Study Reveals What Makes Carrots Orange

A new study of the genetic code of more than 600 types of carrots reveals that three specific genes are required to give carrots an orange color. Surprisingly, these three required genes all need to be recessive or turned off.

Researchers from North Carolina State University (NC State) and the University of Wisconsin-Madison worked to sequence 630 carrot genomes in a continuing examination of the history and domestication of the orange carrot. Their 2016 study produced the first carrot genome and discovered the gene involved in the pigmentation of yellow carrot. In this research, the researchers performed selective sweeps, structural analyses among five different carrot groups to find areas of the genome that are heavily selected in certain groups. They found that many genes involved in flowering were under selection – mostly to delay the flowering process. Flowering causes the taproot, the edible root that we consume, to turn woody and inedible.

The study found evidence that carrots were domesticated in the 9th or 10th century in western and central Asia, where purple and yellow carrots were more common. Both were brought to Europe, but yellow carrots were more popular, likely due to their taste. Orange carrots made their appearance in western Europe in about the 15th or 16th century and may have resulted from crossing a white and yellow carrot, said Massimo Iorizzo, an associate professor of horticultural science with NC State's Plants for Human Health Institute and co-corresponding author of a paper describing the work, published in Nature Plants.

Orange carrots became more popular with farmers because of their color and sweeter flavor. Different types of orange carrots were developed in northern Europe in the 16th and 17th centuries, which matches the appearance of different shades of orange carrots in paintings from that era. Orange carrots later grew in popularity as greater understanding of alpha- and beta-carotenes, the precursor of vitamin A in the diet, progressed in the late 19th and early 20th centuries. “Carotenoids got their name because they were first isolated from carrots,” Iorizzo said.

For more details, read the article in NC State News.