Microsatellite Markers as a Useful Tool for Species Identification and Assessment of Genetic Diversity of the Endangered Species Populus nigra L. in the Czech Republic

The population size of black poplar (Populus nigra L.), once an important part of floodplain forests in the Czech Republic, has greatly declined due to human activity. In this study, we applied microsatellite (SSR) markers to identify species and assess genetic diversity, with the aim of supporting conservation of this endangered species. A total of 378 poplar trees were analyzed following field surveys. Five diagnostic SSR markers with species-specific alleles for P. deltoides Bartr. ex Marsh. enabled the identification of 39 interspecific hybrids, which were distinguished from native P. nigra. Thirteen SSR loci were used to evaluate genetic diversity among confirmed P. nigra individuals. The results revealed high genetic variation, with 66% of pairwise genotype comparisons differing at all loci. After excluding 45 genetically similar individuals, 292 genetically verified and polymorphic P. nigra trees were selected as potential sources of reproductive material. Genetic differentiation (Fst) was highest between P. nigra and P. deltoides (0.27), and lowest between reference Populus ×euroamericana clones and detected hybrid poplars (0.05) from natural localities. Distinct genetic structures were identified among P. nigra, P. deltoides, and hybrid individuals. These findings provide essential data for the protection, reproduction, and planting of black poplar.