Sunday, July 29, 2007

General informations on Wheat

A) Origins and brief history



Wheat is the most widely cultivated cereal grain in the world; it occupies around the 17%(220 million hectares) of the total cultivated land in the world, and is grown in the widest wide range of climates and soils; however wheat gives his best results in temperate regions.

It is the main staple food for the 35% of the world’s population, supplying about 20% of the world’s calories, and has been feeding entire generations. Among developing countries, wheat is planted on about 100 million hectares.

The wheats known today evolved from a type of wild grass native of Asia Minor in an area comprising Syria, the old Mesopotamia and Turkey.

It is thought, according to DNA evidences that the first cultivation of this grain began 12000 to 10000 years ago, after the repeated hybridisations of the Triticum grass family; modern varieties are due to the selection of characteristics from their ancestral relatives such as:


  1. Emmer: closely related to the modern durum wheat, dated around 7000 B.C., of which traces were found in the Pyramids and that was probably the main staple during the prehistoric era.

  2. Einkorn: cultivated extensively during the Neolithic and Iron Age, in Europe. This variety is more resistant to cold, heat, diseases, although yields are not very high compared to others.

  3. Spelt: similar to Emmer but with a tough husk that can’t be removed. Its use started during the Bronze Age.


Repeated cycles of harvesting and reseeding of those pre-wheat cereals, would have selected automatically the mutations in centuries. The importance of this cereal has been pointed out by several religions through the world, that join the origin of the precious grain with direct creation of Gods: the Egyptian imputed its appearing to Isis, the Phoenician to Dagon, the Hindu to Brama, the Arabian to Santo Miguel and the Christians directly to God.

Domesticated wild einkorn became extremely important in the diet of the populations of the Middle East where a family could, with a harvesting period three weeks, survive for a whole year.

Wheat was the ideal crop for Egypt since 4000 B.C. because its production cycle corresponded perfectly with the annual flooding of the Nile River and the efforts of only a part of Egyptians could provide food for all the population.

A wheat seed was the smallest unit of weight, a standard that was very uniform and accurate for that period.

Wheat cultivations fast spread through Europe (there was in the same period a parallel development through the Asian continent): as early as 6700 B.C., Swiss lake dwellers used wheat in flat cakes; Bronze age Greeks could have begun baking high-quality bread as early as 3300B.C.Wheat played such a dominant role in the roman Empire that, at the time, it often was referred to as “Wheat Empire”.

From the Middle Ages to modern times, this cereal becomes the predominant crop on which millions people depended: bad harvest resulted in famines and death for hundreds of thousands, both in country sides and towns. Wheat was also a primary trade good: abundance in the granaries represented power and richness for a Nation.

Wheat was one of the first crop seeds brought to the New World by European immigrants: it was one of the first cultures tried by the Portuguese in Brazil in 1534 at Saint Vincent, before the other Northern and South American colonists, with some success before rust appeared.

In the United States in 1602 on an island off today’s Massachusetts coast, the new crop was planted. But it was more a “hobby” plant then an important agricultural product before the late 1800’s; in fact European varieties hadn’t done well in the New World.

In the 1870’s Mennonites (mostly German peasants ) that left Russia for the U.S. and Canada to escape persecution, settled in Nebraska, Kansas, the Dakotas and central Canada and brought with them Turkey red wheat seeds and the know-how to cultivate.

In Australia settlers brought seeds of this grain in the First fleet in 1788.

Australia’s first wheat was grown at the Botanic Gardens in Sidney, and then successfully cultivated during the 19th century in all the Australian colonies.



B) Characteristics


Wheat may be classed under main divisions (hard-soft, red-white, winter-spring), several subdivisions and species.

The cultivation cycle of the wheat plant varies depending upon the variety being grown.

In the northern hemisphere Winter wheat is planted in September or early October, and the germinated seed lies dormant during the winter. It requires a period of below-zero before the plant resumes its growth in spring (process known as vernalization): after the head with his immature kernels emerges, flowering occurs and the kernels begin to develop until they are full and filled and start to dry quickly.

This quality’s wheat harvest begins in May and usually is completed in August.

