Long Journey into Orange

AT A WOODEN TABLE under the yellow lights of the Walnut Street Greenhouse, Hugo Cuevas presses small, petal-shaped seeds into soil-filled trays with his index finger, gently covering each with dirt and sprinkling them with vermiculite, a mineral that helps keep the soil moist. The scene is typical of the meticulous work of plant breeding, the mundane hours spent toiling over tiny trays and fragile sprouts. But the white kernels Cuevas plants are anything but typical. Like the beans in the children’s fable Jack and the Beanstalk, these seeds were once cast aside, only to be found again. And they may yet have some magic in them.

Some fifteen years ago, the seeds grew cucumbers, oblong fruits that by all appearances looked like any garden-variety pickling cucumber. But inside, the cucumbers were bright orange, a cantaloupe-hued flesh rich in beta carotene that researchers had worked for years to cultivate. They had hoped to introduce the cucumbers as a healthy alternative to standard grocery pickles. But the world wasn’t ready for an orange pickle, and so hundreds of the seeds were dropped into manila envelopes and filed away in a back room at the Walnut Street Greenhouse. During the past two years, Cuevas, a graduate student in the plant breeding and plant genetics program, has been working to refresh the seeds, many of which lost the ability to germinate while sitting on the shelf. At the same time, his advisors’ horticulture professors Philipp Simon PhD’77 and Jack Staub‚ are trying to revitalize their old idea of a healthier pickle, one capable of warding off cancer and heart disease and even aiding the fight against obesity. With the wave of nutraceuticals—–foods and beverages that are stoked with health-promoting additives and ingredients––that has flooded grocery shelves in recent years, the researchers think their pickle’s time may have finally come.

The color orange is a calling card for the antioxidant beta carotene, a natural pigment known for its ability to combat cancer and heart disease.

The tale of these seeds starts in 1986, when Simon came across an academic paper describing an unusual cucumber growing in China. The size and shape of a football, the plant yielded a bitter and ungainly fruit, but one trait piqued Simon’s interest: It was orange inside.

Having spent much of his career studying carrots, Simon knows that the color orange is a calling card for the antioxidant beta carotene. Carrots, melons and squash are especially rich in the substance, a natural pigment known for its ability to combat cancer and heart disease. In the body, beta carotene can also turn into vitamin A, an essential nutrient critical for optimal vision and immune response. In his lab, Simon has worked for more than 20 years to boost the content of such healthful pigments. He has bred a full rainbow of carrots, including orange, red, purple and yellow varieties that have elevated levels of particular compounds. Red carrots, for example, are high in lycopene, a red-hued antioxidant.

When Simon began doing this work in the 1980s, few people had heard of nutraceuticals, which in 2006 was a $20 billion industry whose sales are growing around 13 percent annually. But researchers had signs that a boom was coming. In 1992, for instance, after researchers at Johns Hopkins University announced that broccoli was an excellent source of sulforaphane, a cancer-fighting compound, sales of the green vegetable doubled and remain high to this day.

Seeing what a cancer-fighting reputation could do for something as unloved as broccoli, other food industries began exploring ways to turn their foods into agents of good health. After hearing Simon’s idea to breed a healthier cucumber, two national associations, the Pickle Seed Research Foundation and the Pickle Packers International, jumped aboard to fund the project.

When seeds arrived from China, they were planted at the university‚Äôs Walnut Street Greenhouse. The plants grew and grew, but wouldn‚Äôt flower. “I just kept pruning them back, and they just kept sending out shoots,” says Linda Crubaugh BS’81, the greenhouse manager who tended the plants. Eventually, Crubaugh learned that the Chinese plant was daylight-sensitive, meaning it needed to be exposed to a very specific day length in order to produce flowers, similar to how poinsettias only turn red during the short days around Christmas.

After nearly two years of tweaking conditions in the greenhouse, a few male flowers emerged and produced enough pollen to fertilize the female flowers of some standard varieties growing nearby. The resulting hybrid cucumbers grew and produced seeds, which were then replanted by John Navazio MS’92 PhD’94, a former organic farmer who was pursuing his doctorate in Simon’s lab. Starting in 1993, Navazio grew three cycles of cucumber crops each year, making new crosses to refine the cucumbers’ characteristics. The process was complicated by the fact that the researchers wanted essentially nothing of the Chinese cucumber except its color; American varieties were more suitable in every other measure, including disease resistance, fruit yield and the ease with which the plants flower. “We needed the beta carotene genes from the Chinese cucumber, but didn’t want any of the other Chinese genes,” says Simon.