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Avocado

2007 Schools Wikipedia Selection. Related subjects: Food and agriculture;
Plants

                           iAvocado
   Avocado fruit and foliage, Huntington Library, California
   Avocado fruit and foliage, Huntington Library, California
                   Scientific classification

   Kingdom:  Plantae
   Division: Magnoliophyta
   Class:    Magnoliopsida
   Order:    Laurales
   Family:   Lauraceae
   Genus:    Persea
   Species:  P. americana

                                Binomial name

   Persea americana
   Mill.

   Avocado (Persea americana) is a tree and the fruit of that tree,
   classified in the flowering plant family Lauraceae. It is native to
   Central America and Mexico. The tree grows to 20 m (65 ft), with
   alternately arranged, evergreen leaves, 12-25 cm long. The flowers are
   inconspicuous, greenish-yellow, 5-10 mm wide. The pear-shaped fruit is
   botanically a berry, from 7 to 20 cm long, and weighs between 100 to
   1000 g. It has a large central seed, 3 to 5 cm in diameter.

   An average avocado tree produces about 120 avocados annually.
   Commercial orchards produce an average of 7 tonnes per hectare each
   year, with some orchards achieving 20 tonnes per hectare (FAO
   statistics). Biennial bearing can be a problem, with heavy crops in one
   year being followed by poor yields the next. The fruit is sometimes
   called an avocado pear or alligator pear, due to its shape and rough
   green skin. The avocado tree does not tolerate freezing temperatures,
   and so can be grown only in subtropical and tropical climates.

Co-evolution theory

   Barlow & Martin (2002) identify the avocado as a fruit adapted for
   ecological relationship with large mammals, now extinct (as for example
   the South American herbivorous giant ground sloths or the
   Gomphotheres). This fruit with its mildly toxic pit, co-evolved with
   those extinct mammals to be swallowed whole and excreted in dung, ready
   to sprout. The ecological partners have disappeared, and the avocado
   plant has not had time to evolve an alternative seed dispersal
   technique, aside from human cultivation.

Cultivation

   Avocado fruit (cv. 'Fuerte'); left: whole, right: in section
   Enlarge
   Avocado fruit (cv. 'Fuerte'); left: whole, right: in section

   This subtropical species needs a climate without frost and not too much
   wind. When a frost event does happen, the fruit drops from the tree,
   reducing the yield. The cultivar 'Hass' 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 met only in a few areas of the
   world, particularly in southern Spain, Israel, South Africa, Peru,
   northern Chile, Vietnam, Indonesia, Australia, New Zealand, United
   States, The Philippines, Mexico and Central America, Malaysia, the
   centre of origin and diversity of this species. (In the U.S., avocados
   are produced commercially only in California and Florida, although the
   varieties used are different.)

Propagation and rootstocks

   While an avocado propagated by seed can bear fruit, it will take 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 1 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.

Breeding

   The species is partially unable to self-pollinate, because of dichogamy
   in its flowering. The limitation, added to the long juvenile period,
   make it difficult to breed this species. Most cultivars are clonally
   propagated (via grafting), having originated from random seedling
   plants or minor mutations derived from cultivars. Modern breeding
   programs tend to use isolation plots where the chances of
   cross-pollination are reduced. That is the case of programs at the
   University of California-Riverside, as well as the Volcani Centre in
   Israel.

Harvest and post-harvest

   The avocado fruit does not ripen on the tree, but will fall off or be
   picked in a hard, "green" state, then it will ripen quickly on the
   ground, but depending on the amount of oil that it has, the taste may
   be very different. Generally, the fruit is picked once it reaches a
   mature size, and will then ripen in a few days (faster if stored with
   other fruit such as bananas, because of the influence of ethylene gas).
   Premium supermarkets sell pre-softened avocados, treated with a special
   gas to stimulate ethylene synthesis in the fruit (the same process used
   to de-green lemons). The fruit can be left on the tree until required,
   rather than picked and stored, but for commercial reasons it must be
   picked as soon as possible. Growers can keep the fruit on the tree for
   about 4-6 months after fully developed; if the fruit stays on the tree
   for too long it will fall to the ground.

