Modern wheat cultivars have been developed to resist various diseases such as rusts and smuts. In addition to disease resistance, wheat breeding also focuses on increasing overall grain yield as well as grain quality protein and starch. Wheat is an important cereal grain for export and domestic consumption in many countries throughout the world. In there were about In over 40 million hectares were planted to the crop in North America.
About one third of this area was in Canada. The principal use of wheat grain is the production of flour which, depending on the specific type of wheat, is used in many baked goods. Flour from hard red wheat is used to make bread dough while cakes, pastries, and crackers are made from soft red wheat flour. Flour from hard and soft white wheat is used in the production of oriental noodles.
Additionally, hard white wheat flour is desired for making tortillas while soft white wheat flour has many uses including dough for cakes, crackers, cookies, pastries, and muffins. Durum wheat grain is used primarily to make semolina flour which is the basis for pasta production. Wheat is thus categorized into five main market classes. They include the four common wheat classes: hard red winter, hard red spring, soft red winter, and white.
Durum is the fifth market class. Additional significant classes include the utility wheats CPS and extra strong wheats. Planting and harvest of a commercial wheat crop depends on the type of wheat grown.
Due to the vernalization requirement of winter wheat, it is planted in the early fall September and October so that plants can emerge and develop sufficiently prior to onset of winter. During the winter months, winter wheat plants remain in a vegetative, dormant state. Once the temperature begins to rise, the winter wheat plant will resume growth and switch to a reproductive stage resulting in head development.
In most areas of North America, a winter wheat crop will be ready for harvest by mid-July. Spring wheat plants do not enter a dormant state, therefore the crop requires approximately 90 days, from planting to harvest. Thus, most North American spring wheat crops are planted in mid- spring April-May and harvested in mid to late summer August-September. The minimal temperature for germination of T. Within Canada, the primary production areas are the prairie provinces of Manitoba, Saskatchewan, and Alberta, although there are some production areas in the eastern provinces.
Most wheat grown in the prairies is spring wheat. Winter wheat is produced in eastern provinces. Wheat is the number one food grain consumed directly by humans. A significant amount of wheat is also used for animal feed; mainly of the high-yielding utility wheats and hard red winter types.
Modern wheat breeding programs focus on the improvement of agronomic and grain quality traits. Agronomic traits include winter hardiness, drought tolerance, disease and insect resistance, straw strength, plant height, resistance to shattering, grain yield, and harvest ability. Grain quality traits include seed shape, colour, test weight, protein concentration and type, starch concentration and type, and flour performance Knott, The majority of wheat varieties grown in North America are pure line, derived from inbreeding.
The process of developing a new variety begins with the generation of F1 hybrids. Wheat breeders make many crosses each year in an effort to transfer traits between breeding lines and cultivars. The F2 generation, derived from self-pollinating the F1, exhibits a wide range of genetic differences based upon the genotypes of the parents. Selection of desirable individuals begins in the F2 generation and continues for at least two generations until individuals produce progeny that are genetically uniform.
At that point, usually F6, selection for complex traits such as yield and grain quality will commence. Also, once a line is sufficiently uniform, performance data from small plots are generated for use in deciding which lines will be advanced. It should be noted that spring wheat breeding proceeds faster than winter wheat breeding due to the vernalization requirement of winter wheat. Since spring wheat does not require vernalization, breeders can achieve two to three generations per year using nurseries in greenhouses or fields in Southern regions i.
California, Arizona or regions with opposite production seasons i. New Zealand. Based upon small plot performance data, wheat lines are chosen for pre-registration trials which are comprised of 10 to 20 locations over three years. The data from these trials is used to decide if the line is worthy of registration as a new cultivar. Based on the trial data, administrative groups i. The Prairie Registration Recommending Committee for Grain will decide whether to support the breeder's application for variety registration.
Once a cultivar registration is approved, breeder's seed is distributed to seed growers for increase. Several winter wheat hybrids have been commercialized for limited acreage in the United States; no spring wheat hybrids have been commercialized. In normal agricultural practice, T. In western Canada, a number of rotations are possible and may include barley, canola, or flax, depending on the type of soils, culture practices, etc.
Reproduction of T. Wheat is predominantly self-pollinating. In wheat, Hucl found that the frequency of outcrossing for 10 Canadian spring wheat cultivars varied according to the genotype, where the frequency was always lower than 9 per cent.
Outcrossing tended to be highest among cultivars with low pollen staining, spikes which tapered at the extremities and with greater spikelet opening at anthesis. Martin reported outcrossing rates of 0. Isolation of wheat plants for crossing purposes within the context of plant breeding can be done with greaseproof paper, cellophane bags, or dialysis tubing.
