Polyploidy in Plants

Creating a new species of animal requires many generations of reproductive isolation leading to evolutionary divergence. Plants do not have this requirement for speciation, the process of becoming a new species. Instead, have the capacity to bring about a new species in one generation. In animals having more chromosomes than the baseline may cause inviability problems in the offspring and result in their death. However, in plants, if an offspring receives 2 copies of DNA from parent AA and 2 copies from parent BB then the offspring AABB is viable. It is a completely new species. One such example is the bread wheat we use today. It has 42 chromosomes and has genetic material from 3 other species. The first set of species to cross were Einkorn wheat and Wild Goat Grass resulting in a new species known as Durum wheat. 14 chromosomes AA from the Einkorn and 14 chromosomes BB from Wild Goat Grass came together making 28 chromosome Durum wheat AABB. A second crossing event occurred when 28 chromosome AABB Durum grass crossed with 14 chromosome DD T. tauschii to form 42 chromosome AABBDD bread wheat.

    How is it that plants generate new plants with different chromosome counts? There are 2 ways it may happen. Allopolyploidy, the crossing of 2 different plant species or Autopolyploidy, the self crossing of two gametes from 1 species. Allopolyploidy occurs when gametes of 2 plants are able to fertilize and form one cell that contains half the information from each parent plant. The chromosomes duplicate producing a new chromosome count and therefore a new species. Autopolyploidy requires a non-disjunction event in either the first or second split of the parent reproductive cell. A non-disjunction event is when all the genetic material is pulled towards one side or the other resulting in a cell that contains double the genetic material.