Provenance & quality
The array comprised 49,829 SNPs from several sources, as follows. The majority (N = 49,052) were obtained from transcriptome sequencing of four pine species: Pinus sylvestris, P. mugo, P. uncinata and P. uliginosa (Wachowiak et al., 2015). These included SNPs which were common to all species and also SNPs fixed in one species and polymorphic within and among others. The set of SNPs identified by Wachowiak et al. (2015) was filtered by the array manufacturer (Thermo Fisher) based on p-convert values signifying the SNP array quality, and a list of recommended and non-recommended SNP probes (avoiding SNPs with polymorphisms within 35 bp) was provided to the authors. A further set of SNPs (N = 578) were included from candidate genes (N = 279), which had been resequenced in previous population genetic studies of the pine species (Kujala & Savolainen, 2012; Mosca, Eckert, Di Pierro, et al., 2012; Palmé, Wright, & Savolainen, 2008; Wachowiak, Balk, & Savolainen, 2009; Wachowiak, Zaborowska, et al., 2018). Variation in mitochondrial DNA (mtDNA) was targeted using a set of SNPs (N = 14) which had been discovered by Donnelly et al. (2017). A set of SNPs putatively associated with susceptibility to Dothistroma needle blight (discovered in Pinus radiata, ENA accession numbers ERS1034542-53) were also included (N = 185).