Micropropagation and cryopreservation by vitrification of the Spanish endemic medicinal plant Sideritis leucantha Cav. subsp. leucantha (Lamiaceae)

Abstract

Sideritis leucantha Cav. subsp. leucantha is a Spanish endemic medicinal plant that faces conservation problems. Therefore, this work is aimed to develop a protocol for the in vitro propagation and cryopreservation of shoot tip explants of this species. The morphogenic responses were recorded using Murashige and Skoog medium containing 6-benzyladenine, 2-isopentenyladenine, kinetin, or thidiazuron for multiplication and 1-naphthaleneacetic acid or indole-3-butyric acid for rooting. Maximal shoot proliferation was observed with medium containing 0.088 M sucrose plus 0.22 or 0.44 μM 6-benzyladenine. The longest shoots and greatest number of nodes per shoot were obtained from cultures incubated on medium with 0.44 μM 2-isopentenyladenine. Optimal rooting was achieved with 1-naphthaleneacetic acid at concentrations of 0.05 μM (highest percentage of rooted shoots) and 0.26 μM (highest number of roots). The morphological traits of the regenerated plantlets did not differ from those of wild-type plants, and these plantlets were successfully adapted to ex vitro conditions. After cryopreservation by vitrification, the highest percentage of regenerated shoot tips (70 ± 6%) was obtained with the treatment consisting of 60 min of loading solution (0.4 M sucrose plus 2 M glycerol in liquid medium) followed by exposure to plant vitrification solution 2 for 30 min at room temperature and then immersion in liquid nitrogen for 60 min. This study constitutes the first work on the micropropagation of S. leucantha subsp. leucantha and the first work on the cryopreservation of Sideritis species. The results obtained could be applied commercially and also in the conservation for other species of Lamiaceae.