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Grape (Vitis)
Thomcord grape - USDA photo 01.jpg
Thomcord grapes
Color of berry skinBlue-black
Species Vitis vinifera × Vitis labrusca
Origin California
Pedigree parent 1 Sultanina (Thompson Seedless)
Pedigree parent 2 Concord
Notable regions San Joaquin Valley, California
Hazards powdery mildew (tolerant)
BreederRamming, David W.
Tarailo, Ronald L.
Breeding institute Agricultural Research Service (ARS), USDA
Year of crossing1983
VIVC number 24018

Thomcord is a seedless table grape variety and a hybrid of the popular Thompson Seedless or Sultanina grape (a Vitis vinifera variety) and Concord grape (a Vitis labrusca variety). Thomcord was developed in 1983 by Californian grape breeders working for the Agricultural Research Service (ARS), an agency of the United States Department of Agriculture (USDA), as part of a test to better understand a new seedless grape breeding procedure.

Seedless fruit Seedless frujt

A seedless fruit is a fruit developed to possess no mature seeds. As consumption of seedless fruits is generally easier and more convenient, they are considered commercially valuable.

Table grape

Table grapes are grapes intended for consumption while fresh, as opposed to grapes grown for wine production, juice production, or for drying into raisins.

Hybrid (biology) offspring of cross-species reproduction

In biology, a hybrid is the offspring resulting from combining the qualities of two organisms of different breeds, varieties, species or genera through sexual reproduction. Hybrids are not always intermediates between their parents, but can show hybrid vigour, sometimes growing larger or taller than either parent. The concept of a hybrid is interpreted differently in animal and plant breeding, where there is interest in the individual parentage. In genetics, attention is focused on the numbers of chromosomes. In taxonomy, a key question is how closely related the parent species are.


Its aromatic, "labrusca" flavor is similar to that of Concord, but mellowed by the mild, sweet taste from Thompson Seedless. Thomcord grows well in hot, dry climates, ripens between late July and mid-August, and tolerates powdery mildew. It is a productive variety, yielding an average of 15.1 kg (33 lb) of grapes per vine, but has produced as much as 30 to 32 kg (66 to 71 lb) per vine in grower trials. The berries weigh between 2.72 and 3.38 g (0.096 and 0.119 oz) and have a medium-thick, blue-black skin that adheres to the fruit, unlike Concord, which has a thick skin that can slip off the pulp easily. The aborted seeds in the fruit body are relatively small, but larger than those in Thompson Seedless.

<i>Vitis labrusca</i> species of plant

Vitis labrusca, the fox grape, is a species of grapevines belonging to the Vitis genus in the flowering plant family Vitaceae. The vines are native to eastern North America and are the source of many grape cultivars, including Catawba, Concord, Delaware, Isabella, Niagara, and many hybrid grape varieties such as Agawam, Alexander and Onaka. Among the characteristics of this vine species in contrast to the European wine grape Vitis vinifera are its "slip-skin" that allows the skin of the grape berries to easily slip off when squeezed, instead of crushing the pulp, and the presence of tendrils on every node of the cane. Another contrast with European vinifera is the characteristic "foxy" musk of V. labrusca, best known to most people through the Concord grape. This musk is not related to the mammalian fox, but rather to the strong, earthy aromas characteristic of the grapes that were known by early European-American settlers in the New World. The term "foxy" became a sort of catchall for the wine tasting descriptors used for these American wines that were distinct from the familiar flavors of the European viniferous wines.

<i>Uncinula necator</i> species of fungus

Uncinula necator is a fungus that causes powdery mildew of grape. It is a common pathogen of Vitis species, including the wine grape, Vitis vinifera. The fungus is believed to have originated in North America. European varieties of Vitis vinifera are more or less susceptible to this fungus. Uncinula necator infects all green tissue on the grapevine, including leaves and young berries. It can cause crop loss and poor wine quality if untreated. The sexual stage of this pathogen requires free moisture to release ascospores from its cleistothecia in the spring. However, free moisture is not needed for secondary spread via conidia; high atmospheric humidity is sufficient. Its anamorph is called Oidium tuckeri.

