Maize Leaf Fleck Virus

Maize ( ; ''Zea mays'' subsp. ''mays'', from es, maíz after tnq, mahiz), also known as corn (North American and Australian English), is a cereal grain first domesticated by indigenous peoples in southern Mexico about 10,000 years ago. The leafy stalk of the plant produces pollen inflorescences (or "tassels") and separate ovuliferous inflorescences called ears that when fertilized yield kernels or seeds, which are fruits. The term ''maize'' is preferred in formal, scientific, and international usage as a common name because it refers specifically to this one grain, unlike ''corn'', which has a complex variety of meanings that vary by context and geographic region.

Maize has become a staple food in many parts of the world, with the total production of maize surpassing that of wheat or rice. In addition to being consumed directly by humans (often in the form of masa), maize is also used for corn ethanol, animal feed and other maize products, such as corn starch and corn syrup. The six major types of maize are dent corn, flint corn, pod corn, popcorn, flour corn, and sweet corn. Sugar-rich varieties called sweet corn are usually grown for human consumption as kernels, while field corn varieties are used for animal feed, various corn-based human food uses (including grinding into cornmeal or masa, pressing into corn oil, fermentation and distillation into alcoholic beverages like bourbon whiskey), and as feedstocks for the chemical industry. Maize is also used in making ethanol and other biofuels.

Maize is widely cultivated throughout the world, and a greater weight of maize is produced each year than any other grain. In 2021, total world production was 1.2 billion tonnes. Maize is the most widely grown grain crop throughout the Americas, with 384 million metric tons grown in the United States alone in 2021. Genetically modified maize made up 85% of the maize planted in the United States in 2009.Genetically modified plants: Global Cultivation Area Maize
GMO Compass, March 29, 2010, retrieved August 10, 2010 Subsidies in the United States help to account for its high level of cultivation of maize and its position as the largest producer in the world.

History

Pre-Columbian development

Maize is a cultigen; human intervention is required for it to propagate. Whether or not the kernels fall off the cob on their own is a key piece of evidence used in archaeology to distinguish domesticated maize from its naturally-propagating teosinte ancestor. Genetic evidence can also be used to determine when various lineages split.

Most historians believe maize was domesticated in the Tehuacán Valley of Mexico. Recent research in the early 21st century has modified this view somewhat; scholars now indicate the adjacent Balsas River Valley of south-central Mexico as the center of domestication.

An 2002 study by Matsuoka ''et al.''. has demonstrated that, rather than the multiple independent domestications model, all maize arose from a single domestication in southern Mexico about 9,000 years ago. The study also demonstrated that the oldest surviving maize types are those of the Mexican highlands. Later, maize spread from this region over the Americas along two major paths. This is consistent with a model based on the archaeological record suggesting that maize diversified in the highlands of Mexico before spreading to the lowlands.

Archaeologist Dolores Piperno has said:

Since then, even earlier dates have been published.

According to a genetic study by the Brazilian Agricultural Research Corporation (Embrapa), corn cultivation was introduced in South America from Mexico, in two great waves: the first, more than 6000 years ago, spread through the Andes. Evidence of cultivation in Peru has been found dating to about 6700 years ago. The second wave, about 2000 years ago, through the lowlands of South America.

The earliest maize plants grew only small, corn ears, and only one per plant. In Jackson Spielvogel's view, many centuries of artificial selection (rather than the current view that maize was exploited by interplanting with ''teosinte'') by the indigenous people of the Americas resulted in the development of maize plants capable of growing several ears per plant, which were usually several centimetres/inches long each. The Olmec and Maya cultivated maize in numerous varieties throughout Mesoamerica; they cooked, ground and processed it through nixtamalization. It was believed that beginning about 2500 BC, the crop spread through much of the Americas. Research of the 21st century has established even earlier dates. The region developed a trade network based on surplus and varieties of maize crops.

Mapuches of south-central Chile cultivated maize along with quinoa and potatoes in pre-Hispanic times; however, potato was the staple food of most Mapuches, "specially in the southern and coastal apucheterritories where maize did not reach maturity". Before the expansion of the Inca Empire maize was traded and transported as far south as 40°19' S in Melinquina, Lácar Department. In that location maize remains were found inside pottery dated to 730 ± 80 BP and 920 ± 60 BP. Probably this maize was brought across the Andes from Chile. The presence of maize in Guaitecas Archipelago (43°55' S), the southernmost outpost of pre-Hispanic agriculture, is reported by early Spanish explorers. However the Spanish may have misidentified the plant.

