a ton of research and statistics to answer correctly. I believe a multitude of answers would be found with no specific unified answer to be found. I am assuming that depression would occur fairly swiftly but that depression would occur even sooner if one was working with roses that are already distantly line bred, such as HTs. So I think the best answer for now is to consider your parent choices in context to roses as a whole.

I agree 100% with Russ and Paul. Line breeding is not inherently detrimental and outstanding individuals can result from careful selection by culling weaklings of each subsequent generation and preventing them from being used in breeding. However, line breeding can have unintended consequences. I’m thinking of two for roses. The first is the loss of germplasm. The second is failure or inability to cull inferior offspring in future generations with the result that inferior products of line breeding are incorporated into the line. I know that line breeders of animals struggle with these issues, especially because defects aren’t necessarily apparent before animals reach reproductive age.

Over and over in the history of rose breeding, after a great rose is released - often with its parentage unknown, disguised, misrepresented or undisclosed - breeders start using the great rose in breeding, and its parents and their generation are ignored and eventually lost to all future generations of breeders. With plants, we have the ability to preserve germplasm for many generations, at least.

As for the failure to cull inbred offspring, once the inbred gene pool leaves the hands of the careful breeder, control over culling is lost. Inferior line-bred products give a bad name to the entire line. This happens all the time in animal breeding, and I think it has happened and continues to happen in roses.