Plant scientists have long played a key role in developing fruit and vegetable varieties with added health properties. Now – using traditional plant breeding techniques – this research has helped spur the latest trend: colorful varieties of vegetables that could help Americans consume more nutrients and phytochemcials, many of which are studied for their role in cancer prevention. The colorful carrot is a prime example.
Purple cauliflower and asparagus supply anthocyanin, for example, which lab studies suggest play a role in decreasing inflammation and tumor growth. Red carrots are a source of lycopene and yellow tomatoes provide lutein, phytochemicals commonly studied for prostate and eye health, respectively. But it’s the carrot that stands as the leader in the quest to provide consumers with one vegetable that offers a variety of phytochemicals and health benefits.
“There are different segments of the US population that can benefit from more lutein in their diets for macular degeneration for example, and the same goes for lycopene and some forms of cancer and anthocyanin as an antioxidant,” says Phillip Simon, PhD, a plant geneticist at the University of Wisconsin-Madison and a leading expert of carrot breeding.
These new varieties are important to Americans because the goal is to spur consumption, says Simon.
In the US, only 13 percent and 9 percent of Americans are meeting the recommendations for fruit and vegetable intake respectively, and USDA data indicates consumers limit intake to a few sources, with orange juice and potatoes dominating the pack. Eating high amounts of a variety of fruits, vegetables and other plant foods links to lower risk of cancer, along with other chronic diseases.
“To be honest, the first reason that people buy something in the store is visual appearance … so there is both a nutritional aspect as well as an eye-catching aspect to it.” Simon recognizes that carrots will not be the only source of these pigments, “but if we can add a little bit to it, all the better.”
When it comes to carrots, these colorful varieties are not actually new at all. According to the USDA, the first carrots were purple and yellow dating back to 900-1000 AD in Afghanistan and the eastern Mediterranean region. These varieties made their way to Europe and China in the 1300s, and white carrots were reported in Europe in the 1700s. The familiar orange carrots seen today are thought to derive from gradual selection among yellow carrots and were first cultivated in the Netherlands around this same time. Orange carrots, high in carotenoids, came to dominate the market worldwide.
Today, the yellow and purple wild carrots still exist in Asia and the Middle East, and red carrots are found in Japan. Simon introduced the purple carrot in the early 1990s after spending years crossbreeding anthocyanin-containing purple wild carrots from Turkey with the familiar orange carrots.
Farmers have crossbred plants for centuries. It is the same process that Gregor Mendel used in his famous pea plant experiments of the mid-1800s.
For carrots, the first step is to induce flowering. Simon cuts off most of the stem, the top of the two carrot varieties he wants to crossbreed, leaving some of the green stem on each. Carrots flower after being exposed to cold, so he then places them in the refrigerator for six weeks before replanting.
In the case of purple carrots, Simon plants a wild purple carrot next to an orange carrot, covers them with a mesh cage, and then adds flies to naturally pollinate the plants.
A few months later, he collects the new seeds and plants them. The carrots that grow contain DNA of both carrot varieties.
Although many of these first generation carrots are purple, they may lack the flavor, shape or growth potential desired by farmers and consumers. “It’s a matter of continuing to intercross and then over the years looking for combinations that have things that we’re looking for, be it resistance to disease or resistance to heat or long root shapes or big tops or flavor,” says Simon.
Simon – and his colleagues – then make sure each new carrot variety passes their taste test. When they get one that has everything they’re looking for, he then gives some seeds to the seed producers he knows to try growing it.
This process can take anywhere from 6 to more than 10 years.
Plant scientists even used these methods to develop the familiar orange carrots on the market. Modern day orange carrots have 50 percent more carotenoids than carrots 30 years ago. They also are more flavorful and disease resistant.
Before crossing two carrots together, Simon sequences the carrot’s genome, looking for genes that confer disease resistance or other desired properties. This he says has helped to streamline the process and cut down on the time it takes to create the ideal carrot.
“What we’re doing is the same thing that plant breeders and general vegetable growers have been doing forever. It’s really nothing new, we’re just putting a new spin on it.”
Simon has no shortage of ideas for optimizing the carrot. His team is continuing to strive to improve flavor and color, disease resistance, ability to grow in warmer drier climates, and other new variations that might appeal to growers and consumers. Most of his carrot projects are planned, but he states that serendipity plays a role as well. “Sometimes, I'll get sidetracked with an unusual purple or red carrot that is only four inches long and shaped like a sphere, and then I'll get an idea: maybe this is something the market might be looking for.”
Who wouldn't like to eat a red sphere that tastes like a carrot? Stay tuned.
Published on August 5, 2015