Direct regeneration in vitro and transient GUS expression in Mentha×piperita

Abstract.

Genetic transformation of peppermint is known to be very difficult essentially because of low efficiency regeneration. A regeneration protocol allowing 51% shooting frequency is proposed. Transient β-glucuronidase expression and adjustment of selection pressure with kanamycin are also reported. The final retained method to attempt peppermint transformation is: Agrobacterium inoculation or biolistic treatment of the first apical leaves of in vitro clones, regeneration in the dark with kanamycin (1 mg l^–1) and 6-benzylaminopurine (2 mg l^–1), followed by selection of regenerated shoots with 200 mg l^–1 kanamycin.