Meet Your Carrot

May 11, 2016 | Erica Tennenhouse

A rainbow of carrot varieties. Orange, white, purple, yellow, red.

Genome reveals why carrots are orange, and more!

A team of scientists has just sequenced the carrot genome, gaining insight into the vegetable’s evolutionary origin, its nutrition, and its vibrant orange color. Their findings were published in the journal Nature Genetics.

Carrot evolutionary history appears to be full of tasty surprises. By comparing genetic sequences of carrots to different plants, the researchers determined that carrots diverged from potatoes and tomatoes around 90.5 million years ago, and more recently split with lettuce around 72 million years ago.

The researchers found that some time between the Cretaceous and Paleogene periods — right around the time the dinosaurs went extinct — the carrot genome exploded, doubling the amount of DNA. This event might have provided genetic advantages that allowed carrots to thrive.

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Next, the researchers uncovered the roots of domestication by comparing genetic sequences from the common carrot and 35 other carrot varieties with those of their wild ancestors. The first cultivated carrots were traced to the Middle East and Central Asia, around 1,100 years ago. At that time, domesticated carrots were mainly yellow and purple.

One of the study’s biggest finds was a gene that controls levels of carotenoids — the pigments that make carrots orange. Not only are carotenoids associated with color, but also with nutrition. "Its plentiful carotenoids make carrot an important source of provitamin A in the human diet," the authors wrote.

Over the last 40 years, enhanced breeding has led to more intense orange hues and more nutritious crops. Carrots today contain 50 percent more carotene than they did in 1970.

But the researchers point out that Vitamin A deficiency remains a global health issue. With new knowledge of the genetic mechanism controlling the accumulation of carotenoids, it may be possible to insert the gene into other staple root vegetables such as cassava, which is widely grown in Africa.

The treasure trove of genetic secrets unveiled in this study will also help researchers find genes involved in the carrot’s ability to resist pests and respond to environmental stressors such as drought.

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