Allopolyploidy
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- Allopolyploids are polyploids resulted from the multiplication of chromosome sets of closely related species; however, the different chromosome sets are only partly homologous ( homeologous ), not fully homologous, as they are in autopolyploids.
- The allopolyploidy does not occur naturally in the nature.
- However, some cytologists have produce allopolyploidy in certain plants by selective breeding methods.
- The Russian cytologist, G. D. Karpechenko ( 1928 ) first synthesized an allotetraploid genus called Rhaphanobrassica from the artificial crosses between vegetables belonging to different genera, the radish ( Raphanus satirum, 20 = 18 ) and the cabbage ( Brassica oleracea, 2n= 18 ) in an attempt to produce a hybrid plant with edible portions of the root and the shoot of cabbage.
- However, this hybrid was functionally sterile because the 9 chromosomes from the cabbage parent were different from the radish chromosomes such that pairs did not synapse and segregate normally.
- Fertile amphidiploid arose from spontaneous doubling in the 2n=18 sterile hybrid.
- This kind of allopolyploid is sometimes called an amphidiploid , which means doubled diploid.
- Allopolyploids can be used in plant breeding to combine the useful features of parental species into one type.
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Last modified: Saturday, 17 December 2011, 9:02 AM