Autoploidi

Autoploidi, also called autopolyploidy, is a form of polyploidy in which an organism possesses more than two complete sets of homologous chromosomes that originate from a single species. In contrast to allopolyploidy, where chromosome sets come from different species, autoploidy carries multiple copies of the same genome.

Autoploidi arises through genome duplication within a species or through the formation of unreduced (2n) gametes that fuse with another 2n gamete or with a reduced gamete to yield an organism with 3n, 4n, etc. Common mechanisms include nondisjunction during meiosis producing 2n gametes, or somatic chromosome doubling (endoreduplication) followed by germline transmission.

Meiotic behavior in autoploids differs from diploids because the multiple homologous chromosomes can pair as multivalents rather than strictly as bivalents. This can cause irregular chromosome segregation and reduced fertility, although some autoploids maintain reasonable fertility through meiotic adjustments, such as preferential bivalent pairing or formation of balanced gametes.

Autoploidy can lead to instant reproductive isolation from diploid relatives, providing a mechanism for speciation. It is particularly common in plants and is exploited in agriculture to produce cultivars with desirable traits; induction of autoploidy is often achieved with chemicals such as colchicine or oryzalin.

A well-known example of an autoploid crop is the cultivated potato (Solanum tuberosum), which is typically tetraploid (4x).