A team led by the University of Wisconsin–Madison in collaboration with the University of California, Davis, has deciphered the full genetic code of the carrot.
The study, published online May 9th in the journal Nature Genetics, reveals how the carrot has been touched by domestication and breeding practices, as well as influenced by environmental and geologic change.
It also fills in a family tree of carrot relatives and reveals how carrots have become so good at accumulating carotenoids, the pigment compounds that give them their characteristic colors and nutritional strength.
“The carrot has a good reputation as a crop, and we know it’s a significant source of nutrition — vitamin A, in particular,” said lead researcher Phil Simon, a horticulture professor and U.S. Department of Agriculture geneticist at the University of Wisconsin–Madison. “Now, we have the chance to dig deeper, and it’s a nice addition to the toolbox for improving the crop.”
Knowledge gained from the study could also lead to the improvement of similar crops, such as parsnips and the yellow-fleshed cassava, a staple food throughout much of Africa.
“This was an important public-private project, and the genomic information has already been made available to assist in improving carrot traits such as enhanced levels of beta-carotene, drought tolerance and disease resistance,” said co-author Allen Van Deynze, director of research at UC Davis’ Seed Biotechnology Center. “Going forward, the genome will serve as the basis for molecular breeding of the carrot.”
Domestication dates back to Central Asia
Wild carrot seeds have been found in 3,000-to-5,000-year-old archaeological sites in Germany and Switzerland.
Cultivated carrots were first documented 1,100 years ago in Central Asia. Unlike wild carrots, which are white, those first domestic carrots were purple and yellow. The canonical orange carrot appeared in Europe in the 1500s, as shown in German and Spanish art of the time.
Color genetically linked to nutrients, not flavor
The new study reveals how the orange color occurs and which genes are involved, and also shows that carrot color is not genetically connected to flavor.
It is fortuitous that colored carrots became popular, because the pigments are what make carrots nutritious, and orange carrots are the most nutritious of all.
Nantes variety used for sequencing
The research team used the Nantes carrot — a bright orange variety named for a city in France — to assemble and analyze the full genetic sequence and peer into the vegetable’s evolution.
The researchers uncovered features traced to distantly related plant species, from grapes and tomatoes to kiwi and potatoes. Carrots more recently split from lettuce, and they are in the same family as spice crops, like parsley and fennel.
Carrots advanced as dinosaurs decline
The research team traced carrot evolution as far back as the dinosaurs. Sometime between the Cretaceous and Paleogene periods — roughly around the time dinosaurs went extinct — carrots, along with other plants of the era, picked up genetic advantages that allowed them to thrive.
