Direct Regeneration of Lemon Balm ( Melissa oficinalis L.) Plants from Nodal Explants: A Sample Protocol for Mass Propagation

We developed an efficient in vitro regeneration protocol for the valuable medicinal plant lemon balm ( Melissa officinalis L.) from single node explants. The highest regeneration frequency (100%) and maximum number of shoots were achieved with half-strength Murashige and Skoog (MS) media supplemented with 1 mg L -1 6-benzylaminopurine (BA) alone (2.82 and 9.8 shoots at three and six weeks, respectively) or in combination with 0.2 mg L -1 napthalen-eacetic acid (NAA) (2.73 and 8.13 shoots at three and six weeks, respectively). Maximum shoot elongation was obtained with media containing 0.2 mg L -1 BA alone or in combination with 0.2 mg l -1 NAA (2.26 cm and 2.31 cm, respectively) over a period of three weeks. Elongated shoots were rooted in MS media with or without rooting hormone. However, the best rooting, as measured over a period of two weeks and in terms of rooting percentage, root number, root length, and root, shoot and total dry weight of the plantlets, was obtained in media supplemented with 1 mg L -1 indole-3-butyric acid (IBA). The rooted plantlets were successfully transferred to soil and acclimated under greenhouse conditions.