Corn - SpeedyLook encyclopedia

Botanical aspects

Description

The corn is an annual herbaceous plant, of variable size (of 40 cm up to 10 m, generally between one and three meters for the usually cultivated varieties).

The single Stem and of large diameter full, is lignified and formed with several entrenœuds of a score of centimetres separated by as many nodes. Into the level of each node is inserted a Feuille alternatively on a side and other of the stem. The sheets, typical of graminaceous, but of big size (up to 10 cm broad and a meter length), have a sheath enclosing the stem and a limb lengthened in the shape of ribbon with parallel veins. At the base of the limb the Ligule is which is a few millimetres top. Contrary to the other graminaceous ones, the foot of corn does not tiller not, however one sees sometimes secondary stems, of limited size, at the base of the principal stem. The system racinaire includes/understands a very great number of adventitious roots which are born on the nodes located at the base from the stem, formant of the successive crowns, as well on the nodes buried as on the first air nodes, in a zone where the entrenœuds are very short. These roots form a system booklet which can reach a depth higher than one meter.

The flowers, another characteristic which distinguishes corn from the other graminaceous ones, are unisexuées and gathered in male inflorescences and females made up of épillets of two flowers.

The female flowers are grouped in ear S inserted into the armpit of the median sheets (largest). The axis of ear, called Raid, carries 10 to 20 lines of female flowers. Only one flower by épillet is fertile. It is surrounded by modified sheets, the Spathe S, desiccated with maturity. At the higher end, the spathes let exceed the thread-like Stigmate S or silks. An ear can contain approximately 500 grains with maturity, sometimes thousand. A foot gives rise to three or four ears, but only one generally reaches a complete development.

The male flowers are grouped in a final Panicule which appears after the last sheet. This panicle consists of épillet S gathering each one two flowers with three cheesecloth S.

The corn grain is in fact a Caryopse, made of three parts of different origins:

the Embryo, usually called “germ”, located at the base of the grain which includes/understands the Embryon itself or “gemmule” and the scutellum , i.e. the Cotylédon, body of reserve from which the seedling draws its initial energy; the embryo is resulting from egg formed following the fusion of the core from a Spermatozoïde and Oosphère;
the Endosperm, fabric of reserve, primarily composed of grains of Starch, except the peripheral layer located under the pericarp which contains grains of Aleurone rich in proteins; this fabric is resulting from the fusion of the core of a spermatozoon and the two polar cores of the embryonic Sac (it is thus a fabric with 3n chromosomes);
the outer jacket, fine translucent and fibrous membrane, resulting from the Pericarp of the ovary (thus actually part of the fruit and not of seed).

The starch of endosperm is presented in two forms: the Amylose, polymer linear of glucose, and the Amylopectin, polymeric forming a ramified molecule. According to the mode of assembly of these molecules, it is formed farinaceous starch, with friable structure, located rather at the center, or starch horn, or vitreous, with dense structure and compacts, located in periphery and which contributes to maintain the form external of the grain. The variable proportion of these two starch shapes makes it possible to distinguish various races. It is the starch horn which gives its color to the corn grain, generally yellow, but so white, red, black, whereas the farinaceous starch is always white.

Physiology and development

Germination and raised The germination, started by the imbibition of the grain results by a mobilization of the reserves of the scutellum then of endosperm and in the development of the radicle then secondary seminal roots which appear on the level of the node scutellaire. At the other end of the embryo, the gemmule develops in the form of the Coléoptile which pushes to the top and forms a plate of tillering. On this level are formed a first series of adventitious roots, and sometimes of the secondary stems, then the coléoptile borer the ground and opens by releasing the first sheets. Starting from this stage, the young corn seedling becomes gradually autotrophic.

vegetative Phase

However, the system racinaire of corn is characterized by traçantes roots (known as roots of surface), which take water and the nutrients necessary to the plant in the surface layers of the ground. This imbalance in the exploitation of the resources of the ground makes that the plant is very demanding in nitrogenized manure and water, proportionally with the high outputs which it allows, which poses of serious environmental problems in the moderate areas.

In the moderate zones of the northern hemisphere, the corn is sown in April - May and flowers in July - August. The grains reach maturity in October - November. Harvest takes place when the ears lost their green color. The whole plant can also be collected and ensiled before the maturity of the grain (September).

natural Resistance

The young corn seedlings accumulate a particular substance, the hydroxamic acid (2.4-dihydroxy-7-méthoxy-2H- 1.4-benzoxazine-2 (4H) - one or DIMBOA) which creates a natural resistance against a whole series of enemies of the plant: pathogenic insects, mushrooms and bacteria. One finds this substance, the DIMBOA, also at the connected species, in particular corn. The DIMBOA confers on the young corn seedlings a resistance relating to the bee moth (family of the Crambidae ). However, this resistance declines quickly as soon as the plant exceeded the stage six sheets.

