May 15, 2019

Cranberry Man: Rutgers’ Nicholi Vorsa breeds better berries

Nicholi Vorsa’s work breeding cranberries has followed the demands of the industry through the decades.

Consumer uses have evolved from Thanksgiving dinner sauce to juice, and now sweetened-and-dried Craisins. Growers’ needs have also changed, from producing higher yields to finding a firmer berry for mechanical harvesting, and Vorsa’s extensive work toward fruit rot resistance and better tastes may bear fruit far into the future.

The director of the Marucci Center for Blueberry & Cranberry Research & Extension has worked in cranberries and blueberries since 1985, when he earned his doctorate degree at Rutgers University.

Top photo: Nicholi Vorsa has worked on cranberries and blueberries at Rutgers since 1985. Photo: John O’Boyle/Rutgers University

Filling the gene pool

One of Vorsa’s endeavors, with another post-doctoral researcher, was gathering new germplasm – wild varieties from the same family of plants of blueberries and cranberries – for research and breeding.

That work gathering fresh germplasm took him from south New Jersey to New Brunswick, eastern Minnesota, Alaska and even far-east Russia.

“There’s quite a bit of diversity in that region,” Vorsa said of far-east Russia.

Another source of breeding material was first-generation varieties developed in response to an early 1920s outbreak of false blossom, a virus-like phytoplasma that’s spread by blunt-nosed leafhoppers. Those first-generation breeds included Stevens, Pilgrim, Wilcox, Franklin, Bergman and Beckwith. Of that generation, Stevens was the most popular in part because of its larger berry size resulting in higher yields.

Better berries

Vorsa’s work has involved mapping the cranberry genome and identifying genes identified with beneficial traits such as flavonoids and fruit acid.

Rutgers cranberry varieties have been planted in more than 5,000 acres worldwide, and Vorsa’s work in the Rutgers breeding program has resulted in the release of six different varieties since 2005: Crimson Queen, Demoranville, Mullica Queen, Scarlet Knight, Welker and Haines.

Haines, which debuted in 2015, is a berry for the modern grower, with good color and a firmness of the berry that comes in handy for mechanical harvesting.

“It uniformly colors through the canopy and has extremely good yields,” Vorsa said.

Although some smaller independent growers might regard increased yields as a problem in the current saturated sales market, he said many higher-yielding varieties were developed in the 1990s and early 2000s before there was an industry problem with oversupply. And higher yields are not necessarily a bad thing, in the long term.

“I guess it depends on your philosophy,” he said. “We’re always trying to increase efficiency. It doesn’t matter if you’re producing 30,000 pounds to the acre or 60,000 pounds to the acre – your inputs are essentially the same. So, you’re using a smaller area, basically, to get a larger quantity of product, and so you’re really subjecting the environment to less insecticides, fungicides and pesticides, because you’re producing more. You’re producing more berries per square foot.”

The other market dynamic is that in recent years, Quebec has become a huge producer, approaching Wisconsin in size, while historical producers like New Jersey and Massachusetts are curtailed from further growth by wetlands restrictions.

But Vorsa said even small independent growers benefit from better cranberry breeding.

“They want to put the new varieties in, because production’s going to be a lot higher than some of the other cultivars,” Vorsa said.

Future of fruit rot

Currently, Vorsa’s research focusses heavily on developing fruit rot resistance and fruit chemistry characteristics.

Fruit rot is currently a top concern for growers, he said. It can be caused by up to 15 different fungi, although there are five usual suspects.

Some varieties in the breeding program have shown traits that give them some low-level resistance to fruit rot.

“None are immune,” Vorsa said. “Some are more susceptible than others.”

Phenotyping allows him to track which of the plants in university trials have those desired traits. The goal is to cross plants until a variety has two are more of the traits for low-level fruit-rot resistance.

“The growers really need the fruit rot resistant varieties,” Vorsa said. He feels obligated to “give the Jersey growers something they can survive with.”

Sweeter stuff

The other front is breeding a cranberry that’s sweeter, or at least less acidic, than the status quo. Cranberries remain an unpalatably sour berry in an age where “added” and “sugar” are dirty words for many American consumers, Vorsa said.

Cranberries are different than other fruit crops because of their high acidity and low sugar content. While apples have more fructose than glucose, cranberries contain less fructose than glucose. Cranberries also have about two and a half times more acid than most other fruits, including blueberries, according to Vorsa.

“In cranberry it just took a different evolutionary path,” he said.

Some work has been done finding cranberries with higher sugar content. For instance, the University of Wisconsin-Madison has a test variety called “Sweetie.”

Vorsa has also found a variety with better sugar, but his current work, funded by the USDA, is in lowering the berry acidity to get a better taste.

“That’s my fun project,” he said.

In 2004, Vorsa found two plants with less-acidic berries, and in subsequent breeding has combined their individual acid-prescribing allelles, or genes.

Breeding work on that project began in 2008 and has continued since that time.

“Genetically, we can do crossing. It’s a natural variation,” Vorsa said. “We can probably produce a cranberry plant that has a titratable acidity of about one, which is close to, like, Granny Smith apples.”

One of the problems currently is getting the plant to have enough vigor for commercial production, he said, but progress is being made. He recently spoke about his research, and a student’s doctoral thesis on the subject is on track to be published later this year.

The excitement of breeding a better cranberry motivates him to keep working.

“I’m getting a little bit long in the tooth, you know, but I might have a couple more crosses,” he said, laughing.

– Stephen Kloosterman, associate editor