Overcoming Hancornia speciosa seed recalcitrance: harvest season and storage time

Abstract

Storage of desiccation-tolerant seeds is one of the most effective germplasm conservation strategies; however, several species of tropical and subtropical humid forests have seeds that are sensitive to desiccation, and recalcitrant seeds, making conservation a challenge. Recalcitrant seeds deteriorate during storage due to high respiration rates and metabolic activity, and protocols employing osmoprotective solutions aim to minimize those effects to maintain seed viability for a more extended period. Hancornia speciosa, a fruit tree considered a priority for research in Brazil, is a desiccation-sensitive species. Thus, this study aimed to assess the physiological parameters of viability, vigor, and enzymatic activity of H. speciosa seeds stored in an osmoprotective solution. Germination percentage, water content, electrical conductivity, shoot, root, seedling length, peroxidase activity, and heat-resistant protein concentration were determined for seeds collected during summer and winter harvests. In addition, gene sequences were explored through gene ontology using Blast analysis to identify the biological and molecular processes associated with enzymatic action during storage. Summer-collected seeds performed better in viability and vigor and are recommended for storage in the osmoprotective solution. After being stored in the solution, seeds collected in the winter improved germination and vigor. H. speciosa seeds harvested in the summer or winter and stored in the osmoprotective solution remain viable for up to 90 days. Peroxidase and heat-resistant proteins are active; these enzymes' expression regulation should be investigated in future studies.