Cryopreservation of Citrus aurantifolia seeds and embryonic axes using a desiccation protocol

The desiccation and freezing tolerance of seeds, with and without testas, and embryonic axes of Citrus aurantifolia were investigated. Seeds were desiccated with silica gel, under the laminar air flow cabinet or by placing them on a laboratory bench. Whatever the desiccation method employed, survival before and after cryopreservation was higher for seeds without testas. When freezing intact seeds, the highest survival percentage (41.3 %) was achieved after desiccation to 7.3 % moisture content (fresh weight basis) on the laboratory bench. Survival of seeds cryopreserved without testas could reach up to 85 % after desiccation under the laminar air flow cabinet or on the laboratory bench, corresponding to moisture contents of 7.1 and 4.5 %, respectively. After desiccation with silica gel, survival reached a maximum of 60.0 %, for a seed moisture content of 3.3 %. Survival of control embryonic axes was high (80-100 %) whatever the sucrose concentration in the preculture medium and the duration of the desiccation period. After cryopreservation, no survival was noted with embryonic axes, which had not been precultured nor desiccated. Survival of non-desiccated embryonic axes after cryopreservation increased progressively in line with increasing sucrose concentrations in the preculture medium, from 7.5 % with 0.1 M sucrose to 77.5 % with 0.7 M sucrose. Survival of desiccated and cryopreserved embryos was always high, whatever the preculture treatment and desiccation period, ranging from 55.8 % to 92.5 %.