Eva (Kordes) is tetraploid, coming from diploid seedparent?

I came across this rose: Eva (Kordes, 1933), a tetraploid pollenparent with a diploid seedparent gives tetraploid offspring. I didn’t think you could hope for such a result. I’m assuming JC Thornton to be tetraploid at least.

Robin Hood (hybrid musk, Pemberton, 1927) × J.C. Thornton

How does this work?

Hi Karel,

When meiosis is disrupted (can be in multiple ways) a possible result is some of the gametes containing the same chromosome number as the parent plant versus being halfed. These are called 2n gametes (as they have the 2n or sporophytic chromosome number, just like the parent). Sometimes they are called unreduced gametes, but this term is a little frowned upon since there is something called the reductional division in meiosis and sometimes this can be the reason, but sometimes there is a disruption in another step for the abnormality.

Anyways, a small percentage of gametes that are 2n are common in some genotypes and their production tends to have a high environmental component for the rate of such gametes. For my MS research part of it was testing diploid wild species genotypes in different environments for 2n pollen. The same genotypes consistently produced a low rate of 2n gametes, but from year to year the exact percentage varied a bit.

In roses it seems that the more wide the diploid cross, etc. the more sterility there is in the gametes. If there is fertility in low fertility wide crosses, those fertile gametes that work often seem to be the 2n ones. I suspect with some of the pathways to 2n gametes (parallel spindles, etc.) that it just more readily would lead to gametes that are balanced with complete sets of all the chromosomes.

‘Max Graf’ has produced some 2n eggs (I have a 4x seedling of it). Little MischiefTM, a diploid, produces some 2n pollen. Even some tetraploids produce a small amount of 2n gametes. For instance, ‘Sonia’ produces some. Here’s a paper of mine looking at pollen. http://globalsciencebooks.info/Online/GSBOnline/images/0906/FOB_3(SI1)/FOB_3(SI1)53-70o.pdf

Plants have these mechanisms to go up in ploidy and then also some to go down in ploidy (unfertilized eggs sometimes producing an embryo with half as many chromosomes). These mechanisms help plants survive and balance out at a more conducive ploidy. For instance, R. acicularis is found at multiple ploidy levels with a trend finding the 8x highest ploidy forms in colder more stressful circumstances where they can house more allelic diversity, and then lower ploidy in easier climates so they can replicate their cells faster and be more competitive in growth rates in those climates.

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Unreduced gametes certainly occur, but the idea has sometimes been invoked too often. This came out in the genus Rubus where crosses between diploid raspberries and diploid blackberries result in triploids and the occasional tetraploid. No diploids at all. I read a paper (but can’t find it now) where someone went to the trouble of examining the ova and pollen of the parents. There were not enough unreduced gametes to account for the triploid and tetraploid progeny. Maybe someday I’ll find the paper again.

For now, there is this one, where a triploid parent doubles the unpaired chromosomes routinely, if the weather is warm enough.

And let’s not forget that ‘Eva’ was a grandparent of ‘Baby Château’, which produced some valuable tetraploid offspring when pollinated by the diploid Rosa roxburghii. So maybe the chromosome doubling trick runs in the family.

American Rose Annual, 1959
Cytology of Two Fertile Triploid Roses
Dr H. D. Wulff

The ancestry of Schneeschirm, an ornamental rose, is not quite clear. It blooms twice a year. The first flowering period lasts from June to August. The second begins after a short interval, and ends with the first frosts.

It is a very remarkable fact that the flowers of both periods differ in their meiotic behavior; only those produced during the first period are able to produce hips and viable achenes. Their reduction division is characterized by the occurrence of only 0-3 trivalents, with pairing to 7 bivalents and 7 univalents or 1 trivalent, 6 bivalents and 6 univalents. This reduction division proceeds rather regularly. The univalents, splitting twice, are mostly taken up into the young tetrad nuclei. Chromosome elimination is low, and so viable pollen grains and egg cells will contain 14 chromosomes.

The offspring of about 60 plants were tetraploid, each seedling having 28 chromosomes in the root tips.

I almost forgot … well, I did until I was out watering the garden.

