Crops
Triticum aestivum L. - Common spring wheat
Taxonomic position
Family: Poaceae Barnhart., genus: Triticum L., species: Triticum aestivum L. - Cherepanov S.K., 1995Synonyms:
Triticum vulgare Host; T. hybernum L.; T. sativum Lam.; T. vulgare Vill.; T. aestivum L. emend. Fiori et Paoletti; T. cereale Schrank; T. sativum tenax a. T. sativum vulgare Hack.; T. sativum subsp. Tenax Al.; T. sativum vulgare Asch. Et Gr.; T. compactum Host.Biology and Morphology
2n=42. A herbaceous annual 60 to 180 cm high. Wheat has a fibrous root. Embryo, coleoptile and nodose roots are to be distinguished. Embryo roots appear at seeds' germination while coleoptile roots grow from an underground coleoptile node. Together they form the primary root system which penetrates the soil to a great depth without noticeable branching in the upper soil layers. Nodose roots appear from connivent underground nodes of the main shoot and of lateral shoots. These roots are located in the upper soil layers. During favorable years wheat plants are mostly nourished through nodose roots while during droughty years these roots develop poorly if at all and wheat plants only obtain water and mineral matter through their primary root system. Underground connivent nodes are the bushing out zone or the bushing out node. Lateral shoots are formed in the axils which correspond to these nodes. The occurrence depth of bushing out nodes is very important. The less it is, the greater bushing out is with sufficient moisture. However, insufficiently deep bushing out nodes are more affected by droughts. The wheat plant's stalk is divided into nodes and internodes. It is hollow or full of loose parenchymal matter. Wheat leaves consist of a sheath around the stalk and a linear leaf lamella. There where a leaf's lamella bends out there is a ligule protecting the inner sheath from rain water (even though some wheat varieties have no ligule). The lower part of the sheath is fixed to the base of the stalk node forming above it a bulge - the leaf node. Wheat inflorescence is a compound spike. It consists of a rhachilla and spikelets on its ledges. Each spikelet has 2 glumes and 3 to 4 florets. The best developed florets are located somewhat below the middle of the spike. At the base of the spike there usually are 1 to 2 underdeveloped spikelets. The first and the second florets in the spikelet are developed best of all. A wheat floret consists of an outer pale and an inner pale, the pistil with two pinnate stigmae, three stamens and three lodicules at the base of the floret. While blossoming the lodicules swell and push aside the pales. Wheat fruit is a caryopsis. 1000 wheat grains weigh 10 to 16 g.Ecology
Common wheat is extremely polymorphous. The sprouts of the most cold-resistant varieties can survive short frosts in the spring as low as -10° C. During its vegetation period spring wheat needs average daily effective heat sums of no less than 1300° C. This crop is rather fastidious about moisture, especially while forming leaf tubes and during grain ripening. However, it is more drought-resistant than winter wheat. Its vegetation period lasts for 70 to 110 days. Wheat plants dislike higher soil acidity and are less sensitive to salinization. Wheat plants thrive on black earth and on derno-podzolic soils. Application of fertilizers increases yields of wheat plants. All wheat varieties on the whole grow slowly and weakly during the first 20 to 30 days of their vegetation. With high air temperatures and dry and hot winds wheat plants wither quickly. Hot winds are especially dangerous during the ripening of wheat grains. In those spring wheat cultivation areas where the speed of hot sultry winds exceeds 5 meters per second wheat grains as a rule are hollow. Some wheat varieties protect their tissues from the loss of moisture with their capability to roll up their leaves so that the stomae are hidden on the inner walls of the resulting tube. This greatly reduces transpiration. This rolling up is possible because of some cells capable of changing their volume to form a closer or a looser tube. A waxy film and a thick cuticle on the leaves also help reduce moisture losses from tissues. Spring wheat is a long daylight plant. Most spring wheat varieties react to shorter daylight with a longer vegetation period (delay of the spike formation phase), even though some varieties are indifferent to daylight duration. Spring wheat is self-pollinating. Cross-pollination is also possible as spring wheat blossoms openly (it is chasmogamic). The anthers open up inside a closed flower but some pollen remains in them. After the flower opens up and the anthers emerge, the pollen remaining in them is carried away by the wind. Blossoming begins in the middle of the spike and spreads towards its base and top. The first to blossom are the lower spikelets. Then - the second spikelets, etc. With moderately warm weather each spike blossoms for 3 to 4 days. Blossoming follows a certain pattern and begins at 5 or 6 o'clock in the morning. Its peak in Russian moderate climate areas occurs from 8 to 10 o'clock. Then blossoming slows down. Afterwards there is a second peak and the spike gradually finishes blossoming. The hotter the climate is, the earlier the first peak occurs and the later the second peak occurs (when the heat abates). A few flowers open up at night. In cloudy cool weather the blossoming pattern is smoother. The upper flowers (the 4th or 5th flower in the spikelet are cleistogamic.Distribution
