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The avocado, also known as palta or aguacate in Spanish, or butter pear and alligator pear, is a tree native to the Caribbean, Mexico, South America and Central America. It is classified in the flowering plant family Lauraceae. The name "avocado" also refers to the fruit (technically a large berry) of the kupa shell that contains a pit (hard seed casing) which may be egg-shaped or spherical.
Avocados are a commercially valuable crop whose trees and fruit are cultivated in tropical climates throughout the world (and some temperate ones, such as California), producing a green-skinned, pear-shaped fruit that ripens after harvesting. Trees are partially self-pollinating and often are propagated through grafting to maintain a predictable quality and quantity of the fruit.
Persea americana, or the avocado, has a long history of cultivation in Central and South America; a water jar shaped like an avocado, dating to A.D. 900, was discovered in the pre-Incan city of Chan Chan. The earliest known written account of the avocado in Europe is that of Martín Fernández de Enciso (c. 1470 - c. 1528) in 1518 or 1519 in his book, Suma de Geografía que Trata de Todas las Partidas y Provincias del Mundo. The first written record in English of the use of the word 'avocado' was by Hans Sloane in a 1696 index of Jamaican plants. The plant was introduced to Indonesia in 1750, Brazil in 1809, the Levant in 1908, and South Africa and Australia in the late 19th century.
The word "avocado" comes from the Nahuatl word ahuacatl ("testicle", a reference to the shape of the fruit). Historically avocados had a long-standing stigma as a sexual stimulant and were not purchased or consumed by any person wishing to preserve a chaste image. Avocados were known by the Aztecs as "the fertility fruit". In some countries of South America such as Argentina, Bolivia, Chile, Peru, and Uruguay, the avocado is known by its Quechua name, palta. In other Spanish-speaking countries it is called aguacate, and in Portuguese it is abacate. The fruit is sometimes called an avocado pear and alligator pear (due to its shape and the rough green skin of some cultivars). The Nahuatl ahuacatl can be compounded with other words, as in ahuacamolli, meaning "avocado soup or sauce", from which the Mexican Spanish word guacamole derives.
Cultivation of Avocado
The tree grows to 20 metres (66 ft). Its leaves are alternately arranged. They are 12 centimetres (4.7 in) - 25 centimetres (9.8 in) long. The flowers are inconspicuous, greenish-yellow, 5 millimetres (0.2 in) - 10 millimetres (0.4 in) wide. The fruit is 7 centimetres (2.8 in) - 20 centimetres (7.9 in) long, and weighs between 100 grams (3.5 oz) - 1,000 grams (35 oz) grams. At the centre is a large central seed that measures 5 centimetres (2.0 in) - 6.4 centimetres (2.5 in) long. It is considered by many to be a drupe, but is botanically classified as a berry.
The subtropical species needs a climate without frost and with little wind. High winds reduce the humidity, dehydrate the flowers, and affect pollination. In particular, the West Indian type requires humidity and a tropical climate which is important for flowering. When even a mild frost occurs, premature fruit drop may occur, although the Hass cultivar can tolerate temperatures down to -1°C. The trees also need well aerated soils, ideally more than 1 m deep. Yield is reduced when the irrigation water is highly saline. These soil and climate conditions are available only in a few areas of the world, particularly in southern Spain, the Levant, South Africa, Peru, parts of central and northern Chile, Vietnam, Indonesia, Sri Lanka, Australia, New Zealand, the United States, the Philippines, Malaysia, Central America, the Caribbean and Mexico, the center of origin and diversity of this species. Each region has different types of cultivars. Mexico is the largest producer of the Hass variety, with over 1 million tonnes produced annually.
Propagation of Avocados
Avocado can be propagated by seed. It takes 4 - 6 years to do so, and the offspring is unlikely to resemble the parent cultivar in fruit quality. Thus, commercial orchards are planted using grafted trees and rootstocks. Rootstocks are propagated by seed (seedling rootstocks) and also layering (clonal rootstocks). After about a year of growing the young plants in a greenhouse, they are ready to be grafted. Terminal and lateral grafting is normally used. The scion cultivar will then grow for another 6 - 12 months before the tree is ready to be sold. Clonal rootstocks have been selected for specific soil and disease conditions, such as poor soil aeration or resistance to the soil-borne disease caused by phytophthora (root rot).
Diseases affecting Avocado trees
Avocado trees are vulnerable to bacterial, viral, fungal and nutritional diseases (excesses and deficiencies of key minerals). Disease can affect all parts of the plant, causing spotting, rotting, cankers, pitting and discoloration.
Health benefits of Avocados
High avocado intake has been shown to have an effect on blood serum cholesterol levels. Specifically, after a seven day diet rich in avocados, hypercholesterolemia patients showed a 17% decrease in total serum cholesterol levels. These subjects also showed a 22% decrease in both LDL (bad cholesterol) and triglyceride levels and 11% increase in HDL (good cholesterol) levels. About 75% of an avocado's calories come from fat, most of which is monounsaturated fat. Avocados also have 60% more potassium than bananas. They are rich in B vitamins, as well as vitamin E and vitamin K. They have the highest fiber content of any fruit - including 75% insoluble and 25% soluble fiber. A fatty triol (fatty alcohol) with one double bond, avocadene (16-heptadecene-1,2,4-triol), is found in avocado.
The avocado is very popular in vegetarian cuisine, making an excellent substitute for meats in sandwiches and salads because of its high fat content. The fruit is not sweet, but fatty, distinctly yet subtly flavored, and of smooth, almost creamy texture. It is used as the base for the Mexican dip known as guacamole, as well as a filling for several kinds of sushi, including California rolls. Avocado is popular in chicken dishes and as a spread on toast, served with salt and pepper. In Brazil and Vietnam, avocados are frequently used for milk-shakes and occasionally added to ice cream and other desserts. In Brazil, Vietnam, the Philippines and Indonesia, a dessert drink is made with sugar, milk or water, and pureed avocado. Chocolate syrup is sometimes added. In Australia it is commonly served in sandwiches, often with chicken. In Ghana, it's often eaten alone in sliced bread as a sandwich.
In Mexico and Central America, avocados are served mixed with white rice, in soups, salads, or on the side of chicken and meat. In Peru avocados are consumed with tequeños as mayonnaise, served as a side dish with parrillas, used in salads and sandwiches, or as a whole dish when filled with tuna, shrimps, or chicken. In Chile is used as a puree in chicken, hamburgers and hot dogs, and in slices for celery or lettuce salads. The Chilean version of caesar salad contains large slices of mature avocado. In Kenya, the avocado is often eaten as a fruit, and is eaten alone, or mixed with other fruits in a fruit salad, or as part of a vegetable salad. In Iran it is used as a rejuvenating facial cream. The fruit was the basis for the original alcoholic drink Advocaat, made by the Dutch population of Suriname and Recife, with the name deriving from the same source.