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Wheat ( Triticum aestivum L )

Family : Poaceae
Introduction: Wheat has been described as “Staff of life or king of cereals”. It is the
number one cereal in the world in terms of area. As regards to world production, it is next
only to maize. As a contrast to rice, wheat is grown in all the continents of the world. In
India, wheat stands next only to rice. It has significantly contributed in the success of green
revolution.Wheat is being cultivated in India for more than 5000 years and the original
species Triticum sphaerococcum was grown in Indus Valley Civilization. This species has
disappeared and presently only 3 species have been cultivated in India:

1. Triticum aestivum (common Bread wheat) 2. Triticum durum (Macaroni wheat

or durum wheat ) 3. Triticum dicoccum ( Emmer wheat )

Wheat is the second most important crop after rice and is the main rabi crop in many parts
of India. With rice, it makes the most important cropping pattern of the country called Rice-
Wheat cropping pattern. In India, top three wheat producing states are Uttar Pradesh, Madhya
Pradesh and Punjab. At the time of independence, India was dependent on import of wheat
from US; but today, India is second largest producer of wheat in the world after China with
about 12% share in total world wheat production. In India, a major breakthrough in wheat
production started in 1967-68 with the introduction of dwarf Mexican wheat varieties when
the production increased by more than one-and a half times from 10.4 m tonnes in 1964-65 to
16.5 million tonnes in 1967-68. This introduction of high yielding dwarf Mexican wheat led
to the Green Revolution or rather wheat revolution in India.

Nutritional value per 100 g of wheat:

Energy: 327 Kcal , Carbohydrates : 71.18 g , Sugars : 0.41 g

Dietary fibre: 12.2 g, Fat: 1.54 g , Protein : 12.61 g , Iron : 3.19 mg

Significance of wheat protein: Wheat contains more protein than other cereals. It has
relatively high content of niacin and thiamine. Wheat proteins are of special significance.
Besides, their significance in nutrition, they are principally concerned in providing the
characteristics substance “gluten” which is very essential for bakers. In bakery, gluten
provides the structural framework for the familiar spongy, cellular texture of bread and other
baked products. Flours prepared from other cereals are lacking gluten, therefore not good for
bread making.

Botanical description: The plant is divided in two distinct parts:

1. Root System 2. Shoot system

Root system: a) Primary root system or temporary root system: It forms at the time of seed
germination and absorbs nutrients for the young seedlings. It arises at the depth where the
seed is planted. As plant growth progresses, the primary root system usually dies and they are
replaced by the more permanent secondary root system.
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b) Secondary root system: It arises at a point above the primary root system as the principal
organ of absorption as the young wheat seedling progresses to maturity. It is the root system
which arises near the soil surface at the time of crown root initiation stage usually 21-25 days
after sowing (DAS) in Mexican dwarf wheat. It is a permanent root system.

Shoot system: It is composed of stems, leaves and inflorescence.

Culm: A stem and inflorescence may be called as culm.

Stem: The stem is round or cylindrical. In most varieties of bread wheat the stems are
hollow, except at the nodes where they are solid, but in few varieties the internodes are
completely filled with soft pith.

Leaves: Leaves consist of four parts: a) Leaf sheath: It is the basal part of the leaf. It
encircles the culm and protects the growing buds from the weather and provides some
support to stem. b) Leaf blade: The flattened, parallel and vein portion of the leaf. c) Ligule:
A membranous or cartilaginous fringe at the junction of the sheath and the blade on the side
of the leaf next to the culm. The continuation of the sheath through the collar is known as the
ligule. d) Auricle: Lobes of the leaf blades which extends downward on each side at the
junction of the blade and sheath. These are horn-like or claw-like appendages projecting from
the collar of the leaf.

Inflorescence: The flowering portion of the wheat plant is called “ear” or “head” but in
botanical language it is a spike. Spikelet’s are systematically arranged and are distributed
along a common axis. The central zigzag axis is the rachis.

Spikelets : Spikelets are composed of flowers called florets.

Florets: The outer covering of a floret is made up of a lemma and a palea.

Karnel: Karnel is the fruit (seed), botanically called caryopsis.

