Colchicine induces tetraploids in in vitro cultures of Digitalis lanata Ehrh.: Enhanced production of biomass and cardiac glycosides

•For the first time in vitro tetraploid plants produced in Digitalis lanata.•Polyploidy induction achieved with the treatment of colchicine to the shoot buds.•Tetraploids differ in morphology, stomata, and biochemical characteristics.•Cardiac glycosides (digoxin and digitoxin) content was higher in the tetraploids.•Tetraploid’s biomass has high demand in pharmaceutical industries. This study describes a promising method for tetraploidy induction in the in vitro grown diploid shoots of the cardiotonic herb Digitalis lanata by colchicine treatment to obtain a higher content of the cardiac glycosides’ digoxin and digitoxin. The best frequency of tetraploids (33 %) induction was observed with 0.5 % colchicine treatment for 8 h. The content of digoxin and digitoxin in the tetraploids increased by 1.61-fold and 1.73-fold over the control diploids respectively. The higher cardiotonic glycoside production in the tetraploid plants of D. lanata have the potential to satisfy the increasing demand of superior plant material for pharmaceutical industries.