The cucumber collection of CGN is only composed of the cultivated Cucumis sativus and holds currently (March 2012) 937 accessions. A few accessions of the subspecies C. sativus var. hardwickii and C. sativus var. sikkimensis are present. It is one of the largest collections in Europe and comprises of 375 cultivars, 126 landraces,17 research material, 5 accessions of C. sativus var. hardwickii which is considered to be the wild form and 413 samples of unknown population type which need to be improved. A diversity study with molecular markers revealed that the landraces are genetically clustering apart from the rest of the collection. A quarter of the collection are cultivars originating in Europe of which 144 accessions are from the Netherlands. Unique landraces have been collected in Egypt, Pakistan, Kyrgyzstan and Uzbekistan.
The entire cucumber collection has been screened for Cucumber Green Mottle Mosaic Virus (CGMMV).
In the period 2001 - 2006 a total of 134 accessions were screened for resistance to powdery mildew (Sphaerotheca fuliginea), and downy mildew (Pseudoperonospora cubensis).