Impact of osmotic dehydration on the encapsulated apices survival of two yams (Dioscorea spp.) genotypes from Benin

Abstract

Objective: Cryopreservation is one of the biotechnological methods currently used for long term conservation of plant genetic resources. It requires many steps such as a pretreatment, which involves cells dehydration in order to make them tolerant to desiccation and freezing in nitrogen liquid using high sucrose concentration. The present study aims to establish a protocol for long term conservation of yam germplasm in Benin using encapsulation/dehydration technique. Methodology and Results: The effects of different sucrose concentrations and immersion durations on encapsulated apices of two yams genotypes (Da93G1 from Dioscorea alata and Dcr164 from complex Dioscorea cayenensis/ D. rotundata) were tested. The apices were excised from six months old vitroplants on stereoscope and transferred in M1 medium (MS+2g.L-1 activated charcoal) prior to encapsulation in alginate (3%) beads with calcium chloride (1.32M). Then, the apices were exposed to osmotic dehydration with two concentrations of sucrose (0.75M and 1.25M) at two durations (24h and 40h) before their culture in M2 medium (MS + 2mg.L-1 BAP, 100?g.L-1 d’ANA and 2g.L-1 activated charcoal). Conclusion and application: The results showed that 0.75M sucrose increased high survival rate (80%) and high rate of regenerated plant (70%) at 24h of immersion duration. Furthermore, significant difference was observed between the two genotypes response. This work has allowed adopting in further experiments 0.75M sucrose and 24hours of immersion duration in pretreatment of yam apices for the development of cryopreservation techniques for yam conservation in Benin.