Modest spatial isolation 3 metres is required to prevent outcrossing in the production of foundation seeds in Canada Anonymous, Following dehiscence, wheat pollen viability was observed to range between minutes.
After release, wheat pollen attaches to the stigma branches via a brief electrostatic force followed by absorption of water by the pollen grain through gaps in the stigma cuticle Heslop-Harrison, This process enables the pollen tube to grow which in turn facilitates fertilization. The duration of wheat stigma receptivity depends on variety and environmental conditions; the general range is days. In general, pollen tube growth is initiated hours after pollination followed by fertilization after an additional hours deVries, However, pollen grains can germinate within minutes after landing on the stigmatic surface with fertilization taking place in less than one hour personal communication, George Fedak, The first spikelet to flower is generally in the middle third of the spike and usually near the upper part of this section; the flowering progresses rather rapidly upwards, downwards a little slower.
The primary florets of a spikelet flower first, then the secondary and so on. The stamens are smaller and produce fewer pollen grains per anther; , per plant compared to other cereal grasses.
According to deVries , this compares to 4 million for rye Secale cereale L. Although, the origins of wheat is complicated by various taxonomic opinions most researchers consider that modern wheat cultivars were derived from einkorn T.
Wild einkorn wheat originated in southeastern Turkey where it still grows today. Wild emmer wheat has a similar distribution but also extends into the Mediterranean portions of the middle east. Emmer wheat is often found in mixtures with einkorn wheat. Durum wheat cultivars were derived from domesticated emmer, while common hexaploid wheat originated from a combination of emmer and the diploid T. During the domestication of modern wheat, key traits were modified that benefited early farmers but eliminated the ability of the resulting wheat races to survive in the wild.
Plants with heads that did not shatter were favoured due to easier harvest. While farmers benefited by harvesting heads full of grain instead of gathering grain from the ground, the trait placed the wheat plants at a competitive disadvantage to plants of other species which could more efficiently distribute seed.
In addition, hull-less type-plants were easier to thresh but exposed the developing seed to environmental extremes. Despite these disadvantages, plants of modern wheat cultivars are occasionally found in uncultivated fields and roadsides. These occurrences are usually associated with grain dropped during harvest or transport. Similarly, wheat plants can also grow as volunteers in a cultivated field following a wheat crop. These plants are usually eliminated from the crop via cultivation or the use of herbicides.
Manipulation of wheat genetics has led to ever increasing gains in yield and grain quality, while decreasing the ability of wheat to survive in the wild. In fact, after hundreds of years of cultivation in North America and throughout the world, there have been no reports of wheat becoming an invasive pest.
High salt concentration in is one of the main causes behind decreased soils decreases wheat leaf water potential, turgor productivity Goudarzi et al. Table 4. Research scenario of molecular and genetical characteristics scenario in wheat under salinity stress.
Molecular and genetical characteristics Reference s Proline Singh et al. Low ; Munns et al. Reactive oxygen species CO2 concentration changes the rubisco; a exert a lot of detrimental effects impairing many photosynthesis key enzyme functioning as oxygenase functions such as retarded antioxidant defense Iqbal et al.
Ali et al. Chlorophyll and caratinoides Generally ROS are produced in thalakaloid, amount correlate with the crop yield under salinity mitochondria and peroxisomes during photosynthetic stress Kong et al. Wheat crop exposures to the adverse environmental Table 5. Research scenario of yield characteristics in wheat under salinity stress.
Yield characteristics Reference s Grains protein content Mozafar et al. The enzymatic been accounted by Sairam et al. So far, the enzymes which are overproduced defense system of plants. Research scenario of anatomical characteristics in wheat under salinity. Kong contents under salt-stress induced cultivars in et al.
Stem transverse sections of some wheat cultivars under salinity stress. Leaf midrib transverse sections of some wheat cultivars under salinity. Salinity stress enlarged the accumulation of with compared salt stressed plants Sairam et al. Leaf lamina sections of some wheat cultivars under salinity stress.
Yield and yield components Similarly, Goudarzi et al. It also In concise, extensive research has been made by harmfully affects on wheat crop and yield and yield researcher in respects of grains protein content, spike components Arfan et al. Moreover, dehydrins, to salt stress experience in plants. Various genes have vacuolar acid invertase, late embryo abundant been recognized to be salinity stress influenced and proteins, ABA genes expression and proline induction formed special types of salinity stress associated have been too identified in salinity influenced plants proteins as well as enzymes Ingram and Bartels, Close et al.
Sal 1, Bnd al. Leaf sheath sections of some wheat cultivars under salinity stress. Wheat responds to salt stress conditions with important function in salt stress tolerance. It is changing its genes expression and proteins synthesized from pyrrolinecarboxylate synthetase.
