Tomato

The tomato is the edible, often red fruit/berry of the nightshade Solanum lycopersicum,^[1][2] commonly known as a tomato plant. The species originated in the South American Andes^[2] and its use as a food originated in Mexico, and spread throughout the world following the Spanish colonization of the Americas. Its many varieties are now widely grown, sometimes in greenhouses in cooler climates.

The tomato is consumed in diverse ways, including raw, as an ingredient in many dishes, sauces, salads, and drinks. While it is botanically a fruit, it is considered a vegetable for culinary purposes (as well as under U.S. customs regulations, see Nix v. Hedden), which has caused some confusion. The fruit is rich in lycopene, which may have beneficial health effects.

The tomato belongs to the nightshade family, Solanaceae.^[1][3] The plants typically grow to 1–3 meters (3–10 ft) in height and have a weak stem that often sprawls over the ground and vines over other plants. It is a perennial in its native habitat, although often grown outdoors in temperate climates as an annual. An average common tomato weighs approximately 100 grams (4 oz).^[4][5]

History

Etymology and pronunciation

The word tomato comes from the Spanish tomate, which in turn comes from the Nahuatl word tomatotl /aːˈtomatl͡ɬ/.^[6] It first appeared in print in 1595. A member of the deadly nightshade family, tomatoes were erroneously thought to be poisonous (although the leaves are) by Europeans who were suspicious of their bright, shiny fruit. Native versions were small, like cherry tomatoes, and most likely yellow rather than red. The tomato is native to western South America and Central America.^[6]

The usual pronunciations of tomato are /təˈmeɪtoʊ/ (usual in American English^[7]) and /təˈmɑːtoʊ/ (usual in British English^[8]). In America through the mid-twentieth century, speakers aspiring to high culture sometimes affected the broad vowels of Received Pronunciation, which made the pronunciation variants of tomato a topic of attention via the popular song "Let's Call the Whole Thing Off".

Mesoamerica

Aztecs and other peoples in Mesoamerica used the fruit in their cooking. The exact date of domestication is unknown: by 500 BC, it was already being cultivated in southern Mexico and probably other areas.^[9]:13 The Pueblo people are thought to have believed that those who witnessed the ingestion of tomato seeds were blessed with powers of divination.^[10] The large, lumpy variety of tomato, a mutation from a smoother, smaller fruit, originated in Mesoamerica, and may be the direct ancestor of some modern cultivated tomatoes.^[9]

Spanish distribution

Spanish conquistador Hernán Cortés may have been the first to transfer the small yellow tomato to Europe after he captured the Aztec city of Tenochtitlan, now Mexico City, in 1521, although Christopher Columbus, a Genoese working for the Spanish monarchy, may have taken them back as early as 1493. The earliest discussion of the tomato in European literature appeared in an herbal written in 1544 by Pietro Andrea Mattioli, an Italian physician and botanist, who suggested that a new type of eggplant had been brought to Italy that was blood red or golden color when mature and could be divided into segments and eaten like an eggplant—that is, cooked and seasoned with salt, black pepper, and oil. However it wasn't until ten years later that tomatoes were named in print by Mattioli as pomi d’oro, or "golden apple".^[9]:13

After the Spanish colonization of the Americas, the Spanish distributed the tomato throughout their colonies in the Caribbean. They also took it to the Philippines, from where it spread to southeast Asia and then the entire Asian continent. The Spanish also brought the tomato to Europe. It grew easily in Mediterranean climates, and cultivation began in the 1540s. It was probably eaten shortly after it was introduced, and was certainly being used as food by the early 17th century in Spain. The earliest discovered cookbook with tomato recipes was published in Naples in 1692, though the author had apparently obtained these recipes from Spanish sources.^[9]:17 In certain areas of Italy, such as Florence, however, the fruit was used solely as a tabletop decoration before it was incorporated into the local cuisine in the late 17th or early 18th century.

Italy

The recorded history of tomatoes in Italy dates back to 31 October 1548 when the house steward of Cosimo de' Medici, the grand duke of Tuscany, wrote to the Medici private secretary informing him that the basket of tomatoes sent from the grand duke's Florentine estate at Torre del Gallo "had arrived safely." Tomatoes were grown mainly as ornamentals early on after their arrival in Italy. For example, the Florentine aristocrat Giovanvettorio Soderini wrote how they "were to be sought only for their beauty" and were grown only in gardens or flower beds. The tomato's ability to mutate and create new and different varieties helped contribute to its success and spread throughout Italy. However, even in areas where the climate supported growing tomatoes, their proximity of growing to the ground suggested low status. They were not adopted as a staple of the peasant population because they were not as filling as other fruits already available. Additionally, both toxic and inedible varieties discouraged many people from attempting to consume or prepare them.^[11]

Unique varieties were developed over the next several hundred years for uses such as dried tomatoes, sauce tomatoes, pizza tomatoes, and tomatoes for long term storage. These varieties are usually known for their place of origin as much as by a variety name. For example, Pomodorino del Piennolo del Vesuvio is the "hanging tomato of Vesuvius". Five different varieties have traditionally been used to make these "hanging" tomatoes. They are Fiaschella, Lampadina, Patanara, Principe Borghese, and Re Umberto. Other tomatoes that originated in Italy include San Marzano, Borgo Cellano, Christopher Columbus, Costoluto Genovese, and Italian Pear. These tomatoes are characterized by relatively intense flavor compared to varieties typically grown elsewhere.

