CGN spinach collection
The collection
In short- Over 500 accessions
- Mostly cultivated spinach
- Genetic diversity
CGN’s spinach collection contains over 500 accessions, representing one of the largest genetic resources collections of spinach in the world.
The collection largely consists of accessions of cultivated spinach (Spinacia oleracea). In recent years, the collection was further extended with accessions of S. turkestanicaand S. tetrandra. The collection has widely been used to find traits for cultivar improvement, in particular regarding novel resistances against spinach downy mildew (Peronospora effusa).
Composition
The spinach collection originates from the former Institute for Horticultural Plant Breeding (IVT) whose working collection was adopted by CGN in 1987. The collection was further extended with cultivated material from the Netherlands as well as abroad.
More recently, collecting expeditions were carried out for wild S. turkestanica in Tajikistan and Uzbekistan in 2008 and for wild S. tetrandra in Azerbaijan and Armenia in 2011 (Van Treurenet al., 2019). In 2023, another collecting expedition took place in Uzbekistan where even more S. turkestanica accessions were collected.
Nowadays, the collection is composed of mainly cultivated spinach (S. oleracea) as well as several accessions of S. turkestanica and S. tetrandra, all belonging to the primary gene pool of cultivated spinach. The collection equally represents cultivars, landraces and wild or weedy populations. Most cultivated spinach accessions originate from Europe and Asia. S. turkestanica is found in central Asia while S. tetrandra mainly occurs in the Caucasus.
Maintenance
Spinach accessions are regenerated in case of insufficient seed viability or nearly depleted seed stocks. Breeding companies assist with the regeneration of spinach.
Cultivated spinach and its wild relatives S. turkestanica and S. tetrandra are dioecious species that are wind-pollinated. Hence that 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 and 120 plants for regenerating accessions of wild species.
Characterization
The spinach collection has been screened for a variety of morphological characters by means of field trials. Spinach accessions are typically described using minimum descriptors developed by the ECPGR Leafy Vegetables Working Group. The minimum descriptor list of spinach consists of eight descriptors and can be found at the ECPGR Leafy Vegetables webpage.
The collection has also been used for the screening of quality traits including nitrate content and disease resistance such as Albugo occidentalis (spinach white rust), Fusarium oxysporum and Peronospora farinosa (spinach downy mildew). Most of the data on quality traits are collected in close cooperation with breeding companies affiliated with the Dutch association for the plant reproduction material sector (Plantum NL). The main focus of this collaborative screening program includes resistance against spinach downy mildew. So far, resistance data regarding Peronospora race Pfs1 to Pfs16 have been made available on CGN’s website.
Phenotypic data are integrated in the on-line search and request facility of CGN and are made available in downloadable files on CGN’s website.
Utilization
Plant breeding companies and research institutes are the main users of CGN’s spinach collection. 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 has been carried out for accessions ofS. turkestanicaandS. tetrandrain 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’.
Regeneration of spinach
Germination
No specific treatments are carried out for seeds of cultivated spinach. For the wild species S. turkestanica, the seed clusters are first broken, followed by rinsing of the seeds in running tap water for 3 days. Seeds are then sown in trays with soil, which are placed in the dark at 4°C for 3-5 days. Subsequently, the trays are placed at 15-20°C in a greenhouse for 2 weeks, or under cold/warm uncontrolled but frost-free conditions (short day). Depending on the germination result, the temperature treatments are repeated 1-2 times. For the wild speciesS. tetrandra, the seed clusters are first rinsed in 50°C water for 30 minutes, followed by cooling down in tap water for 10 minutes, sterilization in 4% chloride solution for 24 hours and 3 times rinsing in sterile water. The seed clusters are then dissected into separate seeds and incubated in 4°C water for 5 days (these steps can also be reversed). The seeds are germinated in vitro at 15°C or sown directly in soil, after which plants are raised under short day conditions.
Vernalization
No specific vernalization treatments are applied to induce flowering.
Sowing
In the beginning of January, seeds are sown in trays filled with soil. The trays are placed at ±18°C in a greenhouse. Dehydration of the trays is prevented. Excess water is also prevented to avoid damage by fungi. When the cotyledons have developed well, the seedlings are transplanted to small pots, which are placed at 10-14°C in a greenhouse. The pots are regularly watered to avoid dehydration. For wild species, the regeneration protocol starts at the end of December because of the preceding dormancy breaking treatments. Wild Spinacia species are very sensitive to day length. Too much light should be avoided during growing in order to prevent shooting during the seedling stage.
Planting
Seedlings are transplanted to pots of ±5 liter at the end of January, and kept at 14°C in the greenhouse during the winter. In the beginning of March, the plants of the different accessions are transferred to separate isolation chambers with a temperature of 10-18°C. After inflorescences have started to develop, plants are staked to prevent lodging.
Pest and disease control
Protective measures are applied when aphids (Aphis fabae, Myzus persicae) or spider mites are observed.
Harvesting
Manual seed harvesting takes place from May until mid-June. A single harvest per accession is carried out when the majority of plants have produced ripe seeds. Flower stalks with ripe seeds are collected in cotton bags, which are hung to dry in the greenhouse for a few days before the start of seed drying procedures.
Gene bank for plant resources
View the database or submit a request for genetic material.
Do you have a question?
Do you have a question about the spinach collection? Ask our curator.
LJMJ (Lynn) Vorstenbosch
DLO HBO Onderzoeker