Spring wheat is planted during spring when the temperatures are sufficiently high: it has the same growing features then the winter variety, but its harvest starts in late July and is completed in late August.

Three are the species commonly grown.


1) Triticum aestivum: forms the classes HRW (Hard Red Winter), HRS (Hard Soft Spring), SRW (Soft Red Winter), HW (Hard White), SW (Soft White).


2) Triticum compactum that includes club wheats (a low protein soft white wheat).


3) Triticum Durum includes the durum and red durum classes.


The terms “hard” and “soft” are related to the hardness of the kernel; red and white relates to the presence of a red pigment that colours the kernels in the outer layers.

Durum Wheat is so called because produces grains much harder then common hard wheats.

Hard wheat contains more protein (11 to 18 per cent) than soft wheat (ranging from 8 to 11 per cent); it also contains more gluten then the soft variety.

Each variety is genetically different from the other: these differences in characteristics range from physical attributes and qualities, to yields, resistance to drought or diseases.

Desirable varieties are obtained primarily by breeding; plants containing desired characteristics are crossed, and grown through generations and in the end adopted. However the introduction of the new biotechnology and genetic engineering has greatly shortened the time needed to create new qualities avoiding at the same time unwanted characteristics.

Due to the number of types, wheat needs standards categories. In the US there are eight classes, each divided into five grades, depending on the purity of the wheat and overall quality. In Argentina there are two major wheat types and four grades. Australia has seven wheat types and three grades, while Canada has seven classes and nineteen grades.

The most important wheat part is the kernel: this is divided in three major components.

The bran is the outer layer that protects the whole seed; it includes roughly the 15% of the kernel in weight, and has a high content of minerals and fibres.

The inner part of the seed is the germ that comprises just the 3% of the kernel; however it contains most of the lipids and essential nutrients.

The remaining part is the storage endosperm characterized by high protein and starch content: the endosperm is the main part of the kernel and is the primary component of flour.

Any problem with the plant during its growth cycle can affect characteristics of wheat flour: for example wet conditions during the harvest can cause sprouting (the mature seeds germinate in the field) sometimes negatively affecting the quality of the flour.

To keep into account by farmers is the reverse relation between yields and the protein content of the seeds.

Wheat is subject to more diseases then other grains; among major enemies are molds that in some cases may produce toxins such as vomitoxin: in this case the consequences are severe because the crop will not be suitable for any purposes, including animal feeding.

Farmers also face insect pests and weeds that can contaminate the kernels or diminish the quality of seeds.


  1. Common and alternative uses


The most important use of wheat since early times has been for food use. Bread was the staple food of humanity for many centuries, together with rice.
Today is still such an important food that we can find on the tables of any social class and culture.
Over time the use of wheat has been highly diversified to create different wheat flour products; usually hard wheats are used in the production of breads and others yeast leavened or dough- based products: the ability of this kind of flour, to retain gasses gives bread the traditional texture and structure.
Soft wheats are mostly used for cakes, crackers, cookies and other products that don’t need to be so “elastic”, but, instead tender, flaky or crispy.
Durum wheat with its properties of protein content, and the yellow colour of semolina, is mainly used for pasta and noodles products.
Roughly two thirds of wheat produced in the world is used for human consumption, while around one sixth is used for livestock and poultry.

In most cases low quality wheat, parts of the plant unsuitable as human’s food or by-products of the flour milling industry is used for feed.

The properties that make wheat suitable in food products, gluten (protein) and starch make it a good source of raw material for non-food and industrial applications, where the potentials are huge.

There are also uses for the by-products: straw (composed mainly of cellulose) and bran.

In particular straw transformed in the form of wood sheets (strawboard) is used in “ready to assemble” furniture, flooring, lamination of cabinets and other wood substitutes; these boards are of acceptable quality for interior applications, but not for exterior locations due to the poor durability and lack of resistance to weather.

Bran applications includes stabilisers in paints and other uses in cosmetics; its high value is particularly associated to form mechanically and chemically stable gels to be used as medical delivery systems.

Starch is widely used in industrial and others applications.

