Author Topic: Rhubarb breeding  (Read 2913 times)

Garrett Schantz

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Re: Rhubarb breeding
« Reply #30 on: 2020-12-04, 03:22:36 PM »
Remember when Europeans said not to eat tomatoes because they were toxic?
 Could be something like that. I haven't heard masses of people dying from eating the leaves in WW2 so it probably isn't reliable. Worth looking into I suppose.

Edit: Searching "Rhubarb Leaf Toxicity" reveals that around 11 pounds of rhubarb leaves are pretty toxic. So eating them without removing the oxalic acids properly could be dangerous. The stems don't have as much I suppose. 11 pounds is quite a lot of leaves to go through, but I suppose oxalic acids could have built up enough over a period of time to cause issues. Even more so if someone already had liver problems or something.
« Last Edit: 2020-12-04, 04:43:32 PM by Garrett Schantz »

Dominic J

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Re: Rhubarb breeding
« Reply #31 on: 2020-12-04, 04:43:16 PM »
Remember when Europeans said not to eat tomatoes because they were toxic?
 Could be something like that. I haven't heard masses of people dying from eating the leaves in WW2 so it probably isn't reliable. Worth looking into I suppose.

Well, I wouldn't be inclined to eat a fruit from a family with a reputation for toxicity either. I also heard a story of tomatoes grafted onto nightshades having toxic fruits as a result.

"The large, triangular leaves contain high levels of oxalic acid and anthrone glycosides, making them inedible.".

"DEATH FROM RHUBARB LEAVES DUE TO OXALIC ACID POISONING" (1919). Note, I don't think OA killed her, but if you look at this case report more broadly, you could say "rhubarb leaf caused death".

"Rhubarb leaves contain poisonous substances, including oxalic acid, a nephrotoxin.[36] The long term consumption of oxalic acid leads to kidney stone formation in humans. Humans have been poisoned after ingesting the leaves, a particular problem during World War I when the leaves were mistakenly recommended as a food source in Britain.[39]"

Some "myth busting" websites have stated that "nah, other plants have more OA than rhubarb, so rhubarb is safe!" I think that's pretty recklessly haste of a confusion. Toxic effects, including death, have been reported for eating rhubarb leaf. If there's debunking to be made, it's about the specific molecules in play, and not the safety of the leaves, in my opinion. I've seen other anecdotal accounts of rhubarb leaves poisoning pets.

Which is what makes me pretty reluctant to start dabbling with interspecific crosses for this crop. There's something toxic, and we can't really be sure what it is, and where it is on the other species.

Garrett Schantz

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Re: Rhubarb breeding
« Reply #32 on: 2020-12-04, 04:52:42 PM »
Best best would to only breed species with similar uses I suppose.
https://www.sciencedirect.com/topics/pharmacology-toxicology-and-pharmaceutical-science/rhubarb
 This link says that its common knowledge in Asia, Europe that the leaves contain oxalic acid and are poisonous.
 All of the chemicals in rhubarb have been identified as its an old crop. So its probably just people used the leaves as a salad green and the toxins build up over time, possibly worse on someone with kidney problems.

Dominic J

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Re: Rhubarb breeding
« Reply #33 on: 2020-12-05, 04:54:04 PM »
Best best would to only breed species with similar uses I suppose.
https://www.sciencedirect.com/topics/pharmacology-toxicology-and-pharmaceutical-science/rhubarb
 This link says that its common knowledge in Asia, Europe that the leaves contain oxalic acid and are poisonous.
 All of the chemicals in rhubarb have been identified as its an old crop. So its probably just people used the leaves as a salad green and the toxins build up over time, possibly worse on someone with kidney problems.

"DEATH FROM RHUBARB LEAVES DUE TO OXALIC ACID POISONING" (1919) is behind a paywall so I don't have access to the whole text to see just how reliable the account seems.

But rhubarb doesn't have particularily high OA concentration, and I've never read any account of "death from parsley due to oxalic acid poisoning". Googling it, the closest thing I found was "death of child from oxalic acid poisoning from rhubarb" (1960, approx wording).

I'd like a study stating that all of the chemicals in rhubarb have been identified... that's a pretty dubious claim. Even in more mainstream crops, there's still a lot we don't know. Rhubarb is not a widely grown crop, and there's no major industry behind it. Apples have various conglomerates pumping millions into research and breeding, for example, same for corn, rice, hops, and a whole bunch of other "big" crops. Rhubarb? Not even close.

Besides, your site mentions "dihydroxyanthracene derivatives" contents and Wikipedia mentions "anthrone glycosides".

