Is every rose seed completely unique?

Rose Genetics Ploidy Level
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I am a beginner, new to this forum, and live on the south coast of England.

I have been reading a lot of the threads on here with great interest. I did study biology to A level, but understanding the science will take a huge amount of effort for me.

One of the ideas people here seem to say a lot is that your experience will be different from that of others, and I am thinking that just as the offspring of two human parents will each be unique, surely when you cross two roses then every single seed will be unique? So one person crossing two roses will always get different results from anyone else crossing the same two roses? Quite apart from the influence of micro and macro climates and other factors.

I questioned something I read in a book, that said when you grow a species (wild) rose from seed then all the offspring will be identical to the parent. I suppose that is assuming that the species rose is self-pollinating and can never accept pollen from any other rose? That there are so many species roses implies that they do mutate. Also, why would a plant go to the trouble of reproducing by seed if not to increase variation, which gives ability to adapt and evolve?

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Each seed is unique, or carries a unique combination of the genetic possibilities. However, certain traits may be more common, simply varying the combination. For instance, some families have a passel of kids that look a lot alike. Some siblings may not resemble each other as much.
I have read several times that you need to grow a certain amount of seedlings to see the possibilities of a parent. That would assume that a certain number would at least give you an idea of the traits that parent tends to pass on to its offspring.

I don’t know how the climate effects the seed, as far as what genes are carried in it, but it can greatly effect whether it may even set seed or not.

I’m interested to see what others have to say, you know, those that may know science and genetics, unlike me.
Duane

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Climate might affect the seed by epigenetics, which is when acquired characteristics are passed on to future generations by DNA methylation. I was just reading somebody’s post about that, interesting. Lamarck predicted epigenetics, and Darwin supported his theory, but it was only recently taken seriously by scientists. As well as climate affecting whether the rose survives, thrives, or not, or phenomena like cold weather turning white roses pink.

I was more puzzled about a book saying that the seedlings of species roses are identical to their parents. I would have thought that when a seed is produced there would be variations even if the parents were identical, as in the case of self-pollination. Just as a human will produce eggs or sperm that are unique.

I don’t know anything like enough about rose genetics, or even how many pairs of chromosomes they have…(edit: I looked it up and it seems there can be 14 or 21 pairs of chromosomes in roses, but it still looks extremely complicated),

I take your point about the progeny all being similar to the parent, and it would be interesting to methodically test the parent by combining its genes with a lot of other roses. If roses are anything like humans, it woud make a difference whether it is the pollen (male) or the seed (female) being used too.

I am curious about the variation just from growing species roses from seed, I don’t think all the seedlings are identical.

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In roses the base number for chromosomes is 7. That would be a haploid if it survived. Haploid means half of the pair. So a diploid has 7 pairs = 14 total. Those are usually fertile, and quite a few species, and some cultivated roses such as polyanthas often are diploid. More commonly among the hybrid teas, floribundas, grandifloras they are tetraploid meaning they have 28 chromosomes. A triploid usually arises from crossing a dipolid to a tetraploid, though some triploids can cross with other triploids to produce triploids. Some species seem to be tetraploids. Among the dog roses (R. canina and relatives) things are not so simple and they may go up to octoploid. The caninas also break rules about having same numbers of chromosomes in egg and sperm (pollen).

Ralph Moore, a great breeder of miniatures and other interesting roses famously said “The rose will find a way”. So don’t worry too much about numbers of chromsosomes. Do a test, or look on-line at help-me-find roses to see if a rose has produced notable seedlings. If it has, it will probably make plenty of seeds, either as mother or pollen donor.

Thinking about whether all seedlings might be alike. It depends. Hybrid corn (maize) depends on two highly inbred lines. Each of them has essentially identical chromosome pairs, but these two inbred lines are different from each other somehow. When crossed, all the offspring (F1) are essentially identical to each other but rather different from each parent inbred line. That’s how we can get a 100 ha field with all the plants the same height with the same number of leaves and very close to the same number of seeds per ear, all pollinating on the same time schedule, if the field is uniform in fertility and water supply.