When the corn is attacked by phytophagous larvae like the caterpillar of the bee moth, it emits volatile molecules which attract predatory insects Parasitoïde S of the ravageur, the such Trichogramme S.

reproductive Phase

Photosynthesis and potential output

The corn, as of others Graminaceous S tropical (as the Cane with sugar or the Sorghum for example), belonged to the plants known as “in C4”. These plants carry out to them Photosynthèse in a way more effective than the other plants do it (known as “in C3”). According to various studies the output of photosynthesis (i.e. of the transformation of the luminous energy into Organic matter) at corn is about 5 to 6% under the best conditions expérimementales. The practical output depends on the climatic conditions, sunning and temperature (by supposing that the nutrition of the plant - water, nitrogenizes, etc - is not forced), and of the foliar index. This index which corresponds to the report/ratio of the surface of the sheets to that of the ground translates the capacity of the plant to intercept the light radiation and can usually reach five or six in the South-west of France, even ten to twelve. Consequently, the corn is able to accumulate 600 kg of dry matter per hectare and day, which corresponds to an output in grains of 200 quintals. The really known record was established in a farm of the Illinois (the United States) with 235 q/ha.

Classification

The scientific name of the species is Zea mays subsp. mays . The binomial name was allotted to him by Linné into 1753 which at the time created a new kind for this plant very different from other the graminaceous known ones. The generic name, Zea , come from a Greek name , zeia , which indicated in Antiquity a kind of corn, probably the German wheat.

It belongs to the family of the Poaceae and to the subfamily of the Panicoideae (like the Sorgho and the Canne with sugar and the difference of other large cereals, Blé, Riz, Orge, Seigle, etc, which concern the subfamily of the Pooideae ).

The current classification of the species and the species close results from work to Doebley and Iltis published in 1980. They are gathered in the tribe of the Maydeae (sometimes gathered in the tribe of the Andropogoneae ) which is characterized by the Monoécie, i.e. although the plants are bisexuées, the sexes are separate in flowers and often in distinct inflorescences. Seven kinds there are found:

five originating in the Old world: Coix, Chionachne, Polytoca, Sclerachne and Trilobachne ;
two of American origin:

Zea which is characterized by its male inflorescences and separate females; it is subdivided in two sections:

the section Zea which includes/understands only one species: Zea mays , itself subdivided in four subspecies, the corn and three teosintes annual:

''Zea mays'' subsp. '' mays '' (L.) Iltis, the corn itself,
'' Zea mays '' subsp. '' mexicana '' (Schrader) Iltis,
'' Zea mays '' subsp. '' parviglumis '' Iltis & Doebley,
'' Zea mays '' subsp. '' huehuetenangensis '' (Iltis & Doebley) Doebley, sometimes regarded as a variety of the preceding one.

the section luxuriant which includes/understands four long-lived species of Téosinte S:

Zea diploperennis Iltis, Doebley & R.Guzman, which hybrid easily with corn,
Zea luxurians (Durieu) R.M.Bird,
Zea nicaraguensis Iltis & B.F.Benz,
Zea perennis (Hitchc.) Reeves & Mangelsdorf,

Tripsacum , very close kind which include/understand seventeen species, of which some are able to produce hybrids with corn, divided into two sections, Fasciculata with five species and Tripsacum with twelve species, all long-lived.

The subdivision of the species Zea mays in subspecies is prone to debate, certain authors classifying the teosintes annual in six races: Nobogame, Central Plate, Durango, Chalco, Balsas and Huehuetenango, instead of three subspecies.

All the species and subspecies of the kind Zea have the same number of chromosomes (2n=20) except Zea perennis which is tetraploid (2n=40).

Genetics

The innumerable shapes of corn are cultivated. At the XIXe century an American botanist, Sturtevant, establish a classification in groups, founded mainly on the characteristics of the grain:

Zea mays saccharata , soft Corn,
Zea mays cerotina , waxy Corn,
Zea mays amylacea , farinaceous corn,
Zea mays indentata , toothed corn,
Zea mays indurata , horn corn,
Zea mays everta , corn beaded,
Zea mays tunicata , corn vêtu.

This system, considered as artificial, was replaced during the sixty last years by multicriterion classifications calling upon many of other data. The agronomic data were supplemented by botanical characteristics to constitute a robust initial classification, then genetic data, cytological, and others related on proteins and the DNA, were added. There are from now on various categories: racial forms (little employed), races, complexes and more recently branches.

