Direct regenerationin vitro and transient GUS expression inMentha xpiperita

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 ofin 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 1(-1) kanamycin.