Peach

The peach (Prunus persica) is a deciduous tree, native to Northwest China, in the region between the Tarim Basin and the north slopes of the Kunlun Shan mountains, where it was first domesticated and cultivated. It bears an edible juicy fruit also called a peach.

The specific epithet persica refers to its widespread cultivation in Persia, whence it was transplanted to Europe. It belongs to the genus Prunus which includes the cherry and plum, in the family Rosaceae. The peach is classified with the almond in the subgenus Amygdalus, distinguished from the other subgenera by the corrugated seed shell.

Peach and nectarines are the same species, even though they are regarded commercially as different fruits. In contrast to peaches, whose fruits present the characteristic fuzz on the skin, nectarines are characterized by the absence of fruit-skin trichomes (fuzz-less fruit); genetic studies suggest nectarines are produced due to a recessive allele, whereas peaches are produced from a dominant allele for fuzzy skin.

China is the world's largest producer of peaches.

Description
Prunus persica grows to 4 – tall and 6 in. in diameter. The leaves are lanceolate, 7 – long, 2 – broad, pinnately veined. The flowers are produced in early spring before the leaves; they are solitary or paired, 2.5–3 cm diameter, pink, with five petals. The fruit has yellow or whitish flesh, a delicate aroma, and a skin that is either velvety (peaches) or smooth (nectarines) in different cultivars. The flesh is very delicate and easily bruised in some cultivars, but is fairly firm in some commercial varieties, especially when green. The single, large seed is red-brown, oval shaped, approximately 1.3–2 cm long, and is surrounded by a wood-like husk. Peaches, along with cherries, plums and apricots, are stone fruits (drupes). There are various heirloom varieties, including the Indian peach, which arrives in the latter part of the summer.

Cultivated peaches are divided into clingstones and freestones, depending on whether the flesh sticks to the stone or not; both can have either white or yellow flesh. Peaches with white flesh typically are very sweet with little acidity, while yellow-fleshed peaches typically have an acidic tang coupled with sweetness, though this also varies greatly. Both colours often have some red on their skin. Low-acid white-fleshed peaches are the most popular kinds in China, Japan, and neighbouring Asian countries, while Europeans and North Americans have historically favoured the acidic, yellow-fleshed kinds.

Etymology
The scientific name persica, along with the word "peach" itself and its cognates in many European languages, derives from an early European belief that peaches were native to Persia. The Ancient Romans referred to the peach as malum persicum "Persian apple", later becoming French pêche, hence the English "peach". The scientific name, Prunus persica, literally means "Persian plum", as it is closely related to the plum.

History
Although its botanical name Prunus persica refers to Persia (present Iran) from where it came to Europe, genetic studies suggest peaches originated in China, where they have been cultivated since the early days of Chinese culture, circa 2000 BC. Peaches were mentioned in Chinese writings as far back as the 10th century BC and were a favoured fruit of kings and emperors. As of late, the history of cultivation of peaches in China has been extensively reviewed citing numerous original manuscripts dating back to 1100 BC.



The peach was brought to India and Western Asia in ancient times. Peach cultivation also went from China, through Persia, and reached Greece by 300 BC. Alexander the Great introduced the fruit into Europe after he conquered the Persians. Peaches were well known to the Romans in first century AD, and were cultivated widely in Emilia-Romagna. Peach trees are portrayed in the wall paintings of the towns destroyed by the Vesuvius eruption of 79 AD, while the oldest known artistic representations of the fruit are in the two fragments of wall paintings, dated back to the 1st century AD, in Herculaneum, now preserved in the National Archaeological Museum in Naples.

Peach was brought to the Americas by Spanish explorers in the 16th century, and eventually made it to England and France in the 17th century, where it was a prized and expensive treat. The horticulturist George Minifie supposedly brought the first peaches from England to its North American colonies in the early 17th century, planting them at his Estate of Buckland in Virginia. Although Thomas Jefferson had peach trees at Monticello, United States farmers did not begin commercial production until the 19th century in Maryland, Delaware, Georgia and finally Virginia.

