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, and the most widely known of the many members of genus Malus that are used by humans.
The tree originated in Western Asia, where its wild ancestor, the Alma, is still found today. There are more than 7,500 known cultivars of apples, resulting in a range of desired characteristics. 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 35% of this total. The United States is the second-leading producer, with more than 7.5% of world production. Iran is third, followed by Turkey, Russia, Italy and India.
The apple tree was perhaps the earliest tree to be cultivated, and its fruits have been improved through selection over thousands of years. Alexander the Great is credited with finding dwarfed apples in Kazakhstan in Asia in 328 BCE; those he brought back to Macedonia might have been the progenitors of dwarfing root stocks. Winter apples, picked in late autumn and stored just above freezing, have been an important food in Asia and Europe for millennia, as well as in Argentina and in the United States since the arrival of Europeans. Apples were brought to North America with colonists in the 17th century, and the first apple orchard on the North American continent was said to be near Boston in 1625. In the 20th century, irrigation projects in Washington state began and allowed the development of the multibillion dollar fruit industry, of which the apple is the leading species.
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.
In the wild, apples grow quite readily from seeds. However, like most perennial fruits, apples are ordinarily propagated asexually by grafting. This is because 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. Triploids have an additional reproductive barrier in that the 3 sets of chromosomes cannot be divided evenly during meiosis, yielding unequal segregation of the chromosomes (aneuploids). Even in the very unusual case when a triploid plant can produce a seed (apples are an example), it happens infrequently, and seedlings rarely survive. 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 per year because of constant temperate conditions in a whole year.
Rootstocks used to control tree size have been used in apple cultivation for over 2,000 years. Dwarfing rootstocks were probably discovered by chance in Asia. Alexander the Great sent samples of dwarf apple trees back to his teacher, Aristotle, in Greece. They were maintained at the Lyceum, a center of learning in Greece.
Most modern apple rootstocks were bred in the 20th century. Much research into the existing rootstocks was begun at the East Malling Research Station in Kent, England. Following that research, Malling worked with the John Innes Institute and Long Ashton to produce a series of different rootstocks with disease resistance and a range of different sizes, which have been used all over the world.
During the flowering each season, apple growers usually provide pollinators to carry the 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 enough quantity to be significant pollinators.
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, will grow very large, which allows them to bear much more fruit, but makes harvesting very difficult. Mature trees typically bear 40–200 kilograms (88–440 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. Dwarf trees will bear about 10–80 kilograms (22–180 lb) of fruit per year.
Commercially, apples can be stored for some months in controlled-atmosphere chambers to delay ethylene-induced onset of ripening. The apples are commonly stored in chambers with higher concentrations of carbon dioxide with high air filtration. This prevents ethylene concentrations from rising to higher amounts and preventing ripening from moving too quickly. Ripening continues when the fruit is removed. For home storage, most varieties of apple can be held for approximately two weeks when kept at the coolest part of the refrigerator (i.e. below 5°C). Some types, including the Granny Smith and Fuji, can be stored up to a year without significant degrade.
Pests and diseases
The trees are susceptible to a number of fungal and bacterial diseases and insect pests. Many commercial orchards pursue an aggressive program of chemical sprays to maintain high fruit quality, tree health, and high yields. A trend in orchard management is the use of organic methods. These use a less aggressive and direct methods of conventional farming. Instead of spraying potent chemicals, often shown to be potentially dangerous and maleficent to the tree in the long run, organic methods include encouraging or discouraging certain cycles and pests. To control a specific pest, organic growers might encourage the prosperity of its natural predator instead of outright killing it, and with it the natural biochemistry around the tree. Organic apples generally have the same or greater taste than conventionally grown apples, with reduced cosmetic appearances.
A wide range of pests and diseases can affect the plant; three of the more common diseases/pests are mildew, aphids and apple scab.
Mildew: which is characterized by light grey powdery patches appearing on the leaves, shoots and flowers, normally in spring. The flowers will turn a creamy yellow colour and will not develop correctly. This can be treated in a manner not dissimilar from treating Botrytis; eliminating the conditions which caused the disease in the first place and burning the infected plants are among the recommended actions to take.
Feeding aphids - There are five species of aphids commonly found on apples: apple grain aphid, rosy apple aphid, apple aphid, spirea aphid and the woolly apple aphid. The aphid species can be identified by their colour, the time of year when they are present and by differences in the cornicles, which are small paired projections from the rear of aphids. Aphids feed on foliage using needle-like mouth parts to suck out plant juices. When present in high numbers, certain species reduce tree growth and vigor.
Apple scab: Symptoms of scab are olive-green or brown blotches on the leaves. The blotches turn more brown as time progresses, then brown scabs form on the fruit. The diseased leaves will fall early and the fruit will become increasingly covered in scabs - eventually the fruit skin will crack. Although there are chemicals to treat scab, their use might not be encouraged as they are quite often systematic, which means they are absorbed by the tree, and spread throughout the fruit.
