allopolüploidsus

Allopolüploidsus, or allopolyploidy, is a form of polyploidy in which an organism carries chromosome sets derived from two or more distinct species. In allopolyploids, the genome typically results from interspecific hybridization between different parents, followed by chromosome doubling. The resulting organism contains complete chromosome sets from each parent and often exhibits disomic inheritance, meaning chromosomes pair with their true homolog within each subgenome rather than with homeologous chromosomes from the other parent. This genomic architecture can contribute to reproductive isolation from the parent species and to unique phenotypic combinations.

Formation and genetics: Allopolyploids arise when a hybrid between species gains fertility through genome doubling, which restores proper chromosome pairing during meiosis. Doubling can occur spontaneously or be induced by treatments that promote chromosome duplication. Alternatively, formation can involve unreduced (diploid) gametes that combine to create a polyploid zygote. Over time, redundant gene copies may be retained, lost, or rearranged, leading to changes in gene expression, adaptation, and sometimes novel traits.

Significance and examples: Allopolyploids are common in flowering plants and are important for speciation and crop improvement. Notable examples include bread wheat (Triticum aestivum), an allohexaploid with A, B, and D genomes; Brassica napus (canola), an allotetraploid with A and C genomes; and several cotton species (such as Gossypium hirsutum), which are allotetraploids with AD genomes. Allopolyploids often show increased vigor and tolerance to environmental variation, though they can experience initial meiotic instability that stabilizes over successive generations.