Natural Cloning, Mandarin Style

Mandarin, Citrus reticulata 'Parramatta Sweets'
No prizes for guessing where heritage ‘Parramatta Sweets’ mandarins (Citrus reticulata) originated.

In autumn I sowed 100 mandarin seed. I’ve just potted up the resultant seedlings – all 170 of them! How is this possible? Most flowering plants (angiosperms) generate a single embryo per seed following pollination. Seed results from sexual reproduction and the offspring have some genetic variation. But some cultivars of citrus generate multiple embryos in an individual seed without pollination – they are polyembryonic seed and they’re a result of asexual reproduction. Polyembryonic seed go on to produce multiple seedlings, and you can carefully separate and pot these seedlings individually. My most prolific seed generated five seedlings, but quite a few produced two to three seedlings each. Back in 1719, Linnaeus observed and defined apomixis, a natural cloning process involving polyembryony. Apart from sheer numbers, the other advantage of  apomixis to the gardener is the offspring are genetically identical – true clones – of their mother. I know that the seedlings of my heritage Australian Parramatta Sweets‘ mandarin will mature – with less fuss and effort than modern mandarins – to produce an equally heavy crop of sweet, juicy fruit enclosed by a rind that separates perfectly from the fruit. And I have enough offspring to create a commercial orchard. If you’re interested in delving deeper, read on…

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Polyembryonic seed formation in citrus is one of many apomictic processes that have been described to occur in the ovules of angiosperm species (Koltunow, 1993). In polyembryonic seed formation, many non-zygotic, nucellar embryos are initiated directly from the maternal, nucellar cells surrounding the embryo sac containing a developing zygotic embryo. During embryo sac expansion, embryogenic nucellar cells obtain access to endosperm and develop into embryos alongside the zygotic embryo that may or may not complete development. Nucellar embryos give rise to seedlings that are of the same genotype as the female parent – they are natural clones. Reference, see: Oxford Journals, Annals of Botany Polyembryony in non-apomictic citrus genotypes Pablo Aleza, José Juárez, Patrick Ollitrault and Luis Navarro –  http://aob.oxfordjournals.org/content/early/2010/07/29/aob.mcq148.full Jerry Coleby-Williams 25th August 2012 (while waiting for a radio interviewer to call)

8 Comments Add yours

  1. Hi Jerry – well Karen and I loved your Parramatta Sweets mandarin marmalade we bought at your recent Open Garden Day – Is there any chance of buying a seedling for Parramatta Sweets from you? or even a fruit? It is certainly much more robust than the plants on offer at nurseries.

    Sorry to hear of Colins passing

    Stephen Hutson
    Collombatti NSW

    1. Dear Stephen,

      It was my plan to sell the seedlings raised from the fruit that made the marmalade as a package. But I needed an extra two growing weeks to achieve it.

      Give me your address and I’ll pop one into a mail tube later this spring when they’ve established.

      My friend Noel (who had a sales area during my open day) has bagged the lot. I’m very happy for him to sell them – his home and garden were destroyed by the floods – and any profit from their sale is my contribution to him rebuilding his life.

      Cheers

      Jerry

      1. Thanks Jerry

        Love the marmalade !

        Stephen
        Collombatti NSW

  2. Gerry Schouten says:

    Hi Jerry, Last summer i fell in love with Achacha and planted lots of seeds. Most seeds came up and one was polyembryonic giving me 3 plants. I’m hoping these will be clones of the parent fruit and they will be the ones for my garden.
    Cheers
    Gerry Schouten, Gladtone QLD (soon moving to Valdora Sunshine Coast.)

    1. I would definitely hold on to those and determine their merits.

  3. Lissa says:

    Did you split the multiple plants for potting? From your pics it doesn’t look like you could get enough root for each little plant. Wondering how the multiples would grow together in the long run?

  4. Marion Johnson says:

    Hello Jerry
    Can I buy some Parramatta Sweet seedlings . I live in Murwillumbah NSW.
    Marion

    1. Hello Marion,

      Every year I sell off surplus stock to visitors at my annual Open Day held during the Mother’s Day weekend. If I have any surplus Parramatta Sweets, they will be sold then. I promote my Open Day on this website and my Public Facebook Page.

      Jerry Coleby-Williams’ Facebook page and website are followed by 43 countries. He answers between 8,000 to 12,000 gardening questions free each year. He answers single gardening questions only.

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