Economic importance: Wheat has played a fundamental role in human civilization and
improved food security at the global and regional levels. It provides about 19% of the calories
and 21% of protein needs of daily human requirements at the global level. It is a staple food
for 40% of the world’s population mainly in Europe, North America, and the western and
northern parts of Asia. The demand for wheat is growing fast in new wheat growing regions
of the world such as eastern and southern Africa, West and Central Africa and South Asia.
Wheat is the most traded agricultural commodity at the global level. Many of the developing
countries that depend on wheat as a staple crop are not self-sufficient in wheat production,
and accordingly, wheat is their single most important imported commodity.Wheat also
accounts for the largest share of emergency food aid. The flour of bread wheat is used to
make French bread, Arabic bread, Chapatti, biscuits, pastry products, and the production of
commercial starch and gluten. Durum wheat is specifically grown for the production of
semolina (suji) for use in pasta and macaroni products. In North Africa, durum wheat is
preferred for the preparation of couscous and bulgur. It is also widely used to prepare special
bread made by mixing bread and durum flours.
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Origin: De Candolle believed that wheat originated in the valley of Euphrates and Tigris and
spread from there to China, Egypt and other parts of the world. Vavilov (1950 ) conducted
extensive study on origin of cultivated crops and concluded that durum wheat was probably
originated in the region of Abyssinia and the whole 65 groups of soft wheat ( Triticum spp )
probably originated in the region of Western part of Pakistan, south Western Afghanistan
and the southern parts of mountainous Babshara. Records from China show that it was
cultivated there by 2700 BC and it was known to the inhabitants of Switzerland as early as
the Stone Age. In India, evidences from Mohen-Jo-Daro excavations, indicate that wheat
was cultivated here more than 5000 years ago.

It is generally agreed that wheat was originated in Asia Minor or South West Asia.

Geographic distribution: Wheat is cultivated in 220 mha in the world with a global
production of 763.06 m tonne, global average productivity is 3.47 tonne /ha. (Year: 2017-18).
Maximum area under wheat is in India followed by Russia. In India, area under wheat is
30.54 mha, production: 94.57 m tonnes and average productivity is 3.1 tonne/ ha (year 2017-
18). In production China ranks first and India ranks second. In regards to average
productivity, China ranks first. In India, among the different states, Uttar Pradesh ranks first
in area and total production while Punjab ranks first in productivity. In Assam, wheat is
grown in 0.02 mha area with a production of 0.03 m tonnes and average productivity is 1.5
tonne /ha. ( mha : million ha)

Why wheat yield is high in Punjab? The reasons of higher productivity of wheat in Punjab
are 1. Low temperature prevailed for a long period provides longer duration for wheat growth
2. Assured irrigation 3. Adequate application of fertilizer.

Classification: On the basis of genomic constitutions wheat grown in India belongs to

three classes:

Group No. of pairs of Species Genome Common name

chromosomes
Diploid 7 T. monococcum AA Einkorn
Tetraploid 14 T. dicoccum AABB Emmer
T. durum Durum
Hexaploid 21 T. aestivum AABBDD Common bread
wheat
Growth stages of wheat:

Vegetative Phase: Vegetative phase includes germination, crown root initiation, tillering,
jointing , culm elongation and heading.

Germination: At appropriate temperatures the embryo begins to push out both the coleorhiza
and coleoptile. The seed coat ruptured, the coleoptile turns upwards, and the primary root
pierces the coleorhiza and thrust downwards. As the coleoptile continues to elongate, the first
foliage leaf of the plumule pushes through the vent. As growth continues, the second foliage
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leaf pushes out and seminal root grows. Germination generally takes about 5-7 days
depending upon temperature.

Crown root development: Coronal roots arise from the node of the first foliage leaf and this
becomes the first node of the crown. The crown –root initiation (CRI) occurs in the dwarf
wheat about 20-25 days after sowing (DAS). The crown roots comprise several nodes.
Two, three or more coronal roots are formed at each crown node. These crown roots together
with their branches are principal supply roots of the plant. Adequate moisture supply is
important at this stage and that is why first irrigation in dwarf wheat is recommended
between 21 and 25 DAS.