Journal of Experimental Botany, Volume 62, Issue 10, June 2011, Pages 3587–3597,
Polyploidization mechanisms: temperature environment can induce diploid gamete formation in Rosa sp.
Yann Pécrix, Géraldine Rallo, Hélène Folzer, Mireille Cigna, Serge Gudin, Manuel Le Bris
Polyploidy is an important evolutionary phenomenon but the mechanisms by which polyploidy arises still remain underexplored. There may be an environmental component to polyploidization. This study aimed to clarify how temperature may promote diploid gamete formation considered an essential element for sexual polyploidization. First of all, a detailed cytological analysis of microsporogenesis and microgametogenesis was performed to target precisely the key developmental stages which are the most sensitive to temperature. Then, heat-induced modifications in sporad and pollen characteristics were analysed through an exposition of high temperature gradient. Rosa plants are sensitive to high temperatures with a developmental sensitivity window limited to meiosis. Moreover, the range of efficient temperatures is actually narrow. 36 °C at early meiosis led to a decrease in pollen viability, pollen ectexine defects but especially the appearance of numerous diploid pollen grains. They resulted from dyads or triads mainly formed following heat-induced spindle misorientations in telophase II. A high temperature environment has the potential to increase gamete ploidy level. The high frequencies of diplogametes obtained at some extreme temperatures support the hypothesis that polyploidization events could have occurred in adverse conditions and suggest polyploidization facilitating in a global change context.

More examples:

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We also cant assume all clones of Eva are the same. While I do believe Kordes used Robin Hood where they said they did, one cannot also discount it is not “seedling of Robin Hood” or some other mumbo jumbo. In this instance, I found no reason to believe this was the cased based on results from Robin Hood from other breeders.

That being said, Iceberg is triploid. Eva is tetraploid. I have no idea what Skyrocket is, but I wont take the word of outdated publications for ploidy. Some of those were simply lists of word of mouth, which is not helpful.

The interesting thing I noted is that a local botanical garden/nursery that carries only rare plants had a specimen of ‘Eva’ there for years. IT was definitely ‘Eva’. All traits matched, but it was MUCH shorter than photos I have seen. Roughly the same dimensions and look of the rose in this photo, except with Eva flowers, foliage and stems. 'Funny Face ' Rose Photo

I mention this because we cannot be sure Eva is all that stable, especially given the instability of a plethora of roses descending from Miss Edith Cavell, including Iceberg and its ability to randomly pass on hand painting generations later.

Dear PacificJade,

Good point about not always taking what is reported to heart for ploidy as some of it like you say may be word of mouth and/or be inaccurate as a really good cell spread to count chromosomes well wasn’t really done, etc. There is a key historical rose that I have counted multiple times (it seems like I have the right one), but it doesn’t match the reported ploidy. Sometimes similar looking roses can be mixed up in commerce too. I want to do do more research with this rose before I share about it publicly. ‘Harison’s Yellow’ has been reported as tetraploid, but the many clones Peter Harris sent me from different sites around the country and also the specimen at the MN Landscape Arb. were all triploid. I have some reason to believe ‘Austrian Copper’ may be triploid from ploidy of some of its descendants and also some genetic data on hand (SNP data). I ordered an own root plant of it and look forward to doing a root tip squash this year and seeing. I’m grateful or the ease of use of digital cameras on the microscopes to more readily document chromosome numbers to have a good record to look back on. Years ago people would generally just hand draw what they saw in the microscope or just write down the number of chromosomes they were able to see.

In my paper (http://globalsciencebooks.info/Online/GSBOnline/images/0906/FOB_3(SI1)/FOB_3(SI1)53-70o.pdf) I report a few seedlings out of ‘Robin Hood’. There are a couple diploids out of RH with diploid polys and one triploid out of RH x Buck’s tetraploid ‘Summerwind’ (expected ploidy levels with normal meiosis). There is also the seedling RH x bulked 4x males that is 4x, suggesting a 2n egg from RH for that seedling. Iceberg being triploid from RH x Virgo may just be from a normal gamete out of RH and not be unusual.

I love the topic of ploidy and ploidy transmission and am grateful for access to nice microscopes and the ability to do chromosome spreads. I typically like to look at at least 5 well spread cells before I’m convinced of a ploidy level. Sometimes it is hard to get really good photos as chromosomes aren’t in a flat single plane and one needs to go up and down slightly in focus to see them all at the different planes. With practice I’ve gotten better. Removing unnecessary cellular material from slides to get a better and flatter spread to see things better is tricky. It is hard sometimes to isolate just the highest quality cells just behind the actual tip and remove all the other material so it doesn’t provide resistance making it harder to flatten out the cells of interest to spread their contents better.

