CGN carrot collection

History

In the early years of CGN, it was decided not to include the carrot collection from CPRO (Centre for Plant Breeding and Reproduction Research) in Wageningen, but instead to transfer it to HRI (now Warwick Genetic Resources Unit, University of Warwick) in Wellesbourne, UK. Between 1990 and 1992, approximately 530 accessions from CPRO were moved to the UK, later followed by samples collected in Uzbekistan and Kyrgyzstan in 1997 and 1999, along with several landraces of diverse origins. These 579 accessions are well maintained at Warwick-GRU and remain available for distribution.

Composition

The CGN carrot collection was established in 2011. Initially, this collection consisted of duplicate accessions of wild carrots from the US collection in Ames that were not available in Europe. Additionally, some wild carrot accessions from the Netherlands were included. The largest portion of the current collection consists of Daucus carota accessions collected in Uzbekistan and Kyrgyzstan in 2015, which became available after a five-year embargo period following their multiplication by breeding companies. Recently, CGN has also repatriated several Dutch heritage carrot cultivars, making the CGN collection a combination of both wild and cultivated material.

Regeneration

Wild carrot is typically grown as an annual, while cultivated carrot is biennial. Depending on the genotype, flowering may require vernalization.

For wild carrot, seeds are sown in trays between March and May. If germination is poor, a cold treatment of one week in a refrigerator can enhance germination. After 3–4 weeks, seedlings are transplanted into larger pots. Before flowering, plants are placed in insect-proof isolation cages in an unheated greenhouse to prevent cross-contamination between accessions. Approximately 80 plants per accession are used for regeneration, with a minimum of 40 plants.

For cultivated carrot, sowing occurs later, typically around September. Because cultivated carrot is biennial, plants overwinter before flowering in the second year. Like wild carrot, plants are transplanted to isolation cages in an unheated greenhouse before flowering. About 60 plants per accession are used, with a minimum of 40 plants.

Carrot does not have a self-incompatibility system, meaning that self-pollination is possible. However, sufficient cross-pollination within the isolated population is crucial to avoid inbreeding depression. Pollination is facilitated by flies or bumblebees, which may need to be introduced multiple times to ensure the pollination of late-flowering plants.

Seeds are harvested once the flower heads are sufficiently dried, and seed cleaning is performed using sieves and air blowing. This process applies to both wild and cultivated carrot.

Characterisation & evaluation

CGN’s carrot collection has not yet been extensively characterized or evaluated. In the future, this will be done comprehensively for the carrot collection through characterization fields.