title: RAD-seq of a controlled cross between a Populus alba father and a Populas alba x Populus tremula F1 mother.
design: DNA was extracted from 15-20 mg of silica-dried leaf material with the Qiagen DNeasy Plant Mini Kit (Valencia, CA). The concentration of DNA was measured with a Qubit 2.0 Fluorometer using the dsDNA HS assay kit (Invitrogen), and its integrity verified with electrophoresis on 1.5% agarose gels (1X TBE). Concentrations were standardized to 20 ng/l and individual samples were submitted for library preparation and Restriction site Associated DNA sequencing (RAD-seq) to Floragenex (Eugene, OR). A single library containing all samples (including two and three replicate extractions of J1 and BET, respectively) was prepared according to Floragenex standard commercial protocol: genomic DNA was digested with the restriction endonuclease PstI (chosen according to previous studies on these species - Stlting et al. 2013; Christe et al. 2016) and RAD libraries were prepared with a method similar to the one described in Baird et al. (2008). This protocol included 18 PCR cycles, after which DNA fragments ranging from 300 to 500 bp were retained. The library was sequenced on a single lane on an Illumina HiSeq2500 instrument.