Some ploidy questions

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Re: Some ploidy questions

by Karl K » Fri Feb 08, 2019 1:24 am

There is another matter regarding ploidy that should be mentioned ... gigantism. When a diploid species produces a chance triploid offspring, the latter is usually larger than the parent. Tetraploids are even larger. Here's an example showing Rosa macrophylla and its tetraploid form.

However, this gigantism is not entirely stable. Fagerlind (1958) wrote:
 It has on several occasions been stressed that polyploids which occur spontaneously in nature, and among these also those which may be regarded as intraspecific, often diverge more or less strikingly from the experimentally produced polyploids (cf. for instance Müntzing 1936, Fagerlind 1937, Wettstein 1937). The former frequently have better, the latter poorer fertility qualities; the former are often more feebly, the latter more strongly gigas-accentuated. As the cause of the difference one may of course reckon with the selection that in time takes place in nature. The above-described conditions regarding Solanum, Bryum and Rosa, however, open the way for the interpretation that at least in special cases the differences are due to the presence of a rather slowly running auto-adjustment.
In other words, the enhanced vigor tends to decline over time. This is one way that old roses seem to deteriorate. But how fast does the decay occur?
It is possible, furthermore, that the adjustment proceeds at a different rate in different organisms. In the tomato it would seem to proceed rather rapidly, in Bryum caespiticium-Corrensii more slowly, and in Rosa rugosa, which after 15 years appears to be at the beginning of its adjustment, the rate would seem to be still slower. 
For example, 'Gloire de Dijon' (tetraploid) is believed by some to have been a self-seedling from 'Souv. de la Malmaison' (triploid).

In some cases, reciprocal crosses can give different results. Pollinating a diploid by a tetraploid should give mostly triploid offspring. This represents a 50% increase in the number of chromosomes (or quantity of DNA) that the cytoplasm must accommodate. The reciprocal cross also gives mostly triploids, but this time there is a decrease of 25% in chromosome count and DNA quantity. Of course, this latter cross should not suffer so much loss of apparent vigor in the next few decades.

Re: Some ploidy questions

by Karl K » Wed Jan 30, 2019 6:13 pm

david zlesak wrote:
Fri Jan 25, 2019 10:40 am
I suspect the nice balance in features in some genetic backgrounds between the diploid and tetraploid levels help these triploid seedlings stand out more (bit more branching than many of the tetraploid siblings, etc.).
Many years ago I read (I don't recall where) that while Wilhelm Kordes was working the line that culminated in 'Crimson Glory', he was aiming for a darker counterpart to 'Mme Caroline Testout' and 'Lady Mary Fitzwilliam'. He came close, but if the plants at the SJ Heritage garden are correctly labeled, both Testout and Lady Mary are well worth emulating. In fact, I had wondered whether CG could be crossed onto a red Tea to get a better crimson bedding rose. I looked at 'Souv. de Thérèse Levet', but was not inspired to pursue the project.

Re: Some ploidy questions

by Karl K » Tue Jan 29, 2019 12:34 pm

Fagerlind (1958) reported on his experiments in doubling roses. He worked with both species and hybrids.
"It is now a well-known fact that doubling of the chromosome number brings about rather great physiological changes. There are considerable changes in the relative amounts of the substances involved. Amongst other things, there is a relative increase in the amount of water, with consequent changes in suction power and osmotic properties."

I think the pumping up of cells with extra water would account for the brittleness of newly formed polyploids. Fagerlind went on to describe the adjustment that occurs in the relationship between cytoplasm and nucleus that allows the cells to become somewhat smaller while retaining all their chromosomes.

Some of his results are a bit surprising. For instance, some tetraploids were less hardy than the diploid parents. Also, when some "sterile" hybrids were doubled, the resulting plants were less fertile, apparently violating Darlington's law.

I puzzled over these paradoxes, but then I remembered that Fagerlind was working in Sweden. It's cold there. A diploid species may be just able to survive there, while its tetraploid progeny, being a little slower growing, are more prone to winter kill because they don't have time to ripen their wood. Similarly, doubled hybrids that should be fertile, don't have time to ripen their fruit ... even though they might contain viable seeds.

Finally, it is important to note that many of the weakly fertile chromosome-doubled plants became increasingly fertile as they aged.

