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Miscellaneous Chromosome Numbers in Opuntieae Dc. (Cactaceae) with a Compilation of Counts for the Group

Majure, Lucas C., Puente, Raul, Pinkava, Donald J.
Haseltonia 2012 v.18 pp. 67-78
Opuntia, cacti and succulents, chromosome number, chromosomes, diploidy, genome, hybridization, polyploidy
Chromosome counts of members of the Opuntieae were carried out to further our understanding of ploidal levels, species boundaries, and evolutionary patterns within this group of stem succulents, which has been well-studied cytologically and is well known for hybridization and polyploidy. Here we counted chromosomes of 53 taxa in 4 genera (Consolea Lem., Nopalea Salm-Dyck, Opuntia Mill., and Tacinga Britton & Rose). Thirty of these counts are the first for a given taxon, and six counts represent a different ploidy for a taxon than has been reported previously. We also present a review of chromosome counts reported for Opuntieae. Ploidy in these taxa ranged from diploid, 2n = 2x = 22, to 20-ploid, 2n = 20x = 220. Of the 164 species in the Opuntieae for which chromosome counts have been carried out, including our new counts, 26.2% are diploid, 13.4% are both diploid and polyploid, and 60.4% are polyploid reiterating that the frequency of genome duplication in the group is far more common than diploidy.