It honestly looks way more like a case of "nobody really studied this crop", combined with "one dude in 1919 said someone died from oxalic acid in rhubarb", followed by every later rhubarb death just quoting the first guy.

Em Bracken

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Re: Rhubarb breeding
« Reply #34 on: 2020-12-05, 06:22:18 PM »
Slight tangent, but less scrupulous individuals might access that paper on Sci-Hub - the infamous research publication piracy site described in this article which somehow continues to evade being shut down.

nathanp

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Re: Rhubarb breeding
« Reply #35 on: 2020-12-05, 09:57:23 PM »
Slight tangent, but less scrupulous individuals might access that paper on Sci-Hub - the infamous research publication piracy site described in this article which somehow continues to evade being shut down.

Less scrupulous.  Or more principled, depending on perspective.

Em Bracken

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Re: Rhubarb breeding
« Reply #36 on: 2020-12-05, 10:27:05 PM »
It's a bit of a struggle not to derail this thread, but I'll succumb to play devils advocate - hopefully - succinctly. I wonder how successfully one could make a case that truly open source plant breeding needs to be boot-strapped from the "ground up" (pun intended) starting with open-access/permissively-licensed research. Conversely, could an open source variety actually be considered encumbered if the knowledge or techniques that lead to its creation are themselves encumbered by intellectual property? How about if the process of creating it involved intellectual property violations that themselves aren't present in the resulting variety?

Presumably, there would be no issue if someone learned about working Sci-Hub links being easy to find with Google through a non-endorsing post on this forum and subsequently used that knowledge to learn about the OA toxicity which eventually effected the direction of their open source planting breeding efforts.

I don't know - IANAL - but am curious where the line would be drawn - probably a question for a different thread though... :)

nathanp

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Re: Rhubarb breeding
« Reply #37 on: 2020-12-06, 06:35:14 AM »
First, I am not arguing one side or the other of this topic, but technically, all the papers available through sci-hub are available to those who either can pay for them, or are willing to do so.  It is just a matter of whether the paper is legally or illegally accessed.  The information is what it is, regardless.  All it would take to gain proper and legal access is either pay for the service, or contact one of the original authors who likely has permission to share the paper.  I have done this in several occasions with potato breeding, and been sent papers by one of the authors.  But sciencedirect, springer, etc., all do allow membership or papers purchased individually.

Second, the Dulcinea carrot project is a good example of how breeders started by examining carrot breeding sources and eliminated anything that involved intellectual property as their first step in the process, then just working solely with ones without restrictions.

http://opensourceplantbreeding.org/forum/index.php?topic=304.0
https://osseeds.org/free-the-seed-podcast-s3e4-dulcineacarrot/

I won't link to the papers involved on this project, but they are worth reading for anyone delving into such a project.  There are several by Dr Claire Luby and Dr Irv Goldman.  Nearly all should be available as open-source papers.  That is not always the case for every plant or vegetable, but the path to breed anything similar could be followed with any plant or vegetable.

That is basically all I will say on the matter, without derailing this topic too much.
« Last Edit: 2021-05-13, 08:48:46 PM by nathanp »

nathanp

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Re: Rhubarb breeding
« Reply #38 on: 2020-12-06, 06:45:09 AM »
Back to the topic of Rubarb breeding. 

The remaining question for me that remains unanswered is whether the properties that make 'wild' (ie. non cultivated for food) rhubarb varieties (other Rheum spp.) is the same as that present in Rhubarb cultivated for food (ie. Rheum x rhabarbarum).

I do not think it can be assumed that Oxalic acid is the only factor involved, or is present in a similar amount. There may be other factors involved, and it appears that the available literature does not adequately answer questions about this.  'Safety' or 'edibility' for such things may be similar to glycoalcaloid content in potatoes.  If only a small amount is eaten, perhaps it is 'safe' because the human body can process out the toxins without a healthy person becoming sick.  But eaten in higher amounts, elevated glycoalcaloids can make a person sick.  Generally for potatoes, for example, there are safety thresholds to this, and as long as the total accumulated amount is not ingested, you will not get sick. 

I would not be confident in working with any of the other Rheum species without information being available that does not appear to be available.  Maybe other people would be, however.  It poses interesting questions.  I probably will stick primarily to Rheum x rhabarbarum accessions and let others deal with breeding away from laxative properties, whatever the reason or chemicals involved.

Dominic J

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Re: Rhubarb breeding
« Reply #39 on: 2020-12-06, 08:29:15 AM »
Slight tangent, but less scrupulous individuals might access that paper on Sci-Hub - the infamous research publication piracy site described in this article which somehow continues to evade being shut down.

