Assessing different storage temperatures and protocols for preserving seeds and nodal explants of the African leafy vegetable, Amaranthus dubius

• Amaranthus dubius seeds were stored for 4 years without decreasing germinability. • Cooling at a controlled rate optimally maintained seed viability post-cryostorage. • Controlled-rate cooling promoted post-cryostorage retrieval and propagation of nodal explants. • Nodes maintained genetic fidelity of a stress-responsive marker post-cryostorage. This study investigated the response of seeds and nodal explants of the highly nutritious African leafy vegetable (ALV), Amaranthus dubius , to multiple cryopreservation protocols (controlled-rate cooling, liquid nitrogen (LN) immersion, and LN slurry (semi-solid mix of liquid and frozen nitrogen) immersion) and storage temperatures (24 (room temperature), 4 (fridge), -20 (freezer), -80 (ultrafreezer), -148 (LN vapour) and -196 °C (LN)). This study revealed that A. dubius seeds can be stored for 4 years at -20 and -80 °C without significantly decreasing germination capacity (86 and 88 %, respectively) compared to the non-stored control (92%). Cooling seeds at a controlled rate was found to be optimal in maintaining seed viability, irrespective of storage temperature. Controlled-rate cooling was also optimal for nodal explants across storage temperatures (-20, -80, -148, and -196 °C), which, when multiplied in vitro , yielded 3.6 ± 0.6 shoots per explant with an 80 % shoot development rate. To assess the effect of these treatments on genetic fidelity, a previously identified salinity tolerant A. dubius genotype, expressing a Na + /H + exchanger (NHX1) gene, was stored, and the relative expression of the NHX1 transcript was quantified in root tissues post-acclimatisation. Nodes that were cooled at a controlled rate, in LN slurry, or in LN, maintained genetic fidelity better than those of the control, based on the relative expression of the NHX1 marker gene.