CGN onion and leek collection

The collection was expanded with material collected in a multicrop expedition in Pakistan (Hasmi et al. 1981), material collected in Bulgaria, accessions from multicrop expeditions funded by IPGRI in Egypt, from collecting missions in the framework of the German-Dutch cooperation in Plant Genetic Resources to Turkey, Russia (Daghestan), Armenia, and Georgia, from a multicrop collecting expedition to Uzbekistan (Van Soest et al. 1998) and from a collecting mission to Greece in 2009 (Kik 2009), the latter collection being part of the Special Collection of CGN.

The collection was completed with missing prominent open pollinated Dutch and European varieties and with material from the working collection of the CPRO-DLO. Wild material was also introduced from botanical gardens and from other genebanks. CGN actively participates in the Allium network of the European Cooperative Programme for Crop Genetic Resources Networks. The passport data of the CGN Allium collection are included in EURISCO and GENESYS. CGN gives high priority to the Allium collection and aims to create a representative sample of the total genetic diversity in onion and leek and its wild relatives in cooperation with other European genebanks. For a recent overview on global Allium genetic resources, see the article of Keller and Kik 2018.

The collection presently includes about 440 accessions of seed propagated Alliums:

• The onion collection consists mainly of varieties from the Netherlands and Japan.
• Also landraces from Egypt, Bulgaria, Russia, Pakistan and Uzbekistan are present in the collection and a few wild relatives, among which A. roylei.
• The bunching onions are nearly all varieties from Japan.
• The leek collection consists of cultivars from the Netherlands, France and Denmark, landraces from Bulgaria, and wild relatives of the ampeloprasum complex from Greece.
• The kurrats are landraces originating from Egypt.
• The Chinese chives are landraces from Thailand and Australia.

Regeneration

Constraints in regeneration are faced in the case of short day material, in particular material from Pakistan. Also regeneration of wild material sometimes causes difficulties. It can take several years before enough seed is produced to fulfil the CGN standards. For the regeneration of an accession 60-120 plants are used. After onion bulbs have been harvested, dried and potted, they are placed in a non-heated glasshouse for overwintering. Because of problems with Fusarium attack, seedlings of leek are planted directly in pots and overwintered from November onwards in a glasshouse at 5-10°C. As soon as flowers appear, the plants are transferred to isolation rooms and pollinated by blowflies.

Characterisation and evaluation

Most of the Allium collection has been characterised for 15-20 traits, using descriptorlists developed by CGN (partly derived from UPOV and ECPGR descriptor lists). Cultivars are characterised during bulb/mature plant production for regeneration. Evaluation data on characters such as diseases are obtained in close cooperation with users of the material. Data on resistance to Peronospora destructor, Sclerotinium cepiforum, Botrytis aclada, B. squamosa, Puccinia porri and Thrips tabaci are available.