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Somatic Hybrids Via Grafting ??

Dr Lei
51 years ago

Has anyone ever heard of sprouts arising from tissues that have been grafted being hybridized? Maybe because of language barrier I am not speaking clear ?

Dr Lei

Comments (14)

  • Sparaxis
    51 years ago
    last modified: 6 years ago

    If they produce blooms, you can hybridise them. My only concern is that they may be genetically the same as the plant from which the somatic mutation arose. I gusee the only way to test that is to do crosses with both plants, and compare the offspring.

  • zlesak_rocketmail_com
    20 years ago
    last modified: 6 years ago

    Hi! Are you asking if one can get a somatic hybrid at the point of a graft if a shoot arises? When somatic hybridization is done a lot of work is necessary to strip away cell walls. "Naked" cells in tissue of the two parents are placed together and then through electric pulses or other means researchers try to fuse cells together. The hope is that two cells (one from each selected "parent") fuse and that the nuclei in them fuse. After that one needs to try to regenerate a whole plant out of the fused cells. It can be very difficult. Plants need to be screened to identify the ones that are somatic hybrids. The trauma that the cells went through can stunt them and take a long time for them to outgrow. This has been done with a lot of different species. An officemate did this as part of her graduate work in Germany and fused cultivated potato with wild potato species to try to bring in disease resistance from the wild potatoes. The species she chose are difficult to cross sexually with cultivated potato and somatic fusion was a good alternative.

    Grafting probably won't allow for somatic fusion since the thick cell walls are still in place and there isn't a stimulous like an electrical current to stimulate fusion. Maybe you'll be lucky though. Do you have a shoot that has grown from a graft union that looks like a hybrid between the rootstock and scion?

    Sincerely,
    David

  • Plant_Geek
    19 years ago
    last modified: 6 years ago

    Grafting has produced some chimeras such as +Laburnocytisus (Laburnum and Cytisus), Citrus aurantinium and C. medica, and Crataegus and Mespilus. The plant cells have not fused so the chimeras are unstable and often revert to either parent.

  • keking
    19 years ago
    last modified: 6 years ago

    Graft hybrids are not limited to chimeras and fusion-hybrids. Cytoplasmic male sterility has been transferred by grafting in petunias. Traits affecting the color and shape of peppers have permanently transferred by grafting.

    Michurin warned fruit breeders not to graft cultivated varieties to wild rootstocks if they wanted to use the varieties for breeding. The wild traits do not necessarily turn up in the grafted scions, only in the seedlings from them.

    He grafted tomatoes to tree tomatoes (Cyphomandra), repeatedly removing the leaves of the scions. One or two of the seedlings from these shoots had leaves modified in the direction of the Cyphomandra.

    Seeds can also be grafted. In some Russian experiments a piece of Maize tissue was grafted into Wheat seeds. After the plants started growing, some of the tissue was found to have chromosome numbers different from either of the parent components.

    Karl King

    Here is a link that might be useful: Cytoplasmic graft hybrids, etc.

  • membertom
    19 years ago
    last modified: 6 years ago

    Wow,
    Fascinating stuff! Especially since Mendelism seems to rule traditional plant breeding discussions. These sorts of findings are usually considered hocus-pocus. Thanks for sharing. Tom

  • keking
    19 years ago
    last modified: 6 years ago

    Tom,

    "Traditional"? It's very interesting to compare the work of practical breeders with the theoretical stuff of textbooks.

    For instance, 'Plant hybridization before Mendel' by H. F. Roberts is chock full of useful information on early plant breeders. But no matter how successful they may have been, Roberts "explains" how their work fell short of Mendel's perfection. Phooey! Every time there is a conflict between Mendelism and the real world, theoreticians try to explain how the practical guys got it wrong.

    There's the matter of selective pollination. Donald Forsha Jones (inventor of "Double Cross" hybrid corn) and Mangelsdorf studied the problem of selective pollination in corn. Others had merely averaged the progeny of different generations and different lineages, and buried the discrepancies in their numbers. Mangelsdorf and Jones took the time to look at the matter and found that there was a linkage. A gene that affected the growth of the pollen tube was sometimes linked to one character (normal kernels) and sometimes to another (defective kernels). Thus, sometimes there were too many defectives, sometimes too few. In this case "average" was the least probable condition -- but it was the only one the Mendelists could see.

    Other matters like somatic segregation (discovered and exploited by Naudin and his followers) and cytoplasmic inheritance are outside the confines of Mendelism, but are far from trivial.