Britain

Tomatoes were not grown in England until the 1590s.^[9]:17 One of the earliest cultivators was John Gerard, a barber-surgeon.^[9]:17 Gerard's Herbal, published in 1597, and largely plagiarized from continental sources,^[9]:17 is also one of the earliest discussions of the tomato in England. Gerard knew the tomato was eaten in Spain and Italy.^[9]:17 Nonetheless, he believed it was poisonous^[9]:17 (in fact, the plant and raw fruit do have low levels of tomatine, but are not generally dangerous; see below). Gerard's views were influential, and the tomato was considered unfit for eating (though not necessarily poisonous) for many years in Britain and its North American colonies.^[9]:17 By the mid-18th century, tomatoes were widely eaten in Britain, and before the end of that century, the Encyclopædia Britannica stated the tomato was "in daily use" in soups, broths, and as a garnish. They were not part of the average person's diet, however, and though by 1820 they were described as "to be seen in great abundance in all our vegetable markets" and to be "used by all our best cooks", reference was made to their cultivation in gardens still "for the singularity of their appearance", while their use in cooking was associated with Italian or Jewish cuisine.^[12]

Middle East and North Africa

The tomato was introduced to cultivation in the Middle East by John Barker, British consul in Aleppo circa 1799 to 1825.^[13][14] Nineteenth century descriptions of its consumption are uniformly as an ingredient in a cooked dish. In 1881, it is described as only eaten in the region "within the last forty years".^[15] Today, the tomato is a critical and ubiquitous part of Middle Eastern cuisine, served fresh in salads (e.g. Arab salad, Israeli salad, Shirazi salad and Turkish salad), grilled with kebabs and other dishes, made into sauces, and so on.

The early name used for tomato in Iran was Armani badenjan (Armenian eggplant). Currently, the name used for tomato in Iran is gojeh farangi [exotic plum].

North America

The earliest reference to tomatoes being grown in British North America is from 1710, when herbalist William Salmon reported seeing them in what is today South Carolina.^[9]:25 They may have been introduced from the Caribbean. By the mid-18th century, they were cultivated on some Carolina plantations, and probably in other parts of the Southeast as well. Possibly, some people continued to think tomatoes were poisonous at this time; and in general, they were grown more as ornamental plants than as food. Thomas Jefferson, who ate tomatoes in Paris, sent some seeds back to America.^[9]:28

Alexander W. Livingston was the first person who succeeded in upgrading the wild tomato, developing different breeds and stabilizing the plants. In the 1937 yearbook of the Federal Department of Agriculture, it was declared that "half of the major varieties were a result of the abilities of the Livingstons to evaluate and perpetuate superior material in the tomato". Livingston's first breed of tomato, the Paragon, was introduced in 1870. In 1875, he introduced the Acme, which was said to be involved in the parentage of most of the tomatoes introduced by him and his competitors for the next twenty-five years.^[16]

When Alexander W. Livingston had begun his attempts to develop the tomato as a commercial crop, his aim had been to grow tomatoes smooth in contour, uniform in size and having better flavor. One year, after many attempts, he passed through his fields, picking out particular tomato plants having distinct characteristics and heavy foliage. He saved the seeds carefully. The following spring he set two rows across his family garden located just below the hill and milk house. To his happy surprise, each plant bore perfect tomatoes like the parent vine. After five years, the fruit became fleshier and larger. In 1870, Alexander introduced the Paragon and tomato culture soon became a great enterprise in the county. Today, the crop is grown in every state in the Union. He eventually developed over seventeen different varieties of the tomato plant.^[16]

Because of the long growing season needed for this heat-loving crop, several states in the US Sun Belt became major tomato-producers, particularly Florida and California. In California, tomatoes are grown under irrigation for both the fresh fruit market and for canning and processing. The University of California, Davis (UC Davis) became a major center for research on the tomato. The C.M. Rick Tomato Genetics Resource Center at UC Davis is a gene bank of wild relatives, monogenic mutants and miscellaneous genetic stocks of tomato.^[17] The Center is named for the late Dr. Charles M. Rick, a pioneer in tomato genetics research.^[18] Research on processing tomatoes is also conducted by the California Tomato Research Institute in Escalon, California.^[19]

In California, growers have used a method of cultivation called dry-farming, especially with Early Girl tomatoes. This technique encourages the plant to send roots deep to find existing moisture in soil that retains moisture, such as clayey soil.

Modern commercial varieties

The poor taste and lack of sugar in modern garden and commercial tomato varieties resulted from breeding tomatoes to ripen uniformly red. This change occurred after discovery of a mutant "u" phenotype in the mid 20th century that ripened "u"niformly. This was widely cross-bred to produce red fruit without the typical green ring around the stem on uncross-bred varieties. Prior to general introduction of this trait, most tomatoes produced more sugar during ripening, and were sweeter and more flavorful.^[20][21]

Evidence has been found that 10−20% of the total carbon fixed in the fruit can be produced by photosynthesis in the developing fruit of the normal U phenotype. The u genetic mutation encodes a factor that produces defective chloroplasts with lower density in developing fruit, resulting in a lighter green colour of unripe fruit, and repression of sugars accumulation in the resulting ripe fruit by 10−15%. Perhaps more important than their role in photosynthesis, the fruit chloroplasts are remodelled during ripening into chlorophyll-free chromoplasts that synthesize and accumulate lycopene, β-carotene, and other metabolites that are sensory and nutritional assets of the ripe fruit. The potent chloroplasts in the dark-green shoulders of the U phenotype are beneficial here, but have the disadvantage of leaving green shoulders near the stems of the ripe fruit, and even cracked yellow shoulders, apparently because of oxidative stress due to overload of the photosynthetic chain in direct sunlight at high temperatures. Hence genetic design of a commercial variety that combines the advantages of types u and U requires fine tuning, but may be feasible.^[22]