In April 2010, an International Consortium, The International Peach Genome Initiative (IPGI), that include researchers from USA, Italy, Chile, Spain and France announced they had sequenced the peach tree genome (doubled haploid Lovell). Recently, IPGI published the peach genome sequence and related analyses. The peach genome sequence is composed of 227 millions of nucleotides arranged in 8 pseudomolecules representing the 8 peach chromosomes (2n = 16). In addition, a total of 27,852 protein-coding genes and 28,689 protein-coding transcripts were predicted. Particular emphasis in this study is reserved to the analysis of the genetic diversity in peach germplasm and how it was shaped by human activities such as domestication and breeding. Major historical bottlenecks were individuated, one related to the putative original domestication that is supposed to have taken place in China about 4,000–5,000 years ago, the second is related to the western germplasm and is due to the early dissemination of peach in Europe from China and to the more recent breeding activities in US and Europe. These bottlenecks highlighted the strong reduction of genetic diversity associated with domestication and breeding activities.

Cultivation
Peaches grow in a fairly limited range in dry, continental or temperate climates, since the trees have a chilling requirement that tropical or subtropical areas generally cannot satisfy except at high altitudes (for example in parts of Ecuador, Colombia, Ethiopia, India and Nepal). Most cultivars require 500 hours of chilling around 0 to 10 C. During the chilling period, key chemical reactions occur but the plant appears dormant. Once the chilling period is fulfilled, the plant enters a second type of dormancy, the quiescence period. During quiescence, buds break and grow when sufficient warm weather favorable to growth is accumulated.

The trees themselves can usually tolerate temperatures to around -26 to -30 C, although the following season's flower buds are usually killed at these temperatures, preventing a crop that summer. Flower bud death begins to occur between -15 and -25 C, depending on the cultivar and on the timing of the cold, with the buds becoming less cold tolerant in late winter.

Another climate constraint is spring frost. The trees flower fairly early (in March in western Europe) and the blossom is damaged or killed if temperatures drop below about -4 C. However, if the flowers are not fully open, they can tolerate a few degrees colder.

Climates with significant winter rainfall at temperatures below 16 C are also unsuitable for peach cultivation as the rain promotes peach leaf curl, which is the most serious fungal disease for peaches. In practice, fungicides are extensively used for peach cultivation in such climates, with >1% of European peaches exceeding legal pesticide limits in 2013.

Finally, summer heat is required to mature the crop, with mean temperatures of the hottest month between 20 and 30 C.

Typical peach cultivars begin bearing fruit in their third year and have a lifespan of about 12 years.

Cultivars
There are hundreds of peach and nectarine cultivars. These are classified into two categories—the freestones and the clingstones. Freestones are those whose flesh separates readily from the pit. Clingstones are those whose flesh clings tightly to the pit. Some cultivars are partially freestone and clingstone, and these are called semi-free. Freestone types are preferred for eating fresh, while clingstone for canning. The fruit flesh may be creamy white or deep yellow; the hue and shade of the color depends on the cultivar.

Peach breeding has favored cultivars with more firmness, more red color, and shorter fuzz on fruit surface. These characteristics ease shipping and supermarket sales by improving eye appeal. However, this selection process has not necessarily led to increased flavor. Peaches have short shelf life, so commercial growers typically plant a mix of different cultivars in order to have fruit to ship all season long.

Different countries have different cultivars. In United Kingdom, for example, the following cultivars have gained the Royal Horticultural Society's Award of Garden Merit:-
 * 'Duke of York'
 * 'Peregrine'
 * 'Rochester'
 * 'Lord Napier' (nectarine)

Nectarines
The variety P. persica var. nucipersica (or var. nectarina), commonly called nectarine, has a smooth skin. It is on occasion referred to as a "shaved peach" or "fuzzless peach", due to its lack of fuzz or short hairs. Though fuzzy peaches and nectarines are regarded commercially as different fruits, with nectarines often erroneously believed to be a crossbreed between peaches and plums, or a "peach with a plum skin", nectarines belong to the same species as peaches. Several genetic studies have concluded nectarines are produced due to a recessive allele, whereas a fuzzy peach skin is dominant. Nectarines have arisen many times from peach trees, often as bud sports.

