research update Cranberry ‘off-types’ common

Rutgers geneticist determines through DNA that current varieties aren’t producing fruit as well as the originals. By Judie Steeves

R esearch using DNA

fingerprinting has revealed that many B.C. fields of cranberries contain barely a vestige of the original variety of berry planted, as off-types have taken over the plots.

Geneticist Nick Vorsa, director of the Philip E. Marucci Centre for Blueberry and Cranberry Research and Extension Centre at Rutgers University’s agricultural experimental station in New Jersey, says the fingerprinting he developed shows that many of the cranberries he tested were mixtures of varieties the grower hadn’t planted. Those varieties were producing more plant material than fruit, so, without realizing the meaning of vegetative production in lieu of fruit, growers would use those stems to start new fields, until none of the original variety

Nick Vorsa

remained. Instead of certified plant material sold through nurseries, cranberry growers sell

vines themselves to other growers, which helps to perpetrate the loss of named varieties.

Since production of fruit is actually a stress on the plant, varieties not producing a lot of fruit tend to put their energy into muscling out varieties that are good fruit-producers, he explains. They then continue to produce more plant material but not as much fruit.

“It’s a pretty serious problem in Washington, Oregon and B.C.,” Vorsa notes.


Test plots planted at th B.C. Cranberry Research and Demonstration Farm in Delta.

He did a study of one grower who was frustrated because in five years the 30-40 acres he’d planted to a particular variety were not doing well at all.

Instead of suggesting he change his management of the plot, Vorsa first decided to ensure it was the variety he had planted. Instead, when he concluded DNA fingerprinting of the plants, he found that 90 per cent of the planting was off-types.

The problem is not just in B.C., but throughout the industry in Canada and the U.S., he says.

Some beds of Stevens are fairly pure, 18 British Columbia Berry Grower • Summer 2017

Vorsa explains, and producing 40,000 pounds of fruit per acre, which is a good yield, even though new varieties are much heavier producers. When a new bed is planted, he says if it is managed to produce fruit right away, off-types may overwhelm the Stevens which were planted there. One issue is fruit drop while the bed is getting established, before the first harvest. Those fruit won’t grow the same variety when the seed sprouts, so right away the bed can become contaminated with what are essentially weeds: cranberry plants that are not the original variety.

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