Robert Bird and Major Goodman, in 1977, recognize 14 racial complexes, combining morphological characters and statistical data, identified starting from 20.000 American corn populations:

conical Corn
Corn toothed of the Caribbean,
Popcorn of the South,
Corn sweetened of the North of South America,
farinaceous Corn of the low Grounds,
Chapalote Group,
Group of the North-West of South America,
Group of the South of South America,
horn Corn of the South of the Andes,
Complex of the Andes power station,
modern white Corn toothed of the South,
Cuzco Group,
Hamahuaco Group,
Cravos Group.

The corn has ten pairs of chromosomes (N = 20). The combined length of the chromosomes is of 1.500 CentiMorgan. Certain chromosomes of corn present “bulges hétérochromatiniens”: highly repetitive fields heterochromatic S which are tinted into dark. These bulges are polymorphic as well in the corn stocks as of Téosinte. Barbara McClintock used these bulges as markers to show his theory of the Transposon S which was worth the to him Nobel Prize of physiology or medicine in 1983. The corn remains still today important a Organisme models for the genetics and the Biologie of the development.

There exists in the United States an academy of mutant corn, the Maize Genetics Cooperation - Stock Center , created by the research service agricultural of the American ministry of agriculture and located in the department of agronomic sciences of the Université of Illinois at Urbana-Champaign. The collection includes/understands on the whole close to 80 000 samples. The essence of the collection consists of several hundreds of identified genes, more of the combinations of embarrassments additional and other hereditary variations. There are approximately 1.000 chromosomal aberrations (for example Translocation S and inversions) and of the cases of abnormal numbers of chromosomes (for example tetraploid). The genetic data describing the mutant corn collection as well as many other data on the genetics of corn can be consulted (in English) with the address MaizeGDB, the database of the genetics and genomic of corn.

In 2005, with the the United States, the national Foundation of sciences (NSF), the ministry for Agriculture and the ministry for Energy created a consortium for séquencer the Génome of corn. The Séquençage which will result from this research will be immediately deposited in the GenBank (banks of genes), public institution charged to preserve the data of Séquençage with the genome. The sequencing of the genome of corn was regarded as difficult because of its big size and complex genetic arrangements. The genome counts 50 000 with 60 000 genes distributed among the 2,5 billion bases (molecules which form the DNA) constituting its ten chromosomes (as comparison, the human genome contains approximately 2,9 billion bases and 26 000 genes).

Research in progress with the international Center of improvement of corn and corn (Cimmyt), in collaboration with IRD, aim at creating a corn apomictic by hybridization with a graminaceous connected savage, Tripsacum dactyloides. This modified corn would make it possible to produce seeds without fecundation, thus facilitating the production of powerful seeds.

Origin and distribution

The botanical origin of the corn, plants which does not exist in a wild state under its current form, was prone to controversies a long time.

Many theories were advanced to explain the origin of corn in Mésoamérique, but two schools continue to clash:

that of the wild corn, which existed before the arrival of the man, who is supported by Mangelsdorf;
that of the teosinte ancestor of corn, supported by Beadle.

However, a very great number of evidence resulting from the Molecular biology accredit today the theory according to which the Téosinte is the ancestor of cultivated corn.

The very great morphological differences present between corn and the teosinte are due to a surprisingly low number of Gène S. Of the crossings between cultivated corn seedlings and seedlings of teosinte showed that the principal morphological differences between these two plants are coded by genes present in ten small zones of the genome. For two of these zones, only one gene is present.

The Domestication of corn by selection of transferred seedlings of teosinte which was going to lead to current corn would have started nine millenia ago in the basin of the Balsas river, in the western south of the Mexico.

It is originating in areas clearly recognized and separated by the equator:

in north: Mexico, Central America, Venezuela, Colombia;
in the south: Peru, Ecuador, Bolivia, Chile, Brazil.

History of corn

When Europeans discovered America, the corn was already cultivated north in the south of the continent since banks of the the St. Lawrence (Canada) to those of the Rio of Plata (Argentine). The corn was seen for the first time by Christophe Colomb in 1492 with Cuba. Magellan found it with Rio de Janeiro in 1520 and Jacques Cartier brought back in 1535 that Hochelaga, future the Montreal was in the middle of corn fields, that it compared with “millet of Brazil”.

The Méso-Amerindians (Olmèques, Mayas, Aztec), people of the center of America, of it were very dependant. Some North-Amerindians, also knew it: it is them which us the popcorn comes.

