Apple

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Apple
Honeycrisp.jpg
Fruit
Malus domestica a1.jpg
Flowers
Scientific classification Red Pencil Icon.png
Kingdom: Plantae
Clade: Angiosperms
Clade: Eudicots
Clade: Rosids
Order: Rosales
Family: Rosaceae
Genus: Malus
Species:
M. pumila
Binomial name
Malus pumila
Miller, 1768
Synonyms [1] [2]
  • Malus communisDesf.
  • Malus domesticaBorkh. nom. illeg.
  • M. frutescensMedik.
  • M. paradisiaca(L.) Medikus
  • M. sylvestrisMil.
  • Pyrus malusL.
  • Pyrus malus var. paradisiacaL.
  • Pyrus dioicaMoench

An apple is a sweet, edible fruit produced by an apple tree (Malus pumila). Apple trees are cultivated worldwide and are the most widely grown species in the genus Malus . The tree originated in Central Asia, where its wild ancestor, Malus sieversii , is still found today. Apples have been grown for thousands of years in Asia and Europe and were brought to North America by European colonists. Apples have religious and mythological significance in many cultures, including Norse, Greek and European Christian traditions.

Fruit part of a flowering plant

In botany, a fruit is the seed-bearing structure in flowering plants formed from the ovary after flowering.

Fruit tree a tree which bears fruit that is consumed or used by humans and some animals

A fruit tree is a tree which bears fruit that is consumed or used by humans and some animals — all trees that are flowering plants produce fruit, which are the ripened ovaries of flowers containing one or more seeds. In horticultural usage, the term 'fruit tree' is limited to those that provide fruit for human food. Types of fruits are described and defined elsewhere, but would include "fruit" in a culinary sense, as well as some nut-bearing trees, such as walnuts.

Agriculture Cultivation of plants and animals to provide useful products

Agriculture is the science and art of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that enabled people to live in cities. The history of agriculture began thousands of years ago. After gathering wild grains beginning at least 105,000 years ago, nascent farmers began to plant them around 11,500 years ago. Pigs, sheep and cattle were domesticated over 10,000 years ago. Plants were independently cultivated in at least 11 regions of the world. Industrial agriculture based on large-scale monoculture in the twentieth century came to dominate agricultural output, though about 2 billion people still depended on subsistence agriculture into the twenty-first.

Contents

Apple trees are large if grown from seed. Generally, apple cultivars are propagated by grafting onto rootstocks, which control the size of the resulting tree. There are more than 7,500 known cultivars of apples, resulting in a range of desired characteristics. Different cultivars are bred for various tastes and use, including cooking, eating raw and cider production. Trees and fruit are prone to a number of fungal, bacterial and pest problems, which can be controlled by a number of organic and non-organic means. In 2010, the fruit's genome was sequenced as part of research on disease control and selective breeding in apple production.

Cultivar plant or grouping of plants selected for desirable characteristics

A cultivar is an assemblage of plants selected for desirable characters that are maintained during propagation. More generally, a cultivar is the most basic classification category of cultivated plants in the International Code of Nomenclature for Cultivated Plants (ICNCP). Most cultivars arose in cultivation, but a few are special selections from the wild.

Grafting process of inserting tissues from one plant into those of another

Grafting or graftage is a horticultural technique whereby tissues of plants are joined so as to continue their growth together. The upper part of the combined plant is called the scion while the lower part is called the rootstock. The success of this joining requires that the vascular tissue grow together and such joining is called inosculation. The technique is most commonly used in asexual propagation of commercially grown plants for the horticultural and agricultural trades.

A rootstock is part of a plant, often an underground part, from which new above-ground growth can be produced. It could also be described as a stem with a well developed root system, to which a bud from another plant is grafted. It can refer to a rhizome or underground stem. In grafting, it refers to a plant, sometimes just a stump, which already has an established, healthy root system, onto which a cutting or a bud from another plant is grafted. In some cases, such as vines of grapes and other berries, cuttings may be used for rootstocks, the roots being established in nursery conditions before planting them out. The plant part grafted onto the rootstock is usually called the scion. The scion is the plant that has the properties that propagator desires above ground, including the photosynthetic activity and the fruit or decorative properties. The rootstock is selected for its interaction with the soil, providing the roots and the stem to support the new plant, obtaining the necessary soil water and minerals, and resisting the relevant pests and diseases. After a few weeks the tissues of the two parts will have grown together, eventually forming a single plant. After some years it may be difficult to detect the site of the graft although the product always contains the components of two genetically different plants.

