Wheat: Highly Nutritional & Widely Cultivated Cereal

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More than 600 million tonnes of wheat are harvested annually, making it one of the ‘big three’ cereal crops. It is an extremely nutritious and widely cultivated cereal grain. In many countries around the world, wheat has been grown and harvested for more than seven centuries. It’s one of the most important crops on the planet and has been ranked no. 2 in world production, only after corn.

It is predicted that wheat demand will increase by 50 percent from today’s levels by 2050. At the same time, the crop faces threats such as new and increasingly aggressive pests and diseases, limited freshwater resources, and unstable weather conditions, especially heat.

Wheat Oldest and Most Important Cereal Crop

There are many cereal crops, but it is among the oldest and most important crops. The three types most commonly used for bread, pasta or other meals are common wheat (Triticum aestivum), durum wheat (T. durum), and club wheat (T. compactum). Club wheat is used for baking, crackers, cookies, pastries, and flour. In addition to these uses, some wheat is used to produce starch, paste, malt, dextrose, gluten, alcohol, and other substances.

Scientific classification

• Kingdom: Plantae
• Clade: Tracheophytes
• Clade: Angiosperms
• Clade: Monocots
• Clade: Commelinids
• Order: Poales
• Family: Poaceae
• Subfamily: Pooideae
• Supertribe: Triticodae
• Tribe: Triticeae
• Genus: Triticum L.

Origin and History

Farmers preferred mutant wheat strains (‘sports’) over the strains created by cultivating and harvesting wild grasses. Their cultivation and repeated harvesting and sowing led to the rise of domestic strains. The grains of domesticated wheat are larger, and the seeds (inside the spikelets) remain attached to the ear even after harvesting. Among the wild strains, the rachis is more fragile, allowing the ear to shatter and disperse the spikelets more easily.

In fact, farmers might not have deliberately selected these traits, but they were likely chosen because these traits allowed them to gather seeds more easily, but ‘accidental’ selection played an important role in crop domestication. Due to the loss of natural seed dispersal mechanisms caused by the traits that make it an ideal food, highly domesticated strains of wheat cannot survive in the wild.

Using archaeology techniques, it has been determined that wild emmer was first cultivated in the southern Levant 9600 BCE. In southeastern Turkey, the Karacadag Mountains may have been the origin of wild einkorn wheat based on genetic analysis. Several archeological sites in this region, including one near Abu Hureyra in Syria, contain dated traces of einkorn wheat, supporting its domestication near the Karacadag Mountain Range. There is no carbon-14 date available for einkorn wheat remains at Abu Hureyra that is earlier than 7800 to 7500 years BCE, except for two grains from Iraq ed Dubb.

Remains of harvested emmer from several sites near the Karacadag Range have been dated to between 8600 (at Cayonu) and 8400 BCE (Abu Hureyra), that is, in the Neolithic period. With the exception of Iraq ed-Dubb, the earliest carbon-14 dated remains of domesticated emmer wheat were found in the earliest levels of Tell Aswad, in the Damascus basin, near Mount Hermon in Syria. These remains were dated by Willem van Zeist and his assistant Johanna Bakker-Heeres to 8800 BCE. They also concluded that the settlers of Tell Aswad did not develop this form of emmer themselves, but brought the domesticated grains with them from an as yet unidentified location elsewhere.

Greek, Cypriot, and Indian sub-continent regions were cultivating emmer by 6500 BCE, followed by Egypt shortly after 6000 BCE, and Germany and Spain soon after. By 4000 BCE, it had reached the British Isles and Scandinavia because of the early Egyptians’ invention of bread and use of the oven. Around 2,000 years later, it was found in China.

DNA testing of wheat seeds from Çatalhöyük, which dates from 6400–6200 BCE, has proven that hexaploid wheat was present more than 7,000 years ago. A granary dating from approximately 1350 BCE at Assiros in Macedonia has been found to contain samples of the first wheat known for producing bread containing sufficient gluten for yeasted breads, Triticum aestivum.

Europe continued to consume it after it spread from Asia. Wheat straw was used in the British Isles for roofing as early as the Bronze Age and throughout the 19th century.

