Citrus variegation causes/origins

Discussion in 'Citrus' started by skeeterbug, Jan 3, 2007.

  1. skeeterbug

    skeeterbug Active Member

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    I have a couple very basic question about variegated citrus-- what causes the variegated foilage in citrus? (I am not talking about the disease CVC or citrus variegated chlorosis)

    Are seeds of variegated citrus "true to type"?

    Can new variegated varieties arise from a seed?

    I have read that they are chimeras and can originate from grafting-- is that true?

    Skeet
     
  2. mikeyinfla

    mikeyinfla Active Member

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    i just got 2 piecesof scion wood from a variegated pink lemon and they have been growing for several months so will be a while till i get to plant any seeds from the two plants that are now growing. the little bit i know about variegated plants is that allot of them are mutations/sports on an existing plants. some say it is from a disease some from radiation or from chemicals i did have one hibiscus throw a variegated piece but it was unstable and went away. not sure what caused it. i know some plants where a seed was planted from a variegated plant the seedlings will be albino no green at all not sure about citrus if they may be variegated from seed or not. know very little about graft chimera accept allot of the time they are not stable enough to keep the chimera caracteristics they usually revert one way or the other.and thats just from the limited info about them that i have seen.the only species i have grafted in hopes of a graft chimera is datura onto brugmansia. should be really different looking if one does happen. and also not sure of the percentage of chimera that are variegated. sometimes they just look different than both rootstock and scion and are not variegated. hopefully someone will come along who knows more about all this. its interesting just wish i knew more about it. hope any of my ramblings helped
     
  3. skeeterbug

    skeeterbug Active Member

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    I have found out that at least some varigation is caused by a virus, just not the CVC virus. It is an interesting question. I had a varigated seedling, but it did not make it through the winter.

    Skeet
     
  4. mr.shep

    mr.shep Well-Known Member 10 Years

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    Are seeds of variegated citrus "true to type"?

    The seeds may be true to type for being
    a Lemon from the fruit which they came
    from but most variegated seedlings will
    green out or return to green as seedlings
    as time goes by.

    Can new variegated varieties arise from a
    seed?


    Yes, there have been some varieties that
    came about as seed gathered from a fruit
    but usually these are fruit that had a sectional
    chimera as a result of a branch sport. Then
    again I have a sectional chimera right now
    on a Sanguinelli Blood Orange that did not
    arise from a branch sport. I will save the
    seeds and give them to a nurseryman to
    grow on but I'd prefer to have had some
    variegation showing in the leaves as well.

    Even when we bud a variegated scion onto
    a variegated rootstock the number of seedlings
    that will be and remain variegated is a small
    percentage. (It was this finding is what
    dispelled the sky is falling notion that
    manipulation of the color virus that causes
    variegation in Camellias would automatically
    infect all non variegated forms, thus ruining
    them). That does take the fun away but if the
    mutated or color enhanced gene is present in
    both the rootstock parent and the scion parent
    then the frequency of which we will see seedling
    offspring be variegated is significantly higher
    (the numbers that remain variegated later on is
    not as significant) than if we were to take seed
    from fruit gathered from a variegated scion that
    was budded or grafted onto a green seedling.

    I have read that they are chimeras and can
    originate from grafting-- is that true?


    Whip grafting has been known to help induce
    a so-called chimera or in this case a branch
    sport due to the incompatibility of the two
    woods. We can and have seen cleft graft
    incompatibilities live for upwards of ten
    years and longer in Magnolias and in some
    infrequent cases in Japanese Maples and
    Dogwoods as well, usually Cornus florida.

    We can get an unusual growth emanate from
    the two woods that is genetically neither that
    of the branch parent, nor the bud wood parent.
    At the time of mitosis the genes are doubled
    and we may even get a new shoot growth that
    is tetraploid. This result is the branch chimera
    and people have taken wood from that growth
    and budded it onto another plant. Some of
    the variegated forms were perpetuated in this
    same manner.

