In vitro polyploidy-mediated enhancement of secondary metabolites content in Stachys byzantina L.

Lamb’s-ear ( Stachys byzantina L.) serves as valuable medicinal plant mainly because of its pharmaceutical phyto-metabolites like linalool. Polyploidy induction has been known as an effective approach to enhance phyto-medicines content in various medicinal plants. To fulfill the production of S. byzantin with higher biomass and more secondary metabolites, different colchicine concentrations including 0.1, 0.2 and 0.4 % (w/v), were applied on the apical meristem for different periods including 12, 24, and 48 h, followed by chromosome counting and flow-cytometry to confirm the putative tetraploids, which had been remarked in preliminary morphological screening. The results exhibited that the chromosome number and DNA content successfully duplicated in tetraploids, 2n = 4x = 60 and 2 C DNA = 2.4 pg, when compared to diploids with 2n = 2x = 30 and 2 C DNA = 1.2 pg. A ploidy induction efficiency of ~ 18 % was achieved from the optimal treatment of 0.2 % colchicine for 12 h. The tetraploid plants had the larger and thicker leaves, as well as shorter stems and internodes. Stomata and trichomes of tetraploid plants were larger with lower density than those of diploid plants. The chlorophyll, linalool, α-cadinol, cubenol, α-terpineol, and menthone content significantly increased in tetraploids. Altogether, in vitro polyploidy can improve the important phyto-metabolites content in S. byzantin .