Cultivation

The tomato is now grown worldwide for its edible fruits, with thousands of cultivars having been selected with varying fruit types, and for optimum growth in differing growing conditions. Cultivated tomatoes vary in size, from tomberries, about 5 mm in diameter, through cherry tomatoes, about the same 1–2 cm (0.4–0.8 in) size as the wild tomato, up to beefsteak tomatoes 10 cm (4 in) or more in diameter. The most widely grown commercial tomatoes tend to be in the 5–6 cm (2.0–2.4 in) diameter range. Most cultivars produce red fruit, but a number of cultivars with yellow, orange, pink, purple, green, black, or white fruit are also available. Multicolored and striped fruit can also be quite striking. Tomatoes grown for canning and sauces are often elongated, 7–9 cm (3–4 in) long and 4–5 cm (1.6–2.0 in) diameter; they are known as plum tomatoes, and have a lower water content. Roma-type tomatoes are important cultivars in the Sacramento Valley.^[23]

Tomatoes are one of the most common garden fruits in the United States and, along with zucchini, have a reputation for outproducing the needs of the grower.

Quite a few seed merchants and banks provide a large selection of heirloom seeds. The definition of an heirloom tomato is vague, but unlike commercial hybrids, all are self-pollinators that have bred true for 40 years or more.^[23]

About 161.8 million tonnes of tomatoes were produced in the world in 2012. China, the largest producer, accounted for about one quarter of the global output, followed by India and the United States. For one variety, plum or processing tomatoes, California accounts for 90% of U.S. production and 35% of world production.^[24]

In 2012, tomato production was valued at 58 billion dollars and tomatoes were the eighth most valuable agricultural product worldwide. According to FAOSTAT, the top producers of tomatoes (in tonnes) were:^[25]

Rank	Country	Production (MT)
1	China	50,000,000
2	India	17,500,000
3	United States	13,206,950
4	Turkey	11,350,000
5	Egypt	8,625,219
6	Iran	6,000,000
7	Italy	5,131,977
8	Spain	4,007,000
9	Brazil	3,873,985
10	Mexico	3,433,567

Within the EU, there are several areas that grow tomatoes with Protected Geographical Status. These include:

• Pomodoro di Pachino (PGI), in Sicily
• Pomodoro S. Marzano dell'Agro Sarnese-Nocerino (PDO), in south Italy
• Tomaten von der Insel Reichenau (PGI), from Reichenau Island, Germany
• Pomodorino del Piennolo del Vesuvio (PDO), in Mt Vesuvius area.

Varieties

There are around 7,500 tomato varieties grown for various purposes. Heirloom tomatoes are becoming increasingly popular, particularly among home gardeners and organic producers, since they tend to produce more interesting and flavorful crops at the cost of disease resistance and productivity.^[23] In 1973, Israeli scientists developed the world's first long shelf-life commercial tomato varieties.^[26]

Hybrid plants remain common, since they tend to be heavier producers, and sometimes combine unusual characteristics of heirloom tomatoes with the ruggedness of conventional commercial tomatoes.

Tomato varieties are roughly divided into several categories, based mostly on shape and size.

• "Slicing" or "globe" tomatoes are the usual tomatoes of commerce, used for a wide variety of processing and fresh eating.
• Beefsteak tomatoes are large tomatoes often used for sandwiches and similar applications. Their kidney-bean shape, thinner skin, and shorter shelf life makes commercial use impractical.
• Oxheart tomatoes can range in size up to beefsteaks, and are shaped like large strawberries.
• Plum tomatoes, or paste tomatoes (including pear tomatoes), are bred with a higher solids content for use in tomato sauce and paste, and are usually oblong.
• Pear tomatoes are pear-shaped, and are based upon the San Marzano types for a richer gourmet paste.
• Cherry tomatoes are small and round, often sweet tomatoes generally eaten whole in salads.
• Grape tomatoes, a more recent introduction, are smaller and oblong, a variation on plum tomatoes, and used in salads.
• Campari tomatoes are also sweet and noted for their juiciness, low acidity, and lack of mealiness. They are bigger than cherry tomatoes, but are smaller than plum tomatoes.

Early tomatoes and cool-summer tomatoes bear fruit even where nights are cool, which usually discourages fruit set. There are also varieties high in beta carotenes and vitamin A, hollow tomatoes and tomatoes that keep for months in storage.

Tomatoes are also commonly classified as determinate or indeterminate. Determinate, or bush, types bear a full crop all at once and top off at a specific height; they are often good choices for container growing. Determinate types are preferred by commercial growers who wish to harvest a whole field at one time, or home growers interested in canning. Indeterminate varieties develop into vines that never top off and continue producing until killed by frost. They are preferred by home growers and local-market farmers who want ripe fruit throughout the season. As an intermediate form, there are plants sometimes known as vigorous determinate or semideterminate; these top off like determinates, but produce a second crop after the initial crop. The majority of heirloom tomatoes are indeterminate, although some determinate heirlooms exist.

Most modern tomato cultivars are smooth surfaced, but some older tomato cultivars and most modern beefsteaks often show pronounced ribbing, a feature that may have been common to virtually all pre-Columbian cultivars. While virtually all commercial tomato varieties are red, some cultivars – especially heirlooms – produce fruit in other colors, including green, yellow, orange, pink, black, brown, ivory, white, and purple. Such fruits are not widely available in grocery stores, nor are their seedlings available in typical nurseries, but they can be bought as seed. Less common variations include fruit with stripes (Green Zebra), fuzzy skin on the fruit (Fuzzy Peach, Red Boar), multiple colors (Hillbilly, Burracker's Favorite, Lucky Cross), etc.

