Experimenting Two Cryopreservation Techniques (Vitrification and Encapsulation-Dehydration) as Approaches for Long-term Conservation of in vitro Grown Shoot Tips of Wild Fennel

Wild fennel (Foeniculum vulgare Mill.) is a medicinal plant that is native to Jordan as well as to most of Mediterranean region. Wild fennel is considered an aromatic medicinal plant and is used in cooking as a spice, and in folk medicine for the treatment of gastrointestinal and respiratory tract diseases. Due to the high international demand for this plant, the extensive uncontrolled collection of wild fennel became highly threatened species. In the present study, two cryopreservation techniques (vitrification and encapsulation-dehydration) were experimented as approaches for long term conservation of in vitro grown shoot tips of wild fennel. The results obtained from vitrification experimental part showed that survival and regrowth rates varied with type of loading solution, and the maximum survival (80%) and regrowth (65 and 60%) rates were recorded in shoot tips (STs) preloaded with either (2M glycerol + 0.4M sucrose) or (5% Dimethylsulfoxide, DMSO + 0.5 M sucrose), respectively. Also, data revealed that survival and regrowth rates of wild fennel STs were determined by the type of plant vitrification solution, as the highest survival and regrowth rates (85 and 60%, respectively) were obtained in STs cryoprotected with plant vitrification solution type 2 (PVS2) before exposure to Liquid Nitrogen (LN). Moreover, the best regrowth rate (65%) was recorded in encapsulated STs of wild fennel with 21.1% moisture content obtained after chemical dehydration in MS liquid media supplemented with 0.75 M sucrose for 1 day followed by air dehydration for 6 hrs. However, more research is still needed to optimize the pretreatments protocols prior exposure to LN in terms of ingredients, concentration and duration to improve regrowth rates.