    Pseudohybrids of several types are known, but not widely accepted. Patrogenesis, for example, involves successful fertilization followed by the loss of most or all chromosomes from the ovum. These plants are not purely paternal, though, because the (mostly) paternal nuclei are swimming in mostly maternal cytoplasm, with various consequences. Parthenogenesis may be "purely maternal", but then again we must accept that there is the occasional paternal influence -- cytoplasmic or chromosomal.

    Uniparental dysomy was first identified in humans around 1985. Similar oddities should be expected in plants, where a seedling inherits two copies of a gene or chromosome from one parent, none from the other. The fact that this can occur should encourage us to duplicate sterile hybrids. There really should be some variation if we grow enough seedlings, but the variation will not fit into a Mendelian model.

    Karl King

    Here is a link that might be useful: Heredity: beyond Mendel

  • Plant_Geek
    19 years ago
    last modified: 6 years ago

    Not to be a wet blanket but aren't seedling grown eating apples of poor quality regardless of the rootstock and exhibit so called 'wildtype' characteristics?

    The tomato - tree tomatos grafts. Aside from the leaves looking like tree tomato, what evidence was there that they were gentically modified? We all know grafting onto a dwarfing rootstock will change the normal size of the scion material but that is not a genetic modification.

  • membertom
    19 years ago
    last modified: 6 years ago

    Karl,
    I reread my previous post, and it could sound as if I'm being sarcastic. People get so used to nastiness. I hope it wasn't taken that way. I genuinely, am fascinated by the non-Mendelian ideas.
    As a matter of fact, I had already visited and read, months ago, every article at your link. (Neat stuff)
    I never have been one to think inside the lines anyway. I love to read, or hear ideas (mainstream or otherwise), but the world is a bigger place than any one idea can express. So, we should always be willing to look farther. For another example, take Barbara McClintock and her "jumping genes" (transposons). Her ideas were not received well by the "scientific community" at first, but now are generally accepted as "the truth".
    I guess "traditional" was a poor choice of words. What I was trying to say was... that academia, high schools, colleges etc. have taught Mendelian ideas as if they were the gospel, usually with only a mere mention (if that) of other stuff. I guess the "doers" have always done things according to their own ideas. Even Mendel was thinking "outside the lines" in his time.
    By the way, I got most of my strawberry breeding ideas started, by reading the information on your site. Thanks for sharing such useful information. Tom

  • keking
    19 years ago
    last modified: 6 years ago

    Plant Geek,

    Yes, grafted plants are often modified by the stocks in various ways, but not all of the modifications are passed on to seedlings. An apple growing on a dwarfing stock is not particularly likely to produce inherently dwarfed seedlings.

    And as I stated, some of the traits which have been passed to seedlings were not apparent in the grafted scion -- and could only have come from the stock. (Or vice versa in the case of male sterile Petunias).

    As for apple seedlings being inferior, maybe yes and maybe no. Michurin based his opinions on 60 years of practical experience. You or I can easily test his opinions if we care to, by testing 2 specimens of a named cultivar: one grafted to Malus baccata, the other own-root. We pollinate the flowers of each specimen by the same pollen parent. Which crosses give the best results?

    For example: would seedlings of Jonathan-on-Baccata x Golden Delicious differ significantly and in the same generally wild-like way from those of Jonathan-on-Jonathan x Golden Delicious? Michurin's results suggest that this would be the case.

    I haven't tried it, but I'd bet that apple species differ in their ability to pass their qualities into the seeds of grafted scions. Michurin specifically mentioned M. baccata as doing this, so that would be a good one to test, particularly in the north. (It's an attractive crabapple, by the way, well worth growing for its own merits, is not as rootstock.)

    Karl King

  • membertom
    19 years ago
    last modified: 6 years ago

    Along those lines, I was thinking about relatively well-documented effects of various citrus rootstocks on the fruit quality, cold-hardiness, growth habits... of the scion variety. Choice of rootstock can affect size, sugar content, etc. of the fruit, exacerbate or improve mineral deficiency problems... I would imagine that with the internal environment of the plant modified, it would follow that a certain genotype of gamete (ovule, pollen tube) or embryo could be more suited and have gained an advantage. It seems fairly logical that choice of rootstock could influence the population of offspring. In which direction, and to what extent, would have to be answered by experience. I'd love to see results of experiments like those suggested.
    I just thought of another bit... aside from sugars and minerals being translocated across graft unions, other chemicals (such as hormones, alkaloids, etc.) have been shown to cross over and so, would change the environment for gametes and embryos. For instance, I wonder what effect circulating alkaloids (from a Datura rootstock), would have on tomato ovules, pollen tubes and embryos. What genotypes might be favored in the resulting offspring? If anyone does try this one, please be careful because the tomatoes would be toxic. I read of people being poisoned by grafting tomatoes onto Datura (in an attempt to have hardier tomato plants).
    Just makes you wonder what effects have occurred already(largely unknown) by the common practice of grafting in certain fruits. How might the populations of offspring from breeding programs been affected for the better or worse??