Types of Wheat

Wheat is available in many different varieties, each with different protein qualities and kernel colors. Depending on their growing season, it can be classified as winter wheat or summer wheat. There are then subcategories based on hardness, color, and shape. Details about these subcategories can be found below.

Type of Wheat Properties

• Soft red winter wheat: Due to its baking properties, this wheat is suitable for being incorporated into baked goods like cakes, pastries, and cookies.
• Hard red winter wheat: This type grows in low temperatures and snow-covered regions. It is used for products like flours, flour products, flatbreads, and cereals since it contains high levels of protein. Additionally, it is the most important type of wheat produced in the United States.
• Hard red spring wheat: A hot, dry climate is the best climate to grow this type of wheat. Because of its gluten properties, it can be used for food products like bagels, croissants, and pizza crust.
• Soft white wheat: The softest and sweetest type of wheat. With its low protein content and gluten content, it’s perfect for more delicate pastries and cakes, along with Asian noodles.
• Hard white wheat: In comparison to hard red wheat, this type has fewer proteins and tastes less bitter. These properties make it ideal for soft loaves, like pan loaves.
• Durum wheat: There is no other type of wheat with more protein than this type, which is why pasta is made from it.

Morphological Description

In most varieties, wheat is characterized by long, slender leaves and hollow stems. Various numbers of flowers are inflorescences, ranging from 20 to 100. A spikelet is a group of two to six flowers that promotes the growth of two or three grains after the flowers are shed.

During the transition to reproduction, the shoot apical meristem telescopically extrudes leaves until they sprout into flowers. An individual wheat leaf known as a flag leaf is the last produced by a plant. In order to supply carbohydrate to the developing ear, it is dense and has a high photosynthetic rate. In temperate areas, the flag leaf along with the second and third highest leaves contain the majority of the plant’s carbohydrates and the condition of these leaves is paramount to yield production.

In contrast to other plants, its leaves have more stomata on their outer (adaxial) side than their inner (abaxial) side. Some have suggested that it may be due to its long history of domestication and cultivation. Spring wheat, on the other hand, can produce up to 9 leaves per shoot while winter crops (depending on the cultivar) may produce 35 tillers per plant.

Despite its wide range of planting conditions, it is most suitable for temperate regions with rainfall between 30 and 90 cm (12 and 36 inches). There are two major types of wheat: winter wheat and spring wheat, with the severity of the winter influencing which type will be cultivated. Spring wheat is usually sown in the spring, but in mild climates, it can be sown in the fall as well. Winter wheat is always planted in the fall.

A wheat root can reach a depth of two meters, making it among the deepest of all arable crops. In addition to root growth, a wheat plant accumulates an energy reserve which is stored in its stem as fructans. These fructans provide resistance to drought and disease, but it has been observed that root growth and nonstructural carbohydrate reserves in the stem are not equally important. Drought-adapted crops are likely to prioritize root growth, whereas swards developed for countries where diseases are more prevalent are likely to prioritize stem carbohydrate content.

In wheat, awnings or not awnings may vary according to the variety. In hot, inherently dry countries, awns are much more frequent than leaves in wheat varieties grown in temperate regions because wheat awns are more efficient at photosynthesis than leaves. Climate change is therefore likely to lead to more widespread cultivation of awned varieties. However, there has been an observed decline in the climate resilience of wheat in Europe.

Genetics and Breeding

Traditionally, its populations are derived from landraces, which are privately maintained populations kept by farmers that often possess high levels of genetic variability. In Europe and North America, landraces of wheat are no longer grown; however, they remain important in other parts of the world. It was in the nineteenth century that the first wheat varieties with distinctive properties were developed through selection of seeds from a single plant.

Wheat breeding has a long history and its development is closely linked to the development of Mendelian genetics in the first half of the twentieth century. Breeders commonly cross two lines by hand emasculation, then mate their progeny or use inbreeding to propagate inbred wheat. Prior to being released as a variety or cultivar, selections are identified as having the genes responsible for varietal differences.

Some of the most important breeding objectives are high grain yield, good quality, disease resistance and insect tolerance, as well as tolerance to abiotic stresses, such as moisture, heat, and minerals. The major diseases in temperate environments include the following, arranged in a rough order of their significance from cooler to warmer climates: eyespot, Stagonospora nodorum blotch (also known as glume blotch), yellow or stripe rust, powdery mildew, Septoria tritici blotch (sometimes known as leaf blotch), brown or leaf rust, Fusarium head blight, tan spot and stem rust. Among tropical diseases, spot blotch (also called Helminthosporium leaf blight) is a major issue.

