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Regular Leaf vs Carrot Leaf vs Potato Leaf - Which is dominant over which?

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    Regular Leaf vs Carrot Leaf vs Potato Leaf - Which is dominant over which?

    I did a little science experiment recently. I think I've learned something new - at least something I could not find the answer to online. Regular leaf is dominant over potato leaf. However, what happens when a carrot leaf is tossed in the mix....

    Tomato Leaf-Type Dominance Study – Regular Leaf vs Carrot Leaf vs Potato Leaf

    In tomatoes, regular leaf is dominant over potato leaf. That is taught in genetics 101 and known by anyone who has made this simple cross – RL X PL = RL F1. In the F2 generation, the ratio will be a Mendelian 75% RL & 25% PL. In the F3 generation from a PL F2 plant, the offspring will be 100% PL. That plant is homozygous for PL and the trait is fixed for future generations – genetics 101.

    But what happens when Carrot Leaf is tossed into the mix? Not being able to find anything online to answer that question, I decided to try to figure it out. I worked with F1, F2 and F3 seed from a cross between a carrot leaf micro X a potato leaf indeterminate. Both parents, while not fully stable were fixed for leaf type.

    I did not count how many total seeds were planted, but 641 germinated. I grew each one out long enough to determine whether the leaf type was RL, CL or PL. I also kept track of plant growth type, separating indeterminate vs dwarf/micro. I did not attempt to separate micro from dwarf, as that would have required growing them to maturity and that was beyond the scope of what I was able to do.
    The results from Carrot Leaf X Potato Leaf cross:
    • F1 – 12 plants total germinated = 100% Regular leaf
    • F2 – 546 plants total germinated
      • RL – 343 plants = 62.8%
      • CL – 73 plants = 19.6%
      • PL – 78 plants = 17.6%
    • F3 from PL F2 – 8 plants = 100% PL
    • F3 from CL F2 – 75 plants
      • CL – 58 plants = 77.3%
      • PL – 17 plants = 22.7%
    • RL is dominant over both CL and PL – expected
    • CL is recessive to RL but dominant to PL – learned
    • PL is recessive to RL and recessive to CL – learned.
    With only 8 F3 seeds germinated from PL F2, the results are not conclusive, but strongly indicate that once PL is stabilized from a CL X PL cross, the trait is fixed. However, a CL F2 from the CL X PL cross is not necessarily fixed once it manifests. It acts like the F1 RL in a typical PL X RL cross and still carries the PL gene with the separation being approximately 75:25. Interestingly, there were no RLs in the F3s from the CL F2, only CL & PL- but I think that makes sense (doesn’t it?). I didn’t grow any F3s from RL F2. That also would be interesting to follow up.

    There is a lot more to learn regarding the CL leaf type – especially as it relates to micro tomatoes. I have seen anecdotal results that seem to indicate that there may be some linkages between CL and genes involved in making the micro. In one CL X RL cross, I noticed that the F2s remaining, after culling heavily for size, and working only with the shortest 10%-15% of seedlings were skewed heavily toward CL – well over 50% instead of the expected 25%. I have seen that in at least two different instances, as has one other breeder I shared F2 seeds with. I did not keep track of leaf types in the plants culled so I can’t speak with certainty to overall leaf type results, but that observation begs for more study.

    Really interesting experiment, Dan. I did a bit of digging into the Tomato Genetics Research Center's website to try to see what gene is responsible for carrot leaf. I'm not certain, but I think it may be bipinnata (bip) which is located on chromosome 2. The gene responsible for potato leaf is the cut leaf (c) gene which is located on chromosome 6. Both are recessive genes that don't seem to be related to one another.

    Because they'd be the results of separate genes, it's more complicated than a simple Punnett Square distribution of 75%:25% but not that far off. I made a double Punnett Square to show each genetic combination for the F2 and came up with 56% various combinations of regular leaf, 18.75% homozygous for potato leaf, 18.75% homozygous for carrot leaf, and 6.25% homozygous for both carrot leaf and potato leaf (it looks like those show up as carrot leaf in your experiment). Those percentages are extremely similar to your results!

    Depending on which homozygous carrot leaf plants or homozygous potato leaf plants you picked to self grow out and save seeds from, you might conceivable end up with different ratios of carrot to potato leaf plants. It's really interesting to me how you showed the dominance of carrot leaf over potato leaf when they're different genes. That's where my understanding of genetics breaks down, and I'll need to find some reading material!

    I need to look more closely at my carrot leaf plants to determine if the gene is the bipinnate leaf gene or tripinnate leaf gene or something else entirely. The listing for tripinnate leaf gene mentions retarded growth, so that makes me think it would partly be responsible for the shorter growth of carrot leaf micros. Either of those and most genes that cause leaves to be anything but regular leaf are recessive so the math still works out.

