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Bean pod colour dominance?

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  • Bean pod colour dominance?

    I don't seem to be able to find any info on this. I'm wondering generally what colour points and pods would a purple podded bean crossed with a yellow podded one give in the F1?

    Would it go to being green or stay with purple? Or neither?

  • #2
    This isn't always true, but in general an allele that codes for a lack of something is recessive to the allele that produces that thing normally.

    Going to use peas as an example, because I know peas, but you can probably apply the same principles to beans too (just the genes are different).

    Imagine an allele is like a recipe book which tells the plant how to make a particular substance. This is almost literally true, because mechanically what a gene does is act as a template for making a specific protein (an enzyme) which acts like a little factory that enables the production of a certain chemical.

    The A allele in peas is the instruction manual for making the basic anthocyanin molecule. A (anthocyanin) is dominant over a (no anthocyanin) because if you have one correct recipe for antho and one incorrect recipe, you can still make it. If both of your recipes are incorrect then you can't, of course, but you only need one correct copy to make all the antho you like. "Make this thing" is dominant to "don't make this thing".

    New alleles are created by mutation, which is when the DNA gets muddled up (maybe a bit goes missing, a new nonsense fragment is added in, or a piece gets switched round). Mostly these mutations are deleterious, i.e. they stop making a thing that the original allele makes just fine. I mean, if you mixed up a section of your Yorkshire pudding recipe by deleting bits or mixing words up, the chances are very good that you'd end up eating your roast beef dinner without puddings! So mutations tend to create recessive alleles, because mixing stuff up randomly usually results in a non-functional recipe rather than one that makes a brand new useful chemical.

    I'm struggling to explain this as clearly as I'd like, unfortunately. But what I'm trying to say is that my prediction is that your F1 beans will have purple pods (base green with anthocyanins), because "put anthocyanins in the pods" is very likely to be dominant over a nonsense "put watermelon orangutan pods" instruction? And similarly green pods will be dominant over yellow.

    I bet when I look up bean pod colour genes, that'll be the case.


    • #3
      Cool, colour coding to know a cross has taken, similar way to a potato leaf (pl) tomato crossed to a regular leaf (Rl) will give regular leaf plants at F1.

      Sorry to be dim but am I right, if a green podded bean is crossed to a purple then the F1 will be purple and
      A yellow podded x to a green podded F1 will be green podded?

      I wonder if bean colour will be as complicated as peas?


      • Silverleaf
        Silverleaf commented
        Editing a comment
        You're absolutely right, not dim at all!

    • #4
      Also jumping ahead to further generations once a yellow podded is produced and seed saved it's then captured, yes?

      Is it also likely that purple x yellow podded beans will follow a similar pattern as peas if looking for red podded beans? I think beans can be classed as yellow and white podded, could this lead to 'pink' and 'red' as with the peas?


      • Silverleaf
        Silverleaf commented
        Editing a comment
        I have to point out that I'm only making educated guesses here, but yes, I should think that once you've got yellow pods that will be a stable trait, because I'm confident it will be recessive.

        I reckon since there doesn't seem to be any obvious information out there, the only way is for people like us to observe and draw our own conclusions.

      • Silverleaf
        Silverleaf commented
        Editing a comment
        Also I think crossing a purple pod with a yellow pod will give you some red/pink pods in the F2, just like peas.

      • jayb
        jayb commented
        Editing a comment
        Great, thank you Roll on colour pods!

    • #5
      Are there bean gene lists like the pea genes from the John Innes Institute? That are accessible and understandable? Beans are almost certainly a lot more complicated than peas, because we are dealing with 2 species that have frequently crossed in the existing 'French' bean varieties (ph coccineus and ph vulgaris). Then there are two centres of origin and diversity just for ph vulgaris, the smaller seeded and the larger seeded from South America and from Central America. As these were developing independently, they may have different characteristics and are possibly not behaving identically to each other. There is something like a standard 'wild type' for peas. What would the equivalent be for beans? Can we make predictions based on what we know about peas or is it all different.


      • #6
        I'm not aware of a bean gene list.

        I think we can probably assume that beans and peas will behave quite similarly in terms of genetics. Not exactly the same, but we can use pea knowledge as a foundation until beans show us exactly how wrong we are!

        I assume that the common ancestor of beans and peas would have similar wild type traits. I'm guessing it would be tall/vining/climbing, have purple flowers and pods (green pods with antho on the surface) and dark-coated starchy seeds, so the bean wild type should be like that too.

        There are some (almost) universal concepts in genetics which we can assume apply to anything until we see otherwise. Antho production is dominant to no antho production. Normal green chlorophyll in pods is dominant to yellow chlorophyll in pods. Tall is dominant to dwarf.

        So yeah, we can absolutely make predictions based on what we know about peas (and genetics in general). Sometimes we'll be wrong and have to figure out what's really happening, but it's a good place to start.


        • #7

          Excellent - so we d o have a start. Just found this:

          list of bean genes:

          The gene symbols are organised alphabetically, which is unhelpful. But I have just searched for 'pod' within the list and that gives the pod colour genes. Intrigued by the white pod colour.
          Last edited by Galina; 22-04-2016, 13:16.


          • #8
            Brilliant Galina! I'll have a proper look at that later, but it seems really useful.


            • #9
              There's this with a couple of links

              Oh I can see that site is listed above too.
              Last edited by jayb; 23-04-2016, 09:23.


              • #10
                Looks like you were spot on Silverleaf. This is the F1 of Bean Stephenson's Blue Eye x Robert's Royalty. Stephenson BE is yellow podded and Robert's R is purple. Happy days.

                Click image for larger version

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