allopolyploid A polyploid organism, usually a plant, that contains multiple sets of chromosomes derived from different species. Hybrids are usually sterile, because they do not have sets of homologous chromosomes and therefore pairing cannot take place. However, if doubling of the chromosome number occurs in a hybrid derived from two diploid (2n) species, the resulting tetraploid (4n) is a fertile plant. This type of tetraploid is known as an allotetraploid; as it contains two sets of homologous chromosomes, pairing and crossing over are now possible. Allopolyploids are of great importance to plant breeders as advantages possessed by different species can be combined. The species of wheat, Triticum aestivum, used to make bread is an allohexaploid (6n), possessing 42 chromosomes, which is six times the original haploid number (n) of 7. See also amphidiploid. Compare autopolyploid.

allopolyploid A polyploid (see polyploidy) that is formed from the union of genetically distinct chromosome sets, usually from different species (e.g. bread wheat (Triticum aestivum) derived from three genomes).

allopolyploid A polyploid formed from the union of genetically distinct chromosome sets (usually from different species). Examples are cultivated wheats. Many new species of flowering plants are thought to have originated by allopolyploidy.

allopolyploid A polyploid (see POLYPLOIDY) that is formed from the union of genetically distinct chromosome sets (usually from different species).