Perspectives Online

Rediscovered raspberry holds promise for production in North Carolina

The pretty Mandarin raspberry (left) could be making a comeback, thanks to tissue-culture propagation.
Courtesy Dr. Gina Fernandez

Some say the easiest way to find something is not to look for it. This was the case for Dr. Jim Ballington, professor of horticultural science and specialist in small fruit breeding, who serendipitously re-discovered the Mandarin raspberry, a variety that had vanished nearly 20 years before. Like unearthing an ancient family recipe or a stash of treasured old photos, finding the "lost" berry was like a homecoming for Ballington, who has headed the College's small fruit breeding research program for more than 20 years.

He recently handed over the program's reins for bramble breeding to associate professor and small fruit specialist Dr. Gina Fernandez, who is building on the strengths of Mandarin to re-propagate the variety and evaluate Mandarin hybrids developed by Ballington, as well as create new hybrids that could advance the production of raspberries in North Carolina.

Mandarin was released in 1955 by the N.C. State raspberry breeding program. The program dissolved soon after, and only a few Mandarin plants existed into the 1960s. The problem with the berry, Ballington says, is that it was susceptible to a disease that aggressively killed the young shoots. At the time, he suspects, the researchers might not have known how to manage the disease, so they chose not to promote the raspberry, allowing it to slip into "almost" nonexistence.

Until one day in the late 1980s, when Ballington received a surprising phone call.

"I found out that Mandarin still existed through Dr. Joe Brooks, former Extension small fruit specialist," Ballington says. "He told me that Ashe County Extension agent Chuck Gardner, who is now retired, still had plants of the variety."

It turns out that Gardner's sister-in-law also had a few Mandarin stragglers nearby in Wake County. Ballington contacted her, obtained the plants and immediately embarked on a mission to propagate Mandarin and also to explore possibilities for developing offspring of the variety that could be mass-produced in North Carolina.

Ballington and his team meristemmed the plant, a process by which they placed tiny shoot tips into tissue culture. Typically, plants multiply very rapidly after successful meristemming. Ballington was successful in this first attempt, and soon after, delivered a number in vitro to a nursery in the Northeast.

"Our big problem was commercial propagation," Ballington says. "Since this nursery was in the business of making money and he didn't sell around 10,000 Mandarin plants every year, he soon got rid of them."

Ballington forged ahead. Dr. Turner Sutton, N.C. State professor of plant pathology, determined that the disease problem that had plagued the original Mandarin plants in the 1960s was a type of anthracnose (Colletotrichum gloeosporoides), and simply spacing the plants a little farther apart allowed ample air movement and light through and around the plants to effectively manage the disease.

The Mandarin is a hardy, flavorful raspberry with outstanding tolerance to heat and humidity and resistance to variable temperatures during winter. This is especially significant considering that most raspberries can't survive North Carolina's scorching summers, much less our typically fickle winter season, in which the temperature can dip from 60 degrees to 30 degrees in a day. Mandarin seems perfectly suited for production in North Carolina.

But there hasn't been much awareness of the Mandarin and its characteristics, and interest in commercial propagation has been weak, Ballington says. He and Fernandez hope to change this by getting tissue culture source-propagated plants into commercial channels in the near future, since producing plants by conventional means is slow.

Building on Mandarin's strengths, Ballington also crossed it with more modern types of raspberry to produce berries with larger size, higher yield and a longer production season. Fernandez, who is continuing these efforts, says, "Working with Mandarin has opened the door to a number of exciting possibilities."

- Suzanne Stanard