In addition, some types of it have been genetically modified with gamma, x-rays, ultraviolet light, and harsh chemicals. This method has generated hundreds of varieties of wheat (some dating back to 1960), with the majority being grown in China, which has a higher population density. By gamma radiation breeding and conventional selection breeding, bread wheat has been developed that contains high levels of iron and zinc.

In Mexico, CIMMYT leads international wheat breeding. In the Syrian Civil War, the ICARDA had to relocate from Syria, another major international breeder of wheat in the public sector.

Ploidy Level

It is common for wheat to be polyploid, as it is among many grasses. Among the wild wheat species, two are diploid (non-polyploid), T. boeoticum and T. urartu. T. boeoticum is the wild ancestor of domesticated einkorn, T. monococcum. 

There are two chromosome complements in each of the diploid wheat cells, one from mother and one from father (2n=2x=14, where 2n is the number of chromosomes in each somatic cell, x is the basic chromosome number).

In polyploid wheats, the chromosomes are divided into quadriploid (4 sets of chromosomes, 2n=4x=28) or hexaploid (6 sets of chromosomes, 2n=6x=42). There are three types of wild wheat that are tetraploid: wild emmer, T. dicoccoides, and T. araraticum. Almost all domesticated tetraploid wheats descend from wild emmer. The one exception is that T. araraticum is the wild ancestor of T. timopheevi.

Wild hexaploid wheats do not exist; however, feral forms of common wheat can occasionally be found. Hexaploid wheats have evolved from domesticated wheats. An analysis of the genome showed that original hexaploid wheats were produced by crossing a tetraploid domesticated wheat, such as Trachypodium dicoccum or T. durum, and a wild goatgrass, Ae. tauschii.

There are three reasons why wheat polyploidy is important:

• It will be easier to compare wheats that are within the same ploidy level.
• Certain characteristics of plants are influenced by the ploidy level. Higher levels of ploidy are generally correlated with large cell sizes.
• A species can be polyploid if it acquires new genomes. Aegilops tauschii, for example, brought the D genome into hexaploid wheat, resulting in enhanced cold-hardiness and some distinct morphological characteristics.

Genome

Scientists from the University of Glasgow and the British Biotechnology and Biomedical Research Council (BBSRC) announced in 2010 that they had decoded the wheat genome (95% of the genome of the Chinese Spring line 42 variety of wheat). There is no fully annotated sequence of the genome that has been released in this publication; scientists and plant breeders can use it in basic format. The bread wheat gene set was published in essentially its entirety on 29 November 2012.

The DNA and cDNA samples came from random shotgun libraries of T. aestivum cv. In Chinese Spring (CS42), pyrosequencers from Roche and GS FLX Titanium and GS FLX+ platforms were used to generate 85 Gb of sequence (220 million reads) and identified between 94,000 and 96,000 genes. The implications of research in cereal genetics and breeding include the examination of variations in genomes, population genetics and evolutionary biology, as well as further studies of epigenetic modifications. Another team released a more complete genome for the Chinese Spring in 2018.

These same researchers then sequenced 15 genomes of various plant varieties and locations around the globe in 2020 – the first and most comprehensive genome sequences so far – and analyzed them to locate insect and disease resistance factors. The team expects that future cultivar breeding could benefit from having these sequences available.

Pests and Diseases

In a typical year, the world’s wheat crop is destroyed by pests and diseases by 21.47 percent.

