Author Topic: P. ritensis, P. metcalfei/maculatus, and P. acutifolius (tepary), oh my!  (Read 401 times)

jimbakjones94

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I'm part of a post-college internship in tropical agricultural development. Basically, I know very little about agriculture, and I'm getting a fire-hose of information and random experience on a research and demonstration farm in the Southeastern USA. Part of my internship is to oversee the "semi-arid demonstration," where we showcase a handful of semi-arid and arid growing techniques. One of my projects is to identify a perennial tropical vegetable and write a report on it.

I found something called "perennial tepary bean" in this study:
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0234611 (see table at the bottom of the page "S1 Table" - search in the spreadsheet for "tepary").
For a dryland bean to be perennial caught my attention.

I researched more and found more info on it:
https://www.gbif.org/species/5350515
https://repository.arizona.edu/bitstream/handle/10150/552188/dp_05_02-067-071.pdf?sequence=1

I came across several Latin names:

Phaseolus ritensis
P. metcalfe
P. maculatus

I came across various common names:

Frijole de Monte
Santa Rita Mountain Bean
Perennial tepary bean
Metcalfe bean


My understanding was that the Ritensis and the Metcalfei/Maculatus are different species of tepary that are both perennial, but emailing with some bean and tepary experts with various organizations revealed that they are not true "tepary" (whatever that actually means).

...

Further research and poking around the Internet finally led me here, to OSPBF! I'm left with a few questions:

1. Is it possible that these species could cross-breed? How does one know if two plants can cross-breed?
2. If they can cross-breed, could the perennial nature of the Ritensis and the Metcalfei/Maculatus potentially be passed on to the Acutifolius (tepary)?
3. How does one try to selectively cross-breed beans? How would I isolate the flowers and ensure that only pollen from the plants I wanted was used? A screened growing hut and hand-pollinating?

...

Thank y'all for your thoughts!

Chad Meyer

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I suspect that what someone said about certain plants being "not true tepary" beans, they meant that they were a different species, and perhaps have this common name due to some similarity with P. acutifolius. 

I found this article: https://link.springer.com/chapter/10.1007/978-3-319-97121-6_4 which lists Phaseolus parvifolius as in the secondary genepool and a number of beans including common and runner in the tertiary genepool (one is called P. persistentus; the persistent bean?  Possibly a perennial?).  But, from the phylogenetic tree, the species you mentioned seem to be quite distantly related to the tepary bean.

To the first question: it's really hard for anyone to say it is not possible for two species to successfully interbreed, because sometimes crazy things happen in nature.  It looks like the three species you listed are more closely related to each other than to the tepary bean.  They are all in the same related group as P. polystachios, the thicket bean.

Academic researchers have successfully crossed tepary and common beans, but it required a number of interventions: first, only particular accessions were found to be compatible to crossing, second, embryo rescue was required (and if I remember correctly it really required a multi-step embryo rescue with different growth media for the different stages) and third, viability/fertility was only restored upon multiple generations of successive back-crossing.

To the second question: if the plants could cross breed, then it is possible that the perennial trait could be passed on.  Not sure if that would end up being lost if backcrossing was necessary.  It's hard to predict ahead of time.

To the third: others here can answer that better as I have never done it (yet), but it would generally involve emasculating a flower on the mother plant before it released its pollen and then manually pollinating the flower with mature anthers from the father plant.

Ultimately, I think you'd do better trying to cross more closely related species.  I haven't seen many papers trying to do runner x tepary, but I think it is established in the literature as possible (in both directions, also tepary x runner).  The runner is a perennial, so that could be a possible way to go.  Runners tend to prefer more wet/humid conditions compared to tepary which prefer more arid conditions, so the offspring could be interesting. 

jimbakjones94

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@Chad Meyer

Thank you so much for everything in your response - so helpful! I love that gene tree in the study you cited, it is very helpful to visualize the groupings.

I don't yet know what some of the terms mean or what the processes entail: embryo rescue, backcrossing, anthers -  but I'm slowly collecting and reading through basic foundational plant breeding resources to learn!

Follow-up questions:

1. Why would "particular accessions" of tepary and common beans be able to cross-breed, but others not? What set them apart?
2. In plant breeding lingo, when you say "runner x tepary" or "tepary x runner," what does the order in which the species are stated represent? For example, in "runner x tepary," does that mean the runner is the father or the mother, or something else?

Thank you!

Adrian

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 1.Each variety has different compatibility beetween others.
2.On a cross between a variety A and B (runnerx tepary)
Runner is rhe giver of pollen and tepary the receiver.
« Last Edit: 2021-08-13, 03:30:21 AM by Adrian »

Chad Meyer

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I thought that the naming convention was actually (mother x pollen) (aka ladies first) but I might just be confused.  Either way it's just conventional.

As to why some individual varieties are better at crossing than others, I don't know every detail, but plants have some barriers in place to prevent inter-specific crosses (otherwise they might just be considered a single species).  In some cases, you can get a viable embryo but non-viable endosperm because some genetic combination is missing.  In that case, the seed will start to develop, but then stop, the pod will shrivel up and die.  If you catch that early enough you can excise the embryo and just grow it in growth medium (embryo rescue).  In other cases you won't even get a viable embryo due to genetic incompatibilities.  It comes down to finding the individuals that have the "right" combination of genes (which might mean a doubling of a gene or a missing gene or something controlling expression of genes...).

Again, others can speak to this who have more experience, but the rule of thumb seems to be that domesticated varieties have much higher barriers to crossing and wild plants tend to be more able to cross (likely due to the higher genetic diversity they have).

Chance

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If I remember, ritensis is actually closer to thicket bean P. polystachios.  You could try crossing those two first, gaining the gametic diversity to enhance the potential for a tepary cross.  Would also give greater cold hardiness Id think.  Crossing to tepary may still be too distant though.  Those species may be called tepary due to the similar beam size as true tepary ?   

Adrian

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If i take this exemple i have understand  that maxima is  the giver of pollen in first and moschata the receiver in second
It is write maxima x moschata. The sucess rate is the better in this sens.I don't know but it that i have think understand.
https://www.kcb-samen.ch/product.php?products_id=910532&language=en

A stranger pollen is more long to germinate on a stranger pistil.particular temperatures and humidity rate can help to did a difficult cross.The pollen is viable more long time when he is not exposated to the sun and he is less stiky when the wheather is not rainy for exemple.


« Last Edit: 2021-08-13, 01:25:19 PM by Adrian »

Chance

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Again, others can speak to this who have more experience, but the rule of thumb seems to be that domesticated varieties have much higher barriers to crossing and wild plants tend to be more able to cross (likely due to the higher genetic diversity they have).

Like everything in biology there of course are counter examples.  Many times domesticated plants have less crossing barriers than wild relatives.  The most recent example I read is Allium fistulosum vs altaicum.  Fistulosum is much more open to crossing.

Walt

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@Chad Meyer


1. Why would "particular accessions" of tepary and common beans be able to cross-breed, but others not? What set them apart?
2

Thank you!

In wheat, there are 2 genes named Kr1 and Kr2 that greatly influence whether that whet plant is more able to cross with other species.  That is the only example I know of where genes for compatibility are well known and well studied.  I'm sure there are others.  That said, it is well known by professional breeders and by many amatures as well, that some plants cross more easily than others wthin the same species.  Also it is common for hybrid plants to cross with other species than inbreds to cross with other species.  It is commonly believed this is because it gives a lot of gametes with different gene combinations and some combinations are more compatible than others.   Good luck.