Blossoms, fruits, and leaves of the apple tree (Malus domestica)
Scientific classification
Kingdom: Plantae
Division: Magnoliophyta
Class: Magnoliopsida
Order: Rosales
Family: Rosaceae
Subfamily: Maloideae
Genus: Malus
Species: M. domestica
Binomial name
Malus domestica
Borkh.
The apple is the pomaceous fruit of the apple tree, species Malus domestica in the rose family Rosaceae. It is one of the most widely cultivated tree fruits. The tree is small and deciduous, reaching 5 to 12 m tall, with a broad, often densely twiggy crown. The leaves are alternately arranged simple ovals 5 to 12 cm long and 3–6 cm broad on a 2–5 cm petiole with an acute tip, serrated margin and a slightly downy underside. Flowers are produced in spring simultaneous with the budding of the leaves. The flowers are white with a pink tinge that gradually fades, five petaled, 2.5–3.5 cm in diameter. The fruit matures in autumn, and is typically 5–9 cm diameter. The centre of the fruit contains five carpels arranged in a five-point star, each carpel containing one to three seeds.
The tree originated from Central Asia, where its wild ancestor is still found today. There are more than 7,500 known cultivars of apples resulting in range of desired characteristics. It should be noted however, that cultivars vary in their yield and the ultimate size of the tree, even when grown on the same rootstock.
At least 55 million tonnes of apples were grown worldwide in 2005, with a value of about $10 billion. China produced about two-fifths of this total. The United States is the second leading producer, with more than 7.5% of the world production.Turkey, France, Italy and Iran are among the leading apple exporters.
Botanical information
Wild Malus sieversii apple in Kazakhstan
The wild ancestor of Malus domestica is Malus sieversii. It has no common name in English, but is known in Kazakhstan, where it is native, as alma; in fact, the region where it is thought to originate is called Almaty, or "reach of the apples". This tree is still found wild in the mountains of Central Asia in southern Kazakhstan, Kyrgyzstan, Tajikistan, and Xinjiang, China.
Apple cut horizontally, showing seeds
For many years, there was a debate about whether M. domestica evolved from chance hybridization among various wild species. Recent DNA analysis by Barrie Juniper, Emeritus Fellow in the Department of Plant Sciences at Oxford University and others, has indicated, however, that the hybridization theory is probably false. Instead, it appears that a single species still growing in the Ili Valley, on the northern slopes of the Tien Shan mountains at the border of Northwest China[3] and Kazakhstan, is the progenitor of the apples eaten today. Leaves taken from trees in this area were analyzed for DNA composition, which showed them all to belong to the species M. sieversii, with some genetic sequences common to M. domestica. Other species that were previously thought to have made contributions to the genome of the domestic apples are Malus baccata and Malus sylvestris, but there is no hard evidence for this in older apple cultivars. These and other Malus species have been used in some recent breeding programmes to develop apples suitable for growing in climates unsuitable for M. domestica, mainly for increased cold tolerance.
"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 and 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.
Different kinds of apple cultivars in a supermarket
There are more than 7,500 known cultivars of apples. Different cultivars are available for temperate and subtropical climates. Reputedly the world's biggest collection of apple cultivars is housed at the National Fruit Collection in England. 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 flavour that dessert apples cannot.
A display of apples in a supermarket in Yonkers, NY
Commercially popular apple cultivars are soft but crisp. Other desired qualities in modern commercial apple breeding are a colourful skin, absence of russeting, ease of shipping, lengthy storage ability, high yields, disease resistance, typical "Red Delicious" apple shape, long stem (to allow pesticides to penetrate the top of the fruit), and popular flavour. Modern apples are generally sweeter than older cultivars, as popular tastes in apples have varied over time. Most North Americans and Europeans favour sweet, subacid apples, but tart apples have a strong minority following. Extremely sweet apples with barely any acid flavour are popular in Asiaand especially India.As an example, the U.S. state of Washington made its reputation for apple growing on Red Delicious. In recent years, many apple connoisseurs have come to regard the Red Delicious as inferior to cultivars such as Fuji and Gala due to its merely mild flavour and insufficiently firm texture.
Old cultivars are often oddly shaped, russeted, and have a variety of textures and colours. Some find them to have a better flavour than modern cultivators, but may have other problems which make them commercially unviable, such as low yield, liability to disease, or poor tolerance for storage or transport. A few old cultivars are still produced on a large scale, but many have been kept alive 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 Russett are still commercially important even though by modern standards they are low yielding and disease prone.
In this hybrid of an orchard apple with a red-fruited crabapple cultivar, the pulp is of the same colour as the peel.
Apple breeding
Apple blossom from an old Ayrshire variety.
Like most perennial fruits, apples ordinarily propagate asexually by grafting. Seedling apples are an example of "Extreme heterozygotes", in that rather than inheriting DNA from their parents to create a new apple with those characteristics, they are instead different from their parents, sometimes radically. Most new apple cultivars originate as seedlings, which either arise by chance or are bred by deliberately crossing cultivars with promising characteristics.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.
Breeders can produce more rigid apples through crossing. For example, the Excelsior Experiment Station of the University of Minnesota has, since the 1930s, introduced a steady progression of important hardy apples that are widely grown, both commercially and by backyard orchardists, throughout Minnesota and Wisconsin. Its most important introductions 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 provide crops twice a year because of constant temperate conditions in a whole year.
Pollination
Apple tree in flower
See also: Fruit tree pollination
Apples are self-incompatible; they must cross-pollinate to develop fruit. During the flowering each season, apple growers usually provide pollinators to carry the pollen. Honeybee hives are most commonly used. Orchard mason bees are also used as supplemental pollinators in commercial orchards. Bumble bee queens are sometimes present in orchards, but not usually in enough quantity to be significant pollinators.