Diseases

The main wheat-disease categories are:

• Rust-affected wheat seedlings: A variety of diseases affect wheat crops, mostly due to fungi, bacteria, and viruses. In order to prevent disease, it is important to breed new disease-resistant varieties and implement sound crop management practices. It can be a significant variable cost for wheat producers to deal with fungicides, used to control fungal diseases. Missouri estimates that plant diseases cause 10 to 25% of wheat production to be lost. In wheat, a wide range of organisms exists, of which viruses and fungi are the most common.
• Seed-borne diseases: In addition to seed-borne scabs and stagonospora (formerly Septoria), these are also known as bunts (stinking smut) and loose smuts. A fungicide is used to control them.
• Leaf- and head- blight diseases: The most common maladies are powdery mildew, leaf rust, Septoria tritici leaf blotches, Stagonospora nodorum leaf blotches, and Fusarium head scab.
• Crown and root rot diseases: “Take-all” and Cephalosporium stripe are among the most important of these. Both of them are soil borne diseases.
• Stem rust diseases: Basidiomycete fungi are responsible for the disease, such as Ug99.
• Viral diseases: Viral diseases affecting wheat, barley, and rye include yellow mosaic (yellow mosaic) and barley yellow dwarf. Resistant varieties may be used to control these diseases.

Pests

There are many Lepidoptera (butterfly and moth) species that use wheat as a food source, including the flame, rustic shoulder-knot, setaceous Hebrew character, and the turnip moth larvae. The long-tailed widowbird and other species of birds feed on wheat crops early in the season. Basically, they eat or dig up newly planted seeds or young plants, which can severely damage a crop. Furthermore, they are capable of eating the grain from mature spikes late in the season, damaging the crop.

There have been billions of dollars in losses of cereals in recent years, and wheat has not been immune to various borers, beetles and weevils. The rapid growth of field mice numbers in grain-growing regions can sometimes cause plague proportions because food is so readily available to them. Rodents can also cause significant losses during storage.

Scientists in the Agriculture Research Service have developed an “insect-o-graph,” which detects insects in wheat that are not visible to the naked eye, in order to reduce wheat losses due to post-harvest pests. While the wheat is being milled, the device detects insects through electrical signals. As many as five to ten infested seeds can be detected out of every 30,000 good seeds using the new technology. Food safety and marketing value of the crop depend on tracking insect infestations in stored grain.

Planting and Harvesting

In the furrows created from raking or by using the wheat drill, seeds are sown once the land has been prepared. To effectively spread the seeds by hand, use a simple half circle motion with your wrist. Wheat seeds can be spread evenly and in place with a wheat drill attached to a tractor for large areas. After you have planted the seeds, water the area properly. Water wheat crops thoroughly before planting in order for them to absorb a large amount of water quickly. Nonetheless, don’t leave standing water in the area after watering.

In the hottest months of the year, remember to water the area two or three times before planting summer wheat. Moisture is essential for good wheat growth during the summer seasons. In winter, it is likely that no watering will be necessary during the growing season. Test the moisture content of the ground periodically to make sure it remains within acceptable limits.

Regardless of the season, some kind of insecticide will need to be used. Seasonal factors and the type of infestation indigenous to the area will determine the exact type. In addition to commercial insecticides, county agents can offer recommendations on natural pesticides that will work well depending on the climate and location.

A wheat crop is harvested at the end of its life cycle. A harvest date can be determined once the stalks have developed. Manually harvesting its kernels with a scythe is a time-honored tradition. Combine machines make it easy and fast to harvest acres of wheat over a short time period when harvesting large wheat crops. By separating the chaff after wheat harvest, the end product can be ground into flour or applied to other applications.

There are approximately 60 pounds in a bushel of wheat, which is the unit of measurement of wheat. Wheat seeds are removed from seed heads for weighing after they have been removed. However, only kernels of the plant are weighed. By harvesting more bushels, the farmer has more grain to sell to the local flour mill or elevator operator in Portland for shipment overseas to international millers and bakers.

Wheat Processing

Foods made from wheat are usually processed. In order for the grains to break up fully, they must be cleaned and then conditioned with water. Grinding involves cracking the grain and then passing it through rollers. Upon separating the smaller particles, the coarser particles are passed through other rollers for further reduction. 

More than 72% of the milled grain is utilized to produce white flour. Graham flour refers to the flour made from the entire kernel, which becomes rancid upon prolonged storage due to the oil retained by the germ. When flour without the germ is stored, it is preserved for a longer period of time. Various milling by-products, such as inferior and surplus wheat, are used for livestock feed.

The majority of wheat flour produced goes into making bread. Plants grown in dry climates typically produce hard wheat, containing 12–15% protein and high levels of gluten (elastic protein). These types produce flour that is suitable for making bread. Humid wheat has a lower protein content and a weak gluten content than wheats from other humid areas. Cakes, crackers, cookies, pastries, and household flours are all made from wheat flour produced from softer types. In the alimentary industry, pasta (from wheat endosperm) is made from durum wheat semolina.

