Unveiling the Genetic Factors Behind the Orange Hue of Carrots

Recent investigations into over 600 varieties of carrots have pinpointed three recessive genes that are instrumental in rendering the vegetable its characteristic orange hue. These findings offer valuable perspectives on the domestication history of the carrot, as well as its potential nutritional advantages.

Genomic Analysis Sheds Light on Carrot Domestication and Coloration

A comprehensive genetic analysis of over 600 carrot variants has revealed that the orange coloration in carrots is determined by three specific genes, all of which must be in a recessive state. These insights could be pivotal for the further improvement of this vegetable and may also lead to augmented health benefits.

Massimo Iorizzo, an Associate Professor of Horticultural Science at North Carolina State University’s Plants for Human Health Institute and a co-author of the paper, stated that normally genes need to be activated to serve a function. However, in the case of orange carrots, the genes that control orange carotenoids—a precursor to vitamin A—must be deactivated.

Health Advantages of Orange-Colored Carrots

Particularly in the case of orange carrots, these vegetables are rich in carotenoids that can mitigate the risk of certain health conditions, such as eye diseases. In fact, orange carrots are the primary source of pro-vitamin A in the American diet.

Researchers from North Carolina State University collaborated with the University of Wisconsin-Madison to sequence the genomes of 630 carrot varieties. Their ongoing research, which builds on a 2016 study, aims to explore the history and domestication of the orange carrot and its coloration.

Genetic Selection and Domestication History

The scientists conducted structural genomic analyses across five carrot groups, discovering that several genes linked to flowering were under selection, primarily to delay the flowering process, as this makes the edible root woody and unpalatable.

“Various genes linked to the regulation of flowering were selected in multiple populations of orange carrot to adapt to differing geographic locations,” explained Iorizzo.

Furthermore, the study substantiates previous claims that the domestication of the carrot likely occurred between the 9th and 10th centuries in Western and Central Asia.

Orange carrots gained popularity in Western Europe around the 15th or 16th centuries, likely emerging from a cross between white and yellow carrots, according to Iorizzo.

Historical Trajectory of Orange Carrots

The current study essentially maps out the timeline for the domestication of carrots and the subsequent selection of the orange variant. Different shades of orange carrots appeared in Northern Europe between the 16th and 17th centuries, coinciding with artistic depictions from the same period. The vegetable gained further attention as the understanding of its rich alpha- and beta-carotene content, a precursor to vitamin A, advanced in the late 19th and early 20th centuries.

“Carotenoids were initially isolated from carrots, which is how they received their name,” Iorizzo mentioned.

Reference

The research paper, co-authored by numerous scientists and supported by the National Institute of Food and Agriculture, U.S. Department of Agriculture, is entitled “Population genomics identifies genetic signatures of carrot domestication and improvement and uncovers the origin of high carotenoid orange carrots.” It was published in Nature Plants on September 28, under the DOI: 10.1038/s41477-023-01526-6.

Abstract

This study employs an enhanced carrot reference genome and resequencing of 630 carrot samples to scrutinize the vegetable’s domestication and improvement history. The research pinpoints the Early Middle Ages and the Renaissance period as significant times in the domestication and selection of orange carrots, respectively. The investigation revealed a gradual decrease in genetic diversity accompanying this development process. Genes controlling flowering time and carotenoid accumulation were under selective pressure throughout domestication. Importantly, three recessive genes are crucial for the high alpha- and beta-carotene orange phenotype in carrots, impacting the carotenoid biosynthetic pathway, the photosynthetic system, and chloroplast biogenesis. The study provides molecular-level insights into carrot domestication and carotenoid genetics.

Frequently Asked Questions (FAQs) about Genetic Factors Behind Orange Carrots

More about Genetic Factors Behind Orange Carrots

• Nature Plants Journal
• North Carolina State University’s Plants for Human Health Institute
• University of Wisconsin-Madison Research
• National Institute of Food and Agriculture, U.S. Department of Agriculture (NIFA-USDA)
• 2016 Study on Carrot Genome Sequence
• Carotenoids and Health Benefits
• Genome Sequencing Methods
• History of Carrot Domestication