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Post by Admin on Mar 24, 2022 20:52:24 GMT
I would like to start a discussion about tetraploid tree peonies. What tetraploid tree peonies you might ask, are there any tetraploid tree peonies? And the answer, to my knowledge, is NO. There are no tetraploid tree peony species that anyone knows about and, again to my knowledge, no tetraploid tree peony hybrids either. So, this begs the obvious question "Why Not"?
There are, of course, many tetraploid herbaceous peony species and also now hundreds of new advanced generation herbaceous hybrids (AGHH) that are either confirmed or presumed tetraploids, based on their appearance and fertility. So, this being said, "why then, are there no tetraploid tree peonies"? I once believed that we were well on our way to producing fertile tetraploids with the AGLH tree peonies, as we moved to more advanced generations of these hybrids, which also seemed to be exhibiting greater and greater degrees of fertility. It now appears clear to me that this increase in fertility has been due to these AGLH slowly "regaining their lost" fertility on their way to becoming fully functioning fertile diploids, that have "outgrown" their initial limited and abnormal fertility phase that is associated with the F1 and early generation group of hybrids. Which is to say, that their evolution to full fertility has taken place while remaining at the diploid level, which is generally not the case. This conclusion, seems to be supported by my observations that these higher generation AGLH cultivars (although highly fertile when crossed with each other) are much less effective in producing intersectional hybrids in the IC.
I am particularly interested in getting comments from those, like Nate, who primarily work with the AGLH group. Do you have any woody hybrids that you believe are or might be tetraploid?
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rob
New Member
Posts: 5
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Post by rob on Apr 1, 2022 20:06:51 GMT
Don, your conclusion is supported only by the observations of reduced fertility in producing intersectional hybrids?
Do you consider Golden Era and Golden Experience among AGLH?
I think that only a direct chromosome count of AGLH peonies cells, if and when possible , could solve the question
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Post by Admin on Apr 7, 2022 0:45:46 GMT
Rob, Thanks for your comments and questions. Yes, you are right that my conclusions are based primarily on my observations of the effectiveness of various AGLH as pollen parents in the intersectional cross, but this is because there is almost no information available, at least that I am aware of, about the ploidy level of the hybrid tree peonies. In his new book, Peonies of the World: Part III, Hong reports the ploidy level of all of the tree peony species from actual chromosome counts, thus confirming that all of the tree peony species are diploid. Unfortunately, there have been very few ploidy level measurements reported on the very popular Lutea hybrid tree peony group. I am currently working on trying to finish an article for the APS Bulletin on the chromosome counts of several important members of this group, which I had done some time ago, but unfortunately, which have only been reported, thus far, in a presentation I gave at the APS meeting in 2016. The results of these measurements showed that three of the most effective AGLH pollen parents in the intersectional cross, Golden Era, Golden Experience and Alice Harding are all diploid. Thus, my conclusions regarding the ploidy level of the AGLH group is also partially based on this information as well. And yes, I do consider Golden Era and Golden Experience to be included in the overall AGLH group.
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yangyong
New Member
Posts: 6
What is your main area of hybridizing interest?: More than one of the above
How would you classify yourself as a hybridizer?: Serious
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Post by yangyong on Apr 7, 2022 7:51:17 GMT
Don，the information I got about AGLH chromosome ploidy is different from your results. I learned that Golden Era is tetraploid in 2019, which was mentioned in the report of a master's student of Professor Cheng Fangyun of Beijing Forestry University. She used the young flower buds of Golden Era to make chromosome compression. Later, another master's student of Professor Cheng Fangyun used the same method to study the chromosome number of three AGLH introduced from Bernard Chow in Melbourne, Australia, including Zephyrus, Their chromosomes have also been proved to be 20. Recently, my friend and I used flow cytometry to test the chromosome ploidy of five AGLH, including Golden Era and Golden Experience. we used P. x suffruticosa as the control. The results showed that the chromosomes peak position of these five AGLH was about the twice of P. x suffruticosa, so we think these varieties AGLH are all tetraploid. ![]() |
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nate
New Member
Woody peonies and herbaceous hybrid interests. Some work also with species crosses x ADV.