The first introduction of corn in Europe, and in the Old world, is certainly due to Christophe Colomb to the return of his first (March 4th, 1493) or second (June 11th, 1496) voyage in America according to its own testimony.

South of Spain, it was diffused in all the areas of southernmost Europe to the sufficiently hot and wet climate, Portugal (1515), the Spanish Basque Country (1576), Galicia, the South-west of France and the Bresse (1612), Venezia (1554), then all the plain of Po. From Italy, it was spread towards the east: Serbia, Romania, Turkey.

In Africa, the corn was introduced on the one hand in Egypt about 1540, by Turkey and Syria, on the other hand in the area of the gulf of Guinea by the Portuguese about 1550.

The first drawing of corn in Europe is due to the German botanist Fuchs in 1542. In China, the first drawing of corn is gone back to 1637, but its culture was already widespread there.

The first dedicated work with corn in Europe, the corn or corn of Turkey appreciated under all its reports/ratios, is written by Parmentier in 1784.

The success of corn is due initially to its facility of culture and its output very definitely higher than that of corn or the coarse grains which it replaced, as the millet (of which it took the Portuguese name, milho ) and the Sorgho, then at the XXe century with the genetic progress who allowed him to adapt to increasingly septentrional conditions of culture, while allowing a production of interesting dry matter, that thanks to early varieties. The outputs quadrupled in 25 years.

Symbolism

In the cultures Mexicain be, the corn is the expression of the Sun, the world and the Homme. In the Popol-Vuh, the creation of the world is completed only after the third attempt: the first man, destroyed by a Flood, was made of Argile; second is dispersed by a large rain, it was made of wood; only the third is our father, he is made of corn .

It is the symbol of the prosperity, considered in its origin: the seed.

Use

The corn has currently three large type of uses: the animal Feeds which is by far the first outlet (approximately two thirds overall) and relates to especially the industrialized countries, the human, particularly important consumption in certain countries of the Third world, in particular sub-Saharan Africa and the Latin America, and marginal in the industrialized countries, and finally the agribusiness industries, including for the production of alcohol like Bio-fuel S.

Human consumption

The corn is cultivated for its grains, rich in Amidon (approximately 63%), which constitute the base of the Alimentation of many populations.

Historically, the corn was the basic Aliment of all civilizations précolombiennes. It was spread in other regions, in Europe and Africa, substituent partially or completely with cereals consumed more largely formerly like the millet and the millet. In southernmost Europe, it was consumed largely formerly in the form of Bouillie S (called “gaudes” in the Bresse), constituting a cheap food for the country layers, often perceived negatively (in Italy, the term of mangiapolenta is still long-lived pejoratively to designate the inhabitants of the plain of Po).

A food mode very rich in corn can cause the Pellagre (" shovel will agra " ; shovel : skin, will agra : sourness), disease cutaneous related to a deprives of Vitamine PP. In fact, that is especially due to an ignorance of the mode of consumption of the cornstarch. The steeping of the cornstarch in a solution Alcalin E such as the Eau of lime allows the release of the Niacine (PP vitamin) and of its precursor, the Tryptophane ( Nixtamalisation ). The corn is low in proteins and particularly in Lysine which is an Amino-acid essence. The populations which consume mainly corn are thus likely to suffer from a lysin deficiency if their food mode is not complémenté in addition. However there exist varieties called to proteinic high-quality (corn QPM) of which the content lysin and tryptophan was improved by traditional selection.

Modes of consumption

It is consumed either in the form of whole seeds (separated or on ear), or reduced in flour and is prepared in the form of Bouillie S or of cooked Galette S.

In Central America, and particularly with the Mexico, the cornstarch is used to manufacture traditional wafers called Tortilla S, which are very largely consumed. They can wrap other food, for example of the meat in the Tacos. The Tamal be, kind of curlpapers of Amerindian origin, are also widespread in Latin America.

In the Andean countries , the Amerindians prepare starting from corn a traditional Boisson fermented, the chicha.

In Africa, the corn is consumed roasted on a coal or wood fire (Kanoun), and also pulp or couscous, for example in Casamance

In the Western countries, where the corn plays a secondary part in the human consumption, one consumes it more and more like Légume, in the form of grains of soft Maïs. The soft corn became in France the fifth vegetable by order of importance. It is conditioned several manners appertized (out of preserve), is frozen or fresh, and enters the composition of salads. The French consume of them 1 kg per annum, far behind the Americans (7 kg). The corn burst ( popcorn ) is consumed in the form of nibbling or with aperitif. The semolina of corn is the base of the Polenta, origin Italy, or of its Rumanian alternative, the Mamaliga, but of the derivative products of corn also enter the composition of certain industrial preparations (cereals for the Petit-déjeuner). In the United States, one also prepares. The cornstarch not being suitable for making bread, one adds there sometimes flour of corn and brewers' yeast.

