Thomcord is a

seedless A seedless fruit is a fruit developed to possess no mature seeds. Since eating seedless fruits is generally easier and more convenient, they are considered commercially valuable. Most commercially produced seedless fruits have been developed from ...

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. ''Vitis vinifera'' table grapes can be in the form of either seeded or non-seeded varieta ...

variety and a

hybrid Hybrid may refer to: Science * Hybrid (biology), an offspring resulting from cross-breeding ** Hybrid grape, grape varieties produced by cross-breeding two ''Vitis'' species ** Hybridity, the property of a hybrid plant which is a union of two dif ...

of the popular Thompson Seedless or Sultanina grape (a ''

Vitis vinifera ''Vitis vinifera'', the common grape vine, is a species of flowering plant, 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 curr ...

'' variety) and

Concord grape The Concord grape is a cultivar derived from the grape species '' Vitis labrusca'' (also known as fox grape) that are used as table grapes, wine grapes and juice grapes. They are often used to make grape jelly, grape juice, grape pies, grape-fl ...

(a ''

Vitis labrusca ''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, C ...

'' 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 The United States Department of Agriculture (USDA) is the federal executive department responsible for developing and executing federal laws related to farming, forestry, rural economic development, and food. It aims to meet the needs of com ...

(USDA), as part of a test to better understand a new seedless grape breeding procedure. 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 Powdery mildew is a fungal disease that affects a wide range of plants. Powdery mildew diseases are caused by many different species of ascomycete fungi in the order Erysiphales. Powdery mildew is one of the easier plant diseases to identify, a ...

. It is a productive variety, yielding an average of of grapes per vine, but has produced as much as per vine in grower trials. The berries weigh between 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. 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 The University of California, Davis (UC Davis, UCD, or Davis) is a public land-grant research university near Davis, California. Named a Public Ivy, it is the northernmost of the ten campuses of the University of California system. The inst ...

, and its genetic material is archived at the

National Plant Germplasm System The U.S. National Plant Germplasm System (NPGS) is a network of institutions and agencies (federal, state and private) led by the Agricultural Research Service (ARS) of the U.S. Department of Agriculture in the effort to conserve and facilitate t ...

. After 17 years of testing, it was declared ready for use in 2003. It is currently available in supermarkets.

Description

Thomcord grape is a hybrid of Thompson Seedless grape (''

'', or Sultanina), which is popular in American (?) supermarkets during the summer, and seeded Concord grape (''

''), commonly used to make grape juice and jelly. It is a plump, juicy, seedless

and is slightly firmer than Concord. Thomcord has a blue-black skin with medium thickness and a whitish bloom. 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. It has an aromatic flavor, similar to the Concord in taste (" labrusca"), though lighter due to the sweet, mild taste from Thompson Seedless. 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 The San Joaquin Valley ( ; es, Valle de San Joaquín) 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 ...

, just like Thompson Seedless. The plant is tolerant of (but not resistant to)

, and is less susceptible to the

fungus A fungus ( : fungi or funguses) 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, separately from t ...

than Ruby Seedless, but more susceptible than

Mars Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury. In the English language, Mars is named for the Roman god of war. Mars is a terrestrial planet with a thin at ...

Venus Venus is the second planet from the Sun. It is sometimes called Earth's "sister" or "twin" planet as it is almost as large and has a similar composition. As an interior planet to Earth, Venus (like Mercury) appears in Earth's sky never f ...

, Niabell, and

Cayuga White Cayuga White is a mid-season ripening wine grape developed from crosses of the ''Vitis labrusca'' hybrids Schuyler and Seyval Blanc at Cornell University's New York State Agricultural Experiment Station in Geneva, New York. It is a hardy vine wit ...

varieties. The fungus can affect its leaves, stems,

rachis In biology, a rachis (from the grc, ῥάχις [], "backbone, spine") is a main axis or "shaft". In zoology and microbiology In vertebrates, ''rachis'' can refer to the series of articulated vertebrae, which encase the spinal cord. In this c ...

(stem of the grape cluster), and

berries A berry is a small, pulpy, and often edible fruit. Typically, berries are juicy, rounded, brightly colored, sweet, sour or tart, and do not have a stone or pit, although many pips or seeds may be present. Common examples are strawberries, rasp ...

. The grape ripens in the summer (mid-season), between late July and mid-August.

