CGN cucumber collection

Composition

The cucumber collection of CGN is mainly composed of cultivated cucumber (Cucumis sativus) and currently holds over a thousand accessions. A few accessions of the subspecies C. sativus var. hardwickii and C. sativus var. sikkimensis are present. CGN’s cucumber collection is one of the largest collections in Europe and comprises cultivars, landraces, and research material, as well as C. sativus var. hardwickii, which is considered to be the wild form of cucumber. A diversity study with molecular markers revealed that the landraces are genetically clustering apart from the rest of the collection (Ly et al., 2012). A quarter of the collection consists of cultivars originating from Europe. Unique landraces have been collected from countries such as Egypt, Pakistan, Kyrgyzstan, and Uzbekistan.

Maintenance

Cucumber accessions are regenerated in case of insufficient seed viability or nearly depleted seed stocks. Breeding companies assist in the regeneration of cucumber. Regeneration takes place in insect-free glasshouses on a substrate system where the stems are grown along ropes. Cucumber is a cross-fertilising species, so ten plants are used for regeneration. Fourteen plants are used in the case of heterogeneous samples. During the growing season, plants are monitored by the Dutch Plant Health Service for seed-borne diseases in order to prevent seed contamination.

Characterisation

The characterisation of fruit vegetables takes place during regeneration. Until 2006, about 30 descriptors were used for each crop. Since 2006, the fruit vegetables are characterised using minimum descriptors developed by the ECPGR Working Groups. The minimum descriptor list for cucumber consists of eleven descriptors and can be found at the ECPGR Cucurbits webpage. All characterisation data are made available online and in downloadable files on CGN’s website. The collections are well photo-documented, with many pictures of (un)ripe fruits, plants, and flowers available.

In 2009, the Institute of Vegetables and Flowers of the Chinese Academy of Agricultural Sciences in Beijing, China, used 80% of the CGN cucumber collection in a diversity study with SSR markers in order to develop a core collection (Ly et al., 2012). The results of this study have been shared with CGN and were used to improve the data and composition of the collection.

Evaluation

In the period 2001-2006, over 100 accessions were screened for resistance to powdery mildew (Sphaerotheca fuliginea) and downy mildew (Pseudoperonospora cubensis). The entire cucumber collection was screened for Cucumber Green Mottle Mosaic Virus (CGMMV) in 2008.