Storage

The storage of wheat has always presented a challenge to farmers. Steel and concrete are the materials used to make storage bins on farms. Several farmers have built grain storage bins on their properties in order to separate different varieties of grain and market their crops based on price. Moisture, insects, rodents, and birds are kept out of the silo by its main purpose. After grain is stored in the silo, the silo is always thoroughly cleaned.

It is moisture that is the biggest enemy of stored grain. Moist conditions encourage insect growth and mold. Too much moisture in the grain lowers the quality of the wheat, which means it may not be used in milling and baking. This leads to the grain being sold for a much lower price as feed for livestock.

Nutrition Facts

Variations in climate and soil affect the nutritional composition of wheat grains. According to the USDA, the kernel contains 12 percent water, 70 percent carbohydrates, 12 percent protein, 2 percent fat, 1.8 percent minerals, and 2.2 percent crude fiber. While the bran and germ contain some thiamin, riboflavin, niacin, and vitamin A, most of these nutrients are removed during the milling process.

These are the nutritional facts for 3.5 ounces (100 grams) of whole-grain wheat flour:

• Calories: 340
• Water: 11%
• Protein: 13.2 grams
• Carbs: 72 grams
• Sugar: 0.4 grams
• Fiber: 10.7 grams
• Fat: 2.5 grams

Why has Wheat been so Successful?

Even though bread wheat is a relatively recent crop, it is genetically diverse enough to develop over 25 000 different types with adaptations to many temperate environments. A yield of more than ten tonnes per acre can be achieved, if adequate water and nutrients are supplied as well as effective pest and pathogen control.

Globally, the average yield is low, at about 2.8 tonnes ha-1, due to deficiencies in nutrients and water, as well as pests and pathogens. As long as the water content is below about 15% dry weight and that pests are controlled, it can be harvested using mechanical combine harvesters or traditional methods and stored indefinitely before consumption.

While its adaptability and high yields have certainly contributed to its success, these factors alone cannot explain wheat’s dominance over most of the temperate world. It is distinguished from other temperate crops by the unique property of doughs formed from wheat flour, which allows it to be turned into a wide variety of baked goods (like cakes and cookies), pasta and noodles, and other processed food types. Proteins that form the ‘gluten’ protein fraction have structures and interactions that determine their properties.

Many Uses of Wheat

Human consumption accounts for the majority of wheat demand. Wheat is one of the most widely consumed crops in the world, providing around two-thirds of global food production. Due to its high vitamin and mineral content, wheat is considered a staple food. You can make premium bread, whole-wheat bread, biscuits and cakes using this flour, and feed animals with it.

While it is primarily used for foodstuffs, it also has a wide range of other uses. It has the ability to bind water since gluten and starch are present in wheat. Therefore, it can be used for a variety of products, including:

Paper: To improve paper’s strength, wheat starch is used. Over 5 billion pounds of starch are used by the United States paper industry every year.

Pharmaceuticals: Creating capsules from wheat gluten is common in the pharmaceutical industry.

Adhesives: In addition to wheat starch, postage stamps are also coated with adhesive

Soaps: It is commonly found in soaps and creams that wheat germ contains lots of vitamin E. Besides being used as a source of bioethanol, it plays a small role in producing the fuel in comparison with corn.

Health Effects

Especially in the least-developed countries, wheat products are the primary food for millions of people. It is a major food for human nutrition worldwide, especially in the least-developed countries. A daily serving of whole grain wheat containing a variety of foods that meet the requirements for whole grain-rich foods is an excellent source of multiple nutrients and dietary fiber recommended for children and adults.

In addition to helping people feel full, dietary fiber may also help keep a healthy weight. Wheat is also a major source of dietary fiber, protein, and minerals, as well as natural and biofortified nutrient supplementation.

The United States allows food manufacturers marketing claims for whole grain wheat products, stating: “low fat diets rich in fiber-containing grain products, fruits, and vegetables may reduce the risk of some types of cancer,” and “diets low in saturated fat and cholesterol and rich in fruits, vegetables, and grain products that contain some types of dietary fiber, particularly soluble fiber, may reduce the risk of heart disease, a disease associated with many factors”.