It is also used in the form of Fécule, i.e. of Amidon of corn, sold in particular under the mark Maïzena, to prepare Sauce S. in particular the corn starch makes sauce lighter than the flour of corn.

The cornflakes ( corn flakes ) are prepared starting from grains, or of Grits, dehydrated and reduced in then tostées fine plates, they are generally consumed with milk.

The very young ears also prepare with the vinegar with the manner of gherkins.

One also extracts from the Germe S of corn, separated from the flour in the corn mills, a Edible oil appreciated, the oil of corn germs, rich in polyinsaturés fatty-acids.

Distillation

One can draw from the Fermentation of corn the grains of the alcohol which is useful in particular, in complements of other sources, with the preparation of alcoholic drinks (gin, Whiskey, bourbon…).

Animal feeds

The whole plant can be consumed by the Bétail like Fourrage fresh or dry or like Ensilage. The corn is a plant of breeding of fattening, it thus makes it possible to fatten the bovines more quickly and thus increases the production of Lait of the cows, with the detriment of quality. The rather low content of corn of Protein S and its relative poverty of Lysin and Méthionine oblige to have recourse to complements richer in nitrogen.

On a world level, two thirds of produced corn are used for the animal Feeds, 27% for the human consumption.

There exist nevertheless strong disparities between the continents.

In Western Europe, the totality of the corn ensilage and approximately 80% of the corn grain are used for the animal feeds (bovines, poultry farming and breeding of pigs). The essence of the 20% of the corn remaining grain is used in starch industry and semolina factory.

The corn is the food of predilection of geese and ducks gavés for the production of Foie gras.

Pharmacopeia

The Style S of the female inflorescence, filaments very lengthened carrying the Mark S, called “hair of corn” or “corn barbs”, are registered in the traditional pharmacopeia, in particular in France, for their properties cholagogues, Diurétique S and antilithiasic S. One employs them in the form of Décoction or of liquid extract. Their content of Vitamine K gives them also antihemorragic virtues. They contain moreover mannite, fat contents and rock salt. The germinated seed rootlets are used in Gemmothérapie

Industries

The corn has multiple outlets: Agribusiness industry (cookie factory, pastry making, brewery, distilling, etc), manufacture of adhesive for textile industry, sweetening substance, produced Drug company, plastics biodegradable and Biocarburant S.

The products of the Amidonnerie are used:

in the food products (Starch of corn (Maïzena), like thickener, binder, adhesive or gelling);
industrial uses (Detergent paper, paperboards, paintings, S, adhesives, construction materials…) ;
in the medicinal products and Cosmetic S (Antibiotic S, beauty creams, Toothpaste…) ;
production of ethanol (by fermentation of the starch), which enters the composition of the fuels in particular.

The products of the Semoulerie are used in the food products (Polenta, cereals with breakfast, Brasserie).

The Huile of corn (extracted the germs) is used in human consumption, in the Drug company and the cosmetic industry.

The Distillation of corn allows the manufacture of grain alcohol, gin, Whiskey, in particular the Whiskey of corn (at least corn 80%) and the bourbon (from 51 to 79%).

Industries of the Rafle (axis woody and reinflated ear) of corn provide Compost, Combustible, Abrasif, Litière. In the United States one manufactures cheap pipes with the raids.

Decorative plant

The certain corn shapes are sometimes sown like decorative plants in the gardens, especially for varieties curious by their mixed ears about various colors, or particular form like the corn-strawberry, or by their giant sizes, varieties (up to 10 meters in height) or with giant ears (up to 60 cm length).

A strange use of corn is the creation of Labyrinthe S like estival tourist attractions. The idea of this type of labyrinth cut out in a corn field would have been introduced in the United States by Adrian Fisher, which created the first corn labyrinth in Pennsylvania in 1993. The traditional labyrinths are rather carried out in Haie S of yew S which require several years of growth. On the other hand the high-speed growth of a corn field makes it possible to set up a labyrinth usable at the beginning of the summer. These labyrinths are increasingly popular both in Europe and in North America.

Culture

The culture of corn concerns nearly 150 countries in the five continents, to the 50e northern degree of latitude to the 50e degree of southern latitude and to the sea level to more than 3000 meters of altitude. This culture revêt of the aspects very contrasted: often food crop and manual of traditional varieties in sub-Saharan Africa, intensive culture mechanized among most productive in the industrialized moderate countries.

