Karyotype and genome size variation in genus <i>Ajuga</i> L. (Ajugoideae–Lamiaceae)

16 April 2019

Choi, Bokyung; Yang, Sungyu; Song, Jun-Ho; Jang, Tae-Soo

Chromosome number changes and karyotype evolution play an important role in plant genome diversification and eventually in speciation. The genus Ajuga L. of family Lamiaceae has approximately 50 species distributed in temperate to subtropical regions. Four of these species are currently recognized in Korea (A. decumbens Thunb., A. multiflora Bunge, A. nipponensis Makino, and A. spectabilis Nakai). Understanding the karyotype evolution in Ajuga has been hampered by small sizes of their chromosomes and symmetrical karyotypes. Here we used classic Feulgen staining to establish chromosome numbers and construct karyotypes of four species of Ajuga recognized in Korea. Flow cytometry was used to establish genome size variation in Korean members of the genus Ajuga. The chromosome number of all investigated plants in the genus Ajuga was the same with 2n = 32. The variation of the 2C DNA contents in Ajuga, which ranged from 2.18 pg (A. decumbens) to 4.53 pg (A. multiflora). While the chromosome numbers were the same for all investigated species, the genome size variation could potentially be used as a taxonomic marker in the genus Ajuga.