Thank you David, Karl, PacificJade for the valuable info. I’ve looked into some articles I collected on ploidy over the years after reading the above and found a thesis that also referred to those 2n gametes (understanding and manipulating polyploidy in garden roses (jake allen ueckert)). So not only pollen but also eggs can be 2n and even 3n. I wasn’t sure about that until now.

I remember that we learned about changes in ploidy due to extreme weather conditions in school (a long long time ago) and how one could inhibite those changes with UV lighting or colchicine (some poison in a crocus bulb). Wheat would have undergone such a change on the Anatolic plains thousands of years ago, where the sun would burn very fierce upon the grains.

Anyhow… Those 3n gametes, are those restricted to triploids or is this not related to the ploidy of the parent? I’m guessing not.

Thank’s Karl K. I’ve read the article about triploid parents. I’ve got quite a few triploids in my garden and wanted to do some crosses. But it appears it is not recommended as those crosses would be much more difficult to have good offspring. The article give a lot of info. Some triploids seem to be good parents, give fertile offspring.

Would triploid crosses distribute traits of the parents unevenly due to the fact that you’d have one pair of chromosomes short or extra, when crossing with tetraploids or diploids?

The article talks about some things in which I haven’t got enough background to fully comprehend I’m afraid. Is there a “rose genetics for dummies” of some sort that would help me along? :slight_smile:

Univalents are chromosomesets that do not split en bivalents are the ones that split and match up with those of the other parent I guess? What about trivalents? Those are the ones that cause disruption in the crossing? I’m guessing that pollen with only 13 chromosomes and not 14 (as mentioned in the article (Cytology of Two Fertile Triploid Roses) are not fertile?

I’ve read somewhere that Kordesii had a special ability to give tetraploid offspring when crossed with diploids. Is this also related to 2n gametes or maybe more of a mini-canina-meiosis in which the seedparent keeps a greater proportion of its chromosomesets in its offspring, also giving offspring that looks a great deal more like the seedparent.

So many questions, so little time :slight_smile:

Has anyone confirmed the chromosome count reported for ‘Eva’?

Hi Stefan, I’d be glad to try to confirm ‘Eva’ if you or someone else would be able to get me a few cuttings to try to root to get some good root tips to work with.

Take care,

Look for the paper’ The strong competitive role of 2n pollen in several polyploidy hybridizations in Rosa hybrida’. By Shu-min Gao published online by Springer Link. This helped me.

Hi David, that is wonderful to hear! I don’t know if anyone else has the cultivar, but it might be a little while before I can assist–I had only just obtained a small plant last year from Joy Creek Nursery (which ceased its operations later in 2021), and it’s still barely more than a rooted cutting itself. Hopefully it will hang in there, and hopefully it is correctly identified, though I would think that is fairly likely from this source. I’ll try to give it a little TLC.


In case anyone is hunting for it, here is the paper where the chromosome count for ‘Eva’ was published by Wulff and Heldt in Der Züchter 23(3): 87-93 (1953):


Also, if the oldest reference listed for ‘Eva’ at HMF is faithfully reproduced there and there isn’t some contextual nuance missing, the parentage of ‘Eva’ may actually have been reported first as “seedling of ‘Robin Hood’ x ‘J. C. Thornton’” rather than simply “‘Robin Hood’ x ‘J. C. Thornton’.”

That may or may not mean the same thing. It has often times turned out to be a seedling of the explained cross, and some times turned out to be a seedling product of A crossed with B. It is very dicey wording, and I am glad it is going away. In this instance, the outdated usage may very well be correct.

Agreed. Looking at the other varieties that Kordes introduced the same year, described in the same publication, all of the parentage listings began with the same “Semis de…” opening. It probably had no specific meaning, although taken out of context, it almost sounds as if it might.

Thank you Johannesp for the tip. I’ve found the article.

Thank you Stefan :0). It’ll be fun in the future to hopefully confirm/reconfirm the ploidy of ‘Eva’.