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Re: [AZ] Doing crosses with Rhododendron occidentale?

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  • uuallace
    I just repotted a few seedlings of a cross of Rh. atlanticum and Rh. luteum that a friend in California made. I think both are probably tetraploids. Mike
    Message 1 of 12 , Dec 1, 2005
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      I just repotted a few seedlings of a cross of Rh. atlanticum and Rh.
      luteum that a friend in California made. I think both are probably
      tetraploids.

      Mike Creel, Zone 8A, SC

      This study reported R. atlanticum as diploid and a single triploid.
      There must be tetraploids elsewhere.
      http://www.botany.org/ajb/00029122_di001548.php

      Larry Wallace
    • matthew chappell
      Hello all, There are only two conclusive ways to determine IF any species is tetraploid. Well... one for sure (karyotyping) and another (GC- Mass Spec) will
      Message 2 of 12 , Dec 1, 2005
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        Hello all,

        There are only two conclusive ways to determine IF any species is
        tetraploid. Well... one for sure (karyotyping) and another (GC- Mass Spec)
        will confirm it and tell you the size of the genome as well. The first
        method is simple... staining the chromosomes and making a karyotype. This
        has been done with some azaleas. For reference see:

        Li, Hui-lin. 1957. Chromosome Studies in the Azaleas of Eastern North
        America. American Journal of Botany 44:8-14.

        Sax, Karl. 1930. Chromosome Stability in the Genus Rhododendron. American
        Journal of Botany. 17: 247-251.

        The second method... GC-mass spec literally counts the number of base pairs
        of each chromosome as it passes through an extremely small pore. It will not
        accurately determine if the plant is tetraploid because you must first have
        an image of the chromosomes to see if there are identical chromosomes
        present (hence tetraploid). Together, both methods would give a very
        accurate measurement of ploidy and genome size.

        Hope this helps. Just keep in mind that guessing on ploidy is a tricky
        business. Wheat is a great example. Wheat is a synthetic hexaploid yet is
        neither more vigerous than its ancestors nor self/cross incompatable despite
        having sets of chromosomes from a vast array of the Triticum genus.

        Peace be with you all.


        Matthew R. Chappell
        Georgia Agricultural Experiment Station
        Horticulture Dept.- Plant Breeding & Genetics
        1109 Experiment Street
        Griffin, GA 30223
        Office- (770) 229-3369
        Cell- (770) 715-6585


        -----Original Message-----
        From: azaleas@yahoogroups.com [mailto:azaleas@yahoogroups.com] On Behalf Of
        uuallace
        Sent: Thursday, December 01, 2005 3:16 PM
        To: azaleas@yahoogroups.com
        Subject: Re: [AZ] Doing crosses with Rhododendron occidentale?

        I just repotted a few seedlings of a cross of Rh. atlanticum and Rh.
        luteum that a friend in California made. I think both are probably
        tetraploids.

        Mike Creel, Zone 8A, SC

        This study reported R. atlanticum as diploid and a single triploid.
        There must be tetraploids elsewhere.
        http://www.botany.org/ajb/00029122_di001548.php

        Larry Wallace







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      • Mike Creel
        Larry, thank you for sending the abstract on ploidy studies among American Native azaleas. I think there are at least a few non-diploid forms among all the 16
        Message 3 of 12 , Dec 1, 2005
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          Larry, thank you for sending the abstract on ploidy
          studies among American Native azaleas. I think there
          are at least a few non-diploid forms among all the 16
          species of American native azaleas. I observe
          characters among wild forms like unusually large
          flowers, abnormally large leaves, vigorous growth with
          no fertilizer or water and the setting of multiple
          terminal bloom buds.

          A professor friend at NC State gave me a proven
          tetraploid Rh. atlanticum which has quite large
          flowers and accepts pollen from one of my yellow
          calendulaceums. He thinks that a lot of atlanticums
          are probably tets. I grow two other atlanticums that
          I selected from the wild on my family's farm due to
          the plant's unusually large flowers.

          I have a Rh. prunifolium (named David Ellis because he
          gave me the seedling) that routinely sets multiple
          terminal buds, that open sequentially rather than as a
          ball truss. I also grow a multi-budding Rh.
          alabamense that makes a nice ball truss. There is one
          form of Rh. eastmanii that sets multiple buds and
          large flower heads I think that all three forms might
          be tets. Of course I am no PhD or profesional
          horticulturalist, just a keen observer of nature and a
          seeker of weirdness among plants.

          Mike Creel, SC, Zone 8A

          --- uuallace <Larry.Wallace@...> wrote:

          > I just repotted a few seedlings of a cross of Rh.
          > atlanticum and Rh.
          > luteum that a friend in California made. I think
          > both are probably
          > tetraploids.
          >
          > Mike Creel, Zone 8A, SC
          >
          > This study reported R. atlanticum as diploid and a
          > single triploid.
          > There must be tetraploids elsewhere.
          > http://www.botany.org/ajb/00029122_di001548.php
          >
          > Larry Wallace


          Chromosome Studies in the Azaleas of Eastern North
          America, 8-14
          Hui-lin Li
          Abstract: Chromosomes of 15 species of Rhododendron,
          series Azalea, subseries Luteum, were studied from 271
          plants gathered from 21 states in eastern North
          America. Both somatic cells from stem tips and pollen
          mother cells were examined. The study reveals that the
          majority of the species are diploid with n = 13, and
          2n = 26. A tetraploid species R. calendulaceum may
          have arisen by polyploidization, in part at least from
          the diploid R. cumberlandense. Hybrids of R.
          calendulaceum and diploid populations are mostly
          tetraploid, but triploids occasionally occur. (Diploid
          hybrids identified in the field as involving R.
          calendulaceum probably do not actually involve that
          species at all.) A triploid has been noted in the
          otherwise diploid R. atlanticum. Although occasional
          aberrations such as lagging and non-pairing of
          chromosomes occur in hybrids between the more
          distantly related species, the chromosomes of all
          species seem fully compatible with each other. Fertile
          progeny seems to result from the hybridization of any
          two species. Where hybridization between diploids and
          the single known tetraploid occurs, it appears to be
          unidirectional through the fertilization of the
          tetraploid by unreduced gametes of the diploids. It is
          suggested that spatial and ecological isolation and
          difference in time of flowering are primary factors in
          maintaining such distinctness of the species as they
          possess. Whenever these factors are disturbed
          naturally or artificially, hybridization and genic
          introgression become recognizable phenomena.






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