Why carrots are orange
Orange-coloured carrots are a relatively new variety. It has now been discovered why they turned orange - and why they are so healthy.
People were probably already eating carrots in ancient times; from the 10th century onwards, red-violet and yellow-coloured varieties were cultivated in what is now Iran. And from the 15th or 16th century, the orange-coloured variety finally emerged in Europe, which ultimately became widespread (although yellow and purple carrots are making a comeback). A team led by Kevin Coe from North Carolina State University in Kannapolis has now discovered which genes are responsible for the popular orange-coloured variant - and why this makes carrots vitamin bombs, as they write in "Nature Plants".
The team analysed 630 different carrot varieties and sequenced their genomes. Three specific genes are responsible for selection for the orange-coloured phenotype and also ensure a high content of alpha- and beta-carotene, which belong to the carotenoid class of substances and are converted into vitamin A in the human body. This in turn is essential for eye health, our immune system and other processes in the body: a deficiency can cause serious damage, including blindness.
When the genes were switched off, the carrots produced more pigments that cause the orange colouring, which also makes them vitamin bombs. However, if only one gene was active, the carrots remained purple, yellow or white in colour. The purple and yellow variants have higher levels of carotenoids, which the body cannot convert into vitamin A. Many orange-coloured carrots also have genetic variants that delay their flowering. This is because once flowering begins, the roots normally become woody and inedible. "It turns out that farmers have been unknowingly selecting for these favourable traits through their breeding for centuries," says Massimo Iorizzo, who was involved in the study and is also a researcher at North Carolina State University in Kannapolis.
The orange carrot's colour and sweeter taste contributed to its popularity, and farmers bred for these characteristics. In the 16th and 17th centuries, more and more varieties of orange-coloured carrots were developed in Northern Europe, which matches the various shades of such carrots in paintings from this period. The demand for this variety continued to grow from the 19th century onwards as evidence emerged of how healthy this vegetable was. As a side effect of the study, the working group also confirmed the theory that the root vegetable was first properly cultivated in western and central Asia.
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Cover image: © infrontphoto / Getty Images / iStock (detail) Carrots are one of the most popular and valuable vegetables in our part of the world. The reason for this probably lies in three genetic changes.
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