Re: Some ploidy questions

by philip_la » Tue Jan 29, 2019 11:11 am

Most of the recent research I've seen recently on doubling chromosomes uses Orzalin in their protocol. Has anyone done such using e.g. Surflan? (And how would one convert pound per gallon to a microM solution?)

Re: Some ploidy questions

by MidAtlas » Tue Jan 29, 2019 12:40 am

I'd personally love to see an oddball triploid hybrid like 'Agnes' doubled, then its hexaploid form used to pollinate diploid rugosa cultivars and probably assorted other diploids. It's amazing how perfectly healthy 'Agnes' is, given its background (even here in what seems to be the epicenter of all sorts of BS--Washington, DC), on top of inheriting yellow color and having a really pleasant fragrance. The biggest thing that bothered me about R. rugosa descendants back in central Minnesota was their erratic response to winters there, with certain milder winters doing surprising damage to them while sometimes far more bitterly cold winters left them hardy to the tips. Some of the hardiest Explorer series varieties had the same odd issues. Here a big problem for rugosas is cane borers, although that susceptibility could maybe be reduced through breeding and selection (I'm not sure that 'Agnes' isn't already an improvement over others in the class.)

Unfortunately, I'm not too inclined to play with those chemicals, and even if you were to get a branch of 'Agnes' to double, it would probably need to be propagated initially by someone adept at budding.


Re: Some ploidy questions

by jbergeson » Mon Jan 28, 2019 3:42 pm

I'm replying to the original post and haven't read all the responses yet, as I'm too eager to get started procrastinating.

They talk about R. acicularis as having different ploidy levels. I got a bundle of them from Lawyer Nurseries, and they really seem diploid to me...small leaves and stems. The Robert Erskine rose "Aurora", which is supposedly a selection of native R. acicularis, has much larger foliage than the seedlings I got from Lawyer. If the ID's are correct, that might indicate a difference within a species, based upon ploidy.

I really, really want to bring the combination of full hardiness and remontancy of rugosa roses into breeding with modern garden roses. I've gotten some pretty interesting results crossing rugosas with moderns, but the seedlings are usually sterile. For instance, I have a very nice reblooming seedling that is Henry Hudson x Above & Beyond. It is white...if it were bright pink it might be a releasable rose for northern climates. (and if it was any shade of yellow or orange it would be a bombshell). Anyways, I've had fantasies about in vitro chromosome doubling to create a hexaploid, the pollen of which could then be applied to a diploid to create tetraploid seedlings.

My own attempts at chromosome doubling (using triflurilan) of seedlings at the cotyledon stage have not been successful. Mostly working with rugosas, and I tried with some of the Ole, Lena, and Sven series of compact, hardy, multiflora types. There have been a few seedlings that appeared to be successful doublings, but they lacked hardiness and disease resistance.


Re: Some ploidy questions

by roseseek » Sun Jan 27, 2019 3:46 pm

Karl's final paragraph above may well explain the observed sterility of the early Teas, which led to the presumption that triploids are all sterile. Thankfully, they are NOT!

Re: Some ploidy questions

by Karl K » Sun Jan 27, 2019 2:34 pm

david mears wrote:
Sun Jan 27, 2019 2:20 pm
I had a seniors moment Karl on the breeder of "Peace", yes you are correct it was Meilland.
I had my Ginkgo biloba this morning, so I was ready. ;-)

Now, getting back to ploidy, you can think of "ploid" as "ply" as in plywood and 2-ply paper towels.

In roses, a "ploid" or "layer" is made up of seven chromosomes. These chromosomes are all different. That is an important fact to remember. So when a monoploid (one-layer) pollen tube introduces itself to a monoploid ovum, the result is a diploid cell with two layers or sets of chromosomes. Assuming that pollen and ovum are from the same or similar species, all is well. In time an embryo is formed, which grows into a fertile plant.

But if the monoploid ovum is visited by a pollen tube with two sets of chromosomes, there may be some problems ... eventually.

The triploid plant that results from the cross may grow well and be very healthy: think of 'Iceberg'. Mitosis is not a problem because the 21 (three sets) chromosomes don't have to pair off. Just a bunch of bachelors hanging out.

When the time comes for meiosis (the reduction division that leads to new pollen and ova) the chromosomes can get tangled up looking for partners.

Instead of pairs that are easily separated when the cell divides, there may be some groups of three, each one trying to form cross-overs with the other two. As the cell divides, the three tangled chromosomes may all end up in the same daughter cell, while the other daughter cell does not get even one.

