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What is the Future of Table Grapes in Minnesota?

Author: Laise Sousa Moreira. If you are like many Americans, you love grapes. Table grapes are the third most consumed fruit in the U.S., but growing this delicious fruit is a real challenge in regions with extremely low temperatures.
Seedless table grapes. Photo: Laise Moreira.

Minnesota has a harsh winter and short growing season which creates obstacles for growers to produce grapes year after year or if any at all. Currently, most of the seedless cultivars available in the market were developed for warm climates, dry conditions, or mild winters, which is not the case for the climate here in Minnesota.

There are a few cultivars that are being tested here in Minnesota at the University of Minnesota Horticultural Research Center. Many of these come with restrictions such as burying vines in the ground every year before the winter because these cultivars are not hardy enough to survive the extremely low temperatures during dormancy (time while the plant is not growing). Thus, selecting the appropriate grape cultivar is a key component to successful production in cold regions.

Table grape cultivars for Minnesota

Here it is a list of seedless table cultivars that we can grow in hardiness zone 3 (extreme temperature of -40 to -30°F) and zone 4 (extreme temperature of -30 to -20°F).

‘Somerset Seedless’ (ES 12-7) is the most popular seedless table grape for the cold regions. It’s a red grape with a firm texture, very sweet and tasty, achieving 19 - 23°Brix at full ripeness (mid of September). The berries are round and small (weighing 1.5 to 2g on average), but the clusters are compact with a decent size, weighing on average 100 - 180 grams. The vines are not super vigorous but have good productivity, and are quite resistant to disease. ‘Somerset Seedless’ can be grown in Zone 3, but it requires winter protection such as burying the canes each fall. For more information about winter protection, you can access this extension article. The variety was developed by Elmer Swenson in Wisconsin.

‘Petite Jewel’ - light red, small round berries (smaller than ‘Somerset seedless’), small cluster (50 to 100 grams), and the fruit ripens early (beginning of August). It can be grown in zone 3, but it needs to be buried to survive the winter. The vines have moderate vigor and are said to be resistant to diseases. Variety developed by Elmer Swenson in Wisconsin.

‘Mars’ - dark blue berries, firm texture, concord-like flavor, slip-skin, and clusters are medium size and cylindrical, ripening in late August to early September. The vines are vigorous and very productive, being resistant to mildew but susceptible to Black rot. Developed at the University of Arkansas, Mars along with several other varieties require additional winter protection, but have more typical table grape flavor, texture, and berry size.

‘Trollhaugen’ (ES3-22-18) - black cultivar with berries small to medium size, sweet and mild Concord-like flavor, with slip-skin berries. It is indicated for zoned 4b for hardiness. Variety developed by Elmer Swenson in Wisconsin.

‘Magenta’ - is one of the Elmer Swenson’s hybrid cultivar, red berries with good texture, sweet (achieving 23°Brix) slip-skin, and cluster with a medium size. Indicated for zone 4.

‘Saint Theresa’ or ‘Montreal Blues’ - late-season black grape with a good taste of Concord flavor. The vines are vigorous and very productive. It is ideal for hardiness zone: 4b. Variety developed by Elmer Swenson in Wisconsin.

All these cultivars listed have vestigial of seed trace, which means that the berries are not totally seedless as a ‘Thompson Seedless,’ and the seed trace can be quite big for some cultivars. The environment also can influence the seed trace size.

It is also recommended to protect your grape berries from birds and animals (raccoons, bears, etc..) when the fruits start to ripen. Check the Growing Grapes in Minnesota Guide or the Minnesota Extension website for more information.

Advances in seedless Table Grape Breeding in Minnesota

The University of Minnesota Grape Breeding Program traditionally has developed grape cultivars more adapted to this cold weather, which makes the local wine industry possible and has helped to establish wine regions in areas with similar conditions.
Plants in test tubes before transplanting to
the greenhouse. Photo: Laise Moreira.

Since 2016, the grape breeding team has been gathering effort to breed for seedless table grapes with high-quality, good appearance, crisp texture, tasty flavors, and hardy enough to survive the cold weather. To accomplish this task, we are making crosses using our most hardy cultivars (seeded) and combining with seedless cultivars from different regions as the parents.

Seeking to make this process more efficient, after germination we collect leaves from the new seedlings to do DNA testing where we can identify plants that are predicted to have seeds based on their DNA test results (also called market-assisted selection). This allows us to discard plants that are not seedless before planting them in the field, saving money and time.

This ratio can be increased using two seedless parents, but in nature, these vines do not produce viable seed, and the embryos can't survive without the help of embryo rescue procedures. Thus, seeking to increase our chances to get more seedless plants from one cross, we are using the embryo rescue technique, which allows embryos to grow in Petri dishes under special conditions and nutrition, to form a little seedling in few months. This technique is widely used by many grape breeding programs, promoting the development of the table industry in many countries.

The plants developed last year through the embryo rescue technique were planted in the vineyard after reaching about 4 feet in height in our greenhouse! We are very excited to see how these plants will respond to the Minnesota winter, especially because the polar vortex might injure most of the buds and tissues affecting and delaying the development of seedlings.
Seedlings in the greenhouse.
Photo: Laise Moreira.

This summer we will be starting to collect data from these plants and other selections. More plants are ready in our winter nursery and greenhouse to be planted outside this year; at the same time, new crosses will be done this summer. The Grape Breeding Program also got a new grant from the Minnesota Department of Agriculture to invest in techniques to evaluate table grapes, as their fresh eating and storage traits are unique from our typical process in wine grape selection for three more years.

We are hopeful that in a few years we will have more information and some of these plants will be selected for future research and might be released as a cultivar. Keep checking the University of Minnesota Extension-Fruit and Vegetable News blog for new updates of our research.

Author: Laise Sousa Moreira, PhD student in Horticulture, advised by Dr. Matt Clark. Laise holds a Masters degree in Horticulture from the University of the State of Bahai, Brazil.

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