**2.2.3 Silica gel dehydration and cooling of explants**

Yam explants dehydrated using the same methodology as described above for Frafra potato. Dehydrated explants were placed in cryovials, which were plunged into, and maintained in, liquid nitrogen for one hour, or cooled at 1ºC min-1 in a Nalgene cryo freezing container (Mr Frosty™), to -70°C, and maintained for at least four hours at this temperature. Rewarming was effected immediately on retrieval from the cryogen, in a water bath at 40°C for two to three minutes for all treatments.