Posts: 6
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Post by nate on Apr 19, 2022 4:50:41 GMT
Were the chromosome counts performed in China all performed with flow cytometry? Or were they counted visually under a microscope? I've not seen definitive reporting on this, but have seen some of Don's Karyotypes which would support diploid numbers. There is information that disputes flow cytometry results as being an accurate method in estimating ploidy. The major reason from my understanding is that nuclear mass is used to make calculated estimations. What was found is that larger (more massive) chromosomes are often counted as two chromosomes and are actually only one. The more massive chromosome mislead interpretation and cause those reading the results to believe they are tetraploids, while they are actually diploids with simply larger chromosomes. This was proven out in the genus Hemerocallis when a hybridizer who works with flow cytometry claim a high number of chromosomes in some of his hybrids, but when actually doing visual counts found they were simply tetraploids. Since I'm not expert in this area by any means, I rely on reporting which is understandable to me, but may not be accurate. It would seem that more chromosome counts using highly reliable methods (old visual counts) would be pertinent. Additionally, since genetic behaviors are very unique in peonies, there may be other things happening which we have not yet investigated.
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yangyong
New Member
Posts: 6
What is your main area of hybridizing interest?: More than one of the above
How would you classify yourself as a hybridizer?: Serious
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Post by yangyong on Apr 20, 2022 7:59:04 GMT
The chromosome number of Golden Era and Zephyrus is determined by observing the number of chromosomes under a microscope. Later, we used flow cytometry to analyze the chromosome number of other advanced generation Lutea hybrid cultivars including these two cultivars. The chromosome peak position of the advanced generation Lutea hybrid peony is twice that of P. suffruticosa, and the triploid Itoh hybrid is just in the middle of them. The following are Golden Era and Zephyrus  |
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nate
New Member
Woody peonies and herbaceous hybrid interests. Some work also with species crosses x ADV.
Posts: 6
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Post by nate on Apr 20, 2022 20:46:43 GMT
This is what you'd expect to see for results, but as I recall there may be some different results or some other circumstance which leads to the 'diploid' outcome. Testing and the implications are beyond my capabilities and I depend on others for this information. Ploidy is no longer something I consider heavily when making crosses due to the unusual fertility behaviors found in peonies. Ploidy is helpful, but not may not be as important in making viable crosses as once thought. I really enjoy hearing about the science though and hopefully clearer and agreed upon results can be forthcoming.
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Post by Admin on May 7, 2022 1:20:56 GMT
Sorry for not responding much sooner to the posts by Yang Yong on April 7 and 20. I have been very busy recently with potting up my many germinated and shouting seedlings that had been in cold storage for the winter months. I also needed some time to organize my thoughts and put together an appropriate response to address the serious issues raised in above mentioned posts. My comments are quite lengthy and ended up filling almost 4 pages, including a photo. I felt that this was too long to put in a post, so I have included this Word document as an attachment. I hope that those who are interested in this important topic will take the time to download and read this document. Although, I am not, by any means, an expert in this field, I am a scientist and have spent a good deal of time studying and learning about this subject, as well as actually practicing the art of counting chromosomes, and thus I believe that I understand this topic a lot better than the majority of hybridizers. After carefully reviewing my analysis, results and conclusions over the last few weeks, I continue to have a high degree of confidence in the soundness of my methods and analysis and the accuracy of my conclusions, that were first stated in a presentation to the APS back in 2014 and that were also summarized recently in this forum in my post on April 6. |
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yangyong
New Member
Posts: 6
What is your main area of hybridizing interest?: More than one of the above
How would you classify yourself as a hybridizer?: Serious
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Post by yangyong on May 10, 2022 7:10:04 GMT
Don, Thank you for your detailed reply to my question.
The results of chromosome counts were provided by a team of Beijing Forestry University. The reason why they chose young flower buds instead of root tips is that tree peonies are reproduced mainly rely on grafting. The roots of P. ostii or P. lactiflora are chose as rootstocks to reproduce other cultivars. Therefore, in order to avoid the root tips of rootstocks collected, the young flower buds were used, and young flower buds are also undergoing mitosis.
When we carry out flow cytometry, young leaves were chose in spring. According to the experience provided by other plants, the detection results of young leaf tissue are more reliable.
I agree with you that the result of root tip compression is the most reliable. I got some seeds of AGLH last year and 6 seedlings this spring. I will transplant them this autumn. At this time, I will be able to obtain ideal root tip materials. I will count their chromosomes and collect their young leaves for flow cytometry in the next spring. I believe this experiment will provide a more convincing result.
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