But is a culture of be, characteristic which clearly distinguishes it from the other cereals which are sown for the majority with the autumn or spring. It requires for a germination activates a temperature minimum of 10 °C and at least 18 °C for its flowering. Its output is very depend on the satisfaction of its requirements out of water, in particular in the two weeks preceding and following flowering, the period most critical which intervenes in the moderated areas, the such Paris basin, in July. It is a culture which prefers the deep ground S and rich person but which can put up with more difficult conditions, like sandy or more argillaceous grounds, even limestones, subject to him to ensure the contributions of water and nutritive elements necessary. It is a culture improving thanks to its major rooting and with the organic matter contributions ensured by the residues of culture. Contrary to other cereals, it is a weeded culture , the hoeing being useful to fight against bad grasses and especially to limit the water losses.

The corn can constitute a head of rotation, in front of a corn culture, or can follow a Légumineuse, which will bring a nitrogen complement. It is possible to cultivate corn on corn (monoculture) but with risks of imbalance of the ground and proliferation of the parasites and adventitious. In the United States, one generally practices a rotation over two years with a leguminous plant: corn alfalfa in the freshest areas and corn Soya more in the south.

The fertilizer contributions must ensure the needs for a fast vegetation and compensate for real exports, which vary according to the type of speculation according to whether the grains alone are exported out of the farm or that they are used to fatten animals whose dejections turn over to the field. The nitrogen amounts to be brought vary from 60 to 160 kg with the hectare, but can be reduced of half in the event of preceding leguminous plant or green Manure intercalated.

The output depends initially on the water resources, but is also influenced by various genetic factors, climatic and agronomic. In particular the density of settlement must be sufficiently high because the plant, contrary to corn does not tiller not. Sowing is made using Semoir S of precision, making it possible to control as well the depth, the spacing of the lines as the density on the lines. It must be done as soon as possible, as soon as the ground is sufficiently heated (2nd fortnight of April in the northern hemisphere) to support the rooting of the plants, allowing a better resistance to the dryness of summer and an early harvest in autumn.

The harvest of the corn-grains can be done out of ears or grains. Ear harvest can be done more precociously, ata going water content from 35 to 45%. The ears are dried naturally out of silo-cage ( cribs ). One uses for this purpose of the gatherers-épanouilleurs, tractor drawn or motorized, which collect ears removed from their spathes. The harvest in grains, most widespread currently, requires the operation of beating (realized by gatherers-égreneurs or reaping-machines adapted threshing-machines, provided with nozzle gatherers), and supposes a water content ranging between 25 and 35%. The grains must be dried with the hot air to bring back the content water to 14 15% allowing a prolonged storage. Corn-fodder is collected using Ensileuse S which chops the whole plants when the dry matter rate reaches 30% (grain rayable with the nail). Corn-fodder is intended for the ruminants and can be ensiled or used like fresh fodder.

Varietal selection

The corn was selected empirically during the centuries by the farmers themselves which practiced a selection massale (ears of large size) and cultivated traditional varieties which were in fact of the heterogeneous populations because of Allogamie of the plant.

Largest progress as regards output rests on the development of the Hybride S known as “F1”, hybrids of first generation resulting from the crossing of pure lines. The hybrid F1 are characterized by a very great strength, due to the effect of Hétérosis and by a great morphological homogeneity, which supports the mechanization culture.

The selection of the lines continues various characters, different from one area or a continent to another, according to the objectives of the culture. The independent factors sought in intensive culture are the Productivité, the Précocité and a better resistance to the Verse. Other factors are also interesting, in particular resistance to the dryness, the content of proteins or lipids, the fodder value, resistance to the diseases or the insects, the prolificity (aptitude to produce several ears), etc

Current research relates in particular to the development and the growth of corn, the packing of settlement, on resistance to the stress hydrous, nitrogenized, and with the stress due to the Herbicide S, and on resistance to the bee moth (devastating insect, Ostrinia nubilali ).

The arrival of the hybrids constituted a true revolution in the agricultural world. The farmer became depend on the suppliers of seeds, the collected grains not being able more to be sown (because of the disjunction of the characters to the second generation).

The corn is a demanding plant in care and in work, its culture requires important material and thus investments, the installation of system of Irrigation, the replacement of the traditional cultures… It also implies a stronger bond with the seed-bearer companies, since the seed must be bought each year. In spite of these constraints, largely compensated by the advantages of the new seeds, the surface cultivateds out of corn represent nearly three million hectares in France. In particular, the corn became there the first annual green fodder for the food of the bovines.