    Most variegated forms came about as a branch
    sport that appeared to be variegated. Some held
    true over time when budded onto green rootstock
    and were grown on but most returned back to
    green later. The better way to ensure that the
    variegation stays is to take wood from the
    variegated branch sport and root cuttings
    (Oranges, Mandarins) and select out the
    rooted cuttings that stay variegated from
    them or do whip grafts of the variegated
    branch sports (Lemons, Limes, Calamondin)
    and then continue the cycle of taking wood
    that grows from the whip graft and use it as
    our budwood to t-bud onto a known green
    rootstock. Today people take the variegated
    budwood and bud directly onto a green
    rootstock rather than fooling around with
    rooted cuttings but for some forms of Citrus
    it is better to have both the variegated rooted
    cuttings used as a rootstock and then bud the
    variegated wood onto it. This is what the next
    step would have been for the variegated Cara
    Cara Navel Orange but it did not get that far
    along. Thus some people had to be satisfied
    with having the rooted cuttings if they had
    them instead and some of those cuttings
    later returned to green a few years later as
    was predicted based on the Camellia trials.

    There is more than one virus, either in
    the soil or is insect transmitted, that
    can cause a variegation in the leaves
    as well as on the rind of the fruit of
    some Citrus. Seeds gathered and
    germinated from the speckled fruit
    have usually yielded offspring that
    do not live long. We can see the
    variegation in the first few leaves and
    then wham, the seedling dies. This type
    of viral activity lessons the vigor in the
    plant. What happens when an Orange
    gets hit by Tristeza, it weakens and gets
    overcome by the infecting virus in its
    system. We see the same type thing
    in seedlings that show some variegation
    in a leaf or two and then the juvenile leaf
    falters and the rest of the plant probably
    will cease to function rather soon also.

    Jim
     
  5. skeeterbug

    skeeterbug Active Member

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    Very Interesting Jim,

    Has anyone tried to compare the DNA of the variegated part with the non variegated part of a plant?

    This reminds me of the question of where the node count information resides in a citrus plant.

    Skeet
     
  6. mr.shep

    mr.shep Well-Known Member 10 Years

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    I would prefer tests done on chromosomal DNA
    as my foundation as opposed to chloroplast DNA,
    of which the latter has been conducted on Citrus.

    Years ago there was a Variegated Eureka. What
    would be interesting to know is how that plant
    differs from the standard Eureka, if we can find
    an old plant on its own roots, a seedless Eureka
    and the Variegated Pink Eureka.

    This reminds me of the question of where the
    node count information resides in a citrus plant.


    I believe Dr. Manners in the Citrus Growers
    Forum may be able to offer some more insight
    here. Personally I feel the node count and node
    elongation is more applicable to Grapefruit,
    Pomelo and Pummelo seedlings than it is to
    grafted or budded forms of them. I believe
    an example used in the past and I agree with
    this is that node count and node elongation
    becomes important for seedling Avocados
    and seedling Grapefruit to bear fruit. On the
    other hand there have been 3 foot tall grafted
    Avocados and 3 foot tall budded Grapefruit
    with fruit on them which gives and tells of
    another perspective. I do believe the age of
    the wood used as the scion comes into play
    for the mini Mexicola Avocado that I had
    years ago to bear fruit at such a young age
    and such a small sized tree. Have not owned
    a "super dwarf" Grapefruit but I have seen
    it.

    Jim
     
  7. Millet

    Millet Well-Known Member 10 Years

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    Jim is correct. Obtaining the required node count before a citrus tree matures, ONLY pertains to seedling trees. A grafted citrus tree is mature from the first leaf, by the very fact that a mature bud was removed from a producing tree, and implanted onto the new rootstock. The grafted bud "remembers" that it is a mature bud, and "remembers" its mature node count number. All that is required is for the new scion to obtain a little height. - Millet
     
  8. Millet

    Millet Well-Known Member 10 Years

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    ..............This reminds me of the question of where the
    node count information resides in a citrus plant................