Tillering: A bud primoridum lies in the leaf axil at each crown node. The bud primordia
develop into tillers. Tiller production in wheat often starts about 15 DAS with a new tiller
added every 4-5 days until 45 days. Though tillering is a varietal character, it is also affected
by environmental, edaphic and agronomic factors viz. temperature, light intensity, day length,
soil moisture, fertility status, depth of sowing, spacing between plants and preceding crop etc.

Jointing: This is the peak plant growth stage starting from 45 to 60 DAS. The upper and
intermediate nodes expand during this period. The internodes become progressively longer
from the base to the top. The uppermost internode is the longest. The existing leaves are
pushed upwards and they increase the size

Reproductive Stage: The reproductive phase commences with differentiation of the growing
point in a spike. It is characterized by the swelling of the uppermost internode. The spike is
held inside the last leaf. This last leaf is called flag leaf. The flag develops completely at this
stage. The maximum leaf area is observed at this stage. This stage reaches at 75-85 DAS.

Climatic requirement: Wheat has wide adaptability. It can be grown in tropical, subtropical
and temperate zones. Most ideal climate is cool weather during vegetative growth and
warm weather for maturity stage. Areas with warm and damp climate are not suitable for
wheat cultivation. It can be cultivated from sea level to as high as 3300 m. Grown between
60O N and 60 O S latitudes. Grown in areas with annual rainfall ranges between 25 and 180
cm. Heavy rainfall is harmful for wheat. Rains just after sowing hamper germination and
encourage seedling blight. Optimum temperature varies with the crop growth stages of wheat.
Optimum temperature for seed germination: 20 to 25 OC, tillering: 16- 20 OC and grain
formation: 20-23 OC are the optimum temperature range. Temperature above 25 OC during
grain filling and development reduces the grain weight. During the heading and flowering
stages, excessive high or low temperature and drought are harmful to wheat. Cloudy weather
with high humidity and low temperature is conducive for rust attack.

Soil: Wheat is grown in a variety of soils. Ideal soil for wheat is clay or loam texture with
good structure, moderate water holding capacity, neutral in reaction, well drained and rich in
organic matter. Heavy soils with good drainage are suitable under dry condition. Non suitable
soils: Light, excessively drained soils poorly drained heavy soils. It can be grown in PH range
of 6.0 to 8.5, but nearly neutral soil is most suitable.
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History of varietal development: During 1920s, Japanese scientists released semi dwarf
wheat called varieties called “Norin”. Among the various Norin varieties, Norin 10 has
become historical on account of its extensive use in the development of new semi dwarf
varieties. Dr. Norman Borlaug at CIMMYT, Mexico developed germplasms adapted to
tropics using Norin varieties. He developed semi dwarf varieties such as Yaqua, Lerma Rojo
64, Sonora 64. Dr. Borlaug was awarded the Noble Peace Prize in 1970 for his work on semi
dwarf wheat breeding. During 1960s, the Indian scientists selected two wheat varieties
Kalyansona and Sonalika from the genetic material supplied by Dr. Borlaug. These varieties
occupied 10 M ha and made the green revolution in India happen.

Varieties recommended for Assam:

Variety Duration Yield potential Plant Other features

(Days ) ( q/ha ) height
( cm )
HD-2733 130 50 95 Moderately resistant to smut
and rust diseases
HD-2687 148 55 94 Tolerant to karnal burnt and
moderately reaistant to rust
PBW-373 135 50 90 Resistant to blight and leaf rust
. Moderately resistant to karnal
bunt
HDR-77 105 25 75 Suitable for rainfed condition.
Susceptible to rust
K-8027 130 35 100 Resistant to smut and leaf
blight. Good for rainfed timely
sowing

Land preparation: The land is to be ploughed thoroughly and levelled properly. The first
ploughing is done preferably about one month ahead of sowing. Four to five ploughings
followed by laddering are required to obtain a good tilth. In rice-wheat cropping system, zero
tillage with the use of Zero-till-cum-seed-cum fertilizer drill for sowing of wheat is
recommended in light textured soil of Central Brahmaputra Valley Zone and Upper
Brahmaputra Valley Zone of Assam.