Worldwide production of apples in 2017 was 83.1 million tonnes, with China accounting for half of the total. [3]

Botanical information

Blossoms, fruits, and leaves of the apple tree (Malus pumila) Koeh-108.jpg
Blossoms, fruits, and leaves of the apple tree (Malus pumila)
An apple's side, stem end, and interior Pink lady and cross section.jpg
An apple's side, stem end, and interior

The apple is a deciduous tree, generally standing 6 to 15 ft (1.8 to 4.6 m) tall in cultivation and up to 30 ft (9.1 m) in the wild. When cultivated, the size, shape and branch density are determined by rootstock selection and trimming method. The leaves are alternately arranged dark green-colored simple ovals with serrated margins and slightly downy undersides. [4]

Deciduous trees or shrubs that lose their leaves seasonally

In the fields of horticulture and botany, the term deciduous (/dɪˈsɪdʒuəs/) means "falling off at maturity" and "tending to fall off", in reference to trees and shrubs that seasonally shed leaves, usually in the autumn; to the shedding of petals, after flowering; and to the shedding of ripe fruit.

Leaf organ of a vascular plant, composing its foliage

A leaf is an organ of a vascular plant and is the principal lateral appendage of the stem. The leaves and stem together form the shoot. Leaves are collectively referred to as foliage, as in "autumn foliage".

Apple blossom Apple Blossom @ Manali.jpg
Apple blossom

Blossoms are produced in spring simultaneously with the budding of the leaves and are produced on spurs and some long shoots. The 3 to 4 cm (1.2 to 1.6 in) flowers are white with a pink tinge that gradually fades, five petaled, with an inflorescence consisting of a cyme with 4–6 flowers. The central flower of the inflorescence is called the "king bloom"; it opens first and can develop a larger fruit. [4] [5]

Petal Part of most types of flower

Petals are modified leaves that surround the reproductive parts of flowers. They are often brightly colored or unusually shaped to attract pollinators. Together, all of the petals of a flower are called a corolla. Petals are usually accompanied by another set of special leaves called sepals, that collectively form the calyx and lie just beneath the corolla. The calyx and the corolla together make up the perianth. When the petals and sepals of a flower are difficult to distinguish, they are collectively called tepals. Examples of plants in which the term tepal is appropriate include genera such as Aloe and Tulipa. Conversely, genera such as Rosa and Phaseolus have well-distinguished sepals and petals. When the undifferentiated tepals resemble petals, they are referred to as "petaloid", as in petaloid monocots, orders of monocots with brightly coloured tepals. Since they include Liliales, an alternative name is lilioid monocots.

Inflorescence Term used in botany to describe a cluster of flowers

An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Morphologically, it is the modified part of the shoot of seed plants where flowers are formed. The modifications can involve the length and the nature of the internodes and the phyllotaxis, as well as variations in the proportions, compressions, swellings, adnations, connations and reduction of main and secondary axes. Inflorescence can also be defined as the reproductive portion of a plant that bears a cluster of flowers in a specific pattern.

The fruit matures in late summer or autumn, and cultivars exist in a wide range of sizes. Commercial growers aim to produce an apple that is 2 34 to 3 14 in (7.0 to 8.3 cm) in diameter, due to market preference. Some consumers, especially those in Japan, prefer a larger apple, while apples below 2 14 in (5.7 cm) are generally used for making juice and have little fresh market value. The skin of ripe apples is generally red, yellow, green, pink, or russetted, though many bi- or tri-colored cultivars may be found. [6] The skin may also be wholly or partly russeted i.e. rough and brown. The skin is covered in a protective layer of epicuticular wax. [7] The exocarp (flesh) is generally pale yellowish-white, [6] though pink or yellow exocarps also occur.

Epicuticular wax is a coating of wax covering the outer surface of the plant cuticle in land plants. It may form a whitish film or bloom on leaves, fruits and other plant organs. Chemically, it consists of hydrophobic organic compounds, mainly straight-chain aliphatic hydrocarbons with a variety of substituted functional groups. The main functions of the epicuticular wax are to decrease surface wetting and moisture loss. Other functions include reflection of ultraviolet light, assisting in the formation of an ultrahydrophobic and self-cleaning surface and acting as an anti-climb surface.

Wild ancestors

The original wild ancestor of Malus pumila was Malus sieversii, found growing wild in the mountains of Central Asia in southern Kazakhstan, Kyrgyzstan, Tajikistan, and Xinjiang, China. [4] [8] Cultivation of the species, most likely beginning on the forested flanks of the Tian Shan mountains, progressed over a long period of time and permitted secondary introgression of genes from other species into the open-pollinated seeds. Significant exchange with Malus sylvestris , the crabapple, resulted in current populations of apples being more related to crabapples than to the more morphologically similar progenitor Malus sieversii. In strains without recent admixture the contribution of the latter predominates. [9] [10] [11]

Genome

In 2010, an Italian-led consortium announced they had sequenced the complete genome of the apple in collaboration with horticultural genomicists at Washington State University, [12] using 'Golden Delicious'. [13] It had about 57,000 genes, the highest number of any plant genome studied to date [14] and more genes than the human genome (about 30,000). [15] This new understanding of the apple genome will help scientists identify genes and gene variants that contribute to resistance to disease and drought, and other desirable characteristics. Understanding the genes behind these characteristics will help scientists perform more knowledgeable selective breeding. The genome sequence also provided proof that Malus sieversii was the wild ancestor of the domestic apple—an issue that had been long-debated in the scientific community. [12]