As I mentioned above, the seven chromosomes in the basic set (or ploid) are all different. And they are all needed. You may think of them as recipe cards. All are necessary for the finished product to come out right. Different versions of the recipe are allowed, as we finding when we cross a Tea rose with R. multiflora. And nothing goes terribly wrong when there are three versions of the recipe working together in the triploid 'Iceberg'. It's only when meiosis tries to sort 21 chromosomes into gametes with balanced recipes (sets of 7 chromosomes).

In some triploids there are enough gametes (pollen and ova) with 7 or 14 chromosomes (or nearly) to make them useful parents. Again, I point to 'Iceberg'. But other triploids get closer to half and half, which is never a good thing for a triploid. Figuratively speaking, some of the cakes our recipe is supposed to be making will come out with too much flour and no sugar at all.

Re: Some ploidy questions

by david mears » Sun Jan 27, 2019 2:20 pm

I had a seniors moment Karl on the breeder of "Peace", yes you are correct it was Meilland.

Re: Some ploidy questions

by Karl K » Sun Jan 27, 2019 12:44 pm

david mears wrote:
Sun Jan 27, 2019 1:02 am
Thanks Stefan, most of your answer I can understand. So if I was to have a cross with, lets say "Laevigata" with "Peace" one of Kordes most outstanding achievements. It has stood the test of time. It is possible it "could" work ?
'Peace' came from Meilland.
Hybrids of Rosa laevigata are known, but the one with R. banksiae [R. x fortuniana] is the best known.

I have a list of some others. ... brids.html

In addition, I suspect (but can't prove) that the "Reblooming Anemone" that was growing at the San Jose Heritage garden last time I was there, is really a Rugosa x Laevigata hybrid raised by Luther Burbank. The fifth picture from the top is the typical form of cane, while the sixth looks like the Rugosa ancestry has pushed itself into expression. ... Anemo.html

Shifting dominance is not a rare phenomenon. In fact, I have another case of Rugosa traits behaving strangely.
A Rose Odyssey (1937: p123-124)
J H Nicolas

In 1933 I had found a curious sport on Margaret McGredy. The foliage strongly resembled Rugosa but the plant characteristics also leaned toward R. cinnamomea. I mentioned this fact to Sam III [McGredy] when I visited him in 1934. Sam could not account for the sport. He had never used species in his breeding. His brother-in-law, Walter I. Johnston, spoke up, "Your father did much more work with species." We adjourned to the office, where complete hybridizing records from the early days of the firm are kept, one volume for each year, a valuable library. After several hours of research we traced the origin of Margaret McGredy to crosses of Rugosa and Cinnamomea. They were, of course, many generations back. But as these two species are in the blood stream of Margaret McGredy and all modern McGredy roses, the possibility of the sport was explained. It is an accepted fact that hybrids alone sport (pure species mutate, but rarely, if ever, sport) and can sport only within what is in them.*

Lately, the most unusual thing has happened to that sport. A sport is supposed to be a part of the hybrid compound which "took a walk". But this sport must have carried the whole pack as it has sported again a Hybrid Tea type with a magnificent bloom much more intensely colored than the original Margaret McGredy and is a distinctly a different rose. I am planning to name it "Margaret Second".
Also, my list of Laevigata Hybrids contains a note from Lord Penzance. In his case, the shiny leaves of Laevigata did not appear in any of the seedlings, even when Laevigata was the seed parent.

Re: Some ploidy questions

by roseseek » Sun Jan 27, 2019 1:28 am

You're welcome, David. Of course it "can" work and has innumerable times.

Re: Some ploidy questions

by david mears » Sun Jan 27, 2019 1:24 am

Thanks Kim, so mixing "ploidy" can/could work

Re: Some ploidy questions

by roseseek » Sun Jan 27, 2019 1:22 am

"Possible"? Perhaps. "Probable"? Probably not. Getting anything to cross with Laevigata can be "challenging", to be gracious. There are some types which are simply mulish while others are rabbits on fertility drugs. Minutifolia, diploid, fought me for decades, until I hit on the climate, method and mates making that possible. Serafinii, a pentaploid, resists EVERY attempt, in both directions. Even when trying it with the triploid mate which made the Minutifolia offspring possible. Mixing ploidies can work and can result in some pretty remarkable creations.