As with peaches, nectarines can be white or yellow, and clingstone or freestone. On average, nectarines are slightly smaller and sweeter than peaches, but with much overlap. The lack of skin fuzz can make nectarine skins appear more reddish than those of peaches, contributing to the fruit's plum-like appearance. The lack of down on nectarines' skin also means their skin is more easily bruised than peaches.

The history of the nectarine is unclear; the first recorded mention in English is from 1616, but they had probably been grown much earlier within the native range of the peach in central and eastern Asia. Although one source states that nectarines were introduced into the United States by David Fairchild of the Department of Agriculture in 1906, a number of colonial era newspaper articles make reference to nectarines being grown in the United States prior to the Revolutionary War. 28 March 1768 edition of the New York Gazette (p. 3), for example, mentions a farm in Jamaica, Long Island, New York, where nectarines were grown.

Peacherines
Peacherine is claimed to be a cross between a peach and a nectarine, and are marketed in Australia and New Zealand. The fruit is intermediate in appearance between a peach and a nectarine, large and brightly colored like a red peach. The flesh of the fruit is usually yellow but white varieties also exist. The Koanga Institute lists varieties that ripen in the Southern hemisphere in February and March.

In 1909, Pacific Monthly mentioned peacherines in a news bulletin for California. Louise Pound, in 1920, claimed the term peacherine is an example of language stunt.

Flat peaches
Flat peaches or pan-tao have a flattened shape in contrast to ordinary rounded peaches.

Planting
Most peach trees sold by nurseries are cultivars budded or grafted onto a suitable rootstock. Common rootstocks are Lovell Peach, Nemaguard Peach, Prunus besseyi, and Citation. This is done to improve predictability of the fruit quality.

Peach trees need full sun, and a layout that allows good natural air flow to assist the thermal environment for the tree. Peaches are planted in early winter. During the growth season, peach trees need a regular and reliable supply of water, with higher amounts just before harvest.

Peaches need nitrogen rich fertilizers more than other fruit trees. Without regular fertilizer supply, peach tree leaves start turning yellow or exhibit stunted growth. Blood meal, bone meal, and calcium ammonium nitrate are suitable fertilizers.

The number of flowers on a peach tree are typically thinned out, because if the full number of peaches mature on a branch, they are under-sized and lacking in flavor. Fruits are thinned midway in the season by commercial growers. Fresh peaches are easily bruised, and do not store well. They are most flavorful when they ripen on the tree and eaten the day of harvest.

The peach tree can be grown in an espalier shape. The Baldassari palmette is a palmette design created around 1950 used primarily for training peaches. In walled gardens constructed from stone or brick, which absorb and retain solar heat and then slowly release it, raising the temperature against the wall, peaches can be grown as espaliers against south-facing walls as far north as southeast Great Britain and southern Ireland.

Interaction with fauna

 * Insects

The first pest to attack the tree early in the year when other food is scarce is the earwig (Forficula auricularia) which feeds on blossoms and young leaves at night, preventing fruiting and weakening newly planted trees. The pattern of damage is distinct from that of caterpillars later in the year, as earwigs characteristically remove semi-circles of petal and leaf tissue from the tips, rather than internally. Greasebands applied just before blossom are effective.

The larvae of such moth species as the peachtree borer (Synanthedon exitiosa), the yellow peach moth (Conogethes punctiferalis), the well-marked cutworm (Abagrotis orbis), Lyonetia prunifoliella, Phyllonorycter hostis, the fruit tree borer (Maroga melanostigma), Parornix anguliferella, Parornix finitimella, Caloptilia zachrysa, Phyllonorycter crataegella, Trifurcula sinica, the Suzuki's Promolactis moth (Promalactis suzukiella), the white-spotted tussock moth (Orgyia thyellina), the apple leafroller (Archips termias), the catapult moth (Serrodes partita), the wood groundling (Parachronistis albiceps) or the omnivorous leafroller (Platynota stultana) are reported to feed on P. persica.

The flatid planthopper (Metcalfa pruinosa) causes damage to fruit trees.