Time of sowing: Time of sowing depends upon the following factors:

1.Type of variety ( duration ) 2. Weather condition 3. Soil temperature 4. Irrigation

facilities 5. Land preparation 6. Availability of inputs.

In India, rainfed wheat is generally sown during the period from the second fortnight of
October to early November. Maximum yield of irrigated wheat is obtained by sowing them
between 10 - 25 November.
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Time of sowing for Assam: The optimum time of sowing of wheat is when the mean
temperature of 25°C prevails in the areas. Early sowing helps in utilizing residual soil
moisture and escaping pre-monsoon rain.

Central Brahmaputra Valley Zone : Nov 5- Dec 15

Lower Brahmaputra Valley Zone : Nov 5 – Dec 15

Upper Brahmaputra Valley Zone Nov 5- 30

Hills Zone: Nov 5 -20

North Bank Plain Zone : Nov 5 -20

Seed rate: 100-120 kg / ha is adequate.

Row to row distance: 20 cm is to be maintained for optimum plant population.

Depth of sowing: Depth should be 2.5 -5 cm but not deeper than 5 cm for dwarf varieties.
After sowing the seeds in furrows, laddering should be done along the furrows followed by
another laddering across the furrows. This ensures compaction resulting in uniform and quick
germination. The coleoptile length of dwarf wheat varieties is short, so shallow seeding
within the range of 2.5 to 5 cm depth should be done to hasten the germination process.

Method of sowing: Seeds can be sown in line by ‘Pora’ ‘Kera’ or ‘Sirolua’ methods.

kera : sown behind the country plough. pora : seed is dropped through a funnel attached to
the country plough.

Seed treatment: Should be done with the following fungicides:

Fungicide Dose (g / kg of seed) diseases

Captan 3g Root and foot rot
Carboxyn 3g Loose smut
Carbendazim 3g do

Fertilizer management: The HYVs fully exhibit their yield potential only when supplied
with adequate quantities of nutrients at proper time. A crop of wheat yielding 50 q of grain
per ha removes 100-150 Kg nitrogen, 70-80 Kg phosphorus and 125-150 Kg potash from the
soil.

About 10 to 15 tonnes of well rotted FYM or compost should be applied four to six
weeks before sowing and incorporated uniformly in the soil.

All India recommendation: N: 120 kg/ka, P2O5: 60 kg/ ha and K2O: 40 kg/ha has been
recommended for irrigated timely sown crop in all the zones.
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Time and method of application: Half of N and full quantity of P2O5 and K2O should be
drilled about 5 cm below the seed at the time of sowing. The remaining half N should be
top dressed before first irrigation.

Fertilizer recommended for Assam (irrigated): On the basis of availability, sufficient

quantity of FYM should be incorporated in the soil at the time of field preparation. In
Assam, the doses of fertilizers under irrigated condition have been recommended for each
subdivision of the districts which ranges as follows: N : 60- 80 kg/ ha. , P2O5 : 34 – 46 kg/ha
and K2O : 20 -42 kg/ha.

Time of application: under irrigated condition, half of N and whole quantity of P2O5 and
K2O is to be applied as basal and remaining half of N at CRI stage just before first irrigation.

Water management: Irrigation is provided based on critical physiological growth stages.

Based on supply of water, the following schedule of irrigation should be adopted for best use
of water

Number of Growth stage of crop

irrigation
available
One CRI

Two CRI + flowering

Three CRI + late jointing (booting )+Milky

Four CRI+Tillering+Flowering+Milky

Five CRI+Tillering+Late jointing+Flowering+Milky

Six CRI+Tillering+Late jointing+Flowring+Milky+Dough

It is estimated that each week delay in first irrigation from CRI stage results in yield
reduction of 2-3 quintals per hectare. In case of dry top soil, pre-sowing irrigation is to be
applied 3-4 days before sowing for quick and uniform germination of seeds.

Among the growth stages of wheat, CRI is the most critical stage from irrigation
management point of view. The crown root in dwarf wheat generally develops about
two centimetre below the soil surface. The soil is generally dry in this zone and therefore
soil moisture stress condition is detrimental for the development of crown root which
finally reduces tillering. So, irrigation should be provided at this stage.