Sci-Hub had failed me with other very old studies, so I hadn't tried it with this one. Turns out, access was obtained.

And, having read it... oh lord. Wow, really?

"She died. She had eaten rhubarb. I heard rhubarb is toxic because of OA. Therefore, she died because of OA poisoning." This is pretty much it. No causal link between OA and death was determined.

I'm going firmly into "the link between rhubarb leaf's toxicity and OA is completely unfounded" position. It's just hearsay quoting hearsay quoting hearsay. The authors don't even know how much OA is in there. Heck, the article IS WRITTEN AS A QUESTION. Here's a direct quote: "What the content [of OA] in the leaves is, I do not know." He basically just states "Hey, could this be OA poisoning?", and the editor replies "OA can be toxic." That's all.

It's a bit of a struggle not to derail this thread, but I'll succumb to play devils advocate - hopefully - succinctly. I wonder how successfully one could make a case that truly open source plant breeding needs to be boot-strapped from the "ground up" (pun intended) starting with open-access/permissively-licensed research. Conversely, could an open source variety actually be considered encumbered if the knowledge or techniques that lead to its creation are themselves encumbered by intellectual property? How about if the process of creating it involved intellectual property violations that themselves aren't present in the resulting variety?

Presumably, there would be no issue if someone learned about working Sci-Hub links being easy to find with Google through a non-endorsing post on this forum and subsequently used that knowledge to learn about the OA toxicity which eventually effected the direction of their open source planting breeding efforts.

I don't know - IANAL - but am curious where the line would be drawn - probably a question for a different thread though... :)

Scientific articles aren't an IP issue. Besides, that article is so old, even if it was treated as a book, IP would probably be extinct by now. But that's not the point, the knowledge in said articles isn't intellectual property. These aren't patents. You don't owe anyone anything for making use of something published in a scientific article.

And patents are not major obstacles to breeding. I know of one patent regarding breeding techniques, and there are probably a few others, but these are super rare and not applicable to almost every breeding scenario (the example I have in mind is the use of certain chemicals to cause sex reversal in hops).

Even plant variety protection, for the countries where it was granted, don't restrict the use of a genotype for breeding in any significant way).

The only significant patent obstacle to breeding is an utility patent, which to the best of my knowledge, is an American aberration, and has no force of law outside of the United States. In the grand scheme of things, even these are relatively rare

And all patents end up expiring anyways.

Back to the topic of Rubarb breeding. 

The remaining question for me that remains unanswered is whether the properties that make 'wild' (ie. non cultivated for food) rhubarb varieties (other Rheum spp.) is the same as that present in Rhubarb cultivated for food (ie. Rheum x rhabarbarum).

I do not think it can be assumed that Oxalic acid is the only factor involved, or is present in a similar amount. There may be other factors involved, and it appears that the available literature does not adequately answer questions about this.  'Safety' or 'edibility' for such things may be similar to glycoalcaloid content in potatoes.  If only a small amount is eaten, perhaps it is 'safe' because the human body can process out the toxins without a healthy person becoming sick.  But eaten in higher amounts, elevated glycoalcaloids can make a person sick.  Generally for potatoes, for example, there are safety thresholds to this, and as long as the total accumulated amount is not ingested, you will not get sick. 

I would not be confident in working with any of the other Rheum species without information being available that does not appear to be available.  Maybe other people would be, however.  It poses interesting questions.  I probably will stick primarily to Rheum x rhabarbarum accessions and let others deal with breeding away from laxative properties, whatever the reason or chemicals involved.

The safer assumption is that OA is *not* the only factor involved. Other species, not as well known as the already poorly understood cultivated rhubarb, could have:

1) Different concentrations of rhubarb's toxic chemicals
2) Different distributions of rhubarb's toxic chemicals
3) Different chemical compositions including absence of rhubarb's toxic chemicals or presence of new toxic chemicals

Rheum rhaponticum is the only other species I have found that is reported to have its petioles consumed, so if I were to attempt an intraspecific cross, I think that's the only species I'd be willing to try with. And even then, I'd do a bit more reading before proceeding. Otherwise, it would definitely be safer to only work with Rheum rhubarbarum, even if that narrows the gene pool significantly. On top of which every accession is supposedly tetraploid, while it'd be nice to have access to diploid varieties, and I doubt someone worked out a protocol for anther culture of rhubarb (though I didn't look yet).