Today, technological advances make it possible to develop transgenic varieties by incorporating in laboratory the sought characteristics in it, in particular resistance to insects (bee moth, sesamy) or to weedkillers (glufosinate). The development of the corn GMO cultures took a certain extension in North America (the United States, Canada) or south (Brazil, Argentina), but encountered an opposition marked in Europe, in particular in France where the corn became the symbol of the GMO, especially at the opponents with the GMO.

Varieties

Different corn variety S exists and is cultivated:

the vitreous corn (semolinas);
the horn corn, cultivated in particular in Argentinian and with the the United States, used by industry semoulière (“Corn flakes”);
the toothed corn, characteristic in particular of the Corn Belt American;
the soft corn (human consumption);
the corn to be burst ( Popcorn );
the farinaceous corn (little cultivated);
the white corn whose grain is not pigmented (low content of carotene and xanthophylls). This corn accounts for only 12 to 13% of the worldwide production. It is cultivated especially in the African and Latin-American countries for the human consumption. In the developed countries, its place very reduced and is reserved for special applications: cramming of geese and ducks for the production of foie gras, food of the poultries with white skin (Bresse) or manufacture of in particular required very white starches in pharmacy.

More recently other varieties appeared:

of corn rich in Oil (the Corn oil is appreciated in the human Alimentation by the presence of Antioxydant S which makes it more stable);
of the waxy Corn (strong content of Amylopectin, used by certain agribusiness industries or Paper mill S like thickener);
of the amylomaïs (strong content of Amylose, used by industry for the production of Film S for the packing of food);
of corn rich in Lysin.

Varieties male-deads.

Fight against the enemies and diseases of corn

See also: List of the enemies of the corn

Ravageurs and diseases of corn

Many “a enemy of the cultures ”, ravageurs and diseases, assigns the corn fields to all the stages of the culture since the Semis to formed ears. The animal ravageurs, insects especially, are most dangerous but various average of fight is available. For the diseases, the method of the fight most effective is often to select resistant varieties.

At the beginning of the vegetation, with the stage sowing and young seedlings, the Cast iron of sowings, due to various Mushroom S, a disinfection of the seed S. requires the ground seeds can be attacked by the vertebrate ones: corbels, black and white S, Mulot S, Campagnol S, etc, and seedlings by insects or their Larva S: Courtilière S, taupin S, towards gray (Cut worm S)… A new ravageur, the chrysomèle, hitherto confined in the American continent where coming from Central America, it had invaded the American Corn Belt in the years 1970 and there became the principal ravageur of the corn culture. It appeared in Serbia in 1992 then in Venice in 1998 and was gradually spread in all Europe, often by the airports, in spite of measurements of disease prevention taken in the various countries. The damage is especially due to the larvae which nourish roots.

In the course of vegetation (of the first sheets at the beginning of flowering), phenomena of fading or deterioration of the plants can be caused by gray worms (cut worms,) of the caterpillars of sesamy, white worms (Hanneton S)… of the perforated sheets are the mark of the bee moth, one of the most dangerous ravageurs, pours it can come from attacks of Nématode S of the stems and the bulbs…

At the end of the vegetation, appear various diseases of the stems and the sheets due to the Rouille of the corn ( Puccinia maydis ), with the Anthracnose of the corn ( Colletotrichum graminicola ), with the Helminthosporiose ( Helminthosporium turcicum ), with the Fusariose of the stem ( Fusarium spp. )… The caterpillars of the European corn borer ( Ostrinia nubilalis ) attack the sheets and the stems, often causing the break of these last. Tumors appearing on ears are the mark of the Charbon of the corn ( Ustilago maydis ). Cut worms can also devour Spathe S and grains towards the top of ears.

After harvest, finally, the stored grains can be attacked by various species of insects: Charançon S of the grains, alucites of the cereals, tineas of the grains, two-tone tinea, etc

Methods of fight

The fight can be done in two complementary ways:

is directly by curative or chemical preventive title treatments (weedkillers or fungicides);
is indirectly by various methods:

recourse to resistant varieties,
farming ways supporting resistance of the plants in the course of vegetation,
limitation of the risks of infestation by a rotation studied well.

The treatment of the corn seeds using products containing of the Fipronil was interdict in France since 2004, this substance being shown to harm the bees.

The sensitivity of corn to the bee moth pushed with the development of methods of biological Lutte, based either on the use of pathogenic micro-organisms, like bacteria (Bacillus thuringiensis) or mushrooms (Beauveria bassiana), or on the recourse to a parasite, the Trichogramme, tiny insect parasitoïde about the Hyménoptères, whose female lays in eggs of bee moth. However these techniques did not know a very great diffusion because more constraining and not more effective than the insecticidal treatments available.