But the offspring (F2) from the F1 hybrids, will range widely toward either parent, and everything in between. Roses are rarely so inbred as in a maize production system, but a species can sometimes be very uniform in gross characters. So a cross to something different will give a very mixed F1 hybrid. Even if all the F1 seedlings look the same, their F2 offspring will recombine to make a wide range of offspring. It is claimed that early breeders of HT and HP roses often grew out F2 seedlings from a F1 rose that came from a wide cross, and got interesting results. So if you allow a rose to self-fertilize, or be pollinated by insects randomly, you may get interesting results. That’s why Kim (roseseek) suggests using lots of open pollinated seeds.

It does two things. Let’s you practice and lets you see what are the obvious traits of a parent. When you make crosses there will be surprises through mixing of different genes into a new plant, but on average the offspring will look fairly like their parent(s) or sort of in between the two. How much similarity depends on differences of dominant and recessive traits.

I hope this helps. There are a lot of resources on-line in wiki articles to explain the genetics for something like hybrid corn. For roses we have to make some assumptions and use their rules. In a tetraploid there are many more possibilities than in a diploid.

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All “species” rose seedlings are “identical” within a set of parameters. Nature will never make each one completely identical because no two years are completely identical. Some will germinate immediately without any kind of cold period. Some will require multiple seasons with varying periods of warmth and cold, with every permutation in between. What happens if Nature makes every one require identical conditions in which to germinate, then the climate changes or a volcano goes off, altering the conditions for that one (or multiple) year (s)? There will be physical differences between them, also, but within a range of characteristics. We think, “oh, it’s this species or that one, so all the plants are identical”, but they can never be because of sexual reproduction. Just as children from the same parents but different eggs differ, seedlings from the same parent or parents are going to differ.

Some hybrids when selfed, generate offspring which resemble them closely. Grow the mini, Little Artist. Almost anything you raise from that rose, no matter what the other parent, is bound to resemble it. Others make wide ranges of offspring. It all depends upon what’s behind the hybrid.

Actually, there can be anywhere from 14 to at least 42 genes. R. X Alba is hexaploid, with six sets of 7 chromosomes or 42. R. Serafinii is pentaploid, with 35, as are R. Rubiginosa and R. Canina. Just to give you headaches, some species are found in diploid (14), triploid and tetraploid (28) forms. At one point, I was concerned with ploidy and how it might affect my ability to raise anything of interest. Discussing it with Ralph Moore, he offered that while he read them out of interest, he paid no attention to them because “the rose will find the way”. Now, I most often look for triploids to use as there are fertile ones which produce some really remarkable results.

Thanks, Larry, but I traditionally only raise selfs from really “out there” crosses, such as my mini X R. Minutifolia or mini X Stellata mirifica crosses. I do frequently suggest when learning to germinate rose seedlings, you go find all the self set hips from your garden or any other around you that you have access to and raise those. First, it shows you which roses you have access to makes good seed parents. Second, it allows you a supply of seeds to play with which cost you nothing. You aren’t vested in them. You don’t have weeks to months of effort and time invested in creating them so if they don’t work, there is relatively little pain. If they do, then you can see how selfs can resemble, or not, the parents; which rose in your garden makes good babies; what you did to allow them to germinate and you are already bitten by the seedling bug, with very little invested. Why set yourself up for disappointment by dreaming up your own crosses, accomplishing them then killing them by not knowing what to do to allow them to germinate? Raising all those lovely self set hips around you allows you to explore and experiment while dreaming up your own but without the loss should they fail.

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A classic example of siblings that differ would be Mister Lincoln, Papa Meilland, and Oklahoma, all of which were independently created by different breeders around the same time with similar goals using the exact same cross (Chrysler Imperial x Charles Mallerin). The plants are similar, but differ, much as you might resemble but differ from your siblings.

Crossing a species with the same species will yield that species, and the differences are rarely noticable, but they exist. How important those subtle differences are, I don’t know. I have wondered, for instance, if crossing any R. foliolosa x R. rugosa has the potential to create a Basye’s purple type coloring, or if species clones of a specific provenance would be required. There are certainly subtle morphs within species. (I understand that some weeds growing where perennial lawn mowing cuts them short have been unnaturally selected for shorter morphs that are more likely to set seed without being prematurely decapitated.)