History

Wild Malus sieversii apple in Kazakhstan 95apple.jpeg
Wild Malus sieversii apple in Kazakhstan

The center of diversity of the genus Malus is in eastern present-day Turkey. The apple tree may have been the earliest tree that humans cultivated, [16] and growers have improved its fruits through selection over thousands of years. Alexander the Great is credited with finding dwarfed apples in Kazakhstan in 328 BCE. [4] Winter apples, picked in late autumn and stored just above freezing, have been an important food in Asia and Europe for millennia. [16]

Of the many Old World plants that the Spanish introduced to Chiloé Archipelago in the 16th century, apple trees became particularly well adapted. [17] Apples were introduced to North America by colonists in the 17th century, [4] and the first apple orchard on the North American continent was planted in Boston by Reverend William Blaxton in 1625. [18] The only apples native to North America are crab apples, which were once called "common apples". [19] Apple cultivars brought as seed from Europe were spread along Native American trade routes, as well as being cultivated on colonial farms. An 1845 United States apples nursery catalogue sold 350 of the "best" cultivars, showing the proliferation of new North American cultivars by the early 19th century. [19] In the 20th century, irrigation projects in Eastern Washington began and allowed the development of the multibillion-dollar fruit industry, of which the apple is the leading product. [4]

Until the 20th century, farmers stored apples in frostproof cellars during the winter for their own use or for sale. Improved transportation of fresh apples by train and road replaced the necessity for storage. [20] [21] Controlled atmosphere facilities are used to keep apples fresh year-round. Controlled atmosphere facilities use high humidity, low oxygen, and controlled carbon dioxide levels to maintain fruit freshness. They were first used in the United States in the 1960s. [22]

Society and culture

Germanic paganism

"Brita as Iduna" (1901) by Carl Larsson Carl Larsson Brita as Iduna.jpg
"Brita as Iduna" (1901) by Carl Larsson

In Norse mythology, the goddess Iðunn is portrayed in the Prose Edda (written in the 13th century by Snorri Sturluson) as providing apples to the gods that give them eternal youthfulness. English scholar H. R. Ellis Davidson links apples to religious practices in Germanic paganism, from which Norse paganism developed. She points out that buckets of apples were found in the Oseberg ship burial site in Norway, that fruit and nuts (Iðunn having been described as being transformed into a nut in Skáldskaparmál ) have been found in the early graves of the Germanic peoples in England and elsewhere on the continent of Europe, which may have had a symbolic meaning, and that nuts are still a recognized symbol of fertility in southwest England. [23]

Davidson notes a connection between apples and the Vanir, a tribe of gods associated with fertility in Norse mythology, citing an instance of eleven "golden apples" being given to woo the beautiful Gerðr by Skírnir, who was acting as messenger for the major Vanir god Freyr in stanzas 19 and 20 of Skírnismál . Davidson also notes a further connection between fertility and apples in Norse mythology in chapter 2 of the Völsunga saga when the major goddess Frigg sends King Rerir an apple after he prays to Odin for a child, Frigg's messenger (in the guise of a crow) drops the apple in his lap as he sits atop a mound. [24] Rerir's wife's consumption of the apple results in a six-year pregnancy and the Caesarean section birth of their son—the hero Völsung. [25]

Further, Davidson points out the "strange" phrase "Apples of Hel" used in an 11th-century poem by the skald Thorbiorn Brúnarson. She states this may imply that the apple was thought of by Brúnarson as the food of the dead. Further, Davidson notes that the potentially Germanic goddess Nehalennia is sometimes depicted with apples and that parallels exist in early Irish stories. Davidson asserts that while cultivation of the apple in Northern Europe extends back to at least the time of the Roman Empire and came to Europe from the Near East, the native varieties of apple trees growing in Northern Europe are small and bitter. Davidson concludes that in the figure of Iðunn "we must have a dim reflection of an old symbol: that of the guardian goddess of the life-giving fruit of the other world." [23]

Greek mythology

Heracles with the apple of Hesperides Hercules Musei Capitolini MC1265 n2.jpg
Heracles with the apple of Hesperides

Apples appear in many religious traditions, often as a mystical or forbidden fruit. One of the problems identifying apples in religion, mythology and folktales is that the word "apple" was used as a generic term for all (foreign) fruit, other than berries, including nuts, as late as the 17th century. [26] For instance, in Greek mythology, the Greek hero Heracles, as a part of his Twelve Labours, was required to travel to the Garden of the Hesperides and pick the golden apples off the Tree of Life growing at its center. [27] [28] [29]

The Greek goddess of discord, Eris, became disgruntled after she was excluded from the wedding of Peleus and Thetis. [30] In retaliation, she tossed a golden apple inscribed Καλλίστη (Kalliste, sometimes transliterated Kallisti, "For the most beautiful one"), into the wedding party. Three goddesses claimed the apple: Hera, Athena, and Aphrodite. Paris of Troy was appointed to select the recipient. After being bribed by both Hera and Athena, Aphrodite tempted him with the most beautiful woman in the world, Helen of Sparta. He awarded the apple to Aphrodite, thus indirectly causing the Trojan War. [31]

The apple was thus considered, in ancient Greece, sacred to Aphrodite. To throw an apple at someone was to symbolically declare one's love; and similarly, to catch it was to symbolically show one's acceptance of that love. An epigram claiming authorship by Plato states: [32]

I throw the apple at you, and if you are willing to love me, take it and share your girlhood with me; but if your thoughts are what I pray they are not, even then take it, and consider how short-lived is beauty.