    My understanding of genetics goes way back to high school AP biology so I could totally be off base. This is the kind of science I wish I'd done for the science fair back then!


    • dfollett
      dfollett commented
      Editing a comment
      If you could post your Punnett Square, I would be able to follow it much easier than I could put together my own. Thanks.

    Very interesting indeed. Thanks for doing some research on this!

    The genes you reference at TGRC are all showing as chemically induced mutations, and the cut leaf gene does reference the spontaneous mutation. As far as I'm aware, the carrot leaf phenotype in Dan's work was spontaneous. Is it the same gene as bip? Perhaps - but perhaps not - but the pictures do look somewhat representative of the trait from what I can tell, but I would say that many of the plants with this trait in Dan's work seems to be more extreme in manifestation.

    I think it's also important to note in plants where the potential "bip" gene presents, the extent of the "carrot leafedness" varies from plant to plant. This likely just means there are other genes influencing the growth of the leaves, which is likely to be expected.

    Attached is an example of carrot leaf from two different plants
    Attached Files


      Thanks. I was hoping someone would find it interesting and help me understand what we can learn.

      Your understanding of genetics goes beyond mine. I somehow got through high school and college without ever taking a biology class. I have recently taken three online genetics courses, but they were just the basics.

      I think there is a lot that could be studied here. I'll throw another twist into the RL:CL:PL equation. I think there is a potato carrot leaf and a regular carrot leaf. Here are photos of two different carrot leaf plants from the same cross I did the experiment with 105X. The first is what I think is a potato/carrot leaf - the one you refer to as "homozygous for both carrot leaf and potato leaf". And yes, these would ahve been counted as carrot leaf in my experiment. I didn't make any attempt to distinguish to that level of separation (nor do I think you could). The second photo has a more common carrot leaf appearance.

      I actually separated the leaf type count to another level of detail that I didn't include in the write-up above. I broke out the indeterminates by leaf type and also the dwarf/micro by leaf type. I made no attempt to separate dwarf from micro. The dwarf/micro group showed a higher percentage of CL than the indeterminates did. But there would need to be more study to say for sure.


      I'll attach the complete results here. I'm not sure how a pdf file shows up, but there it is. Apparently I can't upload a spreadsheet.
      Attached Files
      Last edited by dfollett; 05-16-2020, 09:24 PM.


        Somehow I screwed up the posting and ended up with duplicates. Feel free to fix it, Sean.


          Wow Dan! I have been absent from the site for a few weeks and your post is amazing. Thanks for putting your research all-out there for us to think about. I am horrible with the genetics component and learn a lot from all of you. I am also a carrot leaf lover so your study is particularly interesting for me. I have many selected carrot leaf 150x and 88x's growing. Will check today for what you have noted to see if there are some PLClLs in their leaf types. I am not sure I ever thought to specifically classify those.


            I don't think there is any PL in the ancestry of 88X or 150X unfortunately. If you would like to look for and possibly play with some of the PLCL (if there is such a thing) and do a little experimenting of your own, I'd be happy to send you some F2s from 105X.


              I think my hands are full with all my current lines but if we stabilize 51x, I could maybe do some hunting! What is the ancestry of 105x?


                105X is a cross between one of my 33X carrot leaf micros and an F3 potato leaf Brandywine X Ananas Niore cross.


                  This could be interesting to pursue. I like potato leaf plants so many of new varieties for next year are potato leafed. Crossing them to the carrot leaf micro I am being sent could add some more information to this and maybe find some PLCL plants in the F2 from those crosses.
                  Last edited by wykvlvr; 08-07-2020, 08:45 PM.


                    That would be great. It's fascinating to see a cross between a carrot leaf and a potato leaf that has a regular leaf F1. Please do cross some of the carrot leaf micros I sent with potato leaf and follow up on the relationship between the PL and CL.


                      Not a problem I LOVE genetics and working out relationships between things so this is right up my alley. Now to locate a good tasting potato leafed white as I have a request to make a micro with white tomatoes from a friend who is limited to inside growing...


                        Also does anyone know if Blush is considered carrot leafed? or just "wispy" foliage? I did use it is in a couple of my possible crossed this year to regular leaf micros.


                          I'm not familiar with Blush. Do you have any pictures of the foliage, or can you point to some online? I did a quick search, and Johnny's had an image but it's hard to really see the foliage.


                            I don't have any seeds for a white PL tomato. However, I found this - or this -

                            There are several other sources for "White Potato Leaf Tomato". They say it is an open pollinated variety. I have a lot of carrot leaf with different color and fruit size potential it you would like to try for something specific, I'd be happy to send you some seed. Make a few different crosses with the white. Sounds fun, but I'll leave that experiment to you. Please share your CL/PL experiment results. I think there is a lot still to learn there.