In fact wheat starch makes paper stronger; it is used as an adhesive (for example on postage stamps) or for plastic bags and films, packaging, eating utensils, building materials.

In the food industry starch can replace fats in desserts, as milk and cream substitute, and in other non dairy products.

It can be used in the cosmetics and pharmaceutical industry in hair conditioners, moisturizers, detergents.


D) Wheat in the developing countries


In the developing countries wheat is one of the major food resources, providing more calories and protein than any other crop.

Wheat is planted on more then 100 million hectares in the developing world, where two qualities predominate: 1) Bread wheat compose the biggest part of the wheat sown in Central and South Asia, eastern and southern Africa, and parts of South and Central America.

Forty percent of this crop is produced in irrigated environments. Major producers in this special list are China followed by India and Turkey : in the first two countries often wheat is produced in the irrigated rice-wheat rotation.

2) About half of all the Durum wheat production in the world is in the developing countries, especially concentrated in the Middle East, Central India, and the Mediterranean region.

However, in these countries, production of Durum is low because of the difficult climatic and soil situations, low levels of inputs used, such as water and fertilizers, that affect the crop output. Production is for all this reasons fluctuant and yields extremely different between countries.

For all wheat, yields in the developing countries is now around 2.5 tons per hectar, but can be as low as 1 tons per hectar in marginal fields, where local wheats, not resistant to diseases or

others kinds of stress, are mainly used.

In the last 20 years yields has grown consistently because of the expanded use of irrigation, pesticides, and fertilizers; the introduction of new varieties that use nutrients efficiently and tolerate drought and diseases in a better way, was another important reason. Comparing to the developed countries, yields grew in the developing countries with a fast pace reaching a similar level of the the richest one in the mid 90’s.

Most of this increase is due to the excellent growth rate of China (around 2.6 percent per year during 1982-1991), India and Pakistan (with increases of nearly 3%): these three countries produce the biggest slice of total developing nations (around three quarters of total). The main use for this higher availability has been for food use, while the increase for feed or other uses has been only marginal. I

Main problems for wheat farmers in the developing areas come from both abiotic and biotic stress.

Wheat plant can suffer from different kind of abiotic (non-living) stress, such as drought, heat, waterlogging, and from soils with low or too high PH or mineral deficiencies.

Around one third of the crops of developing countries suffers during the growing season some type of drought stress caused by low rainfalls (<500>

Depending from the growing period when drought occurs, yields can drop drastically.

Heat stress may contribute to heavy losses: in fact especially in the sub-tropics countries, daily temperatures are often higher then 18°C during the cold season, too high for the winter wheats mainly used in those countries.

The best insurance against this kind of risks, are given by varieties genetically resistant to heat and drought that can give better yields also during the harshest periods.

An excess of water can be also the cause for a poor crop: this situation, called waterlogging, can be usually occur in the rotation system rice-wheat used in South Asia.

Breeding is the best way to develop water-tolerant wheats, and new breeds from wild relatives of wheat are giving good results.

Other growth-limiting factors are due to the characteristics and minerals present or not in the soil.

In some areas such as in Brazil , other South American regions or Central Africa, soil has a acidity that is too high to grow a good wheat crop; this is often due to the presence of aluminium that is toxic for the plant. In the South of Australia, China, South Asia, Philippines and part of South America the presence of Boron is another cause of toxicity.

In other areas, such as Turkey, Afghanistan, Egypt, Iran, Iraq, Southern Australia and others calcareous territories of arid and semiarid regions, zinc deficiency reduces grain yield and the nutritional qualities of the grain.

Between the biotic stresses, wheat fears diseases such as stem, leaf, yellow rust, Karnal bunt and many others that can be defeated both through chemicals applied to the crop or developing plants genetically resistant to these diseases.

Weeds is another main concern for farmers, especially the very common Phalasis minor that can cause serious problems to the destruction of an entire crop. Weeds are commonly fought with chemicals.

Insects could as well cause losses. Among the most dangerous are the Hessian fly, sunni pest, and sawfly that occurs periodically in Central Asia or Northern Africa where varieties resistant to these pests have been introduced.

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