Melatonin-loaded alginate beads improve cryopreservation of yam (Dioscorea alata and D. cayenensis).

BACKGROUND: The cryopreservation of yam is constrained with many challenges. OBJECTIVE: This study tested the effects of melatonin on shoot tips of D. alata and D. cayenensis accessions exposed to water and liquid nitrogen (LN) stresses. MATERIALS AND METHODS: Sucrose pretreatment (0.3 M) was applied for 48 h before cryopreservation. Shoot tips were encapsulated in beads loaded with 0.75 M sucrose, with and without melatonin and desiccated over sterile dry silica gel for 0 - 9 h. RESULTS: The beads moisture content declined from 100% to ~ 13% after 9 h. The 3 h desiccation period without melatonin produced a significantly higher regeneration compared to 6 h and 9 h. Shoot tips with melatonin had significantly higher regeneration after 3 - 6 h desiccation compared to 9 h and the regeneration of all accessions after 6 h was >80%. Regeneration following 6 h desiccation and LN was significantly greater for melatonin-treated shoot tips compared to non-treated ones. CONCLUSION: The results indicate that melatonin significantly increased regeneration from 15% to 35%.

Cryopreservation of shoot tips and cotyledons of the north american ginseng (Panax quinquefolius l.).

North American ginseng (NAG) (Panax quinqueolius L.) is a medicinal plant in high demand due to its health benefits. Cryopreservation is a good alternative for long-term conservation of NAG germplasm. Pretreatments of shoot tips (0.8-1 mm) and cotyledons (1-2 mm) on sucrose and abscisic acid (ABA) enriched medium were tested to determine the effects on regrowth following cryopreservation in liquid nitrogen. The maximum regrowth (60 percent) following PVS2 vitrification occurred with shoot tips after three weeks of cold acclimation and pretreatment on sucrose (0.3 M) or a combination of ABA (0.1 M) and sucrose in the third week. Cotyledon recovery was best with the combination pretreatment. Shoot tips showed normal development and cotyledons produced embryogenic callus after the cryopreservation process. This is the first report on cryopreservation of shoot tips and cotyledons of Panax species. This cryopreservation protocol provides a safe long-term storage method for important NAG selections and makes it possible to use cryopreservation for improving the security of NAG germplasm.