The plant is not restricted for propagation and distribution. Virus-free propagation material is available from the Foundation Plant Services (FPS) at the University of California, Davis, and its genetic material is archived at the National Plant Germplasm System. After 17 years of testing, it was declared ready for use in 2003. It is currently available in supermarkets. [1]

Plant quarantine is a technique for ensuring disease- and pest-free plants, whereby a plant is isolated while tests are performed to detect the presence of a problem.

University of California, Davis public university located in Davis, California, United States

The University of California, Davis, is a public research university and land-grant university adjacent to Davis, California. It is part of the University of California system and has the third-largest enrollment in the system after UCLA and UC Berkeley. The institution was founded as a branch in 1909 and became its own separate entity in 1959. It has been labeled one of the "Public Ivies", a publicly funded university considered to provide a quality of education comparable to those of the Ivy League.

The U.S. National Plant Germplasm System (NPGS) is a cooperative effort by U.S. state and federal government and private organizations to preserve the genetic diversity of plants.


Thomcord grape is a hybrid of Thompson Seedless grape ( Vitis vinifera , or Sultanina), which is popular in supermarkets during the summer, and seeded Concord grape ( Vitis labrusca ), commonly used to make grape juice and jelly. [2] [3] It is a plump, juicy, seedless table grape and is slightly firmer than Concord. Thomcord has a blue-black skin with medium thickness and a whitish bloom. [2] [3] [4] Unlike Concord, whose tough skin separates easily from the fruit, Thomcord has a more edible skin that clings to the flesh, much like Thompson Seedless. [2] [5] It has an aromatic flavor, similar to the Concord in taste ("labrusca"), though lighter due to the sweet, mild taste from Thompson Seedless. [2] [3] [5]

<i>Vitis vinifera</i> species of plant

Vitis vinifera, the common grape vine, is a species of Vitis, native to the Mediterranean region, Central Europe, and southwestern Asia, from Morocco and Portugal north to southern Germany and east to northern Iran. There are currently between 5,000 and 10,000 varieties of Vitis vinifera grapes though only a few are of commercial significance for wine and table grape production.

Thomcord is suitable for hot, dry growing conditions, more so than Concord and other Concord seedless types. Its adaptability to hot dry climates was derived from Thompson Seedless. It grows well in California's vineyards, particularly the San Joaquin Valley, [2] just like Thompson Seedless. [3] The plant is tolerant of (but not resistant to) powdery mildew, [4] [5] and is less susceptible to the fungus than Ruby Seedless, but more susceptible than Mars, Venus, Niabell, and Cayuga White varieties. [2] The fungus can affect its leaves, stems, rachis (stem of the grape cluster), and berries. The grape ripens in the summer (mid-season), between late July and mid-August. [3] [6]

Wine Country (California) area of Northern California known as a wine-growing region

Wine Country is the region of California, in the northern Bay Area, known worldwide as a premium wine-growing region. The region is famed for its wineries, its cuisine, Michelin star restaurants, boutique hotels, luxury resorts, historic architecture, and culture. Viticulture and wine-making have been practiced in the region since the Spanish missionaries from Mission San Francisco Solano established the first vineyards in 1812.

San Joaquin Valley Southern part of the Central Valley in California

The San Joaquin Valley is the area of the Central Valley of the U.S. state of California that lies south of the Sacramento–San Joaquin River Delta and is drained by the San Joaquin River. It comprises seven counties of Northern and one of Southern California, including, in the north, all of San Joaquin and Kings counties, most of Stanislaus, Merced, and Fresno counties, and parts of Madera and Tulare counties, along with a majority of Kern County, in Southern California. Although a majority of the valley is rural, it does contain cities such as Fresno, Bakersfield, Stockton, Modesto, Turlock, Tulare, Porterville, Visalia, Merced, and Hanford.

Fungus Any member of the eukaryotic kingdom that includes organisms such as yeasts, molds and mushrooms

A fungus is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, fungi, which is separate from the other eukaryotic life kingdoms of plants and animals.