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 per vine, or an average of . In 2002, cane-pruned vines of Thomcord were significantly more productive than Sovereign Coronation and were comparable to the Venus variety, averaging 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 and average , have medium to slightly loose tightness (or are "well-filled", meaning the individual

pedicel Pedicle or pedicel may refer to: Human anatomy *Pedicle of vertebral arch, the segment between the transverse process and the vertebral body, and is often used as a radiographic marker and entry point in vertebroplasty and kyphoplasty procedures ...

s are not easily visible), and have a conical shape with a small wing. Compared with Thompson Seedless, the berry weight and diameter of Thomcord are larger, but cluster tightness is similar. The berry length ranged between and the diameter ranged from in tests between 2001 and 2002. The berries weigh between , averaging 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 Girdling, also called ring-barking, is the complete removal of the bark (consisting of cork cambium or "phellogen", phloem, cambium and sometimes going into the xylem) from around the entire circumference of either a branch or trunk of a woody ...

the vines or by applying

gibberellic acid Gibberellic acid (also called gibberellin A3, GA, and GA3) is a hormone found in plants and fungi. Its chemical formula is C19H22O6. When purified, it is a white to pale-yellow solid. Plants in their normal state produce large amounts of GA3. It ...

when the berries set. The aborted seeds of Thomcord are small, but in some years they can become sclerified (a thickening and

lignification Lignin is a class of complex organic polymers that form key structural materials in the support tissues of most plants. Lignins are particularly important in the formation of cell walls, especially in wood and bark, because they lend rigidity an ...

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

cultivar A cultivar is a type of cultivated plant that people have selected for desired traits and when propagated retain those traits. Methods used to propagate cultivars include: division, root and stem cuttings, offsets, grafting, tissue culture ...

s, it was consistently larger than Thompson Seedless, which had the smallest aborted seeds.

Vegetative description

The mature leaves on the vine have three lobes with open upper lateral

sinuses Paranasal sinuses are a group of four paired air-filled spaces that surround the nasal cavity. The maxillary sinuses are located under the eyes; the frontal sinuses are above the eyes; the ethmoidal sinuses are between the eyes and the sphenoid ...

(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. The

shoot In botany, a plant shoot consists of any plant stem together with its appendages, leaves and lateral buds, flowering stems, and flower buds. The new growth from seed germination that grows upward is a shoot where leaves will develop. In the sp ...

s have at least three consecutive

tendril In botany, a tendril is a specialized stem, leaf or petiole with a threadlike shape used by climbing plants for support and attachment, as well as cellular invasion by parasitic plants such as '' Cuscuta''. There are many plants that have tend ...

s. 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.

History

In 1983, 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. The researchers wanted to demonstrate that plants created from embryo culture were derived from fertilized eggs (

zygotic A zygote (, ) is a eukaryote, eukaryotic cell (biology), cell formed by a fertilization event between two gametes. The zygote's genome is a combination of the DNA in each gamete, and contains all of the genetic information of a new individual ...

) instead of the maternal tissue (somatic). From 1231

emasculation Emasculation is the removal of both the penis and the testicles, the external male sex organs. It differs from castration, which is the removal of the testicles only, although the terms are sometimes used interchangeably. The potential medical ...

s (removal of male flower parts to control pollination) of Thompson Seedless, the researchers produced 130

ovule In seed plants, the ovule is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: the '' integument'', forming its outer layer, the ''nucellus'' (or remnant of the megasporangium), and the ...

s using embryo rescue procedures. From these, 40 embryos developed and three

seedling A seedling is a young sporophyte developing out of a plant embryo from a seed. Seedling development starts with germination of the seed. A typical young seedling consists of three main parts: the radicle (embryonic root), the hypocotyl (embryo ...

s were planted. The original seedling of Thomcord was planted in 1984 in plots in cooperation with

California State University, Fresno California State University, Fresno (Fresno State) is a public university in Fresno, California. It is one of 23 campuses in the California State University system. The university had a fall 2020 enrollment of 25,341 students. It offers bache ...

. 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." 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. Around 2008, trials outside of California were just beginning. Thomcord quickly became a hit at

farmers' market A farmers' market (or farmers market according to the AP stylebook, also farmer's market in the Cambridge Dictionary) is a physical retail marketplace intended to sell foods directly by farmers to consumers. Farmers' markets may be indoors or o ...

s while it was being tested, and it has appeared in the fresh-fruit section at supermarkets. 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. 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 The Flame Seedless (''Vitis vinifera'') is a vigorous, heavy-bearing table grape cultivar that keeps well in storage. It is a hybrid of Thompson Seedless, Cardinal, and several other ''Vitis vinifera'' cultivars. It produces large clusters of me ...

. However, Ramming predicted that it would become a specialty item, much like the Muscat varieties, due to its distinctive, Concord-like flavor. Because of its strong reception at farmers' markets, it could compete with Concord and Niabell varieties in eastern markets, according to Ramming.

Availability

The Foundation Plant Services (FPS) at the

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

, which offers material for research, including development and commercialization of new cultivars. The ARS does not offer Thomcord plants for distribution. Thomcord is a public variety and is not restricted in its propagation and distribution.

References