Introduction to Europe

   The earliest known account of the avocado in Europe is that of Martin
   Fernandez De Encisco in 1519. The plant was first introduced to
   Indonesia by 1750, Brazil in 1809, Palestine in 1908, and South Africa
   and Australia in the late 19th century. (Source: indexfresh.com).

Cultivation in California

   The avocado was introduced to the U.S. state of California in the 19th
   century, and it has become an extremely successful cash crop. 95% of
   United States avocado production is located in California, and 80%
   occurs in San Diego County . Approximately 59,000 acres (approximately
   24,000 hectares) of avocados are grown in California. Fallbrook,
   California claims the title of "Avocado Capital of the World" and hosts
   an annual Avocado Festival.

   While dozens of cultivars are grown in California, 'Hass' (commonly
   misspelled 'Haas') is most common, accounting for more than 80% of the
   crop. In appearance, Hass has a dark, rippled skin and rich, creamy
   flesh. All Hass avocado trees are related to a single "mother tree"
   that was purchased as a seedling by a mail carrier named Rudolph Hass.
   He purchased the tree as a seedling from A.R. Rideout of Whittier,
   California, in 1926. Hass planted the seedling in his front yard in La
   Habra Heights, California, and patented the tree in 1935. All Hass
   avocados can be traced back to grafts made from that tree. The "Mother
   Tree" died of root rot in 2002. Other avocado cultivars include
   'Bacon', 'Fuerte' (pictured), 'Gwen', 'Pinkerton', 'Reed' and 'Zutano'.
   The fruit of the cultivar 'Florida', grown mostly outside of
   California, is larger and rounder, with a smooth, medium-green skin,
   and a less-fatty, firmer and fibrous flesh. These are occasionally
   marketed as low-calorie avocados.

   The avocado is unusual in that the timing of the male and female phases
   differs among cultivars. There are two flowering types, referred to as
   "A" and "B" flower types. "A" cultivars open as female on the morning
   of the first day. The flower closes in late morning or early afternoon.
   The flower will remain closed until the afternoon of the second day
   when it opens as male. "B" varieties open as female on the afternoon of
   the first day, close in late afternoon and re-open in the male phase
   the following morning.

          "A" cultivars: 'Hass', 'Gwen', 'Lamb Hass', 'Pinkerton', 'Reed'.
          "B" cultivars: Fuerte, Sharwil, Zutano, Bacon, Ettinger, Sir
          Prize, Walter Hole. (ref: )

   Certain cultivars, such as the 'Hass', have a tendency to bear well
   only in alternate years. After a season with a low yield, due to
   factors such as cold (which the avocado does not tolerate well), the
   trees tend to produce abundantly the next season. This heavy crop
   depletes stored carbohydrates, resulting in a reduced yield the
   following season, and thus the alternate bearing pattern becomes
   established.

As a houseplant

   Avocado can be grown as a houseplant from seed. Although it will not
   normally bear fruit indoors, people enjoy it for its greenery. It can
   be germinated in normal soil in a large pot, or in a glass of water
   with a piece of charcoal for deodorizing, with the top half (the
   pointed end) held up by toothpicks.

Uses

   Two Avocado fruits
   Enlarge
   Two Avocado fruits

   The fruit of horticultural cultivars range from more or less round to
   egg or pear-shaped, typically the size of a temperate-zone pear or
   larger, on the outside bright green to green-brown (or almost black) in
   colour. Though the fruit does have a markedly higher fat content than
   most other fruits, most of the fat in avocados is monounsaturated fat,
   which is considered healthy in the human diet. A whole medium avocado
   contains approximately 25% of the recommended daily amount of saturated
   fat. Avocados also have 60% more potassium than bananas. They are also
   rich in B vitamins, as well as vitamin E and K.

