Cryopreservation and Genetic Stability Assessment of Threatened Medicinal Plant (Ziziphora tenuior L.) Grown Wild in Jordan

Ziziphora tenuior L. is one of the important medicinal plants that belong to the Lamiaceae family. It is a rare species with a promising medicinal potential and grows wild in the southern part of Jordan. Unfortunately, this plant might be totally extinct from the wild due to over-exploitation. Two cryopreservation techniques (encapsulation-dehydration and encapsulation- vitrification) were applied for in vitro conservation of this valuable medicinal plant, and after that the explants were tested for their genetic stability using Amplified Fragment Length Polymorphism (AFLP) technique. In the encapsulation-dehydration experiment, the results revealed that 40% of the cryopreserved shoot tips survived when they were dehydrated chemically on 0.75 M sucrose in MS supplemented media for one day and exposed to air dehydration for 6 hrs. Moreover, the best recovery rate (20%) was obtained when either 0.5 M or 0.75 M sucrose MS supplemented media were used as preculture media for the shoot tips for one day, followed by air dehydration for 4 or 6 hrs. Meanwhile, in the encapsulation -vitrification experiment, the highest survival (37.5%) and recovery (10%) percentages of the cryopreserved shoot tips were obtained when the encapsulated shoot tips were pretreated for 60 min. with the loading solution before being exposed to PVS2 vitrification solution and LN. AFLP technique had clearly showed that, there were no genetic variations between the shoot tips of Ziziphora tenuior L., before and after cryopreservation.