  • Laeka
    19 years ago
    last modified: 6 years ago

    Not sure how it fits in exactly, but a former professor of mine told an interesting story. According to him, Eckes, the folks that produce 60 billion or so poinsettias every year, payed for all of his graduate work on the condition that he never reveal what he had learned about grafting poinsettias. It seems that when you graft two different varieties together(not sure which two) the new tissue generated can be a third entirely different type. I've never had the energy to try this myself, but it would seem to imply some sort of hybrid being formed! Daniel

  • keking
    19 years ago
    last modified: 6 years ago

    MemberTom,

    Colchicine is found in the tissues of Colchicums and Gloriosa lilies. Hamilton Traub demonstrated that colchicine can be translocated (carried in the sap), so if we could graft a plant that does not produce colchicine to one that does, we could expect the colchicine to harm the grafted or kill the grafted plant by preventing dividing cells from distributing chromosomes equally.

    In other cases, as you seem to imply, substances produced in one plant and transmitted across the graft union might act as a selective filter. Some pollen grains, presumably differing in their genetic makeup, might survive in the presence of some novel substance while others are inhibited or killed. Or, the stock might produce excessive quantities of a substance found in smaller concentrations in the scion. There could be variations in how the pollen, ova and even other cells might respond.

    Members of the Solanaceae are easily grafted, and can serve to illustrate how different substances and different concentrations of substances can affect grafted plants.

    A potato scion on a tomato stock, for example, can produce small tubers in the axils of its leaves -- which potatoes usually do not do. Starch is not a foreign substance to tomatoes, but the tomato stock has no ability to store starch in tubers because it does not (and apparently cannot be persuaded to) produce tubers.

    The reverse graft, tomato on potato, allows the potato stock to produce its tubers underground, but they are inferior to those produced by ungrafted potatoes. The flavor is off. Something produced by the tomato scion is conveyed to the roots and accumulates in the tubers. Meanwhile, the tomato scion produces fruit, but these are also of bad flavor. Something from the potato scion is transmitted across the graft union and into the fruit.

    At this point, the potato-tomato grafting experiments usually end. It may seem like a good idea to have potatoes and tomatoes growing on the same plot of land, but not if only inferior tubers and inferior fruit are produced.

    But why should a bad tasting substance produced in potato plants be noticed in the fruit of grafted tomatoes but not in the potatos own tubers? And why should a bad tasting substance in the tomato plant be found in the tubers of grafted potatoes but not in the tomato plantÂs fruit?

    Both potatoes and tomatoes have been cultivated and selected for centuries. We may suppose that potatoes have been Âtrained to keep their ill-flavorings out of the tubers, just as tomatoes have been selected for absence of bad flavors in the fruit. Accepting this supposition, we may suppose further that potatoes might also be selected for the ability to keep tomato scion flavorings out of the tubers. And that tomato plants might be selected for the ability to produce properly flavored fruit while grafted to potato stocks.

    While it is probable that one could select potato and tomato strains for the ability to produce flavorful fruit and tubers when grafted, it might not be worth the effort except as a curiosity or scientific demonstration. Both the potato and the tomato strains would have to be independently desirable and productive in commercial production. And because potatoes are often planted a month or so earlier than tomatoes, we would face another problem -- how to make tomato plants more frost resistant.

    Karl

  • Bob_Blue
    18 years ago
    last modified: 6 years ago

    In a book by Charles Morrow Wilson - ROOTS: Miracles Below From personal interviews with plant physiologist Johannes van Overbeek (one of the first to identify cytokines) stemgrafting experiments with tomato and tobacco plants reveal that roots are dominant. Grafted young tomato plant to like sized tobacco root crown. Tomato foliage contains nicotine. But when tobacco plant is stem grafted to head of tomato root system no nicotine in the tobacco plant. This was not publishe as far as I could find.
    Any comments or similar experience with other grafts by anyone that may be interpreted as an example of root dominance?

  • kevins_choice
    18 years ago
    last modified: 6 years ago

    so are plants grafted on to rootstocks with certain desirable traits so that the seeds can be planted and then see if any traits transfer in the seedlings from the fruit from the tree that grew from the original bud. kevin