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An important concept to learn when considering this topic is heterozygous vs homozygous.

A heterozygous rose carries a lot of hidden gene characteristics that are being masked by dominant genes. A homozygous rose carries genes in which the hidden, unexpressed genes have quite similar characteristics to those that are expressed.

Modern hybrid roses will generally be very heterozygous. Lots of hidden genes with very different characteristics. Therefore their progeny will be highly variable as genes are shuffled around and those that were hidden become exposed.

Species roses will tend to be very homozygous. Most of their offspring, assuming they’re self-pollinated or pollinated by another clone of the same species, will be similar to each other and to their parents.

Similar, yes, but not identical.

I feel that we make the mistake on this forum of assuming that a particular rose species has a fixed set of characteristics. I respectfully disagree with Philip’s above assertion that the differences are rarely noticable. I seek and cherish variations within a species.

I love walking along the edge of the woods and sampling the fruit of different common chokecherry, Prunus virginiana. Some fruit are larger and sweeter, with less astringency. You can find some yellow fruit amidst the purple. Some specimens are noticeably more resistant to the ugly endemic fungus called black knot.

We have a huge variety of common purslane on the farm…Philip’s statement about variability in a weed species is very true. Tiny-leaved mat-forming types and upright, large-leaved types and everything in between.

I think species designations are a valiant, necessary, and futile human attempt to impose order upon a swirling flux of changing genetics. They are an important tool, but should be remembered to be fallible creations of the human mind.

Even wild roses growing in the same meadow will have varying shades of pink to white, different amounts of spotting on leaves, and differently sized, shaped, and colored hips. What about another rose colony growing a mile away in different soil? Two miles apart? Ten miles apart? Fifty miles? Two hundred miles? Six hundred miles?

When nurseries get involved, things get more messed up. They are likely growing their species roses from seed. Where are they getting their seed? From a patch growing on their farm? Where did they get the original plant? (hint: from another nursery.) Do they have another patch of another species growing nearby? Is it a self-sterile diploid species? Do they have a lot of bees? And mislabeling is a huge thing.

People talk about R. foliolosa as having and lending dark purple blossoms. I think this is because a few influential breeders on the west coast got ahold of a clone that had dark purple flowers and worked with it. My clone, however, had light pink blossoms and passed on that characteristic.

My exhortation is that we remember to take species designations with a grain of salt even as we are discussing their characteristics. Your Rosa carolina is likely not the same as mine. Hopefully they share enough characteristics to make our discussions worthwhile.

1 Like
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My Foliolosa, from Santa Barbara Botanic Garden is pure white and completely prickle-free, Joe. Want a piece?

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…puzzled about a book saying that the seedlings of species roses are identical to their parents…

Truly identical is a high bar to reach, and almost unequivocally such a book is incorrect.

I use what I believe is a common-sense definition of sexual reproduction in plants and animals, wherein sexual reproduction is the production of offspring through the combination of gametes (sperm and egg) with both gametes contributing genetically to the offspring. This definition excludes really odd examples such as the Amazon molly (a fish), which is an all-female species in which mating takes place (with males of another molly species) but the sperm typically does not have any genetic contribution to the offspring. On the other hand, this definition does not consider whether there are 1 or 2 parents, only whether gametes join and both contribute to the offspring genetically.

Respectfully, I will note that one of the earlier-offered definitions of homozygous is incorrect. Homozygous does not have anything to do with carrying hidden, unexpressed genes that have similar characteristics to those that are expressed, nor does heterozygous necessarily indicate hidden genes with very different characteristics. When scientists speak of homozygous or heterozygous, they generally are referring to an individual being heterozygous or homozygous for a certain gene. An individual that is heterozygous for a certain gene will carry different alleles (varieties) of that gene; one of these different alleles may be hidden in the phenotype (as in a classic dominant/recessive allele interaction) or both alleles may be expressed (as in, for instance, incomplete dominance of alleles). An individual that is homozygous for a certain gene will carry identical alleles for that gene.

