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 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’s Walnut Street Greenhouse. The plants grew and grew, but wouldn’t 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.
Nowadays, researchers often use laboratory techniques to monitor the success of this type of breeding project, analyzing the DNA of young plants for signs––called genetic markers––that indicate the presence of genes of interest. Using genetic markers, breeders can know soon after a plant sprouts its first leaf whether or not it will display traits that would not otherwise be observable until much later in the season. But in the early 1990s, the group didn’t know the molecular markers for beta carotene in cucumbers. In fact, they weren’t even sure how many genes were involved. So the work had to be done the old school way, which meant waiting until harvest time to collect the cucumbers, and then assessing each fruit’s size and shape before finally cutting it open to see whether or not it was orange inside.
“We used a good old, classical plant-breeding tool: What you see is what you get,” says Navazio, now a professor of agroecology at Prescott College in Prescott, Arizona.
Navazio found a group of cucumbers from one particular cross that were light orange at an immature stage, when cucumbers are harvested to make pickles. For these promising cucumbers, he did some inter-crossing to enhance the orange color while encouraging the expression of other commercially important traits, such as size, shape, texture and seed side. Then, with the best plants, he used self-pollination to avoid further genetic mixing, and thus to lock in the desirable combination of traits. Analysis revealed that these orange cucumbers had about as much beta carotene, bite for bite, as a summer squash.
This was good news, but left one critical question unanswered: What kind of pickles would these cucumbers make? They needed to exhibit the quintessential crunch of a top-notch pickle, as well as to taste and feel right in the mouth. Perhaps even more pressing was whether the cucumber’s enhanced beta carotene would withstand the pickling process.
Here the team received help from Claussen, a brand of Kraft Foods and a long-time member of Pickle Packers International. The company had previously established a relationship with the university through Jack Staub, a horticulture professor specializing in cucumbers and melons. Staub runs the campus’ brine stock evaluation program, and he had advised Navazio’s master’s work on the effects of drought on cucumbers. In fact, a Claussen representative had trained Navazio to brine cucumbers using the company’s proprietary process when Navazio was in Staub’s lab.
For this new project, Claussen kicked in most of the materials for the pickling process, sending vats of brine, bags of spices and pickling jars to the lab. Navazio prepared a batch and then gathered about a dozen colleagues, mostly from Simon’s and Staub’s labs, to crack open the inaugural jar. Not only had the pickles retained their beta carotene, but they tasted pretty good. “We tested all the sensory evaluators,” says Navazio, who concluded “these pickles were lovely to eat.”
Some of the researchers took pickles home to test them on their children, with mostly promising feedback. “Generally, kids are more willing to try stuff like this,” says Simon. “Adults have more trouble; they’re more set in their ways.”
That proved true of Claussen’s marketing specialists, who after evaluating the lab’s pickles were uneasy about their strange color. “Our marketing guys don’t like anything that looks too different. They’re afraid it’ll scare consumers away,” says Gary Mader, a procurement manager for Claussen who has followed the project over the years. Claussen also had concerns about the product’s shelf life, which the company worried would not equal that of its other products.
The researchers were not deeply dismayed by the reaction. They were confident other industry and academic labs would pick up the project and help refine the pickles. “We decided this genetic material was valuable enough to make it available to the agricultural industry,” says Navazio. The fruits of the team’s labors––literally fruit seeds––were released to the agricultural community in 1997, and the project made the front cover of the journal HortScience.
Then, nothing. A few groups requested seeds, but none initiated the serious breeding program needed to complete the project. With Navazio graduating and no funding to continue the project, the seeds sat, languishing among the hundreds of seed envelopes stored away in the Walnut Street seed library.
Fast-forward eight years. After seeing the nutraceutical boom they imagined would eventually come, Simon and Staub in 2005 secured funding for a new graduate student to jump-start the project. Beyond the potential of orange pickles to be a source of beta carotene, Simon is intrigued by another prospect. He thinks pickles might help America’s fight against obesity. Last year, he gave a talk at the Pickle Packers International’s annual meeting noting that pickles have virtually no calories. “Traditionally, a no-calorie food wouldn’t be considered a health food, but with today’s obesity epidemic, that may well change,” he told the group. “Pickles make a great snack; they help fill up the stomach without adding many calories.”
After the meeting, Gary Mader of Claussen raised the idea with the company’s marketing agents and concluded that it might be time to resurrect the old collaboration with Simon’s lab. “This is something to revisit,” Mader says. “It’s a different era. People are more conscious about eating healthy foods.”
But in plant breeding, it’s not always possible to pick up where you left off. “When you say no to a breeding effort and you don’t move ahead with it, the seeds die,” explains Staub. “You have to start all over again.” And that is what the UW team has done.
Reviving the seeds became a project for Hugo Cuevas, who arrived at UW-Madison from the University of Puerto Rico. Cuevas discovered that some of the decade-old seeds still produced plants, but they no longer generated the orange-fleshed immature cucumbers that the researchers desired. A few of the cucumbers did turn orange later in maturity, a good sign that the color trait wasn’t lost entirely. But Cuevas has had to go back to cross-breeding, essentially recreating Navazio’s work, to restore the desired characteristics.
Cuevas is optimistic that he will locate the genes responsible for making beta carotene in the hybrid cucumbers before he graduates, which would greatly speed future breeding efforts. In that sense, the eight-year hiatus has actually helped the project, as lab techniques for locating such genetic markers are far more advanced these days.
This time, the project looks to avoid a dead end. Simon and Staub have already lined up a graduate student to take over where Cuevas leaves off. The beta carotene trait should be fixed sometime within the next two years, says Simon, and then it’s just a matter of connecting with the right “renegade thinker” in the seed, food processing or restaurant industry. He imagines a restaurant chain spicing up a salad bar with orange cucumbers alongside purple lettuce and red carrots or a seed catalog selling packets to home gardeners. There is also still the possibility that Claussen or some other brand will pick up the idea and start making orange pickles for grocery-store shelves.
In the meantime, the old school breeding program continues. From four-foot-tall cucumber plants supported by poles and string, Cuevas plucks golden male flowers from one plant and then transfers their pollen to nearby female blooms. To ensure the genes from two flowers mix, he uses a twist-tie to bind them together, one enveloping the other. The process must be repeated again and again, making for a summer’s worth of long, tedious days under the hot light of the greenhouse.
But from this laborious winnowing of genes may come those magic seeds, which yield fruit capable of fighting cancer, heart disease and perhaps even obesity. And this time, there are good signs that those seeds are being planted in fertile ground.