Towards better tasting and more nutritious carrots: Carotenoid and sugar content variation in carrot genetic resources

The genetic diversity present in crop species is crucial for crop improvement and consequently enables development of new, nutritious agricultural products. Seed collections held in genebanks facilitate access to this diversity and in the case of carrot (Daucus carota), they consist of material collected from across the world, permitting access to the diversity present in the whole genepool. However to date, no systematic evaluation of chemical composition has been made on this material. This study aimed to determine the available variation in carotenoid and sugar content in the roots of 118 carrot accessions in order to understand how the levels of these nutritious compounds vary across the global carrot genepool. The carotenoid and sugar content in root tissue was assessed. The total carotenoid content was related to root colour and ranged from 0 to 40 mg per 100 g fresh weight. Orange rooted European accessions were more carotenoid-rich than Asian accessions, and advanced cultivars contained on average 20% more carotenoids than older cultivated material (landraces). Sugar content varied from 5.1% to 13.6% and European and American materials contained on average 18% more total sugars than Asian accessions. Orange rooted advanced cultivars had a lower ratio of non-reducing to reducing sugars than landraces. The results obtained indicate that several accessions with elevated content of carotenoids and/or sugars exist in genebank collections. The results are of significance as they support more efficient utilisation of genebank material in breeding programmes which deliver novel cultivars with enhanced nutritional value. The occurrence of such a range of sugar and carotenoid contents supports the role of genebank collections as a source of diversity useful in the creation of novel and nutritionally improved cultivars.