The tree is also a host plant for such species as the Japanese beetle (Popillia japonica), the unmonsuzume (Callambulyx tatarinovii), the Promethea silkmoth (Callosamia promethea), the orange oakleaf (Kallima inachus), Langia zenzeroides, the speckled emperor (Gynanisa maja) or the brown playboy (Deudorix antalus).

It is a good pollen source for honey bees and a honeydew source for aphids.

The European red mite (Panonychus ulmi) or the yellow mite (Lorryia formosa) are also found on the peach tree.
 * Mites

Diseases
Peach trees are prone to a disease called leaf curl, which usually does not directly affect the fruit, but does reduce the crop yield by partially defoliating the tree. The fruit is susceptible to brown rot or a dark reddish spot. Ziram is a fungicide often used on peach trees to protect against fungal infection.

Storage
Peaches and nectarines are best stored at temperatures of 0 °C (32 °F) and high-humidity. They are highly perishable, and typically consumed or canned within two weeks of harvest.

Peaches are climacteric  fruits and continue to ripen after being picked from the tree.

Production
Significant peach-producing regions (see chart) are China, Mediterranean countries, such as Italy, Spain and Greece, and the United States where the three largest producing states are California, South Carolina and Georgia.

The US State of Georgia is known as the "Peach State" due to its significant production of peaches as early as 1571, with exports to other states occurring around 1858.

By crop yield, the most productive farms for peaches and nectarines, on average, were in Israel. In comparison to world average yield of 14 metric tons per hectare, Israeli farm yields were 36 metric tonnes per hectare in 2013.

Cultural significance
Peaches are not only a popular fruit, but are symbolic in many cultural traditions, such as in art, paintings and folk tales such as Peaches of Immortality.

China
Peach blossoms are highly prized in Chinese culture. The ancient Chinese believed the peach to possess more vitality than any other tree because their blossoms appear before leaves sprout. When early rulers of China visited their territories, they were preceded by sorcerers armed with peach rods to protect them from spectral evils. On New Year's Eve, local magistrates would cut peach wood branches and place them over their doors to protect against evil influences. Another author writes:

"The Chinese also considered peach wood (t'ao-fu) protective against evil spirits, who held the peach in awe. In ancient China, peach-wood bows were used to shoot arrows in every direction in an effort to dispel evil. Peach-wood slips or carved pits served as amulets to protect a person's life, safety, and health."

Peach-wood seals or figurines guarded gates and doors, and, as one Han account recites, "the buildings in the capital are made tranquil and pure; everywhere a good state of affairs prevails." Writes the author, further:

"Another aid in fighting evil spirits were peach-wood wands. The Li-chi (Han period) reported that the emperor went to the funeral of a minister escorted by a sorcerer carrying a peach-wood wand to keep bad influences away. Since that time, peach-wood wands have remained an important means of exorcism in China." Peach kernels (桃仁 táo rén) are a common ingredient used in traditional Chinese medicine to dispel blood stasis, counter inflammation and reduce allergies.

It was in an orchard of flowering peach trees that Liu Bei, Guan Yu, and Zhang Fei took an oath of brotherhood in the opening chapter of the classic Chinese novel Romance of the Three Kingdoms. Another peach forest, “The Peach Blossom Spring” by poet Tao Yuanming is the setting of the favourite Chinese fable and a metaphor of utopias. A peach tree growing on a precipice was where the Taoist master Zhang Daoling tested his disciples.

The Old Man of the South Pole one of the deities of the Chinese folk religion fulu shou is sometimes seen holding a large peach, representing long life and health.

The term "bitten peach", first used by Legalist philosopher Han Fei in his work Han Feizi, became a byword for homosexuality. The book records the incident when courtier Mizi Xia bit into an especially delicious peach and gave the remainder to his lover, Duke Ling of Wei, as a gift so that he could taste it as well.

Japan
Momotaro, one of Japan's most noble and semihistorical heroes, was born from within an enormous peach floating down a stream. Momotaro or "Peach Boy" went on to fight evil oni and face many adventures.

