The avocado (Persea americana) is a tree native to Mexico and Central America, classified in the flowering plant family Lauraceae. The name "avocado" also refers to
the fruit of the tree.
The tree grows to 20 metres (65 ft), with
alternately arranged, evergreen leaves, 12–25 centimetres long.
The flowers are inconspicuous, greenish-yellow, 5–10 millimetres wide. The pear-shaped fruit is botanically a drupe, from 7 to 20 centimetres long, weighs
between 100 and 1000 grams, and has a large central seed, 3 to 5 centimetres in
diameter.[citation needed]
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.[1] 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 can be grown only in subtropical or tropical climates.
Etymology
The word "avocado" comes from the Spanish word aguacate, which derives in
turn from the Nahuatl (Aztec) word ahuacatl, meaning "testicle", because of 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 are "alligator pear" and "butter 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.
Cultivation
Worldwide avocado output in 2005
| Food and agriculture |
 |
| Avocado fruit (cv. 'Fuerte'); left: whole, right: in section |
| Country |
Quantity (Tm) |
World Rank1 |
| Mexico |
1,040,390 |
1 |
| Indonesia |
263,575 |
2 |
| United States of America |
214,000 |
3 |
| Colombia |
185,811 |
4 |
| Brazil |
185,811 |
5 |
| Chile |
163,000 |
6 |
| Dominican Republic |
140,000 |
7 |
| Peru |
102,000 |
8 |
| China |
85,000 |
9 |
| Ethiopia |
81,500 |
10 |
| 1Source: FAO (2004) Major Producers of Avocado |
The subtropical species needs a climate without frost and little wind. When mild frost
does occur, the fruit drops from the tree, reducing the yield, although the cultivar
Hass can tolerate temperatures down to −1°C. Contrary to
the conventional wisdom, avocado trees cannot sustain the frost. Avocado farmers in California lost hundreds of millions of
dollars in 2006 due to a temperature drop[citation needed]. 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, the Levant, South Africa, Peru, parts of
central and northern Chile, Vietnam, Indonesia, Australia, New Zealand, the
United States, the Philippines, Malaysia, Mexico and Central America,
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 and rootstocks
While an avocado propagated by seed can bear fruit, 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.
Breeding
The species is partially unable to self-pollinate, because of dichogamy in its flowering. The limitation, added to the long juvenile period, makes the species difficult to
breed. Most cultivars are 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 for
programs at the University of California, Riverside, as well as the
Volcani Centre and the Instituto de Investigaciones Agropecuarias in
Chile.
Diseases
-
Harvest and post-harvest
The avocado is a climateric fruit, which means that it matures on the tree but ripens off the tree. Avocados used in commerce
are picked hard and green and kept in coolers at 38 to 42°F (3.3 to 5.6°C) until they reach their final destination. Avocado must
be mature to ripen properly. Avocados that fall off the tree ripen on the ground, and, depending on the amount of oil they
contain, their taste and texture may vary greatly. Generally, the fruit is picked once it reaches maturity; Mexican growers pick
Hass-variety avocados when they have more than 23% dry matter and other producing countries have similar standards. Once picked,
avocados ripen in a few days at room temperature (faster if stored with other fruits
such as bananas, because of the influence of ethylene gas).
Premium supermarkets sell pre-ripened avocados treated with synthetic ethylene to hasten the ripening process.[2] In some cases, avocados can be left on the tree for several months, which is an advantage to
commercial growers who seek the greatest return for their crop; however, if the fruit stays on the tree for too long it will fall
to the ground.
Introduction to Europe
The earliest known written account of the avocado in Europe is that of Martín Fernández de Enciso (c. 1470–c. 1528) in 1519 in his book, Suma de Geografía que Trata de Todas las
Partidas y Provincias del Mundo. The plant was 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 has become an extremely successful cash crop. Ninety-five percent of United States avocado production is located in California, and 80% occurs in
San Diego County [citation needed]. 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 both Fallbrook and Carpinteria, California host annual
avocado festivals.
While dozens of cultivars are grown in California, Hass (commonly misspelled "Haas") is most
common, accounting for more than 80% of the crop. Hass avocado fruits have a dark, rippled skin and rich, creamy flesh. All Hass
avocado trees are related to a single "mother tree" that was bought as a seedling by a mail carrier named Rudolph Hass. [citation needed] He bought the 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 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, "A" and "B". "A" cultivar flowers open as female on the morning of the first day and close in late morning or early
afternoon. Then they open as male in the afternoon of the second day. "B" varieties open as female on the afternoon of the first
day, close in late afternoon and reopen in the male the following morning.
- "A" cultivars: Hass, Gwen, Lamb Hass, Pinkerton, Reed.
- "B" cultivars: Fuerte, Sharwil, Zutano, Bacon, Ettinger, Sir Prize, Walter Hole.[3][4]
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.
Avocado tree trained as a houseplant
Avocado pit sprouting in a terrarium
Avocado tree grown in the backyard
As a houseplant
Avocado can be grown as a houseplant from seed. It can germinate in normal
soil in a large pot or by suspending a washed pit (generally using toothpicks embedded in the sides) pointed-side up and filling the glass until the bottom quarter of the pit is
covered. The pit will crack as it absorbs water and germinates, and should sprout in 4–6 weeks. When the roots and stem emerge
from the seed, it can be planted in soil. The young tree is amenable to pruning and training but will not normally bear fruit
indoors without sufficient sunlight and a second plant to cross-pollinate.
