The majority of the lettuce collection has been morphologically and molecularly characterized, while the accessions are also well photo-documented. Accessions of cultivated material are described for over 20 morphological features, including seed traits and plant characteristics recorded during field trials that are also used for identity verification with the help of crop experts. Accessions of wild species are described for nine morphological characters during greenhouse regeneration.
All characterization data are made available on-line and in downloadable files. Within the framework of the European Union project ‘Molecular markers for genebanks’, CGN’s entire lettuce collection, which at the time of tissue sampling in 1997 consisted of 2323 accessions, was characterized with microsatellites and AFLPs (Van Hintum 2003; Jansen et al. 2006). The obtained molecular data have been used for various purposes, including studies on core collection strategies (Jansen and Van Hintum 2007), acquisition protocol improvement for modern varieties (Van Treuren et al. 2008), molecular biogeography of L. serriola (Van de Wiel et al. 2010), collection redundancy reduction (Van Treuren et al. 2010) and cultivar authenticity (Van de Wouw et al. 2011). In addition to microsatellites and AFLPs, molecular data were also generated with SSAP, SRAP, TRAP and NBS-DP markers for a selected set of 80 accessions in order to compare the ability of the marker technologies to describe genetic diversity in the collection (Van Treuren and Van Hintum 2009). More recently, plants from 150 accessions were described for over 2,000 secondary metabolites (Van Treuren et al. 2018). DNA resequencing data are currently being generated for the entire collection in cooperation with BGI (Shenzhen, China).