Plato, Epigram VII

Atalanta, also of Greek mythology, raced all her suitors in an attempt to avoid marriage. She outran all but Hippomenes (also known as Melanion, a name possibly derived from melon the Greek word for both "apple" and fruit in general), [28] who defeated her by cunning, not speed. Hippomenes knew that he could not win in a fair race, so he used three golden apples (gifts of Aphrodite, the goddess of love) to distract Atalanta. It took all three apples and all of his speed, but Hippomenes was finally successful, winning the race and Atalanta's hand. [27]

Christian art

Adam and Eve by Albrecht Durer (1507), showcasing the apple as a symbol of sin. Albrecht Durer - Adam and Eve (Prado) 2.jpg
Adam and Eve by Albrecht Dürer (1507), showcasing the apple as a symbol of sin.

Though the forbidden fruit of Eden in the Book of Genesis is not identified, popular Christian tradition has held that it was an apple that Eve coaxed Adam to share with her. [33] The origin of the popular identification with a fruit unknown in the Middle East in biblical times is found in confusion between the Latin words mālum (an apple) and mălum (an evil), each of which is normally written malum. [34] The tree of the forbidden fruit is called "the tree of the knowledge of good and evil" in Genesis 2:17, and the Latin for "good and evil" is bonum et malum. [35]

Renaissance painters may also have been influenced by the story of the golden apples in the Garden of Hesperides. As a result, in the story of Adam and Eve, the apple became a symbol for knowledge, immortality, temptation, the fall of man into sin, and sin itself. The larynx in the human throat has been called the "Adam's apple" because of a notion that it was caused by the forbidden fruit remaining in the throat of Adam. [33] The apple as symbol of sexual seduction has been used to imply human sexuality, possibly in an ironic vein. [33]

Cultivars

There are more than 7,500 known cultivars of apples. [36] Cultivars vary in their yield and the ultimate size of the tree, even when grown on the same rootstock. [37] Different cultivars are available for temperate and subtropical climates. The UK's National Fruit Collection, which is the responsibility of the Department of Environment, Food, and Rural Affairs, includes a collection of over 2,000 cultivars of apple tree in Kent. [38] The University of Reading, which is responsible for developing the UK national collection database, provides access to search the national collection. The University of Reading's work is part of the European Cooperative Programme for Plant Genetic Resources of which there are 38 countries participating in the Malus/Pyrus work group. [39]

The UK's national fruit collection database contains a wealth of information on the characteristics and origin of many apples, including alternative names for what is essentially the same "genetic" apple cultivar. Most of these cultivars are bred for eating fresh (dessert apples), though some are cultivated specifically for cooking (cooking apples) or producing cider. Cider apples are typically too tart and astringent to eat fresh, but they give the beverage a rich flavor that dessert apples cannot. [40]

Commercially popular apple cultivars are soft but crisp. Other desirable qualities in modern commercial apple breeding are a colorful skin, absence of russeting, ease of shipping, lengthy storage ability, high yields, disease resistance, common apple shape, and developed flavor. [37] Modern apples are generally sweeter than older cultivars, as popular tastes in apples have varied over time. Most North Americans and Europeans favor sweet, subacid apples, but tart apples have a strong minority following. [41] Extremely sweet apples with barely any acid flavor are popular in Asia, [41] especially the Indian Subcontinent . [40]

Old cultivars are often oddly shaped, russeted, and grow in a variety of textures and colors. Some find them to have better flavor than modern cultivars, [42] but they may have other problems that make them commercially unviable—low yield, disease susceptibility, poor tolerance for storage or transport, or just being the "wrong" size. A few old cultivars are still produced on a large scale, but many have been preserved by home gardeners and farmers that sell directly to local markets. Many unusual and locally important cultivars with their own unique taste and appearance exist; apple conservation campaigns have sprung up around the world to preserve such local cultivars from extinction. In the United Kingdom, old cultivars such as 'Cox's Orange Pippin' and 'Egremont Russet' are still commercially important even though by modern standards they are low yielding and susceptible to disease. [4]

Cultivation

Breeding

An apple tree in Germany Apfelbaum Winterrambour Hochstamm.jpg
An apple tree in Germany
Blooming apple tree on Kota Batu, Indonesia Blooming apple tree.jpg
Blooming apple tree on Kota Batu, Indonesia

