Wheat is an annual, mostly unburned ear grass. The upright spindle is covered with two rows alternating with 3-6 flower-bearing spikelets. As a rule, only three of the flowers develop grains (caryopses). The grains are elongated and ovoid. On the back they are criss-crossed by a longitudinal furrow and at the top they have a small head of hair. The fertilization occurs mainly through self-pollination. Common to all types of wheat today is a stable spikelet fork (rachis), which prevents the grains from breaking out of the ear after ripening. Wheat is demanding and needs heavy, nutrient-rich soils made of clay or black earth with a high water capacity. Wheat is one of the intensive roots. The roots can reach up to a meter deep into the ground.
Wheat is one of the oldest cultivated plants of mankind and was already collected and cultivated in its wild form 8,000-10,000 years ago. After barley, wheat is the longest cultivated type of grain.
Targeted cultivation and repeated cross-breeding of wild grass species resulted in a selection for advantageous properties at an early stage. A large number of wild grasses have been shown to be involved in the wheat genome. The wild and cultivated species known today can be systematically assigned based on their chromosome relationships:
Of the pelted forms, einkorn ( T. monococcum , diploid 2n = 14) and emmer ( T. dicoccon , tetraploid, 2n = 28) are of no economic importance today. In contrast, spelled ( T. spelta , hexaploid, 2n = 42) is now being grown again in southern Germany. The spelled is harvested when it is ready for milk (50% water content of the grains). The green spelled is produced from spelled by drying and peeling the grains. Durum wheat ( T. durum , tetraploid, 2n = 28) is awned and warmth-loving and is cultivated mainly as spring wheat in the Mediterranean region and in the Middle East. Its processing results in a not very elastic dough, which is mainly used to make pasta products. Common wheat, seed wheat or bread wheat (T. aestivum , hexaploid, 2n = 42), with its numerous, mostly unfurled forms, is in the foreground of global wheat cultivation (90% of total cultivation). Cultivation takes place in all temperate zones, rarely in subtropical areas.
Wheat has a very large polyploid and very complex genome, which has posed great challenges for science so far. At the end of 2012 the 17 Gbp hexaploid genome of wheat was published. It is the largest genome (five times larger than the human genome) that has been fully sequenced to date. It could be shown that the hybrid wheat genome is a combination of three different grasses. Each of the original genomes contributes seven diploid chromosomes to the genome of wheat says rotavator manufacturers in india. Furthermore, the wheat genome seems to have lost individual genes in the course of its evolution, without knowing the exact reason and time for this so far.
Wheat is made up of 70% starch and 10-14% protein. The high gluten content (gliadin and glutenin; gluten / adhesive protein) gives wheat its special baking properties. There are three different levels of adhesive quality. The glue ensures that the dough holds the carbon dioxide produced, the dough can rise and the finished bread retains its shape. However, gluten causes a hypersensitivity reaction (celiac disease) in some people.
The degree of grinding of the flour determines the ash and vitamin content, which is indicated by the type number (mg ash per 100 g in anhydrous flour). The higher the type number, the darker the flour and the more valuable the nutritional properties.
Origin and Distribution
The home of the ancestors of wheat is in the Eurasian area, probably in the north of the Arabian Peninsula, as well as in Iraq, Iran, Syria and Saudi Arabia. Wheat is believed to have come to Europe around 7,000 years ago during the Neolithic, first in the Mediterranean, where it was grown by the Romans in ancient times. It was not until the 11th century that wheat was able to establish itself in Central Europe.
Today wheat occupies the largest cultivation area of all grain types worldwide and achieves the highest production quantities. The share of bread wheat in global calorie consumption is 20%.
The winter wheat is sown in Central Europe in October. It can withstand temperatures down to -22 ° C. In regions with lower temperatures, only spring wheat is grown, which is sown in spring. The share of spring wheat ( T. durum ) in total wheat cultivation is 10%, that of bread wheat ( T. aestivum ) is 90%.
Wheat is processed into flour, pearl barley (polished grain), semolina and groats (crushed pearl barley). In addition to bread and other pasta, pure starch, wheat beer and brandy are made from wheat.
Winter wheat is sown in autumn from mid-September at around 200 to 350 grains per m² (100–220 kg / ha) when the dormancy of the seeds has been overcome. When sowing in the autumn seedbed, it should be noted that wheat is a dark germ. In moist, warm soil, the seeds germinate quickly and lead to field emergence in 15–20 days. The small plants form side shoots (tillering) and overwinter. Like all winter cereals, winter wheat also needs vernalization due to frost temperatures in order to break down the lock. The main stocking does not take place until spring and is heavily dependent on the variety and care measures. With late sowing, which is usually associated with low soil temperatures, germination is slower. Winter wheat tolerates late sowing; sowing is possible until December, but then leads to suboptimal crop yields. Although wheat (depending on the variety) is frost-resistant down to around −20 ° C, it generally prefers a temperate climate.