May 20, 2016

Breeder focuses on developing resistant varieties

Rutgers University cranberry plant breeder Nick Vorsa is striving to complete research started by his predecessors nearly 140 years ago.

When the university’s New Jersey Agricultural Experiment Station was founded in 1880, the station’s own fruit publication addressed the need for a cure for cranberry fruit rot, which was then – and still is – a major plant disease for cranberry growers.

“One could say that we haven’t done anything since that publication came out in 1880. And maybe it’s an impossible dream. But we’re trying,” Vorsa told Wisconsin cranberry growers at a recent meeting in Warrens.

For the past 30 years, Vorsa has been breeding new blueberry and cranberry varieties at Rutgers University, and since 1991 he’s been the director of the Marucci Blueberry and Cranberry Research and Extension Center in Chatsworth, New Jersey.

Focusing on improved yield, fruit quality and genetic diversity of cranberries, Vorsa and his colleagues have evaluated more than 20,000 plant progenies. They released their first new cranberry variety – Crimson Queen – in 2007, followed by Demoranville and Mullica Queen in 2008, Scarlet Knight in 2012, and Haines and Welker in 2015.

Now with the aid of DNA fingerprinting, Vorsa is turning his attention to breeding a cranberry variety with resistance to fruit rot. Vorsa received a USDA grant in collaboration with USDA-ARS scientists Juan Zalapa, University of Wisconsin-Madison, and Jim Polashock, Rutgers, to develop a high- resolution genetic map for cranberries.

The process includes the mapping of locations on the cranberry genome associated with fruit rot resistance and other economically important traits that will allow for marker-assisted selection to facilitate development of improved cranberry varieties.

“We can use these genetic markers to make predictable crosses, getting all the best possible genes for higher yields, fruit rot resistance and other traits into one plant. Or at least that’s the goal,” Vorsa said.

When Vorsa began breeding cranberries in 1985, he was given access to the USDA germplasm maintained at the agency’s facility in Chatsworth, which included the most common varieties in the industry such as Stevens, Early Black, Crowley, Howes, Ben Lear, Pilgrim, Lemunyon, Searles, McFarlin and Franklin.

In an effort to expand on the USDA germplasm and broaden the gene pool as much as possible, Vorsa traveled across the United States and Canada collecting cranberry germplasm from both cultivated beds and wild cranberry stands.

Two varieties to date – Budd’s Blues from New Jersey and US89-3 from Washington – appear to be highly resistant to cranberry fruit rot, while Cumberland from Nova Scotia and Holliston from Massachusetts are moderately resistant. The four varieties are unrelated, offering the possibility of greater genetic diversity. With the aid of genetic mapping, Vorsa’s goal is to combine the genes for fruit rot resistance from all four varieties into one new variety.

Of the more than 50 crosses made to date, Vorsa said 10 progeny are showing great promise for resistance to cranberry fruit rot. The majority of those have Budd’s Blues as a parent.

“One could say (Budd’s Blues) doesn’t have any rot because there’s no fruit. It’s very low yielding, so that is an issue. But the fruit is good,” Vorsa said.

The first crosses were made in 2005 and the progeny have gone through one selection cycle. More progeny will be planted this year.

Vorsa also discussed his two latest cranberry variety releases: Haines and Welker.

Haines is the result of a 1999 cross between Crimson Queen and No. 35, an unpatented variety from a Howes and Searles cross made in the 1940s. Haines was initially selected for its very high yield potential, mid-season ripening, large round berry and uniform fruit color. Haines also has exhibited less fruit rot than Stevens, a widely grown cranberry variety released in 1940s.

The new variety also shows promise for use in the production of sweetened dried cranberries. Processors of sweetened dried cranberries – or SDCs – prefer fruit that is uniformly colored throughout the vine canopy when harvested.

“SDCs have sort of thrown a curveball into the (cranberry) breeding program. Everything selected before the introduction of SDCs was for the juice market, and it didn’t matter if you had some white berries in with the red ones as long as the end point color was sufficient for making juice. As I understand it with SDCs, each individual berry has to be perfect, so that throws a whole different dimension into the selection process,” Vorsa said.

Makers of SDCs have also told Vorsa that a uniformly round fruit and firmness are other important characteristics.

The Haines variety is named in honor of the late William “Bill” Haines Sr., a lifelong New Jersey blueberry and cranberry grower who passed away in 2007. The earliest Rutgers cranberry crosses were maintained at his farm.

The other new cranberry variety Vorsa discussed was Welker, which was named in honor of William Welker, a former USDA weed research scientist at Rutgers University. The Welker cranberry is a cross between No. 35 and NJS98- 34, a selection from a Ben Lear and Franklin cross. Welker was originally selected from 112 progeny for its very high yield potential, precocious production, early to mid-season ripening, large size fruit and uniform fruit color.

“Depending on the region and the season, Welker blooms earlier than Mullica Queen and Stevens and is similar to HyRed and Crimson Queen. The fruit is somewhat teardrop shaped and medium to large in size. It is also one of the most precocious varieties, coming into full production two to three years after planting,” Vorsa said.

Vorsa said the early flowering period of Welker would likely require early fungicide applications for fruit rot control.

With the new cranberry varieties – those from Rutgers and other cranberry breeding programs – Vorsa said growers would likely need to adapt their management practices. He noted that fertilization recommendations for the past 30 years have been developed for Stevens and Ben Lear. With the newer varieties producing more fruit than older varieties, application rates and timing may need modification.

Vorsa said one Wisconsin cranberry grower’s Mullica Queen cranberries produced 773 barrels per acre last season.

“When you starting getting into this realm of productivity, I think there’s a couple of things that probably need some consideration, including how much nitrogen you should be applying and when you should be applying it,” he said.

Harvesting speed is another area growers need to consider with higher- yielding varieties. Vorsa advised growers to operate their harvesting equipment as slowly as possible to avoid clipping off the fruit-laden vines, which would reduce yields the following season.

“If you have uprights with 8 or 9 grams of fruit on them and then you come blasting through with your harrow, it seems to make sense that that upright isn’t going to move and you’re essentially going to clip that upright,” he said.

Vorsa said some of the new varieties – such as Mullica Queen – have a thicker stem, which may withstand injury from harvesting equipment better than others.

When planting new cranberry hybrids in an existing cranberry bed, Vorsa said it is important to make sure all the old vines have been removed during renovation. The old vegetative vines could outcompete the new fruiting vines, resulting in two varieties being present.

“If you don’t have a genetically pure bed, you’re not going to achieve your 100 percent yield potential,” he said.

— Lorry Erickson, FGN correspondent