Many apples grow readily from seeds. However, more than with most perennial fruits, apples must be propagated asexually by grafting to obtain the sweetness and other desirable characteristics of the parent. This is because seedling apples are an example of "extreme heterozygotes", in that rather than inheriting genes from their parents to create a new apple with parental characteristics, they are instead significantly different from their parents, perhaps to compete with the many pests. [43] Triploid cultivars have an additional reproductive barrier in that 3 sets of chromosomes cannot be divided evenly during meiosis, yielding unequal segregation of the chromosomes (aneuploids). Even in the case when a triploid plant can produce a seed (apples are an example), it occurs infrequently, and seedlings rarely survive. [44]

Because apples do not breed true when planted as seeds, grafting is generally used to produce new apple trees. The rootstock used for the bottom of the graft can be selected to produce trees of a large variety of sizes, as well as changing the winter hardiness, insect and disease resistance, and soil preference of the resulting tree. Dwarf rootstocks can be used to produce very small trees (less than 3.0 m (10 ft) high at maturity), which bear fruit earlier in their life cycle than full size trees. [45] Dwarf rootstocks for apple trees can be traced as far back as 300 BC, to the area of Persia and Asia Minor. Alexander the Great sent samples of dwarf apple trees to Aristotle's Lyceum. Dwarf rootstocks became common by the 15th century and later went through several cycles of popularity and decline throughout the world. [46] The majority of the rootstocks used today to control size in apples were developed in England in the early 1900s. The East Malling Research Station conducted extensive research into rootstocks, and today their rootstocks are given an "M" prefix to designate their origin. Rootstocks marked with an "MM" prefix are Malling-series cultivars later crossed with trees of 'Northern Spy' in Merton, England. [47]

Most new apple cultivars originate as seedlings, which either arise by chance or are bred by deliberately crossing cultivars with promising characteristics. [48] The words "seedling", "pippin", and "kernel" in the name of an apple cultivar suggest that it originated as a seedling. Apples can also form bud sports (mutations on a single branch). Some bud sports turn out to be improved strains of the parent cultivar. Some differ sufficiently from the parent tree to be considered new cultivars. [49]

Since the 1930s, the Excelsior Experiment Station at the University of Minnesota has introduced a steady progression of important apples that are widely grown, both commercially and by local orchardists, throughout Minnesota and Wisconsin. Its most important contributions have included 'Haralson' (which is the most widely cultivated apple in Minnesota), 'Wealthy', 'Honeygold', and 'Honeycrisp'.

Apples have been acclimatized in Ecuador at very high altitudes, where they can often, with the needed factors, provide crops twice per year because of constant temperate conditions year-round. [50]

Pollination

Apple blossom from an old Ayrshire cultivar Apple tree blossom.JPG
Apple blossom from an old Ayrshire cultivar
Orchard mason bee on apple bloom, British Columbia, Canada Orchmason.jpg
Orchard mason bee on apple bloom, British Columbia, Canada

Apples are self-incompatible; they must cross-pollinate to develop fruit. During the flowering each season, apple growers often utilize pollinators to carry pollen. Honey bees are most commonly used. Orchard mason bees are also used as supplemental pollinators in commercial orchards. Bumblebee queens are sometimes present in orchards, but not usually in sufficient number to be significant pollinators. [49] [51]

There are four to seven pollination groups in apples, depending on climate:

One cultivar can be pollinated by a compatible cultivar from the same group or close (A with A, or A with B, but not A with C or D). [52]

Cultivars are sometimes classified by the day of peak bloom in the average 30-day blossom period, with pollenizers selected from cultivars within a 6-day overlap period.

Maturation and harvest

Cultivars vary in their yield and the ultimate size of the tree, even when grown on the same rootstock. Some cultivars, if left unpruned, grow very large—letting them bear more fruit, but making harvesting more difficult. Depending on tree density (number of trees planted per unit surface area), mature trees typically bear 40–200 kg (90–440 lb) of apples each year, though productivity can be close to zero in poor years. Apples are harvested using three-point ladders that are designed to fit amongst the branches. Trees grafted on dwarfing rootstocks bear about 10–80 kg (20–180 lb) of fruit per year. [49]

Farms with apple orchards open them to the public so consumers can pick their own apples. [53]

Crops ripen at different times of the year according to the cultivar. Cultivar that yield their crop in the summer include 'Gala', 'Golden Supreme', 'McIntosh', 'Transparent', 'Primate', 'Sweet Bough', and 'Duchess'; fall producers include 'Fuji', 'Jonagold', 'Golden Delicious', 'Red Delicious', 'Chenango', 'Gravenstein', 'Wealthy', 'McIntosh', 'Snow', and 'Blenheim'; winter producers include 'Winesap', 'Granny Smith', 'King', 'Wagener', 'Swayzie', 'Greening', and 'Tolman Sweet'. [19]

Storage

Different kinds of apple cultivars in a wholesale food market MIN Rungis pommes.jpg
Different kinds of apple cultivars in a wholesale food market

Commercially, apples can be stored for some months in controlled atmosphere chambers to delay ethylene-induced ripening. Apples are commonly stored in chambers with higher concentrations of carbon dioxide and high air filtration. This prevents ethylene concentrations from rising to higher amounts and preventing ripening from occurring too quickly.