There is also a considerable gap between commercial and home-gardener cultivars. Home cultivars are often bred for flavor to the exclusion of all other qualities, while commercial cultivars are bred for factors like consistent size and shape, disease and pest resistance, suitability for mechanized picking and shipping, and ability to ripen after picking.

Tomatoes grow well with seven hours of sunlight a day. A fertilizer with an NPK ratio of 5-10-10 is often sold as tomato fertilizer or vegetable fertilizer, although manure and compost are also used.

• 

  Cherry tomatoes

• 

  Cherry tomatoes – various colors upon ripening

• 

  Roma or Bangalore Tomatoes (Indian hybrid)

• 

  Various heirloom tomato cultivars

• 

  A variety of specific cultivars, including Brandywine (biggest red), Black Krim (lower left) and Green Zebra (top left)

Diseases and pests

Tomato cultivars vary widely in their resistance to disease. Modern hybrids focus on improving disease resistance over the heirloom plants. One common tomato disease is tobacco mosaic virus. Handling cigarettes and other infected tobacco products can transmit the virus to tomato plants.^[27] Various forms of mildew and blight are also common tomato afflictions, which is why tomato cultivars are often marked with a combination of letters that refer to specific disease resistance. The most common letters are: LB - late blight,^[28] V – verticillium wilt, F – fusarium wilt strain I, FF – fusarium wilt strain I and II, N – nematodes, T – tobacco mosaic virus, and A – alternaria.

Another particularly dreaded disease is curly top, carried by the beet leafhopper, which interrupts the lifecycle, ruining a nightshade plant as a crop. As the name implies, it has the symptom of making the top leaves of the plant wrinkle up and grow abnormally.

Some common tomato pests are stink bugs, cutworms, tomato hornworms and tobacco hornworms, aphids, cabbage loopers, whiteflies, tomato fruitworms, flea beetles, red spider mite, slugs,^[29] and Colorado potato beetles.

Tomato plants produce the plant peptide hormone systemin after an insect attack. Systemin activates defensive mechanisms, such as the production of protease inhibitors to slow the growth of insects. The hormone was first identified in tomatoes, but similar proteins have been identified in other species since.^[30]

Companion plants

Tomatoes serve, or are served by, a large variety of companion plants.

Among the most famous pairings is the tomato plant and carrots; studies supporting this relationship have produced a popular book about companion planting, Carrots Love Tomatoes.^[31]

Additionally, the devastating tomato hornworm has a major predator in various parasitic wasps, whose larvae devour the hornworm, but whose adult form drinks nectar from tiny-flowered plants like umbellifers. Several species of umbellifer are therefore often grown with tomato plants, including parsley, queen anne's lace, and occasionally dill. These also attract predatory flies that attack various tomato pests.^[32]

On the other hand, borage is thought to actually repel the tomato hornworm moth.^[33]

Other plants with strong scents, like alliums (onions, chives, garlic) and mints (basil, oregano, spearmint) are simply thought to mask the scent of the tomato plant, making it harder for pests to locate it, or to provide an alternative landing point, reducing the odds of the pests from attacking the correct plant.^[34] These plants may also subtly impact the flavor of tomato fruit.^[35]

Ground cover plants, including mints, also stabilize moisture loss around tomato plants and other solaneae, which come from very humid climates, and therefore may prevent moisture-related problems like blossom end rot.

Finally, tap-root plants like dandelions break up dense soil and bring nutrients from down below a tomato plant's reach, possibly benefiting their companion.

Tomato plants, on the other hand, protect asparagus from asparagus beetles, because they contain solanum that kills this pest, while asparagus plants (as well as marigolds^[35]) contain a chemical that repels root nematodes known to attack tomato plants.

Pollination

In the wild, original state, tomatoes required cross-pollination; they were much more self-incompatible than domestic cultivars. As a floral device to reduce selfing, the pistil of wild tomatoes extends farther out of the flower than today's cultivars. The stamens were, and remain, entirely within the closed corolla.

As tomatoes were moved from their native areas, their traditional pollinators, (probably a species of halictid bee) did not move with them.^[36] The trait of self-fertility became an advantage, and domestic cultivars of tomato have been selected to maximize this trait.^[36]

This is not the same as self-pollination, despite the common claim that tomatoes do so. That tomatoes pollinate themselves poorly without outside aid is clearly shown in greenhouse situations, where pollination must be aided by artificial wind, vibration of the plants (one brand of vibrator is a wand called an "electric bee" that is used manually), or more often today, by cultured bumblebees. The anther of a tomato flower is shaped like a hollow tube, with the pollen produced within the structure, rather than on the surface, as in most species. The pollen moves through pores in the anther, but very little pollen is shed without some kind of outside motion. The best source of outside motion is a sonicating bee, such as a bumblebee, or the original wild halictid pollinator. In an outside setting, wind or animals provide sufficient motion to produce commercially viable crops.

Fruit formation

Pollination and fruit formation depend on meiosis. Meiosis is central to the processes by which diploid microspore mother cells within the anther give rise to haploid pollen grains, and megaspore mother cells in ovules that are contained within the ovary give rise to haploid nuclei. Union of haploid nuclei from pollen and ovule (fertilization) can occur either by self- or cross-pollination. Fertilization leads to the formation of a diploid zygote that can then develop into an embryo within the emerging seed. Repeated fertilizations within the ovary are accompanied by maturation of the ovary to form the tomato fruit.

Homologs of the recA gene, including rad51, play a key role in homologous recombinational repair of DNA during meiosis. A rad51 homolog is present in the anther of tomato (Lycopersicon esculentum),^[37] suggesting that recombinational repair occurs during meiosis in tomato.

