Researchers at the University of New Hampshire have found certain varieties of seedless table grapes that they believe may perform well in the Northeastern U.S. 

The research project funded by the New Hampshire Agricultural Experiment Station is intended to benefit regional growers interested in growing table grapes for local markets.

The new research was conducted by experiment station researcher Becky Sideman, extension professor of sustainable horticulture production, and George Hamilton, extension field specialist at the Woodman Horticultural Research Farm.

The project aims to determine which varieties of seedless table grapes are best suited to New Hampshire production, along with the best growing systems.

The results are particularly relevant to growers in New Hampshire and Northern New England in USDA hardiness zone 5B and warmer, according to the experiment station.

The area corresponds approximately to the southern half of New Hampshire and much of the rest of New England - a region which includes the states of Maine, Vermont, New Hampshire, Massachusetts, Connecticut and Rhode Island.

“Seedless table grapes are typically grown in much warmer climates, although several newer varieties released since the 1970s promise increased winter hardiness," Sideman said.

"George Hamilton collaborated with vineyard owner John Lastowka in Merrimack to conduct a preliminary trial, and the best varieties in their experiment were selected for the UNH research vineyard." 

Researchers are evaluating eight varieties that were planted in a vineyard at Woodman Farm in May 2015: Canadice, Concord Seedless, Lakemont, Marquis, Mars, Reliance, Thomcord, and Vanessa. Now in their third year, all varieties are producing fruit.

Most varieties have had 100 percent winter survival and have shown good vigor during summer, according to a release.

However, three varieties - Thomcord, Lakemont, and Marquis - have experienced some winter mortality and poor vigor. The highest mortality and lowest vigor was observed for Thomcord, while Lakemont and Marquis had intermediate mortality and vigor.

Researchers have been taking note of how the different varieties respond to common grape diseases, such as anthracnose, downy mildew, and powdery mildew.

In 2016, all of these diseases were present in the vineyard. Some of the varieties, such as Canadice and Concord Seedless, remained relatively symptom-free in the face of all three diseases, whereas other varieties appeared to be especially susceptible to certain diseases.

For example, Lakemont and Thomcord were particularly susceptible to downy mildew, and Marquis was highly susceptible to both downy and powdery mildew as well as to anthracnose.

This material is based upon work supported by the NH Agricultural Experiment Station, through joint funding of the National Institute of Food and Agriculture, U.S. Department of Agriculture, and the state of New Hampshire.

Photos: Courtesy of the University of New Hampshire

www.freshfruitportal.com