Determining the effect of pretreatments on freeze resistance and survival of cryopreserved temperate fruit tree dormant buds

Authors: TANNER, JUSTIN - Colorado State University; CHEN, KATHRYN - Colorado State University; Jenderek, Maria; STEPHEN, WALLNER - Colorado State University; IONAS, MINAS - Colorado State University

Submitted to: Cryobiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/9/2021
Publication Date: 5/13/2021
Publication URL: https://handle.nal.usda.gov/10113/7374657
Citation: Tanner, J., Chen, K., Jenderek, M.M., Stephen, W., Ionas, M. 2021. Determining the effect of pretreatments on freeze resistance and survival of cryopreserved temperate fruit tree dormant buds. Cryobiology. https://doi.org/10.1016/j.cryobiol.2021.05.003.
DOI: https://doi.org/10.1016/j.cryobiol.2021.05.003

Interpretive Summary: Pretreatment of dormant buds before cryoprocessing increased their viability after liquid nitrogen exposure. Desiccation to 30% of moisture content in combination with presoaking in various sucrose concentrations had the highest positive effect on the viability of peach dormant buds. The effects of the pretreatments were quantified by differential thermal analysis (DTA). Desiccation to 30% moisture content had the greatest impact on increasing freeze resistance and cryosurvival for most fruit species tested. Gradual reduction of moisture content from 40 to 25% increased freeze resistance in peach and increased some recovery outcomes (leaf, shoot and bud swell); however, this was not correlated with equal cryorecovery outcomes as severe bud cracking was observed. The results may support development of species specific efficient cryopreservation procedures for dormant buds.

Technical Abstract: Freeze resistance is critical to successful dormant bud cryopreservation, and is affected by genotype, environmental conditions, dormancy phase and processing techniques. Pretreatment induced freeze resistance may contribute to more successful and efficient protocols for cryopreserving dormant buds. Differential thermal analysis (DTA) was used to quantify the effects of cryopreservation pretreatments on freeze resistance of dormant budwood. Low temperature exotherm profiles created by DTA could rapidly identify pretreatments that are contributing to increased freeze resistance in tree fruit species. In this study, DTA was used to help elucidate the effects of varying pretreatments (sucrose, desiccation and their combination) on peach, a model crop in tree fruit physiology that has shown little cryosurvival using the dormant bud method in the past. Post cryopreservation recovery trials using an antimicrobial forced bud development protocol evaluated the ability of selected pretreatments, that improved freeze resistance based on DTA, to improve recovery rates of dormant budwood of various deciduous tree fruit and nut species. Precryogenic exposure to sucrose solution (5.0 M, 96 hours), desiccation to 30% moisture content (MC) and their combination tested for their efficacy on improving postcryogenic viability in peach, apricot, sweet cherry, little walnut, black walnut, English walnut, apple, and pear. Among the different pretreatments tested, desiccation to 30% MC had the greatest impact on increasing freeze resistance and cryosurvival across most fruit species tested and little walnut. Gradual reduction of MC (40 to 25%) levels increased freeze resistance in peach (R2=0.95) and increased some recovery outcomes (leaf, shoot and bud swell), however, this was not correlated with equal cryorecovery outcomes as severe bud cracking was observed. Overall, our approach linking freeze resistance and preconditioning treatments could help establish efficient species-specific protocols to preserve a number of important temperate woody crops.