The Use of Encapsulation-Dehydration Technique for Short-Term Preservation of Endangered Sweet Potato Landraces (Ipomoea batatas Lam) from Benin

Ex situ conservation of genetic resources remains a challenge for preservation of vegetatively propagated species such as sweet potato. The objective of this study was to establish the protocol based on the encapsulation-dehydration technique for short term preservation of endangered sweet potato landraces produced in Benin. Thus, the evaporative dehydration duration on silicagel was previously determinated on the empty beads which were made using alginate sodium (3%) and calcium chloride (1.32M). Then, the young shoots of two sweet potato landraces (Ko？dokpon and Dokoui carotte) growing in the screen house were cutted aseptically and desinfected with 10% sodium hypochlorite. The apices were excised on stereoscope and were encapsulated prior their dehydration on silicagel during 5 and 6h. The encapsulated apices were finally conserved in eppendorf tubes at 2°C in batches for 15 days and 90 days. The encapsulated apices were cultured in MS medium supplemented with 0.15 mg/l BAP, 0.2 mg/l NAA, 0.08 mg/l GA3 and 80 mg/l adenine sulfate. The survival and the regeneration rates were then evaluated. At our experimentation condition, the dehydration duration which allowed around 20% water content of the beads was 6h. For the encapsulated apices, the highest survival rates (59.26% and 37.04%) and the highest regeneration rate (37.04% and 11.11%) were recorded respectivelly with the landraces ''Ko？dokpon'' and ''Dokoui carotte'' when the apices were dehydrated by 6h and stored for 15 days. The regeneration rates decreased according to the stored duration. Significant difference was noted on the regeneration of apices for the landraces tested. This method can be used to preserve the endangered sweet potato landraces and other species during at least three months without subcultures. It also reduce the cost of conservation in terms of consumables and permit better genotype stability during the storage