Karyology of Aconitum subgenus Lycoctonum (Ranunculaceae) from China, with report of a new base chromosome number of x = 6 for the genus Aconitum
17 January 2016
Hong, Yu; Gao, Qi; Luo, Yan; Luo, Jiang-Ping; Zhang, Yu; Yuan, Qiong; Yang, Qin-erIn order to gain better knowledge of the number and morphology of chromosomes in Aconitum subgen. Lycoctonum from China, 60 populations belonging to 20 taxa of Aconitum subgenus Lycoctonum (Ranunculaceae) from China were cytologically studied. Chromosome numbers of six species (A. apetalum, A. finetianum, A. fletcheranum, A. longecassidatum, A. umbrosum, and A. wangyedianense) are here reported for the first time. One species, A. fletcheranum, has 2n = 12, and thus is diploid based on x = 6, a new base chromosome number for the genus Aconitum. Most of the remaining taxa are diploid (2n = 16) based on x = 8, but five taxa (A. angustius, A. brevicalcaratum var. brevicalcaratum, A. brevicalcaratum var. parviflorum, A.chrysotrichum, and A. crassiflorum) are tetraploid with 2n = 32, and one species (A. apetalum) is hexaploid with 2n = 48, the highest ploidy level currently known in the subgenus. The karyotypes of all the other 2n = 16 species, if disregarding the differences in the presence or absence and number of satellites, are quite uniform (2n = 2m + 6sm + 8st), but A. novoluridum, the only species of A. section Alatospermum, had an intrachromosomally less asymmetric karyotype (2n = 2m + 14sm), which lends further support for the primitive condition of the section as inferred from gross-morphology. Chromosomal variation in the subgenus and the relationships of some of the species are discussed.