Composition

Currently (July 2013), the collection comprises 1127 cultivars, 183 landraces, 20 accessions of research material, 939 samples of wild species and 108 accessions of unknown population type. The accessions of cultivated lettuce cover the seven generally recognized horticultural types, i.e. butterhead, cos, crisp, cutting, latin, stalk and oilseed lettuce.

In general, accessions of cultivated lettuce mainly originate from Europe, with the exception of crisp lettuce (USA), stalk lettuce (China) and oilseed lettuce (Egypt). Accessions of wild species are predominated by samples of L. saligna, L. virosa and particularly L. serriola. Accessions of wild species mainly originate from Europe and the Near East. In 2008 the collection of cultivated lettuce was investigated for the presence of redundancies using passport, molecular and morphological data, after which nearly 200 accessions were removed (Van Treuren et al., 2010). Based on molecular data and a morphological field trial in 2010, 38 accessions of cultivated lettuce were discarded because of non-authenticity (Van de Wouw et al., 2011). In 2011, a redundancy analysis using passport and molecular data was carried out for the collection of wild species, resulting in the removal of 74 accessions. Improvement of collection composition will be continued with the periodical uptake of novel cultivars and with the organization of expeditions aimed at sampling wild species of the primary gene pool that are severely underrepresented in the collection. In 2013 a collecting expedition was carried out in the Transcaucasus.