Korea
In Korea, peaches have been cultivated from ancient times. According to Samguk Sagi, peach trees were planted during the Three Kingdoms of Korea period, and Sallim gyeongje also mentions cultivation skills of peach trees. The peach is seen as the fruit of happiness, riches, honours and longevity. The rare peach with double seeds is seen as a favorable omen of a mild winter. It is one of the ten immortal plants and animals, so peaches appear in many minhwa (folk paintings). Peaches and peach trees are believed to chase away spirits, so peaches are not placed on tables for jesa (ancestor veneration), unlike other fruits.

Vietnam
A Vietnamese mythic history states that, in the spring of 1789, after marching to Ngọc Hồi and then winning a great victory against invaders from the Qing dynasty of China, the Emperor Quang Trung ordered a messenger to gallop to Phú Xuân citadel (now Huế) and deliver a flowering peach branch to the Princess Ngọc Hân. This took place on the fifth day of the first lunar month, two days before the predicted end of the battle. The branch of peach flowers that was sent from the north to the centre of Vietnam was not only a message of victory from the King to his wife, but also the start of a new spring of peace and happiness for all the Vietnamese people. In addition, since the land of Nhật Tân had freely given that very branch of peach flowers to the King, it became the loyal garden of his dynasty.

It was by a peach tree that the protagonists of the Tale of Kieu fell in love. And in Vietnam, the blossoming peach flower is the signal of spring. Finally, peach bonsai trees are used as decoration during Vietnamese New Year (Tết) in northern Vietnam.

Europe
Many famous artists have painted still life with peach fruits placed in prominence. Caravaggio, Vicenzo Campi, Pierre-Auguste Renoir, Claude Monet, Édouard Manet, Henri Jean Fantin-Latour, George Forster, James Peale, Severin Roesen, Peter Paul Rubens, Van Gogh are among the many influential artists who painted peaches and peach trees in various settings. Scholars suggest that many compositions are symbolic, some an effort to introduce realism. For example, Tresidder claims the artists of Renaissance symbolically used peach to represent heart, and a leaf attached to the fruit as the symbol for tongue, thereby implying speaking truth from one's heart; a ripe peach was also a symbol to imply a ripe state of good health. Caravaggio paintings introduce realism by painting peach leaves that are molted, discolored or in some cases have wormholes – conditions common in modern peach cultivation.

Nutrition and research
A medium peach, weighing 100 g, contains small amounts of essential nutrients, but none is a significant proportion of the Daily Value (DV, right table). Nectarines have similar low content of nutrients.

Phytochemicals
Total polyphenols in mg per 100 g of fresh weight were 14–102 in white-flesh nectarines, 18–54 in yellow-flesh nectarines, 28–111 in white-flesh peaches, and 21–61 mg per 100 g in yellow-flesh peaches. The major phenolic compounds identified in peach are chlorogenic acid, catechins and epicatechins, with other compounds, identified by HPLC, including gallic acid and ellagic acid. Rutin and isoquercetin are the primary flavonols found in clingstone peaches.

Red-fleshed peaches are rich in anthocyanins, particularly cyanidin glucosides in six peach and six nectarine cultivars and malvin glycosides in clingstone peaches. As with many other members of the rose family, peach seeds contain cyanogenic glycosides, including amygdalin (note the subgenus designation: Amygdalus). These substances are capable of decomposing into a sugar molecule and hydrogen cyanide gas. While peach seeds are not the most toxic within the rose family (see bitter almond), large consumption of these chemicals from any source is potentially hazardous to animal and human health.

Peach allergy or intolerance is a relatively common form of hypersensitivity to proteins contained in peaches and related fruits such as (almonds). Symptoms range from local effects (e.g. oral allergy syndrome, contact urticaria) to more severe systemic reactions, including anaphylaxis (e.g. urticaria, angioedema, gastrointestinal and respiratory symptoms). Adverse reactions are related to the "freshness" of the fruit: peeled or canned fruit may be tolerated.

Aroma
Some 110 chemical compounds contribute to peach aroma, including alcohols, ketones, aldehydes, esters, polyphenols and terpenoids.