Hydroponic and greenhouse cultivation

Tomatoes are often grown in greenhouses in cooler climates, and there are cultivars such as the British 'Moneymaker' and a number of cultivars grown in Siberia that are specifically bred for indoor growing. In more temperate climates, it is not uncommon to start seeds in greenhouses during the late winter for future transplant.

Greenhouse tomato production in large-acreage commercial greenhouses and owner-operator stand-alone or multiple-bay greenhouses is on the increase, providing fruit during those times of the year when field-grown fruit is not readily available. Smaller sized fruit (cherry and grape), or cluster tomatoes (fruit-on-the-vine) are the fruit of choice for the large commercial greenhouse operators while the beefsteak varieties are the choice of owner-operator growers.^[38]

Hydroponic tomatoes are also available, and the technique is often used in hostile growing environments, as well as high-density plantings.

Picking and ripening

To facilitate transportation and storage, tomatoes are often picked unripe (green) and ripened in storage with ethylene.^[39] Unripe tomatoes are firm. As they ripen they soften until reaching the ripe state where they are red or orange in color and slightly soft to the touch. Ethylene is a hydrocarbon gas produced by many fruits that acts as the molecular cue to begin the ripening process. Tomatoes ripened in this way tend to keep longer, but have poorer flavor and a mealier, starchier texture than tomatoes ripened on the plant. They may be recognized by their color, which is more pink or orange than the other ripe tomatoes' deep red, depending on variety.

A machine-harvestable variety of tomato (the "square tomato") was developed in the 1950s by University of California, Davis's Gordie C. Hanna, which, in combination with the development of a suitable harvester, revolutionized the tomato-growing industry. This type of tomato is grown commercially near plants that process and can tomatoes, tomato sauce, and tomato paste. They are harvested when ripe and are flavorful when picked. They are harvested 24 hours a day, seven days a week during a 12 to 14 week season, and immediately transported to packing plants, which operate on the same schedule. California is a center of this sort of commercial tomato production and produces about a third of the processed tomatoes produced in the world.^[40]

In 1994, Calgene introduced a genetically modified tomato called the FlavrSavr, which could be vine ripened without compromising shelf life. However, the product was not commercially successful, and was sold only until 1997.^[41] Slow-ripening cultivars of tomato have been developed by crossing a non-ripening cultivar with ordinary cultivars. Cultivars were selected whose fruits have a long shelf life and at least reasonable flavor.

At home, fully ripe tomatoes can be stored in the refrigerator, but are best kept at room temperature. Tomatoes stored cold remain edible, but tend to lose their flavor permanently.^[42] Tomatoes stored stem down may also keep from rotting too quickly.^[43]

Yield

The world dedicated 4.8 million hectares in 2012 for tomato cultivation and the total production was about 161.8 million tonnes.^[44] The average world farm yield for tomato was 33.6 tonnes per hectare, in 2012.^[44]

Tomato farms in the Netherlands were the most productive in 2012, with a nationwide average of 476 tonnes per hectare.^[45] Second place: Belgium - 463 tonnes per hectare.^[45] Third place: Iceland - 429 tonnes per hectare.^[45]

Genetic modification

Tomatoes that have been modified using genetic engineering have been developed, and although none are commercially available now, they have been in the past. The first commercially available genetically modified food was a variety of tomato named (the Flavr Savr), which was engineered to have a longer shelf life.^[46] Scientists are continuing to develop tomatoes with new traits not found in natural crops, such as increased resistance to pests or environmental stresses. Other projects aim to enrich tomatoes with substances that may offer health benefits or provide better nutrition.

Consumption

The tomato is now grown and eaten around the world. It is used in diverse ways, including raw in salads, and processed into ketchup or tomato soup. Unripe green tomatoes can also be breaded and fried, used to make salsa, or pickled. Tomato juice is sold as a drink, and is used in cocktails such as the Bloody Mary.

Tomatoes are acidic, making them especially easy to preserve in home canning whole, in pieces, as tomato sauce or paste. The fruit is also preserved by drying, often in the sun, and sold either in bags or in jars with oil.

Tomatoes are used extensively in Mediterranean cuisine. They are a key ingredient in pizza, and are commonly used in pasta sauces. They are also used in gazpacho (Spanish cuisine) and pa amb tomàquet (Catalan cuisine).

Though it is botanically a berry, a subset of fruit, the tomato is a vegetable for culinary purposes, because of its savory flavor (see below).

Nutrition

Red tomatoes, raw

Nutritional value per 100 g (3.5 oz)
Energy	74 kJ (18 kcal)
Carbohydrates	3.9 g
Sugars	2.6 g
Dietary fiber	1.2 g
Fat	0.2 g
Protein	0.9 g
Vitamins
Vitamin A equiv. beta-carotene lutein zeaxanthin	(5%) 42 μg (4%) 449 μg 123 μg
Thiamine (B1)	(3%) 0.037 mg
Niacin (B3)	(4%) 0.594 mg
Vitamin B6	(6%) 0.08 mg
Vitamin C	(17%) 14 mg
Vitamin E	(4%) 0.54 mg
Vitamin K	(8%) 7.9 μg
Trace metals
Magnesium	(3%) 11 mg
Manganese	(5%) 0.114 mg
Phosphorus	(3%) 24 mg
Potassium	(5%) 237 mg
Other constituents
Water	94.5 g
Lycopene	2573 µg
Link to USDA Database entry
Units μg = micrograms • mg = milligrams IU = International units
Percentages are roughly approximated using US recommendations for adults. Source: USDA Nutrient Database

