Tomato

Tomato
Cross-section and full view of a hothouse (greenhouse-grown) tomato
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Eudicots
(unranked):	Asterids
Order:	Solanales
Family:	Solanaceae
Genus:	Solanum
Species:	S. lycopersicum
Binomial name
Solanum lycopersicum L.
Synonyms
Lycopersicon lycopersicum (L.) H. Karst. Lycopersicon esculentum Mill.[1]

The tomato (see pronunciation) is the edible fruit of Solanum lycopersicum,^[2] commonly known as a tomato plant, which belongs to the nightshade family, Solanaceae.^[1]

The species originated in Central and South America. The Nahuatl (Aztec language) word tomatl gave rise to the Spanish word "tomate", from which the English word tomato originates.

Its use as a food originated in Mexico, and spread throughout the world following the Spanish colonization of the Americas. Tomato is consumed in diverse ways, including raw, as an ingredient in many dishes, sauces, salads, and drinks. While tomatoes are botanically berry-type fruits, they are considered culinary vegetables, being ingredients of savory meals.^[3]

Numerous varieties of tomato are widely grown in temperate climates across the world, with greenhouses allowing its production throughout the year and in cooler areas. 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, and grown as an annual in temperate climates. An average common tomato weighs approximately 100 grams (4 oz).^[4][5]

Names

Etymology

The word "tomato" comes from the Spanish tomate, which in turn comes from the Nahuatl word tomatl [ˈtomat͡ɬ].^[6] It first appeared in print in 1595.

The native Mexican tomatillo is tomate (in Nahuatl: tomātl  pronunciation ), meaning "fat water" or "fat thing").^[7] 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. It first appeared in print in 1595.^[6] 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.^[8]

Derivations

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, which means "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 usual pronunciations of "tomato" are /təˈmeɪtoʊ/ (usual in American English) and /təˈmɑːtoʊ/ (usual in British English).^[9] 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".

Fruit versus vegetable

Botanically, a tomato is a fruit, a berry, consisting of 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, in the US, considered a "culinary vegetable". 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: bell peppers, cucumbers, green beans, eggplants, avocados, and squashes of all kinds (such as zucchini and pumpkins) are all botanically fruits, yet cooked as vegetables. This has led to legal dispute in the United States. In 1887, US 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 US 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)). 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.

Botany

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.^[11]

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.^[12]

The leaves are 10–25 cm (4–10 in) long, odd pinnate, with five to 9 leaflets on petioles,^[13] 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 can 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.

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.^[14] This name came into wide use, but was technically in breach of the plant naming rules because Linnaeus's species name lycopersicum still had priority. Although the name Lycopersicum lycopersicum was suggested by Karsten (1888), this is not used because it violates the International Code of Nomenclature^[15] barring the use of tautonyms in botanical nomenclature. The corrected name Lycopersicon lycopersicum (Nicolson 1974) was technically valid, since Miller's genus name and Linnaeus's species name differ in exact spelling, but since Lycopersicon esculentum had become so well known, it was officially listed as a nomen conservandum in 1983, and would be the correct name for the tomato in classifications which do not place the tomato in the genus Solanum.

Genetic evidence has now shown that Linnaeus was correct to put the tomato in the genus Solanum, making Solanum lycopersicum the correct name.^[1][16] Both names, however, will probably be found in the literature for some time. Two of the major reasons that 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,^[17] 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, galapagense, and 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^[18] 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.

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.^[19] 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.

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.^[20][21] A prerelease version of the genome was made available in December 2009.^[22] 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.^[23] 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.^[24]

Breeding

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, and Bejoseed have breeding programs that attempt to improve production, size, shape, color, flavor, disease tolerance, pest tolerance, nutritional value, and numerous other traits.

