New England Researchers Study Viability of Seedless Table Grapes Varieties

New England Researchers Study Viability of Seedless Table Grapes Varieties

University of New Hampshire (UNH) researchers have found certain varieties of seedless table grapes do better growing in Southern New Hampshire and New England than others. 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.

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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, a facility of the New Hampshire Agricultural Experiment Station.

The project aims to determine which varieties of seedless table grapes are best suited to New Hampshire production, and to determine which growing systems are best suited to those varieties. The results are particularly relevant to growers in New Hampshire and Northern New England in USDA hardiness zone 5B and warmer, which corresponds approximately to the southern half of New Hampshire, and much of the rest of New England.

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

Researchers are evaluating eight varieties of seedless table grapes 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 excellent winter survival and have showed good vigor during summer. 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 disease, 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, USDA, and the state of New Hampshire. This work also was supported by the New Hampshire Department of Agriculture, Markets & Food through NH Specialty Crop Block Grant.

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