Tomatoes are now eaten freely throughout the world. They contain the carotene lycopene, one of the most powerful natural antioxidants. In some studies, lycopene, especially in cooked tomatoes, has been found to help prevent prostate cancer,^[47] but other research contradicts this claim.^[48] Lycopene has also been shown to improve the skin's ability to protect against harmful UV rays.^[49] A study done by researchers at Manchester and Newcastle universities revealed that tomato can protect against sunburn and help keeping the skin looking youthful.^[50] Natural genetic variation in tomatoes and their wild relatives has given a genetic plethora of genes that produce lycopene, carotene, anthocyanin, and other antioxidants. Tomato varieties are available with double the normal vitamin C (Doublerich), 40 times normal vitamin A (97L97), high levels of anthocyanin (resulting in blue tomatoes), and two to four times the normal amount of lycopene (numerous available cultivars with the high crimson gene).

Potential health effects

Some studies have indicated that the lycopene in tomatoes may help prevent cancer, but taken overall the research into this subject is inconclusive.^[51] There has been some research interest in whether the lycopene in tomatoes might help in managing human neurodegenerative diseases.^[52] The lycopene from tomatoes has no effect on the risk of developing diabetes, but may help relieve the oxidative stress of people who already have diabetes.^[53]

Storage

Tomatoes keep best unwashed at room temperature and out of direct sunlight. It is not recommended to refrigerate as this can harm the flavor.^[54] Tomatoes that are not yet ripe can be kept in a paper bag till ripening.^[55] Storing stem down can prolong shelf life.^[56]

Safety

Plant toxicity

Leaves, stems, and green unripe fruit of the tomato plant contain small amounts of the toxic alkaloid tomatine.^[1][57] They also contain solanine, a toxic alkaloid found in potato leaves and other plants in the nightshade family.^[58][59] Use of tomato leaves in herbal tea has been responsible for at least one death.^[57][58] However, levels of tomatine in foliage and green fruit are generally too small to be dangerous unless large amounts are consumed, for example, as greens. Small amounts of tomato foliage are sometimes used for flavoring without ill effect, and the green fruit is sometimes used for cooking, particularly as fried green tomatoes.^[57] Compared to potatoes the amount of solanine in green or ripe tomatoes is low; however, even in the case of potatoes while solanine poisoning resulting from dosages several times normal human consumption has been demonstrated, actual cases of poisoning resulting from excessive consumption of potatoes that have high concentration of solanine are rare.^[59]

Tomato plants can be toxic to dogs if they eat large amounts of the fruit, or chew plant material.^[60]

Salmonella

On 30 October 2006, the U.S. Centers for Disease Control and Prevention (CDC) announced tomatoes might have been the source of a salmonellosis outbreak causing 172 illnesses in 18 states.^[61] Tomatoes have been linked to seven salmonella outbreaks since 1990.^[62]

The 2008 United States salmonellosis outbreak caused the removal of tomatoes from stores and restaurants across the United States and parts of Canada,^[63] although other foods, including jalapeño and serrano peppers, may have been involved.

Botanical description

Tomato plants are vines, initially decumbent, typically growing 180 cm (6 ft) or more above the ground if supported, although erect bush varieties have been bred, generally 100 cm (3 ft) tall or shorter. Indeterminate types are "tender" perennials, dying annually in temperate climates (they are originally native to tropical highlands), although they can live up to three years in a greenhouse in some cases. Determinate types are annual in all climates.

Tomato plants are dicots, and grow as a series of branching stems, with a terminal bud at the tip that does the actual growing. When that tip eventually stops growing, whether because of pruning or flowering, lateral buds take over and grow into other, fully functional, vines.^[64]

Tomato vines are typically pubescent, meaning covered with fine short hairs. These hairs facilitate the vining process, turning into roots wherever the plant is in contact with the ground and moisture, especially if the vine's connection to its original root has been damaged or severed.

Most tomato plants have compound leaves, and are called regular leaf (RL) plants, but some cultivars have simple leaves known as potato leaf (PL) style because of their resemblance to that particular relative. Of RL plants, there are variations, such as rugose leaves, which are deeply grooved, and variegated, angora leaves, which have additional colors where a genetic mutation causes chlorophyll to be excluded from some portions of the leaves.^[65]

The leaves are 10–25 cm (4–10 in) long, odd pinnate, with five to 9 leaflets on petioles,^[66] each leaflet up to 8 cm (3 in) long, with a serrated margin; both the stem and leaves are densely glandular-hairy.

Their flowers, appearing on the apical meristem, have the anthers fused along the edges, forming a column surrounding the pistil's style. Flowers in domestic cultivars tend to be self-fertilizing. The flowers are 1–2 cm (0.4–0.8 in) across, yellow, with five pointed lobes on the corolla; they are borne in a cyme of three to 12 together.

Tomato fruit is classified as a berry. As a true fruit, it develops from the ovary of the plant after fertilization, its flesh comprising the pericarp walls. The fruit contains hollow spaces full of seeds and moisture, called locular cavities. These vary, among cultivated species, according to type. Some smaller varieties have two cavities, globe-shaped varieties typically have three to five, beefsteak tomatoes have a great number of smaller cavities, while paste tomatoes have very few, very small cavities.

For propagation, the seeds need to come from a mature fruit, and be dried or fermented before germination.

Botanical classification

In 1753, Linnaeus placed the tomato in the genus Solanum (alongside the potato) as Solanum lycopersicum. In 1768, Philip Miller moved it to its own genus, naming it Lycopersicon esculentum.^[1][67] This name came into wide use, but was in breach of the plant naming rules.^[1] Technically, the name Lycopersicon lycopersicum would be more correct, but is rarely used^[1] (except in seed catalogs, which frequently used it and still do).

