Cryopreservation of Coffea spp. seeds: thermal, hygroscopic, oxidative stress and targeted metabolomics characterization, associated with the physiological quality

Abstract

The conservation of Coffea genetic resources remains challenging because the seeds exhibit intermediate to recalcitrant storage behavior, limiting the use of conventional conservation strategies in seed banks and increasing reliance on field collections. This study investigated the effects of seed water content, packaging type, the calorimetric properties of water in seed tissues, and targeted metabolomics on the physiological response of Coffea seeds subjected to immersion in liquid nitrogen. Seed physiological quality was evaluated by tetrazolium viability, electrical conductivity, and germination tests. Biochemical analyses included antioxidant responses, lipid composition, soluble sugars, cell wall carbohydrates, and biomass fractions. The results showed that successful cryopreservation depends on a narrow range of seed water content and is strongly affected by packaging type, which influences rewarming efficiency and tissue integrity. The absence of detectable freezable water was not sufficient to predict postcryopreservation performance, indicating that water behavior alone does not fully explain seed survival. Physiological recovery was associated with specific biochemical profiles, including soluble compounds, structural carbohydrates, lipid composition, and protein preservation. Compounds such as verbascose and galactose were consistently associated with higher viability and germination, indicating their potential as biochemical indicators of physiological quality. These findings show that cryopreservation tolerance in Coffea seeds is related to the interaction between water status, packaging conditions, and the intrinsic biochemical characteristics of the seeds.