For home storage, most cultivars of apple can be held for approximately two weeks when kept at the coolest part of the refrigerator (i.e. below 5 °C). Some can be stored up to a year without significant degradation.[ dubious ] [54] [ verification needed ] Some varieties of apples (e.g. 'Granny Smith' and 'Fuji') have more than three times the storage life of others. [55]

Non-organic apples may be sprayed with 1-methylcyclopropene blocking the apples' ethylene receptors, temporarily preventing them from ripening. [56]

Pests and diseases

Leaves with significant insect damage Apple tree leaves with insect damage.jpg
Leaves with significant insect damage

Apple trees are susceptible to a number of fungal and bacterial diseases and insect pests. Many commercial orchards pursue a program of chemical sprays to maintain high fruit quality, tree health, and high yields. These prohibit the use of synthetic pesticides, though some older pesticides are allowed. Organic methods include, for instance, introducing its natural predator to reduce the population of a particular pest.

A wide range of pests and diseases can affect the plant. Three of the more common diseases or pests are mildew, aphids, and apple scab.

Among the most serious disease problems are a bacterial disease called fireblight, and two fungal diseases: Gymnosporangium rust and black spot. [58] Other pests that affect apple trees include Codling moths and apple maggots. Young apple trees are also prone to mammal pests like mice and deer, which feed on the soft bark of the trees, especially in winter. [59] The larvae of the apple clearwing moth (red-belted clearwing) burrow through the bark and into the phloem of apple trees, potentially causing significant damage. [60]

Production

Apple production – 2017
Country(millions of tonnes)
Flag of the People's Republic of China.svg  China
41.4
Flag of Europe.svg  European Union
14.2
Flag of the United States.svg  United States
5.2
Flag of Turkey.svg  Turkey
3.0
Flag of Poland.svg  Poland
2.4
Flag of India.svg  India
2.3
Flag of Iran.svg  Iran
2.1
World
83.1
Source: FAOSTAT of the United Nations [3]

World production of apples in 2017 was 83.1 million tonnes, with China producing 50% and the European Union 17% of the total (table). [3] Other significant producers each with 3-5% of the world total were the United States, Turkey, and Poland. [3]

Nutrition

Apples, with skin (edible parts)
Nutritional value per 100 g (3.5 oz)
Energy 218 kJ (52 kcal)
13.81 g
Sugars 10.39
Dietary fiber 2.4 g
Fat
0.17 g
0.26 g
Vitamins Quantity%DV
Vitamin A equiv.
0%
3 μg
0%
27 μg
29 μg
Thiamine (B1)
1%
0.017 mg
Riboflavin (B2)
2%
0.026 mg
Niacin (B3)
1%
0.091 mg
Pantothenic acid (B5)
1%
0.061 mg
Vitamin B6
3%
0.041 mg
Folate (B9)
1%
3 μg
Vitamin C
6%
4.6 mg
Vitamin E
1%
0.18 mg
Vitamin K
2%
2.2 μg
Minerals Quantity%DV
Calcium
1%
6 mg
Iron
1%
0.12 mg
Magnesium
1%
5 mg
Manganese
2%
0.035 mg
Phosphorus
2%
11 mg
Potassium
2%
107 mg
Sodium
0%
1 mg
Zinc
0%
0.04 mg
Other constituentsQuantity
Water85.56 g
Fluoride 3.3 µg

Percentages are roughly approximated using US recommendations for adults.

A typical apple serving weighs 242 grams and provides 126 calories with a moderate content of dietary fiber (table). [61] Otherwise, there is generally low content of essential nutrients (table).

Human consumption

An apple core, part of an apple not usually eaten, containing the seeds Apple stark s.jpg
An apple core, part of an apple not usually eaten, containing the seeds

All parts of the fruit, including the skin, except for the seeds, are suitable for human consumption. The core, from stem to bottom, containing the seeds, is usually not eaten and is discarded.

Apples can be consumed various ways: juice, raw in salads, baked in pies, cooked into sauces and spreads like apple butter, and other baked dishes. [62]

Several techniques are used to preserve apples and apple products. Apples can be canned, dried or frozen. [62] Canned or frozen apples are eventually baked into pies or other cooked dishes. Apple juice or cider is also bottled. Apple juice is often concentrated and frozen.

Apples are often eaten raw. Cultivars bred for raw consumption are termed dessert or table apples.

Apples are an important ingredient in many desserts, such as apple pie, apple crumble, apple crisp and apple cake. When cooked, some apple cultivars easily form a puree known as apple sauce. Apples are also made into apple butter and apple jelly. They are often baked or stewed and are also (cooked) in some meat dishes. Dried apples can be eaten or reconstituted (soaked in water, alcohol or some other liquid).