Genetic evidence has now shown that Linnaeus was correct to put the tomato in the genus Solanum, making Solanum lycopersicum the correct name.^[3][68] Both names, however, will probably be found in the literature for some time. Two of the major reasons some still consider the genera separate are the leaf structure (tomato leaves are markedly different from any other Solanum), and the biochemistry (many of the alkaloids common to other Solanum species are conspicuously absent in the tomato). Hybrids of tomato and diploid potato can be created in the lab by somatic fusion, and are partially fertile,^[69] providing evidence of the close relationship between these species.

Wild species

Including Solanum lycopersicum, there are currently 13 species recognized in Solanum section Lycopersicon. Three of these species—S. Cheesmaniae, S. Galapagense, and S. Pimpinellifolium—are fully cross compatible with domestic tomato. Four more species—S. chmielewskii, S. habrochaites, S. neorickii, and S. pennelli—can be readily crossed with domestic tomato, with some limitations. Five species—S. arcanum, S. chilense, S. corneliomulleri, S. huaylasense, and S. peruvianum—can be crossed with domestic tomato with difficulty and usually require embryo rescue to produce viable plants. The Lycopersicon section has not been fully sampled within wild species in the South American range, so new species may be added in the future.

Solanum section Lycopersicoides and section Juglandifolium are represented by two species each that are considered bridge species genetically intermediate between tomato and non-tuber bearing potato species. S. Lycopersicoides can be crossed with domestic tomato and introgression lines ^[70] have been developed. This species was significant in moving the domestic tomato from separate genus status into the Solanum group because it directly links the tomato into the potato family.

Genome sequencing

An international consortium of researchers from 10 countries, among them researchers from the Boyce Thompson Institute for Plant Research, began sequencing the tomato genome in 2004, and is creating a database of genomic sequences and information on the tomato and related plants.^[71][72] A prerelease version of the genome was made available in December 2009.^[73] The genomes of its mitochondria and chloroplasts are also being sequenced as part of the project. The complete genome for the cultivar Heinz 1706 was published on 31 May 2012 in Nature.^[74] Since many other fruits, like strawberries, apples, melons, and bananas share the same characteristics and genes, researchers stated the published genome could help to improve food quality, food security and reduce costs of all of these fruits.^[75]

Breeding

Active breeding programs are ongoing by individuals, universities, corporations, and organizations. The Tomato Genetic Resource Center, Germplasm Resources Information Network, AVRDC, and numerous seed banks around the world store seed representing genetic variations of value to modern agriculture. These seed stocks are available for legitimate breeding and research efforts. While individual breeding efforts can produce useful results, the bulk of tomato breeding work is at universities and major agriculture-related corporations. These efforts have resulted in significant regionally adapted breeding lines and hybrids, such as the Mountain series from North Carolina. Corporations including Heinz, Monsanto, BHNSeed, Bejoseed, etc., have breeding programs that attempt to improve production, size, shape, color, flavor, disease tolerance, pest tolerance, nutritional value, and numerous other traits.

Fruit or vegetable?

Botanically, a tomato is a fruit: the ovary, together with its seeds, of a flowering plant. However, the tomato has a much lower sugar content than other edible fruits, and is therefore not as sweet. Typically served as part of a salad or main course of a meal, rather than at dessert, it is considered a vegetable for most culinary uses. One exception is that tomatoes are treated as a fruit in home canning practices: they are acidic enough to process in a water bath rather than a pressure cooker as vegetables require. Tomatoes are not the only food source with this ambiguity: green beans, eggplants, cucumbers, and squashes of all kinds (such as zucchini and pumpkins) are all botanically fruits, yet cooked as vegetables.

This dispute has led to legal speculation in the United States. In 1887, U.S. tariff laws that imposed a duty on vegetables, but not on fruits, caused the tomato's status to become a matter of legal importance. The U.S. Supreme Court settled this controversy on 10 May 1893, by declaring that the tomato is a vegetable, based on the popular definition that classifies vegetables by use, that they are generally served with dinner and not dessert (Nix v. Hedden (149 U.S. 304)).^[76] The holding of this case applies only to the interpretation of the Tariff Act of 3 March 1883, and the court did not purport to reclassify the tomato for botanical or other purposes.

Tomatoes have been designated the state vegetable of New Jersey. Arkansas took both sides by declaring the South Arkansas Vine Ripe Pink Tomato both the state fruit and the state vegetable in the same law, citing both its culinary and botanical classifications. In 2009, the state of Ohio passed a law making the tomato the state's official fruit. Tomato juice has been the official beverage of Ohio since 1965. A.W. Livingston, of Reynoldsburg, Ohio, played a large part in popularizing the tomato in the late 19th century; his efforts are commemorated in Reynoldsburg with an annual Tomato Festival.

Names

The scientific species epithet lycopersicum means "wolf peach", and comes from German werewolf myths. These legends said that deadly nightshade was used by witches and sorcerers in potions to transform themselves into werewolves, so the tomato's similar, but much larger, fruit was called the "wolf peach" when it arrived in Europe.^[77]

The native Mexican tomatillo is tomate (in Nahuatl: tomātl, meaning 'fat water' or 'fat thing').^{[78][79][80][81][82][83]} When Aztecs started to cultivate the Andean fruit, bigger and red, they called the new species xitomatl (or jitomates) (pronounced /ʃiːˈtomatɬ/), ('plump thing with navel' or 'fat water with navel'). After their conquest of Tenochtitlan, Spaniards exported tomatoes (jitomates) to the rest of the world with the name tomate, so numerous languages use forms of the word "tomato" (tomate) to refer to the red tomato instead of the green tomatillo.

