Preservation of Juniperus thurifera L.: a rare endangered species in Algeria through in vitro regeneration

Abstract

Juniperus thurifera L. is an endemic Cupressaceae from the Aurès Mountains of north eastern Algeria and endangered, in part, due to the scarcity of viable seeds. It is threatened by other abiotic factors and the lack of an effective management strategy will increase its risk of extinction. The dearth of information on its in vitro regeneration impedes its application in forest management programs. We therefore developed a micropropagation protocol using microcuttings with auxiliary buds. Cuttings were grown on different combinations of media supplemented with plant growth regulators at different concentrations. The highest number of shoots and branches regenerated from original shoots was obtained on Woody Plant Medium (WPM) supplemented with 6-benzylaminopurine (BAP) (0.5 mg L⁻¹) and 2,4-dichlorophenoxyacetic acid (2,4-D) (0.25 mg L⁻¹). The best elongation of shoots was achieved with WPM supplemented with 0.5 mg L⁻¹ of BAP and 0.25 or 1 mg L⁻¹ of 2,4-D. On the second subculture, shoots had a higher number of branches than those of the first. The highest rooting rate, 38.8%, was obtained with shoots cultured in ½ Murashige and Skoog (MS) medium supplemented with 5.0 mg L⁻¹ each of indol-3-butyric (IBA) and naphthalene acetic acid (NAA). Similarly, the highest root numbers and lengths were produced on ½ MS medium supplemented with IBA and NAA (5.0 mg L⁻¹ each). During transfer to acclimatization, rates of plant losses of 50% occurred. The second part of the experiment showed that the best shoot callusing was on WPM supplemented with BAP and 2,4-D, with either the combination 0.5 + 0.25 or 0.25 + 0.25 mg L⁻¹. The results of this research provide a starting point for further studies on in vitro regeneration of J. thurifera for the sustainable management of its unique ecosystem in the Mediterranean basin.