   A ripe avocado will yield to a gentle pressure when held in the palm of
   the hand and squeezed. The flesh is typically greenish yellow to golden
   yellow when ripe. The flesh oxidizes and turns brown quickly after
   exposure to air. To prevent this, lime or lemon juice can be added to
   avocados after they are peeled; vitamin C in the juice acts as an
   antioxidant. 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, strongly
   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. In the Philippines and
   Indonesia, a dessert drink is made with sugar, milk, and pureed
   avocado. In Central America, avocados are served mixed with white rice.
   The fruit is also pressed for avocado oil production. In Chile it is
   often used in hamburgers, hot dogs and celery salads. Avocado flesh has
   also been used by some Native American tribes in the Southwestern
   United States in the mixing and application of adobe, a natural
   building material .

Toxicity

   Feeding avocados to any animal should be totally avoided. There is
   documented evidence that animals such as cattle, horses, goats,
   rabbits, birds, dogs, cats, and even fish can be severely harmed or
   even killed when they consume the leaves, bark or fruit. Avocados
   contain a toxic fatty acid derivative known as persin and many animal
   organizations recommend total avoidance of all parts of the plant. The
   symptoms include gastrointestinal irriation, vomiting, diarrhea,
   respiratory distress, congestion, fluid accumulation around the tissues
   of the heart and even death. Birds seem to be particularly sensitive to
   this toxic compound.

   Negative effects in humans seem to be primarily in allergic
   individuals.

Names

   The English name for the avocado is derived from its usual Spanish
   language name, "aguacate", which in turn is derived from its Nahuatl
   name, 'ahuacatl', meaning testicle (due to its shape). 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 name avocado pear is sometimes used in
   English, as is alligator pear. 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. In Chinese, the
   avocado is evocatively called the "butter fruit" (牛油果 níuyóu gǔo), but
   also occasionally "alligator pear" (鳄鱼梨). In Taiwan, the word
   "alligator pear" is used.

Avocado related trade war

   First transcontinental, international air shipment of avocados from Los
   Angeles, CA to Toronto for the Canadian National Exposition.
   Enlarge
   First transcontinental, international air shipment of avocados from Los
   Angeles, CA to Toronto for the Canadian National Exposition.

   After the NAFTA treaty was signed, Mexico tried exporting avocados to
   the USA. The U.S. government resisted, claiming that the trade would
   introduce fruit flies that would destroy California's crops. The
   Mexican government responded by inviting U.S. Department of Agriculture
   inspectors to Mexico, but U.S. government declined, claiming fruit fly
   inspection is not feasible. The Mexican government then proposed to
   sell avocados only to the northeastern U.S. in the winter (fruit flies
   cannot withstand extreme cold). The U.S. government balked, but only
   gave in when the Mexican government started throwing up barriers to
   American maize.

   Today avocados from Mexico are allowed in 47 states, excluding in
   Florida, California, and Hawaii. This is because USDA inspectors in
   Uruapan, Michoacan (the state where 90% of Hass avocados from Mexico
   are grown) have cut open and inspected millions of them, finding no
   problems. Imports from Mexico last season (2004-2005) exceeded 100
   thousand tonnes.

   Avocados are much more expensive in the USA than other countries due to
   the fact that they are grown almost exclusively in California and
   Florida, and the main potential competitor (Mexico) is banned from
   three states in the market - Florida, California, and Hawaii. Mexican
   farmers have argued against the ban, pointing out that not a single
   shipment has been found to contain pests since the U.S. Department of
   Agriculture began inspections in 1997 . Another argument is that the
   lower prices generated by the Mexican and Chilean imports would
   increase the popularity of avocados outside of California, thereby
   assuaging the loss of profits due to the new competition. In the year
   2007, Mexican avocados will be permitted in all 50 U.S. States.
   Retrieved from " http://en.wikipedia.org/wiki/Avocado"
   This reference article is mainly selected from the English Wikipedia
   with only minor checks and changes (see www.wikipedia.org for details
   of authors and sources) and is available under the GNU Free
   Documentation License. See also our Disclaimer.