History

The tomato is native to western South America and Central America.^[6] Native versions were small, like cherry tomatoes, and most likely yellow rather than red. A member of the deadly nightshade family, tomatoes were erroneously thought to be poisonous by Europeans who were suspicious of their bright, shiny fruit. The leaves are in fact slightly poisonous, although the fruit is not.^[25]

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.^[26]:13 The Pueblo people are thought to have believed that those who witnessed the ingestion of tomato seeds were blessed with powers of divination.^[27] 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.^[26]:15

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 may have taken them back as early as 1493. The earliest discussion of the tomato in European literature appeared in a 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. It was not until ten years later that tomatoes were named in print by Mattioli as pomi d’oro, or "golden apples".^[26]: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.

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 habit 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 any other varieties.^[28] In certain areas of Italy, such as Florence, the fruit was used solely as a tabletop decoration, until it was incorporated into the local cuisine in the late 17th or early 18th century. The earliest discovered cookbook with tomato recipes was published in Naples in 1692, though the author had apparently obtained these recipes from Spanish sources.^[26]:17

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 a relatively intense flavor compared to varieties typically grown elsewhere.

Britain

Tomatoes were not grown in England until the 1590s.^[26]:17 One of the earliest cultivators was John Gerard, a barber-surgeon.^[26]:17 Gerard's Herbal, published in 1597, and largely plagiarized from continental sources,^[26]:17 is also one of the earliest discussions of the tomato in England. Gerard knew the tomato was eaten in Spain and Italy.^[26]:17 Nonetheless, he believed it was poisonous^[26]: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.^[26]:17

However, 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, 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 exotic Italian or Jewish cuisine.^[29]

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.^[30][31] 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".^[32] 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.

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.^[26]: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.^[26]: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.^[33]

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.^[33]

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.^[34] The Center is named for the late Dr. Charles M. Rick, a pioneer in tomato genetics research.^[35] Research on processing tomatoes is also conducted by the California Tomato Research Institute in Escalon, California.^[36]

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.^[37][38]

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.^[39]

Cultivation

The tomato is grown worldwide for its edible fruits, with thousands of cultivars.^[40] 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.

Production

In 2014, world production of tomatoes was 170.8 million tonnes, with China accounting for 31% of the total, followed by India, the United States and Turkey as the major producers (table).^[41] In 2014, tomatoes accounted for 23% of the total fresh vegetable output of the European Union, with more than half of this total coming from Spain, Italy and Poland.^[42]

In 2013, global tomato exports were valued at 88 billion US dollars.^[43]

Rank	Country	Production millions of tonnes[41][44]
1	China	52.6
2	India	18.7
3	United States	14.5
4	Turkey	11.9
5	Egypt	8.3
6	Iran	6.0
7	Italy	5.6
8	Spain	4.9
	World	170.8

Varieties

There are around 7,500 tomato varieties grown for various purposes having been selected with varying fruit types, and for optimum growth in differing growing conditions.

Tomato varieties can be divided into categories based on shape and size.

• Beefsteak tomatoes are 10 cm (4 in) or more in diameter, often used for sandwiches and similar applications. Their kidney-bean shape, thinner skin, and shorter shelf life makes commercial use impractical.
• Plum tomatoes, or paste tomatoes (including pear tomatoes), are bred with a lower water /higher solids content for use in tomato sauce and paste, for canning and sauces and are usually oblong 7–9 cm (3–4 in) long and 4–5 cm (1.6–2.0 in) diameter; like the Roma-type tomatoes, important cultivars in the Sacramento Valley.^[45]
• Cherry tomatoes are small and round, often sweet tomatoes, about the same 1–2 cm (0.4–0.8 in) size as the wild tomato.
• Grape tomatoes are smaller and oblong, a variation on plum tomatoes.
• Campari tomatoes are sweet and noted for their juiciness, low acidity, and lack of mealiness, bigger than cherry tomatoes, and smaller than plum tomatoes.
• Tomberries, tiny tomatoes, about 5 mm in diameter
• Oxheart tomatoes can range in size up to beefsteaks, and are shaped like large strawberries.
• Pear tomatoes are pear-shaped and can be based upon the San Marzano types for a richer gourmet paste.
• "Slicing" or "globe" tomatoes are the usual tomatoes of commerce, used for a wide variety of processing and fresh eating. The most widely grown commercial tomatoes tend to be in the 5–6 cm (2.0–2.4 in) diameter range.