The scientific opinion of the European Food Safety Authority (EFSA) related to health claims on gut health/bowel function, weight control, blood glucose/insulin levels, weight management, blood cholesterol, satiety, glycaemic index, digestive function and cardiovascular health is “that the food constituent, whole grain, is not sufficiently characterized in relation to the claimed health effects” and “that a cause and effect relationship cannot be established between the consumption of whole grain and the claimed effects considered in this opinion.”

Concerns

The gluten in wheat – a major component of wheat protein – has been linked to coeliac disease in genetically susceptible people. It is estimated that people in developed countries with coeliac disease account for 1% of the general population. Research indicates that this condition is frequently undiagnosed and untreated. In order to treat gluten-sensitive individuals, a gluten-free diet must be strictly adhered to for life.

Having coeliac disease is not the same thing as having a wheat allergy, as wheat proteins are responsible for the disease. Non-coeliac gluten sensitivity, gluten ataxia, and dermatitis herpetiformis are also potential wheat-related diseases.

According to some researchers, non-coeliac gluten sensitivity is caused by FODMAPs (mainly fructans) present in wheat. Review articles concluded as recently as 2019 that FODMAPs only explain certain gastrointestinal symptoms, such as bloating, but not other symptoms presented by individuals with non-coeliac gluten sensitivity, such as neurological disruptions, fibromyalgia, and psychological disturbances.

In cases of coeliac disease and non-coeliac gluten sensitivity, other proteins in wheat, called amylase-trypsin inhibitors (ATI), are thought to be involved. The natural defense mechanism of plants against insects is the anti-toxin, which can cause inflammation of the intestinal tract in humans mediated by the toll-like receptor. Gluten-containing cereals are the only ones marketed with these TLR4-stimulating ATIs. An animal study conducted in 2017 showed that ATIs worsen inflammation at extraintestinal sites, as well as exacerbate preexisting inflammation. People with preexisting diseases might experience greater inflammation if they consume grains containing ATIs.

Wheat Fun Facts

The Wheat Foods Council has compiled a list of fun facts about wheat.

• Grasses such as wheat produce a single-seeded, dry fruit that is commonly referred to as a kernel.
• The seeds of plants were gathered and eaten by humans more than 17,000 years ago. Raw, parched or simmered kernels got their chewing juices from rubbing off the husks.
• It was grown in the valleys of the Tigris and Euphrates, near Iraq, which is known as the cradle of civilization.
• Historically, grains were called cereal after the Roman goddess Ceres who was regarded as the protector of grains.
• For more than 200 years, wheat has been the primary cereal crop used for white bread, pastries, pasta, and pizza.
• The first English colonists introduced wheat to the New World, and it soon became the main cash crop for rural farmers, who sold it to cities and to foreign countries. As colonial cities developed, Middle Eastern culture developed as well.
• In the history of colonialism, the “bread colonies” became well-known.
• The thousands of wheat varieties are grouped into six classes. They are: hard red winter (HRW), hard red spring (HRS), soft red winter (SRW), hard white (HW), soft white (SW) and durum.
• Approximately one million individual kernels of wheat are found in a bushel.
• There are approximately 60 pounds in a bushel of wheat.
• Approximately 42 pounds of white flour are produced from one bushel of wheat OR 6 pounds of whole-wheat flour from one bushel of wheat.
• For every bushel of wheat, 42 one-and-half-pound shipments of commercial white bread can be produced OR 90 one-pound shipments of whole wheat bread.
• A loaf of bread weighing one and a half pounds contains about 16 ounces of flour.
• As a result of saving Austria from Turkish invasion, a baker from Vienna Austria created the first bagel in 1683. Baking the bread resembled King’s stirrup, so the local baker reshaped it. In German, “bugel” refers to stirrup and was also called “beugel.”
• In order to make bread, the only way to boil it before baking is through bagels.

Source: Britannica, Trade Finance Global, Wheat World, Wikipedia, Oregonaitc.; P. R. Shewry, Wheat, Journal of Experimental Botany, Volume 60, Issue 6, April 2009, Pages 1537–1553, doi.org/10.1093/jxb/erp058

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