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Growing the Next-Generation Carrot

Philipp Simon  

Philipp Simon is the research leader of the Vegetable Crops Research Unit in Madison, WI. Over the course of a 45-year career, his research has transformed the underground vegetable with lots of vitamins — and a mysterious history.

Welcome Dr. Simon to Under the Microscope

UM: What are the main topics in carrot research? What has your work focused on?

PS: I have focused on genetics and breeding approaches to improving the crop. Specifically, that includes: genetic improvement of fresh (raw) carrot flavor; nutritional value (primarily the value attributed to carotenoid and anthocyanin pigments); pest and disease resistance (root-knot nematode, Alternaria leaf blight, and cavity spot diseases); domestication and crop history; genetic mapping and sequencing the genome; development of tools to facilitate the breeding process; and, development of seed stocks to release and share with other researchers and seed companies. Beyond my field and lab research, I have also led about a dozen expeditions focusing on gathering carrot, onion, and garlic seed and bulbs in Central Asia, southern Europe, Turkey, the Middle East, and North Africa.

UM: What role do carrots play in human nutrition? How have you addressed nutrition in your work?

PS: When we eat orange carrots, the carotenoid pigments that are abundant in typical carrots provide us with vitamin A. With this fact in mind, we have been breeding carrots with more of these pigments. Our work has focused on orange carrots, but we have also developed purple, red, and yellow carrots. All of the naturally-occurring pigments have nutritional value. 

UM: What is the relationship between domesticated carrots and their wild relatives? Can we eat wild carrots?

PS: Like many crops, the domestication of carrots has a very sparse written history, but based on the DNA fingerprints, we believe that carrots were domesticated from their wild relative, commonly known as Queen Anne’s Lace. Domesticated carrot DNA fingerprints are most similar to wild carrots of Central Asia — places like Afghanistan, Uzbekistan, and Iran, so we suspect that is where carrots may have been domesticated. But since wild carrots occur throughout much of the world, along roadsides and in vacant lots, there could very well have been intercrosses between wild and cultivated carrots in many places throughout history. It’s important to understand the relationship between domesticated and wild carrots because there may be genes in wild carrots that are useful to carrot growers today — genes for characteristics like disease and stress tolerance. The flavor of wild carrots is the same as that of cultivated carrots, but much stronger. I’d stick with eating cultivated carrots.

UM: Carrots come in several colors, each of which has different nutritional properties. Why have orange carrots become the norm? Is there demand for other carrot colors?

PS: Yellow carrots and purple carrots (purple in the root cortex and yellow in the inner cortex and core) were the first reported colors of carrots in Central Asia 1,100 to 1,200 years ago. When carrots started becoming popular in Europe in the 1500s, orange carrots were first reported in written accounts there, and orange carrots started showing up in still life artwork. There is no clear answer as to why orange carrots became popular, but most of the new European varieties developed back to the 1500s were orange, and Europeans coming to the Americas brought orange carrots with them. Purple and yellow carrots continue to be popular in some other regions, and red and white carrots were also developed in Asia and Europe along the way to the carrot crop grown globally today.

With a heightened interest in heirloom vegetables, along with dietary guidelines encouraging consumption of a wide range of colorful foods, there is growing demand for a broad range of carrot colors. The organic market has been particularly interested in the wide range of colors found in carrots.

UM: What are the major challenges involved in growing carrots? How does research address them?

PS: The top biotic challenges are root-knot nematodes, which occur widely in carrot-growing soils and disfigure carrots in ways that make them unmarketable; Alternaria leaf blight, which damages leaves and consequently slows or stops plant growth; and cavity spot, which develops in stored carrots after harvest.

The top abiotic challenge is drought, since most of the U.S. carrot crop is irrigated, but heat and saline soils and water also pose threats. My research approaches these challenges from a genetics and breeding perspective, by looking for variation in genetically diverse cultivated and wild carrots to identify plants that tolerate these challenges; determining what genes may limit the damage from these challenges; and breeding those genes into new carrot breeding stocks, which we share with other researchers and seed companies. There is also a range of very good research in other projects where colleagues are developing crop production and management strategies to limit damage inflicted by these challenges too.

UM: What kinds of climates and growing conditions are best for carrots? Where are they grown now?

PS: Today, carrots are primarily grown in temperate climates globally, but also in warmer climates like those subtropical regions of Central and South Asia where carrots originated. South America, Asia, and Australia also provide good growing conditions for carrots.

UM: How might carrots be affected by climate change? What research are we doing to address these effects?

PS: Like nearly all crops, climate change is a challenge for carrot growers — partly from the increasingly warmer and drier weather, and also from the wider variation of weather extremes. We are collaborating with researchers in drier and warmer regions of the US, but also in Asia, Europe, South America, North Africa, and the Middle East, where we can establish collaborative field trials in more challenging climates.

UM: What do you view as your most significant contributions over the course of your time at ARS? What do you hope that people will take away from your work?

PS: During my career we’ve seen carrots change substantially — 40 years ago there were no baby carrots, only whole fresh carrots. The nutritional value of average carrots in the US today is ~45% more nutritious than in the 1970s. And the sequencing of the carrot genome has been a game-changer as a tool for accelerating carrot improvement.

Having said that, there continue to be almost unlimited possibilities to further improve the crop — both for the grower to reduce production inputs and increase farm value; and for the consumer to develop new carrot uses and products, nutritional value, and convenience.  Ever-changing global markets, new production and research technologies, climate change, and a growing human population will drive the need for even more research to include carrots as a part of sustaining a secure food supply in the future.