By at least 1000 BCE, the Olmec in Mesoamerica had based their calendar, language, myths and worldview with maize at the center of their symbolism.

Columbian exchange

After the arrival of Europeans in 1492, Spanish settlers consumed maize, and explorers and traders carried it back to Europe and introduced it to other countries. Spanish settlers much preferred wheat bread to maize, cassava, or potatoes. Maize flour could not be substituted for wheat for communion bread, since in Christian belief only wheat could undergo transubstantiation and be transformed into the body of Christ. Some Spaniards worried that by eating indigenous foods, which they did not consider nutritious, they would weaken and risk turning into Indians. "In the view of Europeans, it was the food they ate, even more than the environment in which they lived, that gave Amerindians and Spaniards both their distinctive physical characteristics and their characteristic personalities." Despite these worries, Spaniards did consume maize. Archeological evidence from Florida sites indicate they cultivated it as well.Earle, ''The Body of the Conquistador'', p. 144.

Maize spread to the rest of the world because of its ability to grow in diverse climates. It was cultivated in Spain just a few decades after Columbus's voyages and then spread to Italy, West Africa and elsewhere.
Widespread cultivation most likely began in southern Spain in 1525, after which it quickly spread to the rest of the Spanish Empire including its territories in Italy (and, from there, to other Italian states). Maize had many advantages over wheat and barley; it yielded two and a half times the food energy per unit cultivated area, could be harvested in successive years from the same plot of land, and grew in wildly varying altitudes and climates, from relatively dry regions with only of annual rainfall to damp regions with over . By the 17th century it was a common peasant food in Southwestern Europe, including Portugal, Spain, southern France, and Italy. By the 18th century, it was the chief food of the southern French and Italian peasantry, especially in the form of polenta in Italy.

Names

The word ''maize'' derives from the Spanish form of the indigenous Taíno word for the plant, ''mahiz''. Using the maize common name, Linnaeus included it as the species epithet in ''Zea mays''. It is known by other names including "corn" in some English speaking countries.

''Maize'' is preferred in formal, scientific, and international usage as a common name because it refers specifically to this one grain, unlike ''corn'', which has a complex variety of meanings that vary by context and geographic region. International groups such as the Centre for Agriculture and Bioscience International also consider maize the preferred common name. According to Ohio State University, the US and a handful of other English-speaking countries primarily use corn, but the rest of the world calls this maize or maíz. The word maize is considered interchangeable with corn in the West; during early British and American trade, all grains were considered corn. Maize retained the name corn in the West as the primary grain in these trade relationships.

The word "corn" outside the US, Canada, Australia, and New Zealand is synonymous with grain referring to any cereal crop with its meaning understood to vary geographically to refer to the local staple. In the United States, Canada, Australia, and New Zealand, ''corn'' primarily means maize; this usage started as a shortening of "Indian corn". "Indian corn" primarily means maize (the staple grain of indigenous Americans), but can refer more specifically to multicolored "flint corn" used for decoration. Other common names include barajovar, makka, silk maize, and zea.

In a 1999 journal article, Betty Fussell describing calling maize as corn was "to plunge into tragi-farcial mistranslations of language and history." Similar to the British, the Spanish referred to maize as panizo, a generic term for cereal grains, as did Italians with the term polenta. The British later referred to maize as Turkey wheat, Turkey corn, or Indian corn with Fusell commenting that "they meant not a place but a condition, a savage rather than a civilized grain", especially with Turkish people later naming it kukuruz, or barbaric.

The word ''maize'' is used by agricultural bodies and research institutes such as the UN's FAO, the International Maize and Wheat Improvement Center based out of Mexico, and the Indian Institute of Maize Research. National agricultural and industry associations often include the word ''maize'' in their name such as the Maize Association of Australia, and the National Maize Association of Nigeria.