    Probably resides on the trees DNA chain. - Millet
     
  9. Millet

    Millet Well-Known Member 10 Years

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    Skeeter asks the question....." what causes the variegated foliage".......

    Plastids which are in the tree's leaf contain genes that contribute to the development of the chloroplasts (the green color in leaves). These genes are passed from generation to generation by duplication and division of the plastids (their inheritance is distinct from that of nuclear genes). Since egg cells contribute plastids to the zygote while pollen cells usually do not, only the maternal parent has a part to play in plastid inheritance. Effects on the chloroplast genes are especially noted in the inheritance of variegated color patterns in the leaves of the tree. Here the egg cell contains both normal plastids and plastids that cannot develop into green chloroplasts because of defective genes. Some cells in the embryo have only the defective plastids. These cells divide further to produce the distinctive white or yellow patches on the leaves and stem of a variegated tree. - Millet
     
  10. skeeterbug

    skeeterbug Active Member

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    Thanks Millet, that is the first time I have heard that explanation and it helps to understand the biology.

    As for the node count question, I was telling my wife about the node count requirement for seedlings and she asked me and interesting question-- How do the various limbs on the tree communicate "the node count" or does each limb have to reach the required node count separately?

    Skeet
     
  11. mikeyinfla

    mikeyinfla Active Member

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    my limited understanding is that node count has to do with, when the plant decides its an adult and goes thru hormonal changes telling it to start flowering and fruiting. when a bud or scion is taken off of the plant it still knows its an adult it just may take a few years to get big enough for the plant hormones to build up to a point of making it flower and fruit. and i may be way off track but again thats my limited understanding.
     
  12. Millet

    Millet Well-Known Member 10 Years

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    You start with the seed as node zero, and count up from there. When the plant makes its first side branch, say at node 14, the next node above that on the main trunk will be 15, AND the first node on the new side branch will ALSO be 15. So on a big old tree, there may be hundreds of node 4762. Each node "knows" and "remembers" its own number. If you bud/graft node 4762 into the base of a rootstock seedling, you don't change the seedling's node count at all, but when the scion grows out, it makes 4763, 4764, etc. on the scion stem.
    The result of all this is that a seedling must grow rather far away from the seed to flower, hence the problem with flowering a seedling in the house. If you prune it back, you remove some node numbers. If you pruned to #43, throwing away nodes up to 100, when the house tree resumes growth, it resumes at 44, NOT 101. So a constantly pruned house tree may never flower. And even an ancient seedling tree which has been flowering and bearing fruit for 100 years, if cut down and the stump resprouts, it will be juvenile again. The nodes never forget their numbers.

    But this is also why the technique of air layering or rooting a cutting from the top of a seedling house tree, and replacing the original plant with the new propagation is a good way to get flowers and fruit, eventually. If you take a cutting that contains nodes 56, 57, 58, and 59, root it, and make a new potted plant of it, it will resume growth at 60. So you've done away with several feet of stem length in the process of getting to the minimum needed node number for flowering. (coppied from a response to Millet from Malcolm Manners ) - Millet
     
  13. sabagal

    sabagal Member

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    Millet,

    Thank you, thank you, thank you for that information. I was actually going to ask that question myself. My 5 lemon trees are getting tall (2 are about 6 foot) and I will probably be moving in the next few months. I was not happy about moving tall trees possibly in cold weather. I will start air layering now and hopefully will have new rooted, much smaller trees when the big day comes.

    I so appreciate all your knowledge and willingness to share. Thanks again.

    Sabagal
     
  14. egardens

    egardens New Member

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    I have grown a bunch of etrong lemons and one is totally white and growing very well strange....does anyone know if this is a new species if it survives.
     
  15. Junglekeeper

    Junglekeeper Esteemed Contributor 10 Years

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    Unfortunately albino seedlings will eventually die.
     

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