CGN crucifers collection

The CGN collection of cruciferous crops includes 1800 accessions. The collection contains cultivars (1130), landraces (325), and research material (170). Additionally, there are wild populations (27), and for 150 accessions the population type is unknown. B. oleracea is represented with the highest number of accessions followed by B. rapa, B. napus, B. carinata and Raphanus sativus. Part of the material was collected in the Netherlands in the framework of the EU project ‘The collection of landraces of Cruciferous crops in the EC countries’ (Van der Meer et al. 1984). CGN developed the European Brassica Database: ecpgr.cgn.wur.nl/Brasedb/ (Bras-EDB) in the framework of the Brassica Working Group of the European Cooperative Programme for Crop Genetic Resources Networks (ECPGR, Maggioni et al. 1997). The ECPGR Brassica database contains passport data of most of the European Brassica collections.(Van Hintum and Boukema 1993, Boukema and Van Hintum 1998, Bas and Menting 2009). As EURISCO is now functioning as the European database of PGR, the Bras-EDB has not been updated and is not online searchable since 2019. All data are still downloadable.

CGN coordinated a European project on Brassica: "Brassica Collections for Broadening Agricultural Use" including ‘Characterising and utilising genetic variation in Brassica carinata for its exploitation as an oilseed crop’ (RESGEN CT 99 109-112). This project deals with characterisation, evaluation, regeneration and documentation of B. napus, B. oleracea, B. rapa and B. carinata. Results of this project are available via the BrasEDB website.

The Brassica oleracea collection

CGN gives high priority to the B. oleracea collection and aims to create a representative sample of the total genetic diversity in this crop in cooperation with other European genebanks in the Brassica network of the ECPGR.

Much attention has been given to rationalizing the B. oleracea collection by bulking duplicates into groups. The bulked accessions comprise selections of the same 'umbrella' varieties, which were regarded as duplicates on the basis of their historical background and morphological resemblance in the field. Crop specialists advised in this activity. This effort resulted in a considerable reduction of the collection. A genetic analysis on the basis of electrophoresis of isozymes of part of the rationalised material justified the procedure (Van Hintum et al. 1996). In a further study, using AFLP’s, while taking into consideration the changes over regenerations, it was concluded that accessions which display similar levels of differentiation may be combined safely (Van Hintum et al. 2007).

Hybrids are not included in the collection and wild species are only represented with very low numbers. The B. oleracea collection provides a good representation of the old Dutch open pollinated varieties. Danish material is also well-represented. Egyptian landraces are included in the cauliflower and white cabbage collections. The white cabbages also include material from the former Soviet Union. The Chinese kale originates mostly from Thailand and Taiwan. In the B. oleracea collection, cauliflower is represented with the highest numbers. In this crop, almost no rationalisation has taken place, because the accessions are morphologically rather distinct.

With the help of the Bras-EDB, a core collection of B. oleracea was developed (Boukema et al. 1997) for an EU project entitled ‘The location and exploitation of genes for pest and disease resistance in European genebank collections of horticultural Brassicas’ (Leckie et al. 1996). A more balanced core, including more European Brassica collections, has been developed in the EU project RESGEN CT 99 109-112.

Other crucifers

The B. rapa collection is a very diverse collection including vegetable, fodder and oilseed crops. Although most material involves varieties from Europe, including fodder turnips from Belgium, part of the vegetables originates from Asia. A large part of the B. rapa collection has been used in a study assessing the genetic diversity between the different crop types (Zhao et al. 2005, 2007).

The B. napus collection represents, besides oilseed, also fodder and swede types, and includes mainly varieties from Europe. The B. carinata and B. nigra collections represent mainly Ethiopian landraces and the B. juncea collection includes both oilseed and vegetable crops. The Raphanus collection includes mainly radish cultivars from Europe and giant radish from Asia. The fodder radish accessions originate mainly from the former Soviet Union, the Netherlands and Germany. The Sinapis alba collection is predominantly of European origin.

Collection management

Regeneration

For regeneration, 60-120 plants are used. All crucifers are regenerated in isolated plots, tunnels or in cages in glasshouse compartments. Most of the B. oleracea crops are biennial and need vernalisation. In general, the B. oleracea material is planted in the field. The vegetative mature plants are potted in autumn and placed for overwintering in a glasshouse at 5-10°C. This provides the possibility to do some negative selection against off-types. Before overwintering, the cabbages are decapitated. From early cabbages, cuttings are made from shoots after decapitation in the field and the resulting plants overwinter. Before flowers appear, the plants are transferred to cages. When 50% of the plants flower, blowflies (Dotinga et al. 1988) or bumble bees are introduced to pollinate.

Another method is 'stullenteelt' which is performed on not-mature plants, grown in pots. The plants must have at least 7 leaves before they are overwintered in a greenhouse between 5-10°C. Some accessions have a stronger vernalisation requirement and plants need to be more developed. This vernalisation method can only be used when no selection needs to take place of plants contributing to the regeneration of the accession. Dutch breeding companies assist in the regeneration work.

The field crops of the crucifer collection are regenerated in spatially isolated fields in winter rye or Triticale, in tunnels or isolation cages in the greenhouse. Characterisation and evaluation

Parts of the collection have been characterised and evaluated and data of more than 70 traits are available. Most of the B. oleracea material has been characterised for morphological traits, according to CGN descriptor lists, partly derived from UPOV and ECPGR descriptor lists (IBPGR 1990). Also part of the radish and vegetable turnip collection has been characterised. Evaluation data on characters such as disease resistance are obtained from users of the material. Parts of the collection were screened in the framework of two EU projects for resistances to different pests and diseases, glucosinolates and seed storage components. More information, results and literature from these projects can be found at the BrasEDB website .

Data on resistance in B. oleracea accessions to Fusarium oxysporum, Plasmodiophora brassicae and Thrips tabaci are also available. Phosphate and phytate contents have been assessed for more than 130 B. rapa accessions (Zhao 2007). Part of the B. napus collection was screened for resistance to Heterodera schachtii and for cadmium uptake. Part of the B. nigra collection was screened for resistance to Phoma lingam. For the B. carinata collection, the fatty acid composition was determined by Mahler and Auld (1988).