Longer season berry developed by UAEX

Fruit breeder John R. Clark shows Prime-Ark Horizon, a primocane-fruiting blackberry variety released by the Division of Agriculture in 2020.

CLARKSVILLE — Blackberry plants produce canes that have a lifespan of two years, said John R. Clark, Distinguished Professor of horticulture and fruit breeding for the Arkansas Agricultural Experiment Station, the research arm of the University of Arkansas System Division of Agriculture. Most blackberries flower and fruit on the second-year canes, known as floricanes. Primocane fruiting blackberries flower and bear fruit in spring or early summer on those floricanes.

This new blackberry, the Prime-Ark Horizon had harvestable berries about June 12 at the Division of Agriculture’s Fruit Research Station near Clarksville. Then they flower and fruit on the first-year canes, or primocanes, later in the summer. For Prime-Ark Horizon, the first harvest on primocanes begins about Aug. 4 and extends to as late as mid-October, which offers an extended fruiting season and high yield potential.

“That’s a fruiting period of over 60 days, which is longer than any other primocane-fruiting variety from our breeding program,” Clark said. “Prime-Ark Horizon just fruits longer, and that makes for a nice extended picking season for Arkansas growers.”

Prime-Ark Horizon is a thorny variety and the sixth primocane-fruiting blackberry from the experiment station’s fruit breeding program. Experiment Station fruit breeders have released 21 public blackberry varieties since James N. Moore began the program in 1964. Clark said Prime-Ark Horizon makes an excellent complement to Prime-Ark 45, which has similar postharvest potential and ripens about six days earlier.

Prime-Ark Horizon’s floricane berry crop has high yield potential, exceeding 30,000 pounds per acre in some years, Clark said. He advises pruning to control the harvest and to balance the yield between floricanes and primocanes. A very large floricane crop can also lead to smaller leaf size and upward leaf curling on floricanes, which can hurt plant health, he said. The primocane yields at the Fruit Research Station ranged from 3,000 to 9,000 pounds per acre.

Berries average 7.8 grams overall, Clark said, and floricane berries can get as big as 10 grams.Primocane berries average 7.3 grams. Prime-Ark Horizon berries have good flavor with light aromatics, though they can be tart, especially when floricane yields are high.

Post-harvest storage for seven days has been comparable to Prime Ark 45 for reversion, a postharvest disorder in which black drupelets revert from fully black to a reddish color, Clark said.

The berries retain excellent firmness. Leakage and decay are minimal, measuring among the best in the Arkansas program. Prime-Ark Horizon plants have shown good health, except when floricane yields were excessive. Clark said he observed no orange rust or anthracnose on the plants, and they showed very little winter damage in temperatures down to 1 degree Fahrenheit.

Clark said he and breeding colleague Margaret Worthington, assistant professor of horticulture, have more exciting primocane and floricane blackberries in the pipeline as they continue to develop improved varieties. To learn more about the Arkansas Agricultural Experiment Station fruit breeding program, visit the program’s website: https://aaes.uark.edu/fruit-breeding. Prime-Ark Horizon is available for licensing to propagators. Contact Cheryl Nimmo for licensing information at 479-575-3953 or by email at cnimmo@uark.edu.

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