Euterpe edulis seed recalcitrance: difficult, yes, but not impossible to genebank

Euterpe edulis is a key palm species in the Atlantic Forest that is threatened by predatory exploitation, habitat reduction and slow seedling recruitment in the wild. The dire need for ex situ conservation is further limited by high sensitivity of embryos to desiccation. In vitro technologies are needed to genebank genetic resources from wild populations using cryogenic storage. We quantified the sensitivity of isolated embryos to desiccation, cryopreservation, and cryoprotectant solutions. We explored cell cryoprotection from lethal ice by balancing water and freezing stress with and without the addition of exogenous cryoprotectants. Embryos were recovered in vitro in MS medium with hormones and antioxidants to achieve normal seedling growth. Viability and germination speed index gradually decreased as embryos were progressively dried. Germination declined from 100% to 42 and 0% in embryos dried to 0.2 gH₂O/gDW, and 0.1 gH₂O/gDW, before cryo-exposure. Nearly 38% of embryos dried to 0.2 gH₂O/gDW survived cryo-exposure, but only 14% developed normal seedlings having both shoot and root development. Cryoprotectant solutions (PVS2 and PVS3) were toxic, reducing germination to about 29% without liquid nitrogen exposure. The work shows that in vitro embryo germination is a feasible approach to produce seedlings quickly and assay embryo survival after water and freezing stresses. The strategy to balance water and freezing stresses proves reliable for E. edulis embryo cryopreservation; however, higher sensitivity to desiccation and unusual water freezing patterns, compared to tissues of other recalcitrant species, explain low survival reported here.