Allohexaploidy

Allohexaploidy refers to a specific type of polyploidy where an organism contains three sets of chromosomes, with each set originating from a different species. This is distinct from autopolyploidy, where all chromosome sets come from the same species. In an allohexaploid, there are effectively six copies of each chromosome, but these six copies are organized into three distinct pairs, each pair representing the contribution from a different ancestral species. The formation of an allohexaploid typically involves hybridization between two different species, followed by chromosome doubling. This doubling event is crucial because it restores diploidy within each ancestral genome, allowing for homologous pairing and thus fertility in the resulting allohexaploid. Without this doubling, the initial hybrid would likely be sterile due to unpaired chromosomes during meiosis. Allohexaploidy is a significant mechanism in plant evolution, contributing to the diversity of many crop species, such as wheat. It can lead to novel traits and increased vigor in the allohexaploid organism compared to its parent species.