Any given individual will likely be homozygous for some of the genes in its chromosomes and heterozygous for other genes.

Similarly, almost any species will have genetic variation and will contain individuals that are heterozygous for at least some (probably many, many) genes. Maintenance of variation within a species has advantages for that species. Some species are highly variable (i.e. grey wolf) and some have low variation (evidently cheetahs and at least one species of sea lions) but a species with truly no variation would be extremely unusual.

Obviously individuals within a certain sexually-reproducing wild rose species will all share certain characteristics, which of course allows those individuals to be classified as a species. That said, the rose species will still contain some genetic variation. Whether this variation is obvious to our human eyes is less guaranteed, but some genetic variation will be present. Within that species, any given individual is extremely likely to be heterozygous for some genes and homozygous for other genes. Even if that rose self-fertilized, the chance that the offspring would be truly genetically identical to the parent would be extremely low. For instance, some offspring from self-pollination could be homozygous for a gene which the parent was heterozygous for, thus the offspring would be different genetically (a difference which might or might not show up in the offspring’s phenotypes).

Matt

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surely when you cross two roses then every single seed will be unique? So one person crossing two roses will always get different results from anyone else crossing the same two roses?

You would think so but roses are so heavily inbred that this is not usually true. If you cross any two modern rose you can expect to get a mild degree of variation among the offspring but not a lot. The progeny will be like Mama and Papa with some being more like Mama than Papa and vice-versa.

The gene pool from which modern roses originate is relatively small coming from only a handful of different species. A lot of us have been working to integrate additional species into the gene pool. Some people are targeting particular ‘new’ traits like the blotch from hulthemia and thornlessness from moyesii. Others are focused more broadly on disease resistance, winter hardiness, heat tolerance and on recovering recurrent bloom from the wide outcrosses that are needed to bring these additional species into the fold.

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Thanks, Matt for the clarification of my zygosity mumbo jumbo. Your explanation was precise and helpful. I regularly throw around terms that I don’t fully understand and this was one of those occurrences.

I think we’ve all teamed up to confuse the heck out of the original poster. She seems to have touched a trigger that makes us want to blab.

Kim, thanks for the offer…I’m kind of in that stage of having way too many roses to keep track of. I dug out my foliolosa because it got a bad case of reed canary grass. It was interesting in that it threw some rebloomers. Yours is interesting due to the thornlessness. I’m gonna say skip it, please don’t send me a piece, and I will reimburse you for the postage. While you’re at it, don’t send any cuttings of that gorgeous Blue for You X (First Impression X April Mooncrest) seedling nor any cuttings of Art Nouveau, which I have lost.

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Joe, around what date should I not send anything to the frozen north? I’m not sure when it might be safe to not mail things across wide swaths of outrageously cold real estate.

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I would agree with this. Ive got three distinct types of Palustris grown from seed (bought from sheffields seed) which differ again from a bareroot sold in Australia. They have the same narrow shape but the texture and thickness of leaves vary.

Then theres obvious differences in things like multiflora (thorns, leaf texture), californica(thorns), etc.

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That is mostly what I am doing at the moment.

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Thanks everyone for wonderful answers. I read through everything and it does seem that the book was using the word “identical” loosely, and not genetically identical as in identical twins. Maybe the phenotype looks extremely similar, most of the time. It takes a lot of energy for a plant to make seeds, and their purpose is variations.

Rose genetics are very interesting.

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Point taken. “Rarely noticeable” was poorly worded and not my meaning. It was intended solely to contrast with my follow up comments. I meant only to acknowledge that, to an untrained eye, the variations often might not be remarkable. The offspring are “identical” only inasmuch as they are the same species.

My further point being that I get frustrated when reading pedigrees showing a species parent. Without knowing the exact provenance of the particular clone, I wonder if the genetics that might have created the cross I am studying would actually be available to me were I to try and create, if you will, a half-sibling to the cross in question. (I would not be able to create a true half-sibling if I’m limited to knowing the species of the parent in question.)