The Italian word, pomodoro (from pomo d'oro "apple of gold") was borrowed into Polish, and via Russian, into several other languages. Similarly, the now rare German term Paradeisapfel (for "apple of paradise") is still heard in the form paradeiser in the Bavarian and Austrian dialects, and was borrowed into modern Hungarian, Slovenian and Serbian.

Pronunciation

The pronunciation of tomato differs in different English-speaking countries; the two most common variants are /təˈmɑːtoʊ/ tə-MAH-toh and /təˈmeɪtoʊ/ tə-MAY-toh. Speakers from the British Isles and most of the Commonwealth typically say /təˈmɑːtoʊ/, while most North American speakers usually say /təˈmeɪtoʊ/.

The word's dual pronunciations were immortalized in Ira and George Gershwin's 1937 song "Let's Call the Whole Thing Off" ("You like /pəˈteɪtoʊ/ and I like /pəˈtɑːtoʊ/ / You like /təˈmeɪtoʊ/ and I like /təˈmɑːtoʊ/") and have become a symbol for nitpicking pronunciation disputes. In this capacity, it has even become an American and British slang term: saying "/təˈmeɪtoʊ/ /təˈmɑːtoʊ/" when presented with two choices can mean "What's the difference?" or "It's all the same to me."

Tomato records

The heaviest tomato ever, weighing 3.51 kg (7 lb 12 oz), was of the cultivar 'Delicious', grown by Gordon Graham of Edmond, Oklahoma in 1986.^[84] The largest tomato plant grown was of the cultivar 'Sungold' and reached 19.8 m (65 ft) in length, grown by Nutriculture Ltd (UK) of Mawdesley, Lancashire, UK, in 2000.^[85]

The massive "tomato tree" growing inside the Walt Disney World Resort's experimental greenhouses in Lake Buena Vista, Florida may be the largest single tomato plant in the world. The plant has been recognized as a Guinness World Record Holder, with a harvest of more than 32,000 tomatoes and a total weight of 522 kg (1,151 lb).^[86] It yields thousands of tomatoes at one time from a single vine. Yong Huang, Epcot's manager of agricultural science, discovered the unique plant in Beijing, China. Huang brought its seeds to Epcot and created the specialized greenhouse for the fruit to grow. The vine grows golf ball-sized tomatoes, which are served at Walt Disney World restaurants.

The world record-setting tomato tree can no longer be seen by guests along the Living With the Land boat ride at Epcot, as the tree developed a disease and was removed in April 2010 after approximately 13 months of life.^[86]

On 30 August 2007, 40,000 Spaniards gathered in Buñol to throw 115,000 kg (254,000 lb) of tomatoes at each other in the yearly Tomatina festival.^[87]

Flavr Savr was the first commercially grown genetically engineered food licensed for human consumption.^[88]

Cultural impact

The town of Buñol, Spain, annually celebrates La Tomatina, a festival centered on an enormous tomato fight. Tomatoes are a popular "nonlethal" throwing weapon in mass protests, and there was a common tradition of throwing rotten tomatoes at bad performers on a stage during the 19th century; today this is usually referenced as a metaphor. Embracing it for this protest connotation, the Dutch Socialist party adopted the tomato as their logo.

The US city of Reynoldsburg, Ohio calls itself "The Birthplace of the Tomato", claiming the first commercial variety of tomato was bred there in the 19th century.^[16]

Several US states have adopted the tomato as a state fruit or vegetable (see above).

See also

• Blue tomato, varieties of naturally-bred tomatoes to produce anthocyanins
• Genetically modified tomato, genes introduced from other organisms to improve various qualities
• List of countries by tomato production
• List of tomato cultivars
• Marglobe, an early attempt at breeding a disease-resistant tomato
• Ring culture
• Tomatillo, a similar fruit from the related genus Physalis that is also used in cooking
• Tomato jam

References

Further reading

• David Gentilcore. Pomodoro! A History of the Tomato in Italy (Columbia University Press, 2010), scholarly history

External links

Wikimedia Commons has media related to Solanum lycopersicum.

Wikibooks Cookbook has a recipe/module on Tomato

The Wikibook Horticulture has a page on the topic of: Tomato

External identifiers for Solanum lycopersicum
Encyclopedia of Life	392557
NCBI	4081
Also found in: Wikispecies

• Data related to Solanum lycopersicum at Wikispecies
• Media related to Tomatoes at Wikimedia Commons
• The dictionary definition of tomato at Wiktionary
• Tomato at the National Center for Biotechnology Information
• "Solanum lycopersicum". Integrated Taxonomic Information System. 
• Tomato at the Encyclopedia of Life
• Tomato Pests (NCSU) – Overview of the entomological threats to tomato cultivation.
• Tomato Genome Sequencing Project – Sequencing of the twelve tomato chromosomes.
• Tomato core collection database – Phenotypes and images of 7,000 tomato cultivars
• The On-line Tomato Vine (Keith Mueller) – Practical information on growing and breeding tomatoes
• The case against heirloom tomatoes at Scientific American
• Red menace: How the ‘strange and horrible’ tomato conquered Italy, and America at The Boston Globe
• Paul Lunde, New World Foods, Old World Diet, 1992, Saudi Aramco World
• Meet the TomTato: Tomatoes and potatoes grown as one – CBS News (26 September 2013)
• Solanum lycopersicum L. on Solanaceae Source – Images, specimens and a full list of scientific synonyms previously used to refer to the tomato.