Existing information on salt-responsive During salt-stress, concentration of kDa protein genes and proteins is yet limited because their and proline content was observed significantly high in functions have not been systematically determined. CDNA- shocks.
Changes in 3A and and studied by Wu et al. Study Iqbal et al. In summarizing, elevated salt stress Yambao et al. Therefore, xylem cells with smaller and genetic level which retards the plants functioning narrow vessels are physiologically more confined properly Table 4.
Due to narrow xylem vessels, risk of cavitation Anatomical characteristics is reduced resulting in better water uptake.
Root is the first Salinity is a threatening abiotic stress limiting normal organ which experiences the earliest salinity stress growth and development of wheat reap which Solomon et al. Akram et al. Hameed salt-stress. But, lots of assessments and investigations et al. The dermal tissues showed conditions. Therefore, it is need of the hour for some considerable decrease in epidermal cell thickness and combined approaches to accelerate the detection and area, stomatal area and increased number of stomata.
The tendency of reduction of The authors are thankful to Assistant Professors, Dr xylem vessel area by increasing salt stress was. Nargis Naz and Dr. Morphological and molecular genetic variation in wheat for salinity tolerance at Ashraf M, O'leary JW. Responses of Some germination and early seedling stage. Wheat to Salt Stress: 1. Yield Components and Ion Distribution. Science, 2 , Wheat growth aestivum L. Bread wheat. Series FAO , Pakistan journal of biological sciences, 10 15 , Maniruzzaman AFM.
The effect of salinity on Effect of aestivum L. Plant and cell salt and osmotic stresses on germination in durum physiology, 33 7 , Plant and soil, 2 , Geoderma, 95 1 , Plant responses to water deficit. Journal of Plant Trends Plant Science.
Physiology, 6 , Isolation and Panjehkeh N. Salinity effects on seed characterization of salt-associated protein in Citrus. Trakia journal of Sciences, 9 1 , Hernandez JP, Bashan Y. Structural stress in wheat seedlings by a gfp-tagged Azospirillum features of some wheat Triticum Spp. Arid Land Research and Management, 28 3 , Iqbal et al. Dehydrins: emergence of a contents in wheat. Biologia plantarum, 35 4 , biochemical role of a family of plant dehydration Physiologia Plantarum, 97 4 , Flowers TJ.
Salinity stress and salt Alleviation of salinity stress on and durum wheat. Agronomy Journal, 78 6 , wheat yield, yield components, and nutrient uptake The use of cell Recent molecular advances on downstream plant responses to abiotic stress.
Salt of molecular sciences13 7 , Genome, 30 4 , Elshintinawy F, Elshourbagy MN. Partial NaCl-stressed wheat seedlings by thiamine. Planta, 4 , The importance of tolerance of wheat genotypes using multiple initial seed size in wheat plant response to parameters. European journal of agronomy, 22 3 , salinity. Plant and Soil, 2 , Gupta S, Srivastava J.
Indian U. A comparison of screening criteria for salt Journal of Plant Physiology, 32, Journal of agronomy and Goudarzi M, Pakniyat H. Evaluation of crop science, 5 , Journal of Egamberdieva D. Alleviation of salt stress by Agriculture and Social Sciences, 4, 35— Amirnia R, Salehzadeh, H. Effect of osmopriming with polyethylene glycol on El-Samad HA. Research Journal Iqbal et al. Exact status definitions can vary from state to state.
For details, please check with your state. Triticum aestivum L. Triticum vulgare Vill. Fields, roadsides, waste places, areas of cultivation. Native: indigenous. Facts Bread wheat is thought to have been domesticated in Fertile Crescent around 12, years ago. Habitat Anthropogenic man-made or disturbed habitats , meadows and fields. Characteristics Habitat terrestrial New England state Connecticut Maine Massachusetts New Hampshire Rhode Island Vermont Leaf blade width 6—20 mm Inflorescence branches there are no branch points between the base of the inflorescence axis and the flowers, or they are not obvious Spikelet length 10—15 mm Glume relative length neither glume is quite as long as all of the florets Awn on glume the glume has an awn One or more florets there is more than one floret per spikelet Lemma awn length 0— mm Leaf sheath hair type there are hairs on the surface of the leaf sheath, but the hairs do not have blisters at their bases there are no hairs on the surface of the leaf sheath.
Groove on seed the caryopsis has a groove running most of its length Seed length 5—7 mm. Horizontal rooting stem no Lifespan the plant lives only a single year or less Rhizomes no Roots there are only slender roots on the plant. Hairs at nodes the stem nodes are hairless or they have very sparse hairs Plant height 14— cm Stem node number 6—7 Stem orientation the stems are upright Stem spacing the stems grow close together in compact clusters or tufts.
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