Abstract
The poplar species Populus davidiana and P. koreana are widely grown in plantations and as biofuel resources, but little is known about ex-situ seed conservation in poplar. To identify the optimal long-term seed storage conditions for these species, we evaluated the viability of seeds with different seed water contents (SWCs) at various storage temperatures and time periods. P. davidiana seeds with <6% SWC could be stored at room temperature (RT) for 4 weeks, while P. koreana seeds showed no storability at RT. P. davidiana seeds with 3% SWC showed 74% viability after 36 months of storage at 4°C, while those with 9-18% SWC showed >89% viability after 48 months of storage at -18°C. Long-term storage at -80°C was best for P. davidiana seeds with a wide range of SWCs (3-24%), with 91-98% of normal germination after 48 months of storage. However, the normal germination of P. koreana seeds with 3-24% SWC declined to <20% after 36 months of storage, even at -18°C and -80°C. No significant difference was observed between seeds immersed vs. not immersed in liquid nitrogen for both species. Our findings increase the possibility for long-term seed conservation for both Populus species.