Garrett Schantz

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Re: Rhubarb breeding
« Reply #40 on: 2020-12-06, 12:37:36 PM »
For now only attempting to breed species known for stem uses with each other and species with leaf use together I suppose.

This link mentions Anthraquinone glycosides as well, some types used in pesticides have been shown to harm animals,  some types are safe - so some rhuem species could have different types which could intermix and make something more harmful or safer. Seems to be fine in small amounts. Its found in most rhuem species from what I can tell. Too bad there isn't much information available on it.
https://www.compoundchem.com/2015/04/16/rhubarb/

Good luck with the Rheum x rhabarbarum breeding.

Dominic J

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Re: Rhubarb breeding
« Reply #41 on: 2020-12-06, 01:56:19 PM »
For now only attempting to breed species known for stem uses with each other and species with leaf use together I suppose.

This link mentions Anthraquinone glycosides as well, some types used in pesticides have been shown to harm animals,  some types are safe - so some rhuem species could have different types which could intermix and make something more harmful or safer. Seems to be fine in small amounts. Its found in most rhuem species from what I can tell. Too bad there isn't much information available on it.
https://www.compoundchem.com/2015/04/16/rhubarb/

Good luck with the Rheum x rhabarbarum breeding.

A bit disconcerting that some of these other chemicals can also add color, and that selecting for more vivid color may inadvertently select for higher toxicity...

Probably, ideally, new cultivars should be screen through gas chromatography, but that's not really tech that's accessible to everyone, and without really knowing what to look for, would probably be hard to interpret.

nathanp

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Re: Rhubarb breeding
« Reply #42 on: 2020-12-06, 09:27:25 PM »
Here is a link that mentions Oxalic acid is not the only thing poisonous with Rheum undulatum/rharbaratum.  Presumably, cooking it is not to remove the oxalic acid, but the other items.

Quote
All parts of the plant contain oxalic acid, which has been implicated in cases of poisoning. However, other potentially poisonous compounds also are produced, including citric acid and anthraquinone glycosides (W. H. Blackwell 1990). Raw or cooked leaf blades are poisonous to humans and livestock if ingested in sufficiently large quantities. The petioles typically are used as food and contain mostly malic acid, which is nontoxic. Plants traditionally are propagated and moved by taking cuttings from larger plant

https://plants.jstor.org/compilation/Rheum.rhabarbarum

And some of the other wild species appear to possess a few other odds and ends.
Quote
Rheum officinale, R. palmatum, and other species of Polygonaceae contain chrysophanic acid, rhein, emodin (purgative anthraquinone formerly used as a laxative, but is now used mainly as tool in toxicity studies), and other anthraquinones. Has also been used extensively in liquor distilling because of its pleasant aroma and digestive qualities. Jams and jellies have been made using the leaf petioles as a basis; these have a slight laxative quality. The purgative effect is similar to senna and alder buckthorn.

https://www.jstor.org/action/doBasicSearch?Query=rheum+palmatum#

nathanp

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Re: Rhubarb breeding
« Reply #43 on: 2020-12-06, 09:44:54 PM »
This paper mentions the following:

Quote
Three different species were grown as vegetable crops
in England and later also in Scandinavia (Hintze
1951), namely R. rhaponticum, R. undulatum L. (= R.
rhabarbarum L., Englund 1983), and R. hybridum
(Turner 1938). These three species hybridise readily,
and development of culinary rhubarbs (R. 9 hybridum
Murray, synonym R. V rhabarbarum L., USDA 2018)
started in England by selecting from open-pollinated
seeds of them. R. hybridum (origin unknown, found
between 1771 and 1779, Turner 1938) was often used
as a parent.

Genetic diversity of Finnish home garden rhubarbs (Rheum spp.) assessed by simple sequence repeat markers
https://link.springer.com/article/10.1007/s10722-018-0692-8

Also, this one is interesting.  I need to reread both of these.
https://journals.ashs.org/jashs/view/journals/jashs/133/4/article-p587.xml

This two were both very helpful in looking at which varieties to request from the USDA genebank. 

Dominic J

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Re: Rhubarb breeding
« Reply #44 on: 2020-12-07, 09:58:51 AM »
Rhubarb is not always cooked, though. A lot of people eat them raw, either with sugar or with salt. As for the death incident in 1919, the leaves had been cooked and remained toxic nonetheless.

I'm not sure cooking actually does anything, either to petioles or leaf blades. OA isn't denatured by heat, and the leaves remain toxic despite cooking. It's plausible some molecules might be broken down by cooking, but doesn't look like any of the ones of interest are.