Comparison between the Thomcord and its pedigree parents [2] [5]
ColorSkin typeSeed typeAborted seed sizeGrowing conditionsFlavor profile
Thompson SeedlessWhiteAdhering, thinAbortedVery smallHot, dry climateMild & sweet
ConcordBlueSeparable, thick & toughViableN/AHigh humidity"Foxy"
ThomcordBlue-blackAdhering, medium thicknessAbortedSmallHot, dry climate"labrusca", but mild & sweet

Production details

Thomcord is a productive variety, with a yield comparable to Thompson Seedless. When two cordons (arms) of the vines are trained horizontally on wires ("bilateral-trained") and are pruned to remove most of the previous year's growth ("spur-pruned") during the winter, it can produce up to 13–16 kg (29–35 lb) per vine, or an average of 15.1 kg (33 lb). [2] [4] In 2002, cane-pruned vines of Thomcord were significantly more productive than Sovereign Coronation and were comparable to the Venus variety, averaging 21.3 kg (47 lb) per vine. Unlike Thompson Seedless, which has its cluster size thinned as a normal production practice, Thomcord's is not thinned because of its smaller cluster size. The grape clusters range in weight between 259 and 534 g (0.571 and 1.177 lb) [2] and average 340 g (0.75 lb), [4] have medium to slightly loose tightness (or are "well-filled", meaning the individual pedicels are not easily visible), and have a conical shape with a small wing. [2] [4]

Vine training

The use of vine training systems in viticulture is aimed primarily to assist in canopy management with finding the balance in enough foliage to facilitate photosynthesis without excessive shading that could impede grape ripening or promote grape diseases. Additional benefits of utilizing particular training systems could be to control potential yields and to facilitate mechanization of certain vineyard tasks such as pruning, irrigation, applying pesticide or fertilizing sprays as well as harvesting the grapes.

Coronation (grape)

Coronation grapes are a hybrid variety of table grape developed in Canada. Coronation grapes are popular throughout Canada, and are available during a short period in late summer and early fall. These grapes are characterized by their "vibrant blue-purple" colour, similar to the related Concord variety.

Pedicel (botany) A structure connecting flowers or fruit to the main stem of a plant

A pedicel is a stem that attaches a single flower to the inflorescence. Such inflorescences are described as pedicellate.

Compared with Thompson Seedless, the berry weight and diameter of Thomcord are larger, but cluster tightness is similar. The berry length ranged between 18.2 and 18.3 mm (0.72 and 0.72 in) and the diameter ranged from 16.7 to 17.2 mm (0.66 to 0.68 in) in tests between 2001 and 2002. The berries weigh between 2.72 and 3.38 g (0.096 and 0.119 oz), averaging 2.85 g (0.101 oz) in 2002, which is on par with Venus, but heavier than Sovereign Coronation, and even more so than Thompson Seedless. The fruit's size has not been shown to increase appreciably by girdling the vines or by applying gibberellic acid when the berries set. [2]

The aborted seeds of Thomcord are small, but in some years they can become sclerified (a thickening and lignification of the walls of plant cells and the subsequent dying off of the protoplasts), making them more noticeable inside the medium-soft flesh. There are usually two aborted seeds per berry, which averaged between 14 and 22.3 mg in 2001 and 2002. This varied in comparison to Venus depending on the year and location, was comparable to the Sovereign Coronation, and was significantly smaller than the Sovereign Rose and Saturn varieties. However, as with the other cultivars, it was consistently larger than Thompson Seedless, which had the smallest aborted seeds. [2]

Vegetative description

The mature leaves on the vine have three lobes with open upper lateral sinuses (spaces between the lobes) of medium depth. The main vein is slightly longer than the petiole (stalk attaching the leaf blade to the stem), and the petiole sinus opens widely. Between the veins on the underside of both the mature and young leaf there are dense hairs that lie flat against the surface. The teeth on the edge of the leaf blade are convex on both sides, medium in size, and short relative to their width. Young leaf blades are dark copper red on the upper surface. [2]

The shoots have at least three consecutive tendrils. Young shoots are fully open and have very dense hairs of medium anthocyanin coloration that lie flat against the tip. The internode of the young shoot is green with red stripes on the front (dorsal) side and solid green on the back (ventral) side. [2]


Thompson seedless grapes.JPG
The Thomcord grape is a hybrid of the Thompson Seedless grape (left) and the Concord grape (right).

