We finally know what makes orange carrots orange

The genes that make carrots orange have finally been identified, giving biologists a better understanding of what makes them so nutritious.

The first domesticated carrots were grown in central Asia during the 10th century, and they were originally purple or yellow. Orange carrots first appeared in western Europe in the 1400s, probably as a result of crossing yellow and white carrots.

Since then, orange carrots have surged in popularity, due to their bright colour and sweetness. “By the early 1900s, there was an understanding that the juice of orange carrots was medically active,” says Massimo Iorizzo at North Carolina State University. “This all contributed to carrots’ status as an iconic healthy vegetable.”

Now, Iorizzo and his colleagues have uncovered the science behind their distinctive colour. The researchers sequenced the genomes of 630 types of carrot, then looked for gene variants associated with particular traits.

They found three specific genes where orange carrots had variants that resulted in the gene being switched off. In purple, yellow or white carrots, at least one of the three genes was turned on.

These genes regulate levels of alpha-carotene and beta-carotene – chemicals that belong to a group of pigments called carotenoids. Alpha and beta-carotene are converted to vitamin A in the human body, which is important for the health of the eyes, immune system and other parts of the body.

When these genes are switched off, carrots produce more of these pigments, which generate their signature orange hue as well as making them a particularly rich source of vitamin A, says Iorizzo. Other carrots have higher levels of different carotenoid pigments that aren’t converted into vitamin A.

Many orange carrots also had gene variants that delay flowering, which usually makes them tougher and inedible. “It turns out farmers have been unknowingly selecting these beneficial traits for centuries,” says Iorizzo.

He and his team hope that a more comprehensive understanding of carrot genetics can help to breed even better carrots in the future.

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