Chromosome numbers and karyotype of five species from Seriphidium (Asteraceae)

Chromosome data are important for elucidating intergeneric relationships and delimiting infrafamilial tribes in plants. This paper reports karyological data for 12 Seriphidium (Bess.) Poljak. species from China, of these, five count as new reports and the others have been reported elsewhere. We also report the tetraploid level in S. schrenkianum for the first time. The karyotype formulae and types for the five new reports are: S. schrenkianum (Ledeb.) Poljak. 2n = 4x = 36 = 22m + 12sm + 2st, S. sublessingianum (Kell.) Poljak. 2n = 2x = 18 = 14m + 4sm and S. transiliense (Poljak.) Poljak. 2n = 2x = 18 = 4M + 6m + 2m(SAT) + 4sm + 2sm(SAT), belong to 2A type; S. cinum (Berg. ex Poljak.) Poljak. 2n = 2x = 18 = 8m + 10sm and S. sawanense Y. R. Ling et C. J. Humphries 2n = 2x = 18 = 10m + 2m(SAT) + 6sm, belong to 2B type. Furthermore, we estimated karyotype asymmetry in the 12 species by using an intrachromosomal asymmetry index and an interchromosomal asymmetry index. The data increase information about the karyosystematics of Seriphidium.