The lettuce collection originates from the former Institute for Horticultural Plant Breeding (IVT) where it was used as a working collection for breeding purposes, particularly as a source for resistances to downy mildew and aphids. The collection was adopted by CGN in 1985, after which the taxonomic status of the accessions was verified through analysis of seed characteristics, accession names of varieties were checked for synonyms and the passport data were complemented as much as possible (Rulkens, 1987).
Subsequent collection management focussed on improvement of collection composition in order to develop a collection representing the total genetic variation in cultivated lettuce (Lactuca sativa) and its wild relatives as wide as possible, and on assessment of accession characteristics through characterisation and evaluation trials and other research activities (Boukema et al., 1990). The collection was regularly improved by uptake of a selection of the most important cultivars released during a certain time period in The Netherlands and abroad (De Groot & Boukema, 1992; Van Treuren et al., 2008). The collection has also been extended through IPGRI funded expeditions to Egypt, collecting missions to Turkey, Russia (Daghestan), Armenia and Georgia in the framework of the German-Dutch cooperation in Plant Genetic Resources and collecting expeditions to Uzbekistan in cooperation with the Uzbekistan Research Institute of Plant Industry and the Vavilov Institute in Russia (Van Soest et al., 1998). The collection was also extended with wild Lactuca samples from colleague genebanks and botanical gardens and from collecting activities in Israel (Eenink & Roelofsen, 1977). During 2008-2011 the collection was rationalized by removing redundant germplasm and non-authentic varieties based on analysis of passport, molecular and morphological data.