Common wheat is originally from Transcaucasia. It has been cultivated in Turkey, Iran, Iraq, Syria, and Turkmenistan since the 7th or 6th millennium B.C. In Western Europe - since the 6th or 2nd millennium B.C. In Northern Caucasia - since the 1st millennium B.C. On the territory of Belorus and the Baltic countries - since the 4th or 5th century A.D. Wheat was introduced to South America in 1528, to the US territory - in 1602. In Canada it has been cultivated since 1802, in Australia - since 1788. Wheat's habitat encompasses all the world's agricultural areas. In the north wheat is cultivated up to 66° N in Sweden. In is cultivated as far down south as the southernmost territories of Australia, South America and Africa. Wheat is mainly a steppe crop. In Europe it is cultivated mainly in the steppe and forest-steppe areas, in North America - in the prairies, in South America (Argentina) in the pampas. In the foothills wheat is cultivated at elevations of 4,000 m above sea level. Common spring wheat is cultivated in Russia everywhere (it occupies two thirds of all agricultural lands) but mostly in the steppe and forest-steppe in Siberia, the Urals, the Volga Region, the Central Black Earth Belt, the Non-Chernozem areas. 157 wheat varieties have been approved for cultivation in specific areas of the Russian Federation in 2004. The main varieties are: Altayskaya 100, Altayskaya 50, Albidum 28, Albidum 29, Voronezhskaya 12, Voronezhskaya 6, Ivolga, Ikar, Iren, Lada, L 503, L 505, Novosibirskaya 15, Omskaya 18, Omskaya 32, Prioksksya, Saratovskaya 29, Saratovskaya 42 , Yugo-Vostochnaya 2, etc. The main breeding agencies are: Altai Research Institute for Agriculture, Research Institute for Agriculture of the central part of the Non-Chernozem areas, N.M. Tuleykov Samara Research Institute for Agriculture, Omsk State Agricultural University, Primorye Research Institute for Agriculture, Siberian Research Institute for Agriculture, South-Eastern Research Institute for Agriculture, V.V. Dokuchayev Research Institute for Agriculture of the Central Black Earth Belt, Krasnoufimsk Breeding Station, Penza Research Institute for Agriculture, etc. In 2001 wheat (both winter and spring) was sown on all categories of farms on 23757 thousand hectares (50.3 % of all the areas occupied by cereal crops). On average wheat yields 2,000 kg per hectare.Economic value
Wheat is a leading crop in the world. No other crop occupies larger territories or yields more. It is a staple food crop. Wheat grains are processed to produce flour (for bakery and confectionery products), cereal, etc. They are also used to produce mixed fodder. Those wheat varieties that have big rounded grains with a shallow furrow yield more flour than the others. Common wheat includes strong wheat varieties (with hard grains), medium wheat varieties and soft wheat varieties which are distinguished by their bakery properties. Grain hardness of strong improving wheat is usually no less than 70 %, its raw protein content is no lower than 15 to 16 % of absolutely dry matter, raw gluten content of 100 % yield flour should be no less than 28 %, and of 70 % yield four no less than 30 to 35 %. Gluten must be of high quality (with good elasticity and stretchability along the measuring rod within 12 to 18 cm). It should ensure production of considerable amount of high quality bread. Strong wheat varieties possess the ability to preserve their high bakery qualities even with the addition to their grains of 20 to 40 % of soft wheat grains. Fodder wheat varieties are high in protein and deficient amino-acids (lysine, tryptophan), but bakery qualities of their flour are low. Bran and other grinding waste are a concentrated fodder. Wheat straw is used as bedding, for production of paper, cardboard, wicker goods, and as a livestock roughage. Wheat green matter is used as additional livestock fodder in spring. The best wheat precursors are bare fallow, maize, sunflowers, leguminous crops, winter cereal crops, etc. Mineral fertilizers (20 to 30 kg of N per hectare, 30 to 45 kg of P2O5 per hectare, and 20 to 35 kg of K2O per hectare) are applied as main fertilizers. When sowing, 10 to 15 kg of P2O5 per hectare are applied to the drills. With watering and cultivation of intensive varieties, doses of fertilizers are increased. Wheat is sown with drill (with 15 cm between drills) and closed drill (7 to 8 cm) techniques. 180 to 250 kg of seeds are usually planted per hectare (4 to 7.5 million seeds). Planting depth is 3 to 8 cm. Wheat is harvested with two-phase technique or with direct harvesting. The soil is prepared with general purpose machines. Wheat is sown with grain sowing-machines. It is harvested with harvesters-threshers and reaping machines.References
State Register of Breeding Achievements Approved for Practical Application in the Russian Federation in 2004. Moscow: 2004, pp. 5-7Dorofeev, V.F., Korovina, O.N. Cultivated Flora. Wheat. Leningrad: 1979. p. 347.
Zhukovsky, P.M. Cultivated Plants and Their Congeners, Leningrad: 1964. pp. 99-144.
Wheat Varieties of the World. Ed. Brezhnev D.D. Leningrad: 1976. 487 p.
Individual Selection of Field Crops. Ed. Konovalov, Y.B. Moscow: 1990. pp. 216-235.
Cherepanov, S. K. Vascular Plants of Russia and Neighboring Countries. Moscow: 1995. pp. 770-774.