In 1983, [4] research horticulturist David W. Ramming and technician Ronald L. Tarailo—Californian grape breeders working for the ARS, the chief scientific research agency of the USDA—crossed Thompson Seedless and Concord in order to answer a technical question about a newly developed procedure for breeding novel, superior seedless grapes. [3] The researchers wanted to demonstrate that plants created from embryo culture were derived from fertilized eggs (zygotic) instead of the maternal tissue (somatic). [2] From 1231  emasculations (removal of male flower parts to control pollination) of Thompson Seedless, the researchers produced 130  ovules using embryo rescue procedures. [2] [4] From these, 40  embryos developed and three seedlings were planted. The original seedling of Thomcord was planted in 1984 in plots in cooperation with California State University, Fresno. [2] It was later selected in 1986 by Ramming and Tarailo and tested in the San Joaquin Valley under the name A29-67, and was introduced as "Thomcord." [2] [3]

The new hybrid was tested and scrutinized for 17 years before it was declared ready for growers and gardeners and was released on 11 September 2003. [2] [3] Around 2008, trials outside of California were just beginning. [2] Thomcord quickly became a hit at farmers' markets while it was being tested, and it has appeared in the fresh-fruit section at supermarkets. [1] This continued the long-standing success of the ARS' grape-breeding research in California, which has developed some of the most popular seedless grapes on the market as well as red, white, and black grapes varieties for hobbyists and professional growers since 1923. [3]

Although it has been called a "sentimental favorite" at farmers' markets, it is not expected to become a major commercial variety because its flavor is not as neutral as more popular grapes, such as Thompson Seedless, Crimson Seedless, or Flame Seedless. However, Ramming predicted that it would become a specialty item, much like the Muscat varieties, due to its distinctive, Concord-like flavor. [5] Because of its strong reception at farmers' markets, it could compete with Concord and Niabell varieties in eastern markets, according to Ramming. [2]


The Foundation Plant Services (FPS) at the University of California, Davis indexed Thomcord and found it to be free of known viruses. The FPS offers certified virus-free propagation material. The FPS also deposited genetic material in the National Plant Germplasm System, which offers material for research, including development and commercialization of new cultivars. The ARS does not offer Thomcord plants for distribution. [2]

Thomcord is a public variety and is not restricted in its propagation and distribution. [4]

See also

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<i>Vitis riparia</i> species of plant

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Massasoit (grape)

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Delaware (grape) grape

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<i>Vitis arizonica</i> species of plant

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  1. 1 2 "Thomcord Seedless Grapes". 14 August 2014. Archived from the original on 28 September 2015. Retrieved 27 September 2015.
  2. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 Ramming, D.W. (2008). "'Thomcord' Grape" (PDF). HortScience. The American Society for Horticultural Science. 43 (3): 945–946. Archived from the original (PDF) on 2 January 2011. Retrieved 2 January 2011.
  3. 1 2 3 4 5 6 7 8 9 Wood, M. (16 June 2006). "Thomcord Grape: Flavorful, Attractive—and Seedless!". United States Department of Agriculture. Archived from the original on 2 January 2011. Retrieved 2 January 2011.
  4. 1 2 3 4 5 6 7 8 "Sweet Scarlet and Thomcord — Two New Table Grape Varieties Released from ARS" (PDF). FPS Grape Program Newsletter. Foundation Plant Services: 4. October 2004. Archived from the original (PDF) on 2 January 2011. Retrieved 2 January 2011.
  5. 1 2 3 4 5 Pollock, D. (31 July 2006). "THOMCORD: New Grape Variety Draws Ready Fans". Sacramento Bee. Archived from the original on 2 January 2011. Retrieved 2 January 2011.
  6. Ramming, D.W. "The USDA/ARS grape breeding program at Parlier, CA" (PDF). National Viticulture Research Conference. Archived from the original (PDF) on 2 January 2011. Retrieved 2 January 2011.