Trigo
Keywords: Trigo, Agricultura, Alimentação, Alimento, Amido, Animais, Arqueologia, Arroz, Canadá
- REDIRECT Predefinição:Emtraducao2
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Classificação Científica
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O trigo (Triticum spp.) é uma gramínea que é cultivada em todo mundo. Globalmente, é a segunda-maior cultura de cereais, a seguir ao milho; o terceiro é o arroz. O grão de trigo é um alimento básico usado para fazer farinha e, com esta, o pão, na alimentação dos animais domésticos e como um ingrediente no fabrico de cerveja. O trigo é plantado também estritamente como uma forragem para animais domésticos, como o feno.
Pensa-se que o trigo foi primeiramente domesticated no Crescente Fértil, no Médio Oriente.
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Cultivares
Os cultivares de trigo são classificados segundo a estação do ano em que crescem (trigo de inverno ou trigo da primavera) e pelo conteúdo em gluten (trigo duro (elevado conteúdo em gluten ) ou trigo macio (elevado conteúdo em amido)).
Principais cultivares de trigo
- Trigo Comum - (T. aestivum) Uma espécie hexaplóide que é a mais cultivada no mundo.
- Einkorn - (T. monococcum) Uma espécie diplóide com variedades selvagens e domesticadas. Foi uma das primeiras espécies cultivadas, mas raramente utilizada actualmente.
- Emmer - (T. turgidum var. dicoccum) Uma espécie tetraplóide species com variedades selvagens e domesticadas. Cultivada em tempos antigos, mas pouco actualmente.
- Durum - (T. turgidum var. durum) A única variedade tetraplóide largamente usada presentemente.
- Kamut® - (T. turgidum var. polonicum) Uma variedade tetraplóide cultivada em pequenas quantidades, mas extensivamente comercializada. Originária do Médio Oriente
- Spelt - (T. spelta) Outra espécie hexaplóide cultivada em pequenas quantidades.
História
O trigo é originário da antiga Mesopotâmia. Os atigos arqueólogos demonstraram que o cultivo do trigo é originário da Síria, Jordânia, Turquia e Iraque. Há cerca de 8.000 anos atrás, uma mutação ou hibridização ocorreu, resultando em uma planta com sementes grandes, porém que não podiam espalhar-se pelo vento. Esta planta não poderia vingar como silvestre, porém, poderia produzir mais comida para os humanos e, de facto, ela teve maior sucesso que outras plantas com sementes mais pequenas e tornou-se o ancestral do trigo moderno.
Estatísticas de produção e consumo
Wheat_in_sack.jpg
Na colheita do ano 2002, a produção internacional do trigo totalizou 563,2 milhões toneladas e os países que mais produziram trigo foram:
- China: 89 milhões toneladas
- India: 71.5 milhões toneladas
- Rússia: 50.6 milhões toneladas
- Estados Unidos: 44 milhões toneladas
- França: 39 milhões toneladas
- Canadá: 15.7 milhões toneladas
1997 global per capita wheat consumption was 101 kg, led by Denmark at 623 kg.
Past International wheat production statistics.
Agronomia
Crop development
thumb|Wheat spiklet with its three antheres sticking out.
Crop management decisions require the knowledge of stage of development of the crop. In particular, spring fertilizers applications, herbicides, fungicides, growth regulators are typically applied at specific stages of plant development.
Por exemplo, current recommendations often indicate the second application of nitrogen be done when the ear (not visible at this stage) is about 1 cm in size (Z31 on Zadok scale). Knowledge of stages is also interesting to identify periods of higher risk, in terms of climate. For example, the meïosis stage is extremely suceptible to low temperatures (under 4°C) or high temperatures (over 25°C). Farmers also benefit from knowing when the flag leaf (last leaf) appears as this leaf represents about 75% of photosynthesis reactions during the grain filling period and as such should be preserved from disease or insect attacks to insure a good yield.
Several systems exist to identify crop stages, with the Feekes and Zadoks scales being the most widely used. Each scale is a standard system which describes successive stages reached by the crop during the agricultural season.
Wheat stages
- Wheat at the anthesis stage (face and side view)
Imagem não encontrada WheatFlower1.jpg | Imagem não encontrada WheatFlower3.jpg |
Diseases
Wheat is subject to more diseases than other grains, and, in some seasons, especially in wet ones, heavier losses are sustained from those diseases than are felt in the culture of any other culmiferous crop with which we are acquainted. Wheat may suffer from the attack of insects at the root; from blight, which primarily affects the leaf or straw, and ultimately deprives the grain of sufficient nourishment; from mildew on the ear, which operates thereon with the force of an apoplectic stroke; and from gum of different shades, which lodges on the chaff or cups in which the grain is deposited.
