High regrowth of potato crop wild relative genotypes after cryogenic storage

Evaluating shoot-tip regrowth of 25 Rubus L. species and hybrids after 15 to 20 years of cryopreserved storage

Rubus L. species are pan-global in their distribution and used as food throughout the world. Their fruits, collectively called brambles, come in a variety of colors from black, through various shades of red and yellow to white. The USDA-ARS, National Plant Germplasm System maintains >2250 accession seed- and screenhouse-based Rubus collection in Corvallis, OR and the USDA-ARS, National Laboratory for Genetic Resources Preservation in Fort Collins, CO has cryopreserved and maintains 200 accessions in liquid nitrogen (LN). We investigated regrowth of 25 selected Rubus accessions cryopreserved by droplet vitrification and stored cryogenically for 15-20 years, to determine the need for possible repropagation and reprocessing. The initial regrowth of the stored accessions after 24 h in LN ranged from 50 to 100 %. After long-term LN storage, overall regrowth was significantly lower than the initial regrowth (on the average for the 25 accessions by 8.7 %). However, except for one accession with recovery of 23 % (R. laciniatus PI 553651), the regrowth of the other 24 accessions ranged from 40 to 100 %, with 16 accessions at >73 % regrowth. High initial viability was important for recovering large numbers of living shoots after long-term storage. Extending regrowth of five accessions from six to 12 wk did not significantly increase the regrowth, suggesting that a 6-wk cultivation is sufficient for regrowth assessment. Knowledge of changes in viability over time in cryopreserved collections is vital information for curators to determine what repropagation intervals are needed for specific germplasm collections. These studies also provide large-scale information on changes that might be needed in the cryopreservation protocol for the next storage cycle.

Effect of Freezing Temperature on the Thermal, Rheological, and Gelatinization Properties of Freeze-Thaw-Dehydrated Potato Powder

To promote the application of freeze-thaw-dehydrated (FTD) potatoes and their gels, this study aimed to investigate the effects of freezing temperature on the physicochemical and gel properties of FTD potato powder and their correlation. The results revealed that, as the freezing temperature decreased, the solubility exhibited an overall downwards trend resulting from soluble solids and amylose liberation. Owing to the better cell integrity at -20 °C, the solubility was greater than that of the other treatment groups. In contrast, the trough viscosity and melting enthalpy increased, and the final viscosity, and setback first increased but then decreased. Regarding the properties of the FTD potato powder gel, the storage modulus, loss modulus, hardness, adhesiveness, chewiness, and consistency first increased but then decreased with decreasing freezing temperature. At a moderate freezing temperature (-20 °C), the solubility and stability of the FTD potato powder were well maintained, and the final viscosity, setback, and hardness reached their highest values. Correlation analysis revealed that, with decreasing freezing temperature, the amount of FTD potato powder initially increased, followed by a decrease in the final viscosity and setback. This trend was positively correlated with the hardness of the FTD potato gel (r = 0.98, r = 0.93).

Cryopreservation of human semen by inherently-controlled icing probability: Or how the surface profile of superhydrophobic carbon soot coatings and the sperm volume affect the outcome of slow freezing?

The restoration of initial functionality of human spermatozoa subjected to cryopreservation is challenging, because the deleterious intracellular icing and the occurrence of osmotic shocks due to prolonged exposure to increased concentrations of intracellular solutes are oppositely dependent on the cooling rate. This longstanding problem could be overcome if using superhydrophobic soot coatings delaying the heat transfer rate, reducing the ice formation probability and triggering balanced and timely dehydration of the cells, but the effect of their surface profile and sperm volume on the success rate of slow freezing is unclear. Here, we show for the first time that the two-factor freezing injury is entirely avoidable by tailoring the solid-to-gas voids (pores) fraction in the soot, leading to increased nucleation free energy barrier, presumable incipiency of ice crystals with controllable shape and size and hence, fully (100 %) recovered post-thaw sperm motility. It is demonstrated that the reason for such a unique scientific result is the selection of soot coatings with appropriate morphochemical features, hypothetically (not directly proven yet) inducing equilibrium among the solution composition and ice crystals formation, retarding the undesirable compression of liquid-filled "slush ice" channels surrounding the cytoplasm and impeding the ice recrystallization. The novel insights introduced in this article open endless horizon for customizing and revolutionizing the technical protocols in cryobiology.