Among the most serious disease problems are fireblight, a bacterial disease; and Gymnosporangium rust, and black spot, two fungal diseases.
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.
Guinness World Records reports that the heaviest apple known weighed 1.849 kg (4 lb 1 oz) and was grown in Hirosaki city, Japan in 2005.
Apple output in 2005At least 55 million tonnes of apples were grown worldwide in 2005, with a value of about $10 billion. About two-fifths of this total was produced in China. More than 7.5% world production occurs in the United States.
In the United States, more than 60% of all the apples sold commercially are grown in Washington state. Imported apples from New Zealand and other more temperate areas are competing with US production and increasing each year.
Apples are often eaten raw; excepting the seeds, which are slightly poisonous (see below), the whole fruit including the skin is suitable for human consumption. Varieties bred for this purpose are termed dessert or table apples.
Apples can be canned or juiced. They are milled to produce apple cider (non-alcoholic, sweet cider) and filtered for apple juice. The juice can be fermented to make cider (alcoholic, hard cider), ciderkin, and vinegar. Through distillation, various alcoholic beverages can be produced, such as applejack, Calvados, and apfelwein. Pectin and apple seed oil may also be produced.
Apples are an important ingredient in many desserts, such as apple pie, apple crumble, apple crisp and apple cake. They are often eaten baked or stewed, and they can also be dried and eaten or reconstituted (soaked in water, alcohol or some other liquid) for later use. Puréed apples are generally known as apple sauce. Apples are also made into apple butter and apple jelly. They are also used (cooked) in meat dishes.
In the UK, a toffee apple is a traditional confection made by coating an apple in hot toffee and allowing it to cool. Similar treats in the US are candy apples (coated in a hard shell of crystallised sugar syrup), and caramel apples, coated with cooled caramel.
Apples are eaten with honey at the Jewish New Year of Rosh Hashanah to symbolize a sweet new year.
Farms with apple orchards may open them to the public, so consumers may themselves pick the apples they will buy.
Sliced apples turn brown with exposure to air due to the conversion of natural phenolic substances into melanin upon exposure to oxygen. Different cultivars vary in their propensity to brown after slicing. Sliced fruit can be treated with acidulated water to prevent this effect.
Organic apples are commonly produced in the United States. Organic production is difficult in Europe, though a few orchards have done so with commercial success, using disease-resistant cultivars and the very best cultural controls. The latest tool in the organic repertoire is a spray of a light coating of kaolin clay, which forms a physical barrier to some pests, and also helps prevent apple sun scald.
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Eating fallen apples (known as 'windfalls'), rather than picking directly from the tree, is generally safe. There may be a risk of food poisoning if the orchard is also the area of keeping cattle or other animals, which may contaminate the apples with feces. Still, the risk may be significantly higher if the apples are used to make home-made unpasteurized, unfermented cider or juice, thus letting E. coli multiply.
On the other hand, if the apples are eaten unprocessed, and kept free from risk of contamination with animal feces, then eating fallen apples is generally safe, even if there is some general decay or worms in them. Still, they may be submerged in water with salt added, which kills the worms. Apparent molds may be largely removed by putting in water with some vinegar added, but if they are of a large quantity, then there might be mold or mold products left to evoke mold health issues such as allergic reactions and respiratory problems.
Health benefits of apple consumption.The proverb "An apple a day keeps the doctor away.", addressing the health effects of the fruit, dates from 19th century Wales. Research suggests that apples may reduce the risk of colon cancer, prostate cancer and lung cancer. Compared to many other fruits and vegetables, apples contain relatively low amounts of vitamin C, but are a rich source of other antioxidant compounds. The fiber content, while less than in most other fruits, helps regulate bowel movements and may thus reduce the risk of colon cancer. They may also help with heart disease,weight loss, and controlling cholesterol. The fiber contained in apples reduces cholesterol by preventing reabsorption, and (like most fruits and vegetables) they are bulky for their caloric content.
There is evidence that in vitro apples possess phenolic compounds which may be cancer-protective and demonstrate antioxidant activity. The predominant phenolic phytochemicals in apples are quercetin, epicatechin, and procyanidin
Apple juice concentrate has been found to increase the production of the neurotransmitter acetylcholine in mice, providing a potential mechanism for the "prevention of the decline in cognitive performance that accompanies dietary and genetic deficiencies and aging." Other studies have shown an "alleviat[ion of] oxidative damage and cognitive decline" in mice after the administration of apple juice.
Researchers at the Chinese University of Hong Kong discovered that fruit flies who were fed an apple extract lived 10 percent longer than other flies who were fed a normal diet.
However, apple seeds are mildly poisonous, containing a small amount of amygdalin, a cyanogenic glycoside; it usually is not enough to be dangerous to humans, but can deter birds.