For Assam: Two irrigations of 6 cm depth recommended for all the agro-climatic zones -
First at CRI stage (20-25 DAS) and the second at heading stage (70-75 DAS).
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(Heading stage: the ear emerges at this stage which is immediately followed by flowering).
Irrigation should be avoided when ground water table remains within 50 cm of the surface.

Method of irrigation: Border method most suitable for wheat.

Weed management: 10- 40 percent yield loss, if weeds are not controlled at early stages.
The first 30-40 days are critical for competition between crop and weeds. So, weed must be
controlled in this critical crop weed competition period. Both monocot and dicot weeds
infested in wheat. Two grassy weeds viz ., little canary grass ( Phalaris minor ) and Wild
oats (Avena fatua ) have become problematic weed. During initial growth stages the
morphology of Phalaris minor closely resemble wheat seedlings causing difficulty in weed
control. (Mimicry of weeds). Most dicot (broad leaf) weeds can be controlled by application
of 2, 4-D @ 0.4 kg a.i. /ha in 700 litres of water about 35 DAS.

Recommendation for Assam: Post emergence application of isoproturon @ 1.00 kg a.i./ha +

metsulfuron methyl 4.00 g/ha, or sulfosulfuron 25g/ha in 700 litres of water controls weeds
effectively. Running twin wheel hoes in between rows once at 20 DAS controls weed
effectively.

Cropping system: Most common cropping system in India:

One year duration: 1. Rice - wheat 2. Maize - wheat 3. Pigeon pea -wheat

4. Pearl millet-wheat

Two years duration: Maize – wheat – cotton - barseem , Rice – wheat –sorghum -
chickpea

Three years duration: Maize- wheat-sugarcane-ratoon

Harvesting: Wheat is to be harvested during sunny days as soon as it matures. The mature
grain produces a cracking sound when passed between teeth.

Storage: Steps for storage of wheat for seed purpose are as follows:

1. Seeds should be collected from disease free fields.

2. Wet seeds should not be kept for seed purpose.

3. Seeds must be dried for 4 to 6 days or more to bring the moisture content below 12 per
cent.

4. Malathion 5% dust @ 2.5 g/kg of seeds should be added as a protective measure against
stored grain pests.

5. Seeds can be preserved in sealed thick polythene bags or in tightly closed metallic
containers. When stored in metallic bin, grains may be fumigated with EDB @ 3 ml/q of
seed.

6. Seeds should be examined periodically and if necessary it should be dried and repacked.
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Protection of wheat seeds from insect pests during storage with the following practices: -

# Dry the wheat seeds to reduce moisture content up to 11-12%

# Mix black peeper seed powder @ 6 g / kg seed thoroughly

# Store in gunny bags impregnated with polyethene in dry places

Yield: High yielding dwarf varieties under good management produces:

Irrigated condition: 45- 55 q/ ha

Rainfed condition: 20-25 q/ ha

Straw yield: Straw yield of rainfed wheat is same as grain yield. The straw yield of
irrigated wheat is about 1.5 to 2.0 times the grain yield. Straw yield of dwarf varieties is less
than traditional tall varieties.

Wheat is a gambling crop of Assam and NE region :

Wheat is not extensively cultivated in the NE states including Assam. There are several
constraints of growing wheat in NE region. These are as follows:

a) Occurrence of pre monsoon shower at the time of harvesting of wheat: Wheat seeds
start germination in the standing crop due to the pre monsoon rainfall. It is known as
pre harvest sprouting of wheat seed. This is a major production constraint in wheat
cultivation in NE region particularly in Assam. So, success of wheat is dependent on
rainfall behaviour. Hence, it is known as a gambling crop of NE region.
Other constrains are:
b) Long duration paddy varieties occupy the suitable land up to the month of December.
c) Difficulty in storage of wheat seed due to high humidity.
d) Lack of irrigation facility
e) Soil acidity
f) Short winter season
g) Pest / diseases / weeds
h) Lack of farm mechanization etc.

Research Institutes on wheat:

1. CIMMYT : International Maize and Wheat Improvement Centre,

Headquarter: Texcoco, Mexico
2. Indian Institute of Wheat and Barley Research ( IIWBR) , Karnal, Haryana

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