Should we stop using Grex and switch to Groups?

Discussion in 'Taxonomy' started by eds, May 23, 2020 at 4:00 PM.

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  1. May 23, 2020 at 4:00 PM #1

    eds

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    I have recently got into cacti and succulents alongside my small slipper collection and a discussion there got me thinking - isn't the grex system a flawed one with seed raised orchids such as slippers?

    My thinking is that a grex such as Saint Swithin can have plants that are F1 crosses (Roth x philippense) and then any subsequent generational selfing or Saint Swithin X Saint Swithin cross.

    This means that anything beyond an F1 primary cross could have a genetic make up anywhere between a theoretical 100%:0% or 0%:100% of the parent species.

    This means a Saint Swithin could look like any subsequent backcrosses to the parent species and giving them a separate grex name seems a little pointless, especially if they are then propagated by selfing or sibling crosses.

    Wouldn't it make more sense to start putting these together as seed strain groups? So all plants that are just Roth x philippense would be Saint Swithin Group and could then have a cultivar epithet if so desired afterwards.

    Once a third species is mixed in it would need a different group name.

    I think system would much more accurately reflect the variability of slipper crosses as well as taking out some frankly pretty pointless grex names!

    I hope that makes sense and would be interested in hearing your thoughts.
     
  2. May 23, 2020 at 9:09 PM #2

    Tony

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    I find the grex system to be superior to other plant groups where cultivar names are given freely with no indication of or concern for parentage. There are so many NOIDs with cultivar names in the cactus and succulent world, doing away with the grex system would be a massive step backwards.
     
  3. May 24, 2020 at 7:02 AM #3

    eds

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    I didn't say to get rid of the system at all in my post above - I said that grexes are flawed when you're reproducing by seed and we should alter the system to have something analogous to seed strains but with a higher fidelity. These would still be like the grex system but all plants with a genetic make up of the same two or more species would have the same name regardless of the cross that created them as this part is dubious when reproducing by seed.

    Grex would be fine if it was only used for the primary cross and plants, such as Saint Swithin, we only called that if they were the product of a Roth x philippense cross. But when Saint Swithin X Saint Swithin plants are also called Saint Swithin then you dilute the meaning.

    You are also conflating accuracy of the grex system with the fact that less orchids are sold as noid.

    Shoddy labelling happens as people can't be bothered, not because the world of orchids has the grex system. If other aspects of horticulture valued accurate labelling as much as many orchid growers then it would happen a lot less in these areas! See what happens when slipper orchids or phals are mass produced. Grex or no grex they are often passed on unlabelled.
     
  4. May 24, 2020 at 12:46 PM #4

    Tony

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    I guess I don't understand what you're getting at then. Saint Swithin x Saint Swithin is not Saint Swithin and needs a new name? I don't know of any other group of plants with a better naming system, cacti and succulents are an absolute clusterfuck and not something we should aim to emulate in the orchid world lol
     
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  5. May 24, 2020 at 1:08 PM #5

    Ray

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    I think the potential flaw in your proposal is the the genetics of a primary cross are meaningfully different than those of later generations.

    Does anyone know the genome of paphs or phrags? The smallest, most primitive single-called organisms have about 500,000 base pairs. Lillies have almost 100-billion. That’s a lot of potential combinations.
     
  6. May 24, 2020 at 1:36 PM #6

    eds

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    You're right Tony, most plants are a mess and certainly not something to emulate at all.

    However is still think, as good as grexes are, there is a flaw where plants are propagated by sexual reproduction.

    In Phals, a certain grex (certainly of complex hybrids) is likely a single cross and then meristem propagated to distribute it more widely. The grex name therefore gives you a good clue as to the likely appearance of the plant.

    In Paphs, Saint Swithin coming from a roth X phili cross will give you a plant 50% roth and 50% phili. There will still be some variation due to the nature of sexual reproduction but this F1 cross will be pretty uniform and so the grex name will give you a good idea of what to expect.

    From that point on it is much less useful. If two F1 Saint Swithin are used to make an F2 generation then the progeny can vary from theoretically 100% roth to a theoretical 0%! So these SS will form a wide spectrum of forms not seen in the F1 generation or most other types of orchid AFAIK.

    You also have the situation where a backcross of SS to either parent gives you a new grex, with a new name (Gary Romagna / Moustache) but a plant that genetically sits in the range that these F2 or subsequent generations.

    Maybe a grex name should be reserved for the F1 cross and anything else is named with the suffix Group? E.g. Saint Swithin Group?
     
  7. May 24, 2020 at 1:39 PM #7

    eds

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    Maybe this is a key and links to my last paragraph above.

    It would also get rid of some situations where hybrids are backcrossed and backcrossed to parent species. The same result could easily be achieved by selecting within an F2 population of the hybrid.
     
  8. May 24, 2020 at 4:30 PM #8

    Tony

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    Calling all of these plants Wössner Black Wings just because a sib cross of WBW might occasionally create a roths dominant plant seems like it would create more confusion than just calling the backcrosses by their registered name.
     

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  9. May 24, 2020 at 5:57 PM #9

    Ray

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    Is that true?

    Sexual reproduction is not simply a mixing of the genetic information. There are dominant and recessive traits, so back-crosses to parents would likely "load up" on the parent's dominant traits.
     
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  10. May 24, 2020 at 9:55 PM #10

    eds

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    Sexual reproduction is exactly that! The selection that follows afterwards might skew the outcome but the mixing of chromosomal material is just that.

    Whether something is dominant or recessive is governed by other genes. If it's heterozygous for the gene then there are two different copies. However they are expressed, they are still there. When you then select within that initial F1 population would be where you could select different factors and some dominant traits may appear. However you will get some individuals showing the recessive traits and these could be selected. If it was a standard dominant recessive single gene locus then you'd have the traditional punnet square situation arising in the F2, with 50% still being heterozygous but showing the dominant traits.

    Once you get away from single gene loci you have to consider as a continuum of genetic expression at different loci and you will see a larger array of plant types. It would be really interesting to see an entire seed pod of an F2 cross grown to maturity and flowered to see what the range of expression looks like but I'm not sure anyone would ever grow all of them out to see!

    With some hybrids you can see an F1 that resembles one parent more than the other but this is often (at least outside orchids) due to different chromosome counts - the parent with higher chromosome counts will dominate the appearance of the offspring.
     
  11. May 24, 2020 at 9:59 PM #11

    eds

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    But then don't they all look like variations on a theme which is exactly what selection within a variable population would give? Calling them Wossner Black Wings Group with cross information if it was available would be no less valid, in fact it might be even more useful.

    Maybe it should just be that the grex name is only used for an F1 cross to keep that fidelity and then different backcrosses etc. should be an F1 crosses back to species to have a standard grex name?

    Or maybe we ought to get breeders to use the filial system more? F2 Saint Swithin would let you know that you can expect more variation than an F1.
     
  12. May 25, 2020 at 12:04 AM #12

    Tony

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    No, the backcrosses are very roths dominant and don't look anything like a typical WBW. I don't see how lumping dissimilar plants could provide any clarity or advantage to anyone. As for filial designations, breeders already give the clonal names of the parent plants which makes such a designation redundant.
     

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