Genetic variability to assist in the delineation of provenance regions and selection of seed stands and gene conservation units of wild service tree (Sorbus torminalis (L.) Crantz) in southern Germany

The conservation and sustainable use of forest genetic resources (FGR) in the face of the threat posed by climate change has become a challenging task for scientists and foresters. Genetic variability and diversity of FGR and forest reproductive material (FRM) will play a key role in forest adaptation under future environmental conditions. The need for protection of FGR has been widely discussed on the pan-European and national scales. However, at the national level, in some countries, the conservation and use of rare and scattered tree species FGR is overlooked or given low priority. Our study focuses on the delineation of provenance regions, selection of seed stands and gene conservation units of wild service tree in southern Germany. A total of 106 natural populations of wild service tree were screened based on demographic and phenotypic criteria. In order to represent the distribution range of wild service tree in southern Germany, 34 populations were selected for genetic analysis with eight variable microsatellite markers in Bavaria (BY) and Baden-Württemberg (BW). Results of AMOVA (analysis of molecular variance) showed that genetic variation is mainly distributed within populations (96%), while only a small amount occurred among them (FST = 0.04). The Mantel test indicated isolation by distance, and Bayesian clustering indicated the highest probability of four genetic clusters of wild service tree in southern Germany. Finally, 12 stands out of 34 were proposed as seed stands based on high-quality phenotypes and high genetic diversity (effective no. of alleles Ne ≥ 5.5). Five populations were proposed as gene conservation units, and seven forest stands were included in the list as potential future seed stands. Overall, assessment of genetic diversity should be applied in future to evaluate the level of genetic diversity of all selected seed stands. Our study thus presents a concept for delineation of provenance regions, selection of seed stands and gene conservation units based on demographic–phenotypic parameters and genetic markers.