Nutritional value
A whole medium avocado contains approximately 55% of the United States FDA's
recommended daily amount of fat, though they are high in monounsaturated fat.
Avocados also have 60% more potassium than bananas. They are
rich in B vitamins, as well as vitamin E and
vitamin K.[5]
A fatty triol (fatty alcohol) with one double bond, avocadene (16-heptadecene-1,2,4-triol), is found in avocado
and has been tested for anti-bacterial and anti-inflammatory properties. These properties are likely related with the curative
effects of avocado described for a number of ailments (diarrhea, dysentery, abdominal pains and high blood pressure).[6]
Uses
The fruit of horticultural cultivars ranges 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
color. The fruit has a markedly higher fat content than most other fruit, mostly monounsaturated fat. 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.
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 considered sweet fruits, so are frequently used
for milk-shakes and occasionally added to ice cream and other desserts. In Vietnam, 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. In Chile its consumption is widespread and 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.
Avocado flesh has also been used by some Native American tribes
in the southwestern United States in the mixing and application of adobe.[citation needed]
Avocado is also thought to promote physical beauty and is used in cosmetics to this day. The Aztecs ate the fruit as an aphrodisiac.
Toxicity to animals
There is documented evidence that animals such as cats, dogs, cattle, goats, rabbits, birds, parrots, fish and particularly,
horses[7][8] can be severely harmed or even killed when they consume the avocado leaves, bark, skin, or pit. The
avocado fruit is poisonous to birds in some cases, so on a practical level feeding the fruit to birds should be avoided. Avocado
leaves contain a toxic fatty acid derivative known as persin, which in sufficient quantity can
cause equine colic and with lack of veterinary treatment--death.[9] The symptoms include gastrointestinal irritation, vomiting, diarrhea, respiratory distress,
congestion, fluid accumulation around the tissues of the heart and even death. Birds also seem to be particularly sensitive to
this toxic compound.
Negative effects in humans seem to be primarily in allergic individuals.
Co-evolution hypothesis
The avocado may be an example of an 'evolutionary anachronism', a fruit adapted for ecological relationship with now-extinct large mammals (such as the giant
ground sloth or the Gomphothere). The fruit, with its
mildly toxic pit, co-evolved with megafauna mammals to
be swallowed whole and excreted in their dung, ready to sprout. The avocado's hypothesized ecological partners have disappeared,
and the avocado plant has not had time to evolve an alternative seed dispersal technique, aside from human cultivation.[10] However, given the effectiveness of human intervention in
dispersing the plant across the globe, there is no evolutionary pressure on the avocado that favors the development of
alternative dispersal techniques.
Avocado-related trade war
After the NAFTA treaty was signed, Mexico tried exporting
avocados to the USA. The U.S. government resisted, claiming that the trade would introduce vegetable
flies that would destroy California's crops. The Mexican government responded by inviting U.S. Department of Agriculture
inspectors to Mexico, but the U.S. government declined, claiming vegetable 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 gave in when the Mexican government started throwing up barriers to American maize.
Legitimate pest invasion issues exist, as avocado pests originating in Mexico have made their way to California, including the
persea mite and avocado thrips. These pests have increased pest
control costs and made previously-relied-upon biological control less feasible. Other potentially disastrous pests, including a
weevil, remain risks. 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.
Today avocados from Mexico are allowed in all 50 states. This is because USDA inspectors in Uruapan, Michoacán (the state
where 90% of Hass avocados from Mexico are grown), have cut open and inspected millions of fruit, finding no problems. Imports
from Mexico last season (2005-2006) exceeded 130,000 tonnes[11].
Avocados are much more expensive in the USA than in other countries[citation needed], due to the fact that those consumed in the USA are grown almost
exclusively in California and Florida. California produces about 90% of the nation's avocado crop.
Trivia
- Previously, 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.[citation needed] Growers had to sponsor a public relations campaign to debunk the avocado's
unsavory reputation before they eventually became popular. Avocados were known by the Aztecs as "the fertility
vegetable".[citation needed]
- In the pre-Incan city of Chan Chan, archaeologists have unearthed a large water jar, dated
around 900 A.D., in the shape of an avocado.[12]
- Stating something extremely obvious is a very common thing in jokes in spanish speaking countries. A popular joke involving
avocado is used to show a slow or dim-witted attitude towards something: "What is green on the outside, green on the inside, and
has an Avocado seed on the middle?" [citation needed]
References
- ^ FAO statistics on avocado production
- ^ Ethelene gas and produce
- ^ Agriculture handbook on avocados
- ^ Avocado Growing in the Florida Home Landscape
- ^ Nutritiondata.com article on avocados
- ^ [1]
- ^ CFIB article on avocados
- ^ Article on avocados
- ^ Toxic fatty acids in avocados
- ^ Barlow, C. & Martin, P. (2002). The Ghosts of Evolution: Nonsensical
Fruit, Missing Partners and other Ecological Anachronisms. ISBN 0-465-00551-9
- ^ Mexico praises lifting of last U.S. avocado import barriers
- ^ http://www.turtletrack.org/Issues01/Co04072001/CO_04072001_Recipes.htm Archaeologists unearth jar in shape of
avocado
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