Spermidine Treatments Improve Germination of Long-Term Stored Seeds: A Case Study of Populus alba Clone ‘Villafranca’

Populus alba clone ‘Villafranca’ (white poplar), highly suitable for biomass production and ecosystem restoration, is a model system for molecular and physiological studies, but no reports are available concerning seed quality. Although clonal propagation is the preferred approach for commercial purposes, attention should be given to face genetic variability losses in the existing germplasm. To address this challenge, new populations should be developed starting from seeds, overcoming the issues of low germinability and viability during storage. This study proposes to develop tailored treatments to improve the germination of long-term stored white poplar seeds. Priming and soaking protocols, based on the use of water or spermidine (Spd, 50 and 100 μM), were tested. Treatment efficacy was assessed based on germination parameters, reactive oxygen species (ROS) profiles, and the expression patterns of genes with key roles in early seed germination. Soaking with 100 μM Spd for 4 h significantly enhanced germination percentage and speed. Low ROS levels were evidenced in the Spd-treated seeds, compared to water-soaked seeds. High expression of genes involved in desiccation tolerance acquisition, polyamine biosynthesis, and antioxidant defense was observed only in dry seeds. The results are discussed in view of the potential protective role of Spd.