Tomatoes are also 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 semi-determinate; 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.

Early tomatoes and cool-summer tomatoes bear fruit even where nights are cool, which usually discourages fruit set. There are varieties high in beta carotenes and vitamin A, hollow tomatoes and tomatoes that keep for months in storage. In 1973, Israeli scientists developed the world's first long shelf-life commercial tomato varieties.^[46]

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.^[45] The definition of an heirloom tomato is vague, but unlike commercial hybrids, all are self-fertile varieties that have bred true for 40 years or more. Quite a few seed merchants and banks provide a large selection of heirloom seeds.^[45] 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. Hybrid plants remain common, since they tend to be heavier producers, and sometimes may combine unusual characteristics of heirloom tomatoes with the ruggedness of conventional commercial tomatoes.

Most modern tomato cultivars are smooth surfaced, but some older tomato cultivars and most modern beefsteaks 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 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. Variations include multicolored fruit with stripes (Green Zebra), fuzzy skin on the fruit (Fuzzy Peach, Red Boar), multiple colors (Hillbilly, Burracker's Favorite, Lucky Cross), etc.

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

Diseases, pests, and disorders

Tomato cultivars vary widely in their resistance to disease. Modern hybrids focus on improving disease resistance over the heirloom plants.

Various forms of mildew and blight are 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,^[47] V – verticillium wilt, F – fusarium wilt strain I, FF – fusarium wilt strain I and II, N – nematodes, T – tobacco mosaic virus, and A – alternaria.

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,^[48] and Colorado potato beetles. The tomato russet mite, Aculops lycopersici, feeds on foliage and young fruit of tomato plants, causing shrivelling and necrosis of leaves, flowers, and fruit, possibly killing the plant.^[49]

A common tomato disease is tobacco mosaic virus. Handling cigarettes and other infected tobacco products can transmit the virus to tomato plants.^[50]

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

After an insect attack tomato plants produce systemin, a plant peptide hormone . 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.^[51]

Although not a disease as such, irregular supplies of water can cause growing or ripening fruit to split. Besides cosmetic damage, the splits may allow decay to start, although growing fruits have some ability to heal after a split. In addition, a deformity called cat-facing can be caused by pests, temperature stress, or poor soil conditions. Affected fruit usually remains edible, but its appearance may be unsightly.

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.^[52]

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.^[53]

Borage is thought to repel the tomato hornworm moth.^[54]

Plants with strong scents, like alliums (onions, chives, garlic) and mints (basil, oregano, spearmint) are 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.^[55] These plants may also subtly impact the flavor of tomato fruit.^[56]

Ground cover plants, including mints, 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.

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 can protect asparagus from asparagus beetles, because they contain solanum that kills this pest, while asparagus plants (as well as marigolds^[56]) 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.^[57] The trait of self-fertility became an advantage, and domestic cultivars of tomato have been selected to maximize this trait.^[57]

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.^[58] 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 externally-induced motion. The best source of outside motion is a sonicating bee, such as a bumblebee, or the original wild halictid pollinator. In an outdoors setting, wind or animals usually 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),^[59] 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.^[60]

Hydroponic 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.^[61] 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.^[62]

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.^[63] Slow-ripening cultivars of tomato have been developed by crossing a non-ripening cultivar with ordinary cultivars.

Yield

The world dedicated 4.8 million hectares in 2012 for tomato cultivation and the total production was about 161.8 million tonnes.^[64] The average world farm yield for tomato was 33.6 tonnes per hectare, in 2012.^[64]

Tomato farms in the Netherlands were the most productive in 2012, with a nationwide average of 476 tonnes per hectare, followed by Belgium (463 tonnes per hectare) and Iceland (429 tonnes per hectare).^[65]

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.^[66] 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.^[67]

A massive "tomato tree" growing inside the Walt Disney World Resort's experimental greenhouses in Lake Buena Vista, Florida may have been 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).^[68] It yielded 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 grew golf ball-sized tomatoes, which were served at Walt Disney World restaurants. The tree developed a disease and was removed in April 2010 after about 13 months of life.^[68]

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.