Another technique was diffused considerably in the world, although it is very disputed, the development by Transgenèse of varieties naturally resistant to the bee moth. It is the Maïs LT authorized in the United States since 1995.

Bad grasses

The corn is sensitive to the competition of the very diverse plants Adventice S which can affect the output considerably. The methods of fight rest on the one hand on the farming ways, being contrary to other cereals a culture weeded, on the other hand on the chemical weed control. Mechanized weeding is practiced in the first phase of vegetative growth, but is relatively expensive. The chemical weed control calls upon weeding selective. To note that the products containing of the Atrazine are prohibited in France since September 2003. to avoid the pollution of the ground water, this active substance having a great remanence. They had to be replaced by other more expensive and less effective products.

Economic aspects

Production and emerged

The corn is the cereal most cultivated in the world, the production of grains slightly preceding those of the Riz and the Blé. Important surfaces are also devoted to the production of corn-fodder intended for the animal feed either in green, or in the form of Ensilage. As example, in France, corn-fodder occupies 44% of the plate planted out of corn, that is to say approximately 3,2 million hectares.

The first two producers, the United States and China, represent nearly 60% to the world total, 40% for the first and 20% for the second. In Europe, the France, the Italy and the Romania are the principal producers.

The world Exportation S represent approximately 100 million tons, that is to say 14% of the production. The five principal exporting countries, more than 80% of the world total, are, in 2005, the United States of America (49,2 MT), Argentina (14,8 MT), China (9,1 MT), France (7,8) and the Ukraine (3,1). France exports mainly towards its partners of the European Union which is overall overdrawn.

The importing countries are diversified much; the five first, representing a little more than 50% of the total are, in 2005, Japan (16,7), South Korea (8,7 MT), Mexico (6,0 MT) Egypt (5,9 MT) and China (5,3 MT).

The corn cultures transgenic related, in 2006, to 25,2 million hectares distributed in 13 country, that is to say 25% of the total of the transgenic cultures on a world level and approximately 17% of the surface cultivateds out of corn

Worldwide consumption (1999): 593 million tons, of which

the United States: 187 MT
China: 120 MT
European Union: 37 MT
Brazil: 34 MT
Mexico: 23 MT

Environmental problems in Europe

The corn is a plant originating in tropical zones, of which the roots remain on the surface. Culture of spring like the sunflower or the sorghum, the corn has its maximum period of growth and of formation of the grains at the end of the spring and summer, period of weaker pluviometries in moderate zones. These characteristics enabled him to develop naturally in the tropical areas. In moderated areas, like France, the recourse to the irrigation can prove to be necessary for 25% of the surface cultivateds; controlled and thought well, the irrigation of corn like that of other cultures (corn, market gardenings,…) allows to achieve the production targets laid down by the strong demand of the European consumers. Lastly, from its tropical origin, the corn has a physiology more effective than of other cultures resulting from Europe (physiology called in C4). Indeed, to produce 1 kg of corn grains one needs less water than to produce 1 kg of corn grains. Admittedly, it concentrates its requirements in summer. Therefore the storage of water resulting from precipitations of autumn or the winter must be favoured.

In Europe, the maïsiculteurs receive direct aids with the hectare within the framework of the common Agricultural policy. These assistances, also applicable to other cereals, in certain cases are modulated according to the type of culture, dry or irrigated, and higher in this last case, the outputs of reference being definitely high. These direct aids are intended to disappear within the framework from the reform in progress.

Example of the Marsh poitevin

In the Marsh poitevin, wetland formerly wider, part of the grounds were drained to make them cultivable. The Marais is today divided into two parts, one still wet and the other dries, of the locks allow to retain water until June and provide then a minimum provisioning in this area during the hot season.

Certain farmers cultivate various cultures whose corn in the drained zone, and pump, when that is necessary, of water in the Ground water for to irrigate these cultures, causing the salt water increase depths. That causes to extend the zone of Salinité, and to make grounds completely inapt for certain cultures. The Bovin S feeding this salted grass are however a characteristic of the area.

Corn and GMO

Taking into account the very important economic issues that it represents on a world level and particularly in the United States, the corn is a field of application privileged for GMO. Varieties modified genetically to resist weedkillers or certain ravageurs were produced by large the seed-bearer international ones, in particular American Monsanto, but their importation is prohibited by certain States.

In Europe, this question is the subject of important debates. For more details, to see the article GMO.

Varieties of corn GMO

Corn LT

International standards of marketing

Standards Codex for the corn
Standards Codex for the whole-wheat corn starch
Standard Codex for dwarf corn
Standard Codex for soft preserve corn

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