Apples are milled or pressed to produce apple juice, which may be drunk unfiltered (called apple cider in North America), or filtered. Filtered juice is often concentrated and frozen, then reconstituted later and consumed. Apple juice can be fermented to make cider (called hard cider in North America), ciderkin, and vinegar. Through distillation, various alcoholic beverages can be produced, such as applejack, Calvados, and apfelwein. [63]

Sliced apples turn brown with exposure to air due to the conversion of natural phenolic substances into melanin upon exposure to oxygen. [64] Different cultivars vary in their propensity to brown after slicing [65] and the genetically engineered Arctic Apples do not brown. Sliced fruit can be treated with acidulated water to prevent this effect. [64] Sliced apple consumption tripled in the US from 2004 to 2014 to 500 million apples annually due to its convenience. [66]

Organic production

Organic apples are commonly produced in the United States. [67] Due to infestations by key insects and diseases, organic production is difficult in Europe. [68] The use of pesticides containing chemicals, such as sulfur, copper, microorganisms, viruses, clay powders, or plant extracts (pyrethrum, neem) has been approved by the EU Organic Standing Committee to improve organic yield and quality. [68] A light coating of kaolin, which forms a physical barrier to some pests, also may help prevent apple sun scalding. [49]

Phytochemicals

Apples are a rich source of various phytochemicals including flavonoids (e.g., catechins, flavanols, and quercetin) and other phenolic compounds (e.g., epicatechin and procyanidins) [69] found in the skin, core, and pulp of the apple; [69] they have unknown health value in humans. [64]

Phenolic compounds, such as polyphenol oxidase, are the main driving force behind browning in apples. Polyphenol oxidase catalyzes the reaction of phenolic compounds to o-quinones causing the pigment to turn darker and therefore brown. [70]

Ideain (cyanidin 3-O-galactoside) is an anthocyanin, a type of pigment, which is found in some red apple cultivars. [71]

Phlorizin is a flavonoid that is found in apple trees, particularly in the leaves, and in only small amounts if at all in other plants, even other species of the genus Malus or related plants such as pear trees. [72]

Other products

Apple seed oil [73] and pectin can be produced.

Health effects

Preliminary research is investigating whether nutrients and/or phytochemicals in apples may be preventive against the risk of some types of cancer. [69] [74]

Allergy

One form of apple allergy, often found in northern Europe, is called birch-apple syndrome and is found in people who are also allergic to birch pollen. [75] Allergic reactions are triggered by a protein in apples that is similar to birch pollen, and people affected by this protein can also develop allergies to other fruits, nuts, and vegetables. Reactions, which entail oral allergy syndrome (OAS), generally involve itching and inflammation of the mouth and throat, [75] but in rare cases can also include life-threatening anaphylaxis. [76] This reaction only occurs when raw fruit is consumed—the allergen is neutralized in the cooking process. The variety of apple, maturity and storage conditions can change the amount of allergen present in individual fruits. Long storage times can increase the amount of proteins that cause birch-apple syndrome. [75]

In other areas, such as the Mediterranean, some individuals have adverse reactions to apples because of their similarity to peaches. [75] This form of apple allergy also includes OAS, but often has more severe symptoms, such as vomiting, abdominal pain and urticaria, and can be life-threatening. Individuals with this form of allergy can also develop reactions to other fruits and nuts. Cooking does not break down the protein causing this particular reaction, so affected individuals can eat neither raw nor cooked apples. Freshly harvested, over-ripe fruits tend to have the highest levels of the protein that causes this reaction. [75]

Breeding efforts have yet to produce a hypoallergenic fruit suitable for either of the two forms of apple allergy. [75]

Toxicity of seeds

Apple seeds contain small amounts of amygdalin, a sugar and cyanide compound known as a cyanogenic glycoside. Ingesting small amounts of apple seeds causes no ill effects, but consumption of extremely large doses can cause adverse reactions. It may take several hours before the poison takes effect, as cyanogenic glycosides must be hydrolyzed before the cyanide ion is released. [77] The United States National Library of Medicine's Hazardous Substances Data Bank records no cases of amygdalin poisoning from consuming apple seeds. [78]

Proverbs

The proverb "An apple a day keeps the doctor away", addressing the health effects of the fruit, dates from 19th century Wales, according to Caroline Taggart, author of "An Apple a Day: Old-Fashioned Proverbs and Why They Still Work". The original phrase, Taggart said, was: "Eat an apple on going to bed, and you'll keep the doctor from earning his bread". In the 19th century and early 20th, the phrase evolved to "an apple a day, no doctor to pay" and "an apple a day sends the doctor away", while the phrasing now commonly used was first recorded in 1922. [79]

See also

Related Research Articles

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The pear tree and shrub are a species of genus Pyrus, in the family Rosaceae, bearing the pomaceous fruit of the same name. Several species of pear are valued for their edible fruit and juices while others are cultivated as trees.

Peach species of plant

The peach is a deciduous tree native to the region of Northwest China between the Tarim Basin and the north slopes of the Kunlun Mountains, where it was first domesticated and cultivated. It bears an edible juicy fruit called a peach or a nectarine.

