Optimisation of in vitro propagation of Hyssopus officinalis L. using two-node explants and N-phenyl-N’-benzothiazol-6-yl-urea (PBU), a new urea-type cytokinin

An in vitro, vegetative propagation protocol for Hyssopus officinalis was optimised. The best results, in terms of multiplication factor (MF) and quality of shoots, were obtained using two-node explants cultured on Murashige and Skoog (MS) medium supplemented with 1.0 µM 6-benzylaminopurine (BAP). Shoots were rooted in the presence of indole-3-butyric acid (IBA), as auxin, and the well-developed plantlets were acclimatised under greenhouse conditions. The same MF value was obtained when two-node explants were cultured in the presence of 1.0 µM N-phenyl-N’-benzothiazol-6-yl-urea (PBU), a new derivative of urea showing cytokinin-like activity. Shoots obtained from the PBU treatment exhibited significantly better performance in terms of the percentage of micropropagated shoots that rooted and the mean number of roots per rooted shoot. These results demonstrate that PBU also exibits cytokinin-like activity during plant propagation.