Optimal seed water content and storage temperature for preservation of Populus nigra L. germplasm

Context Black poplar (Populus nigra L.) is an alluvial forest tree species whose genetic pool is decreasing in Europe. Poplar trees produce short-lived seeds that do not store well. Aim The feasibility of seed storage in conventional and cryogenic conditions after their desiccation from water content (WC) of 0.15 to 0.07 g H2O g−1 dry mass (g g−1) was investigated. Methods Seed germinability was evaluated (seeds with a radicle and green cotyledons were counted) after storage of seeds for a period of 3 to 24 months at different temperatures: 20°, 10°, 3°, −3°, −10°, −20° or −196°C. Results Seeds desiccated to a 0.07 g g−1 WC can be stored successfully at −10 °C and −20 °C for at least 2 years. A significant decrease in germination was observed only after 12 months of seed storage (WC 0.15 g g−1) at temperatures above 0 °C. We demonstrated that both fresh (0.15 g g−1 WC) and desiccated (0.07 g g−1 WC) seeds can be preserved at −196 °C for at least 2 years. Conclusions Seed storage temperature and time of storage were statistically significant factors affecting seed storability. The presented data provide a foundation for the successful gene banking of P. nigra seeds.