CGN spinach collection

The largest part of the collection consists of accessions of cultivated spinach (Spinacia oleracea). Recently, the collection was extended with accessions of S. turkestanica and S. tetrandra. The collection has been widely used to find useful traits for cultivar improvement, in particular regarding novel resistances against spinach downy mildew.

History

The spinach collection originates from the former Institute for Horticultural Plant Breeding (IVT), where it was used as a working collection for breeding purposes, in particular as a source for resistances to spinach downy mildew. The collection was adopted by CGN in 1987.

Since 1987, the collection has been extended with cultivated material from the Netherlands and abroad. More recently, expeditions were carried out for wild S. turkestanica in Central Asia (Tajikistan and Uzbekistan) in 2008 and for wild S. tetrandra in the Trans Caucasus (Azerbaijan and Armenia) in 2011 (Van Treuren et al. 2019). These expeditions were organised in cooperation with breeding companies from the Netherlands and abroad.

Composition

Currently (August 2024), the collection comprises about 430 accessions of S. oleracea, 75 of S. turkestanica and 40 of S. tetrandra, all belonging to the primary gene pool of cultivated spinach. With respect to population type, the collection consists of about 140 cultivars, 125 landraces, 100 samples of wild/weedy populations, and 140 unspecified accessions.

The majority of accessions of cultivated spinach originate from Europe and Asia. The accessions of S. turkestanica mainly were collected during an expedition in Tajikistan and Uzbekistan in 2008, and those of S. tetrandra during an expedition in Azerbaijan and Armenia in 2011. The majority of these expedition samples have been made available for distribution. CGN is currently working on extension of the collection with a selection of modern varieties.

Maintenance

To ensure sufficient seed viability, the germination ability of spinach accessions is monitored at regular intervals (Van Treuren et al., 2013). Threshold values for regeneration are 80% germination for cultivated material and 60% for accessions of wild species. Accessions are also regenerated when the remaining seed weight has dropped below 29 grams.

As cultivated spinach and its wild relatives S. turkestanica and S. tetrandra are dioecious species that are wind-pollinated, accessions are regenerated in isolation under controlled greenhouse conditions or in outdoor regenerations tunnels. In general, at least 80 plants are used for the regeneration of cultivated spinach, 120 plants for regenerating accessions of wild species. Regenerations are carried out in close cooperation with 9 breeding companies affiliated to the Dutch association for the plant reproduction material sector (Plantum NL).

Phenotypic data

A large part of the spinach collection has been screened for a variety of morphological characters by means of field trials, during which also the identity of the accessions is checked with the help of crop experts.

The collection has also been used for the screening of quality traits, including nitrate content and resistance to diseases, such as Albugo occidentalis (spinach white rust), Fusarium oxysporum and Peronospora farinosa (spinach downy mildew). Phenotypic data are integrated in the on-line search and request facility of CGN and are made available in downloadable files via CGN’s website.

The majority of data on quality traits are collected in close cooperation with 9 breeding companies affiliated to the Dutch association for the plant reproduction material sector (Plantum NL). Main focus of this collaborative screening program includes resistance against spinach downy mildew, which has so far resulted in over 12,000 observations. Data on Peronospora race Pfs1 to Pfs16 are downloadable from CGN’s website.

Utilisation

Samples of 100-200 seeds are made available to users for the purpose of food and agriculture under the terms and conditions of the standard material transfer agreement (SMTA) of the International Treaty on Plant Genetic Resources for Food and Agriculture. Plant breeding companies and research institutes are the main users of CGN’s spinach collection.

Spinach belongs to CGN’s most requested collections. Between 1988 and January 2020, CGN has distributed a total of 13,369 spinach seed samples for external use. This number corresponds to an average distribution of more than 400 seed samples per year and to approximately 26 times the current collection size. The collection has proven its value for crop improvement as novel disease resistances found in CGN accessions have formed the basis for the development of new cultivars. DNA resequencing is planned for accessions of S. turkestanica and S. tetrandra in the context of a collaborative project between CGN, WUR and several breeding companies, entitled ‘Exploitation of crop wild relatives for more sustainable and healthier spinach’.