Autopolyploidy

Autopolyploidy is a form of polyploidy in which an organism gains extra chromosome sets that are all derived from a single species. In contrast, allopolyploidy results from hybridization between distinct species followed by chromosome doubling, producing multiple subgenomes from different lineages. Autopolyploids therefore carry more than two complete chromosome sets that are homologous to each other.

Formation of autopolyploids typically occurs by genome doubling within a species. This can arise when unreduced (diploid) gametes fuse with another unreduced gamete, producing a tetraploid zygote, or when a somatic set of chromosomes doubles, and the resulting plant reproduces sexually. Artificial induction using mitotic inhibitors (such as colchicine or oryzalin) is a common method to create autopolyploids for research and breeding.

Meiosis in autopolyploids often involves multivalent chromosome associations (for example, tetravalents in tetraploids), which can lead to irregular segregation and reduced fertility. Over time, some autopolyploids achieve more stable meiosis through genetic and cytological adjustments, producing balanced gametes and higher fertility. Autopolyploids commonly exhibit the gigas effect, where increased cell and organ size accompanies higher ploidy.

Ecologically and evolutionarily, autopolyploidy can generate immediate reproductive isolation from the parent population and contribute to speciation, particularly in plants. It also provides raw material for adaptation through increased genetic variation and novel phenotypes.

Examples of autopolyploid crops include alfalfa (Medicago sativa) and potato (Solanum tuberosum). Detection and study typically involve chromosome counting, flow cytometry to estimate genome size, and genetic analyses to determine the origin of the chromosome sets.