Examples of wheat diseases:
Bacterial diseases
- Bacterial leaf blight Pseudomonas syringae subsp. syringae
- Bacterial sheath rot Pseudomonas fuscovaginae
- Basal glume rot Pseudomonas syringae pv. atrofaciens
- Black chaff = bacterial streak Xanthomonas campestris pv. translucens
- Pink seed Erwinia rhapontici
Fungal diseases
- Alternaria leaf blight Alternaria triticina
- Anthracnose Colletotrichum graminicola
- Ascochyta leaf spot Ascochyta tritici
- Black head molds = sooty molds Alternaria spp., Cladosporium spp.
- Common bunt = stinking smut T. tritici, T. laevis
- Downy mildew = crazy top Sclerophthora macrospora
- Dwarf bunt Tilletia controversa
- Ergot Claviceps purpurea
- Foot rot = dryland foot rot Fusarium spp.
- Leaf rust = brown rust Puccinia triticina
- Pink snow mold = Fusarium patch Microdochium nivale
- Powdery mildew = Blumeria graminis
- Scab = head blight Fusarium spp., Gibberella zeae, Microdochium nivale
- Septoria blotch Septoria tritici
- Storage moulds Aspergillus spp., Penicillium spp.
Nematodes, parasitic
- Grass cyst nematode Punctodera punctata
- Root gall nematode Subanguina spp.
Viral diseases and viruslike agents
- Agropyron mosaic genus Rymovirus, Agropyron mosaic virus (AgMV)
- Barley stripe mosaic genus Hordeivirus, Barley stripe mosaic virus (BSMV)
- Oat sterile dwarf genus Fijivirus, Oat sterile dwarf virus (OSDV)
- Tobacco mosaic genus Tobamovirus, Tobacco mosaic virus (TMV)
- Wheat dwarf genus Monogeminivirus, Wheat dwarf virus (WDV)
- Wheat yellow mosaic Wheat yellow mosaic bymovirus
Phytoplasmal diseases
- Aster yellows phytoplasma
Economics
Harvested wheat grain is classified according to grain properties (see below) for the purposes of the commodities market. Wheat buyers use the classifications to help determine which wheat to purchase as each class has special uses. Wheat producers determine which classes of wheat are the most profitable to cultivate with this system.
Wheat is widely cultivated as a cash crop because it produces a good yield per unit area, grows well in a temperate climate even with a moderately short growing season, and yields a versatile, high-quality flour that is widely used in baking. Most breads are made with wheat flour, even many breads named for the other grains they contain, including most rye and oat breads. Many other popular foods are made from wheat flour as well, resulting in a large demand for the grain even in economies with a significant food surplus.
Wheat in the United States
Imagem não encontrada Wheat_harvest.jpg Wheat harvest on the Palouse. |
Imagem não encontrada CombineWheat0654.jpg Combining wheat in Hemingway, South Carolina. |
Classes used in the United States are
- Durum - Very hard, translucent, light colored grain used to make semolina flour for pasta.
- Hard Red Spring - Hard, brownish, high protein wheat used for bread and hard baked goods.
- Hard Red Winter - Hard, brownish, very high protein wheat used for bread, hard baked goods and as a adjunct in other flours to increase protein.
- Soft Red Winter - Soft, brownish, medium protein wheat used for bread.
- Hard White - Hard, light colored, opaque, chalky, medium protein wheat planted in dry, temperate areas. Used for bread and brewing
- Soft White - Soft, light colored, very low protein wheat grown in temperate moist areas. Used for bread.
Hard wheats are harder to process and red wheats may need bleaching. Therefore, soft and white wheats usually command higher prices than hard and red wheats on the commodities market.
Much of the following text is taken from the Household Cyclopedia of 1881:
Wheat may be classed under two principal divisions, though each of these admits of several subdivisions. The first is composed of all the varieties of red wheat. The second division comprehends the whole varieties of white wheat, which again may be arranged under two distinct heads, namely, thick-chaffed and thin-chaffed.
The thick-chaffed varieties were formerly in greatest repute, generally yielding the whitest and finest flour, and, in dry seasons, not inferior in produce to the other; but since 1799, when the disease called mildew, to which they are constitutionally predisposed, raged so extensively, they have gradually been going out of fashion.
The thin-chaffed wheats are a hardy class, and seldom mildewed, unless the weather be particularly inimical during the stages of blossoming, filling, and ripening, though some of them are rather better qualified to resist that destructive disorder than others.
See also
- Norin 10 wheat
- Fusarium ear blight or "Wheat Scab"
- Granular material
- Commons
External links
- The Kansas Wheat Commission.
- The North Dakota Wheat Commission.
- ITIS 42236 2002-09-22</small>