In Southern Africa, maize is commonly called ''mielie'' (Afrikaans) or ''mealie'' (English), words possibly derived from the Portuguese word for maize, ''milho'', but more probably from Dutch ''meel'' or English ''meal'', meaning the edible part of a grain or pulse.

Structure and physiology

The maize plant is often in height, though some natural strains can grow , and the tallest recorded plant reached almost . The stem is commonly composed of 20 internodes of length. The leaves arise from the nodes, alternately on opposite sides on the stalk, and have entire margins.

The apex of the stem ends in the tassel, an inflorescence of male flowers. When the tassel is mature and conditions are suitably warm and dry, anthers on the tassel dehisce and release pollen. Maize pollen is anemophilous (dispersed by wind), and because of its large settling velocity, most pollen falls within a few meters of the tassel.

Ears develop above a few of the leaves in the midsection of the plant, between the stem and leaf sheath, elongating by around per day, to a length of with being the maximum alleged in the subspecies. They are female inflorescences, tightly enveloped by several layers of ear leaves commonly called husks.

Elongated stigmas, called silks, emerge from the whorl of husk leaves at the end of the ear. They are often pale yellow and in length, like tufts of hair in appearance. At the end of each is a carpel, which may develop into a "kernel" if fertilized by a pollen grain. The pericarp of the fruit is fused with the seed coat referred to as "caryopsis", typical of the grasses, and the entire kernel is often referred to as the "seed". The cob is close to a multiple fruit in structure, except that the individual fruits (the kernels) never fuse into a single mass. The grains are about the size of peas, and adhere in regular rows around a white, pithy substance, which forms the cob. The maximum size of kernels is reputedly . An ear commonly holds 600 kernels. They are of various colors: blackish, bluish-gray, purple, green, red, white and yellow. When ground into flour, maize yields more flour with much less bran than wheat does. It lacks the protein gluten of wheat and, therefore, makes baked goods with poor rising capability. A genetic variant that accumulates more sugar and less starch in the ear is consumed as a vegetable and is called sweet corn. Young ears can be consumed raw, with the cob and silk, but as the plant matures (usually during the summer months), the cob becomes tougher and the silk dries to inedibility. By the end of the growing season, the kernels dry out and become difficult to chew without cooking.

File:Cornsilk 7091.jpg, Female inflorescence, with young silk
File:Corn blooming.jpg, Mature silk
File:GreenCorn.JPG, Stalks, ears and silk
File:Männliche Blüte einer Maispflanze 2009-08-19.JPG, Male flowers
File:ZeaMays.jpg, Full-grown maize plants
File:Klip kukuruza uzgojen u Međimurju (Croatia).JPG, Mature maize ear on a stalk

Planting density affects multiple aspects of maize. Modern farming techniques in developed countries usually rely on dense planting, which produces one ear per stalk. Stands of silage maize are yet denser, and achieve a lower percentage of ears and more plant matter.

Maize is a facultative short-day plant and flowers in a certain number of growing degree days > in the environment to which it is adapted. The magnitude of the influence that long nights have on the number of days that must pass before maize flowers is genetically prescribed and regulated by the phytochrome system. Photoperiodicity can be eccentric in tropical cultivars such that the long days characteristic of higher latitudes allow the plants to grow so tall that they do not have enough time to produce seed before being killed by frost. These attributes, however, may prove useful in using tropical maize for biofuels.

Immature maize shoots accumulate a powerful antibiotic substance, 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA). DIMBOA is a member of a group of hydroxamic acids (also known as benzoxazinoids) that serve as a natural defense against a wide range of pests, including insects, pathogenic fungi and bacteria. DIMBOA is also found in related grasses, particularly wheat. A maize mutant (bx) lacking DIMBOA is highly susceptible to attack by aphids and fungi. DIMBOA is also responsible for the relative resistance of immature maize to the European corn borer (family Crambidae). As maize matures, DIMBOA levels and resistance to the corn borer decline.

Because of its shallow roots, maize is susceptible to droughts, intolerant of nutrient-deficient soils, and prone to be uprooted by severe winds.

File:Ab food 06.jpg, Maize kernels
File:Maize plant diagram.svg, Maize plant diagram
File:Aa maize ear irregular 01.jpg, Ear of maize with irregular rows of kernels






While yellow maizes derive their color from lutein

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