<i>Citrus</i> genus of fruit-bearing plants (source of fruit such as lemons and oranges)

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Fruit tree propagation is usually carried out vegetatively (non-sexually) by grafting or budding a desired variety onto a suitable rootstock.

Avocado species of plant

The avocado, a tree with probable origin in South Central Mexico, is classified as a member of the flowering plant family Lauraceae. The fruit of the plant, also called an avocado, is botanically a large berry containing a single large seed.

Guava tropical fruit

Guava is a common tropical fruit cultivated in many tropical and subtropical regions. Psidium guajava is a small tree in the myrtle family (Myrtaceae), native to Mexico, Central America, the Caribbean and northern South America. Although related species may also be called guavas, they belong to other species or genera, such as the "pineapple guava" Acca sellowiana. In 2016, India was the largest producer of guavas with 41% of the world total.

Blackcurrant species of plant

The blackcurrant or black currant is a woody shrub in the family Grossulariaceae grown for its berries. It is native to temperate parts of central and northern Europe and northern Asia where it prefers damp fertile soils and is widely cultivated both commercially and domestically. It is winterhardy, but cold weather at flowering time during the spring reduces the size of the crop. Bunches of small, glossy black fruit develop along the stems in the summer and can be harvested by hand or by machine. The raw fruit is particularly rich in vitamin C and polyphenol phytochemicals. Blackcurrants can be eaten raw but are usually cooked in a variety of sweet or savoury dishes. They are used to make jams, jellies and syrups and are grown commercially for the juice market. The fruit is also used in the preparation of alcoholic beverages and both fruit and foliage have uses in traditional medicine and the preparation of dyes.

There are a number of lines of defence against pests and diseases in the orchard, principal among these being the practice of good husbandry, creating healthy soil and ensuring high standards of garden hygiene. But no matter how diverse and healthy the garden eco-system may be, there will always be a degree of disease and pest presence. In many ways, some level of pathogen population in the garden can be not only acceptable but desirable as they are indicative of a generally healthful and diverse environment, and add to the overall robustness of the system as an immunity to such detrimental influences will build up, particularly in a balanced polycultural regime. Indeed, most of the plants we grow will tend to be selected because they are trouble free, and those that are more susceptible to attack will have fallen by the wayside over time. However, most farmers find it unacceptable that the food crops they grow are damaged by pests.

<i>Malus</i> genus of plants

Malus is a genus of about 30–55 species of small deciduous trees or shrubs in the family Rosaceae, including the domesticated orchard apple – also known as the eating apple, cooking apple, or culinary apple. The other species are generally known as crabapples, crab apples, or wild apples.

Quince species of plant

The quince is the sole member of the genus Cydonia in the family Rosaceae. It is a deciduous tree that bears a pome fruit, similar in appearance to a pear, and bright golden-yellow when mature. Throughout history the cooked fruit has been used as food, but the tree is also grown for its attractive pale pink blossoms and other ornamental qualities.

<i>Passiflora edulis</i> species of plant

Passiflora edulis is a vine species of passion flower that is native to southern Brazil through Paraguay and northern Argentina. It is cultivated commercially in tropical and subtropical areas for its sweet, seedy fruit, commonly called passion fruit. The fruit is a pepo, a type of berry, round to oval, either yellow or dark purple at maturity, with a soft to firm, juicy interior filled with numerous seeds. The fruit is both eaten or juiced, the juice often added to other fruit juices to enhance aroma.

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Orange (fruit) citrus fruit

The orange is the fruit of the citrus species Citrus × sinensis in the family Rutaceae. It is also called sweet orange, to distinguish it from the related Citrus × aurantium, referred to as bitter orange. The sweet orange reproduces asexually ; varieties of sweet orange arise through mutations.

Tomato Edible berry of the tomato plant, originating in South America

The tomato is the edible, often red, berry of the plant Solanum lycopersicum, commonly known as a tomato plant. The species originated in western South America. The Nahuatl word tomatl gave rise to the Spanish word tomate, from which the English word tomato derived. Its use as a cultivated food may have originated with the indigenous peoples of Mexico. The Spanish encountered the tomato from their contact with the Aztec during the Spanish colonization of the Americas and brought it to Europe. From there, the tomato was introduced to other parts of the European-colonized world during the 16th century.

<i>Malus baccata</i> species of plant

Malus baccata is an Asian species of apple known by the common names Siberian crab apple, Siberian crab, Manchurian crab apple and Chinese crab apple. It is native to much of northern Asia, but is also grown elsewhere as an ornamental tree and for rootstock. It is used for bonsai. It bears plentiful fragrant white flowers and edible red to yellow fruit of about 1 cm diameter.

Applecrabs are various hybrids between crabapples and apples. They are bred for varying reasons, including disease resistance and use in cold climates (because they are often hardier than apple trees and their fruit has the good eating qualities of apples.

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Further reading

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