The chromosome numbers of 56 populations belonging to 25 species and 4 varieties of Artemisia L. (Asteraceae) from China were examined, and those of 13 species and four varieties are reported here for the first time. The karyotypes of 39 populations in 23 species and four varieties were also studied. Among them, twelve species and one variety were found to be diploid, with 2n = 16 or 18; nine species and three varieties were found to be tetraploid, with 2n = 32 or 36; and two species were found to have both diploid and tetraploid cytotypes. Two species were found to have aneuploid cytotypes. The karyotypes of Artemisia are similar, with most chromosomes belonging to median-centromeric (m) and a few belonging to submedian-centromeric (sm) or subterminal-centromeric (st). The high level of polyploids in Artemisia from the Qinghai-Tibetan Plateau indicates that polyploidy has played an important role in the evolutionary speciation of this highly diversified genus in this region.
Keywords: Asteraceae; Qinghai–Tibetan Plateau; chromosome number; cytology; karyotype.