Re: Some ploidy questions

by david mears » Sun Jan 27, 2019 1:02 am

Thanks Stefan, most of your answer I can understand. So if I was to have a cross with, lets say "Laevigata" with "Peace" one of Kordes most outstanding achievements. It has stood the test of time. It is possible it "could" work ?

Re: Some ploidy questions

by MidAtlas » Sat Jan 26, 2019 11:37 pm

David M., I think the simplest answer to that is probably "yes, they will", although it would also be safe to add "it's complicated". Generally speaking, if there's a combination you'd like to make and you can get pollen from one parent and the other is a plausibly willing recipient, then you should never let considerations of any ploidy differences completely derail any plans--those factors should only inform your approach and shape your expectations. Based on the body of evidence there are some things that you might tend to expect when crossing roses having certain disparate chromosome numbers (and those tendencies can at times be exploited to help achieve certain breeding outcomes), but there are also numerous variables at play like unreduced gametes that keep everything unpredictable and interesting.


Re: Some ploidy questions

by david mears » Sat Jan 26, 2019 10:24 pm

Again please excuse my question, will all of these "ploidy" things cross with other ploids ?

Re: Some ploidy questions

by MidAtlas » Sat Jan 26, 2019 10:15 pm

David, thank you for the link to that very interesting paper! The pink flower color and the apparent reduction in seed fertility are surprising results, but a lot of the other changes seem in line with those seen in the chromosome doubling of diploids. It would have been useful to know if the hexaploid's pollen was mostly 3n (unless I missed something!), but that seems the most likely scenario. I suppose that you might get some unreduced 3n pollen from the triploid as well, but the odds would be lower.


Re: Some ploidy questions

by Karl K » Sat Jan 26, 2019 5:37 pm

henry kuska wrote:
Sat Jan 26, 2019 12:52 am
The following 2016 paper may be of interest: ... ba23).html
Thanks for the link. I will admit, right off the bat, that I cringed while reading that abstract.

"In most rose species only one ploidy level is observed. However, some can have different ploidy levels. For example R. chinensis can be di-, tri- or tetraploid, while R. acicularis can be tetra-, hexa- or octoploid."

As far as anyone can determine, Rosa chinensis Jacq. was based on a garden variety rose derived from two or more ancestral species. Even the Crimson China (Slater never saw it) carried genes derived from R. multiflora and R. luciae, among others. We really should stop confusing groups of garden plants with formal species. China roses are not Rosa chinensis, just as Rugosas are nor R. rugosa and Gallicas are not R. gallica.

And it's not just roses that get mistreated in this way. The German Irises are not derived from Iris germanica, despite what some Catalog writers have claimed.

Is Rosa acicularis really "tetra-, hexa- or octoploid?" Did the speaker forget the diploid R. acicularis nipponensis Crépin?

Unlike so many other botanists, Hurst (1932) was able to consider more than a handful of traits at one time:
"... we have the interesting case of Rosa acicularis, which is said by different cytologists to have diploid, tetraploid, hexaploid and octoploid forms. A critical taxonomic diagnosis of the material used shows clearly, however, that the original R. acicularis of Lindley is octoploid and includes two distinct genetical species with septets AACCDDEE and BBCCDDEE, while the American hexaploid "acicularis" are either R. Bourgeauiana Crép. which is BBCCDD, or R. Sayi Schwein., which is CCDDEE. The tetraploid "acicularis nipponensis" of Willmott (non Crép.) found in the Kew collection is a subspecies of R. pendulina L., which is DDEE, while the original diploid R. acicularis nipponensis of Crépin is a subspecies of R. rugosa Thunb., which is CC."

For those not familiar with Hurst's shorthand, each of the letters, A through E, represents a set of 50 traits that Hurst found to hold together in species around the world. For example, The A group includes the Synstylae, Indicae and Banksiae.

Hurst's terminology is out-of-date. Back in the 1920s, when he got started, he assumed (as almost everyone else did) that the identifying traits of a species must involve genes scattered among the seven chromosomes of the haploid set. Since then, however, we have a better (though imperfect) understanding of "supergenes".

Re: Some ploidy questions

by david mears » Sat Jan 26, 2019 3:00 pm

Thanks for the reply to my question

Re: Some ploidy questions

by david zlesak » Sat Jan 26, 2019 1:13 pm

Here is a paper that Dr. Kermani and her colleagues have reporting on chromosome doubling the triploid rose 'Iceberg'. The hexaploid interestingly is soft pink. ... 104925.pdf