Although tomatoes originated in the Americas, they have become extensively used 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).

Storage

Tomatoes keep best unwashed at room temperature and out of direct sunlight. It is not recommended to refrigerate them as this can harm the flavor.^[69] Tomatoes stored cold tend to lose their flavor permanently.^[70]

Storing stem down can prolong shelf life,^[71] as it may keep from rotting too quickly.^[72]

Tomatoes that are not yet ripe can be kept in a paper bag till ripening.^[73]

Safety

Plant toxicity

Leaves, stems, and green unripe fruit of the tomato plant contain small amounts of the toxic alkaloid tomatine.^[25] They also contain small amounts of solanine, a toxic alkaloid found in potato leaves and other plants in the nightshade family.^[74][75] Use of tomato leaves in herbal tea has been responsible for at least one death.^[25][74] 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.^[25] 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.^[75]

Tomato plants can be toxic to dogs if they eat large amounts of the fruit, or chew plant material.^[76]

Salmonella

Tomatoes were linked to seven salmonella outbreaks between 1990 and 2005,^[77] and may have been the cause of a salmonellosis outbreak causing 172 illnesses in 18 US states in 2006,^[78] The 2008 United States salmonellosis outbreak also caused the removal of tomatoes from stores and restaurants across the United States and parts of Canada,^[79] although other foods, including jalapeño and serrano peppers, may have been involved.

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
Minerals
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

A tomato is 95% water, contains 4% carbohydrates and less than 1% each of fat and protein (table). In a 100 gram amount, raw tomatoes supply 18 calories and are a moderate source of vitamin C (17% of the Daily Value), but otherwise are absent of significant nutrient content (table).

Potential health effects

There is no conclusive evidence that the lycopene in tomatoes or in supplements affects the onset of cardiovascular diseases or cancer.^[80][81]

In the United States, supposed health benefits of consuming tomatoes, tomato products or lycopene to affect cancer cannot be mentioned on packaged food products without a qualified health claim statement.^[82] In a scientific review of potential claims for lycopene favorably affecting DNA, skin exposed to ultraviolet radiation, heart function and vision, the European Food Safety Authority concluded there was insufficient evidence for lycopene having any of these effects.^[83]

In popular culture

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.^[84]

In Ontario, Canada, member of provincial parliament Mike Colle named the tomato the official vegetable of the province and designated July 15 as Tomato Day under the Tomato Act in 2016.^[85][86]

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.

Flavr Savr was the first commercially grown genetically engineered food licensed for human consumption.^[87]

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.^[33]

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

See also

References

Further reading

• David Gentilcore. Pomodoro! A History of the Tomato in Italy (Columbia University Press, 2010), scholarly history
• Tieman, D; Bliss, P; McIntyre, LM; Blandon-Ubeda, A; Bies, D; Odabasi, AZ; Rodríguez, GR; van der Knaap, E; Taylor, MG; Goulet, C; Mageroy, MH; Snyder, DJ; Colquhoun, T; Moskowitz, H; Clark, DG; Sims, C; Bartoshuk, L; Klee, HJ (5 June 2012). "The Chemical Interactions Underlying Tomato Flavor Preferences". Current Biology. 22 (11): 1035–1039. PMID 22633806. doi:10.1016/j.cub.2012.04.016. 

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

• Data related to Solanum lycopersicum at Wikispecies
• Media related to Tomatoes at Wikimedia Commons
• The dictionary definition of tomato at Wiktionary
• Tomato Genome Sequencing Project – Sequencing of the twelve tomato chromosomes.
• Tomato core collection database – Phenotypes and images of 7,000 tomato cultivars