Wheat quality: A review on chemical composition, nutritional attributes, grain anatomy, types, classification, and function of seed storage proteins in bread making quality

Abstract

Wheat (Triticum aestivum L.) belonging to one of the most diverse and substantial families, Poaceae, is the principal cereal crop for the majority of the world’s population. This cereal is polyploidy in nature and domestically grown worldwide. Wheat is the source of approximately half of the food calories consumed worldwide and is rich in proteins (gluten), minerals (Cu, Mg, Zn, P, and Fe), vitamins (B-group and E), riboflavin, niacin, thiamine, and dietary fiber. Wheat seed-storage proteins represent an important source of food and energy and play a major role in the determination of bread-making quality. The two groups of wheat grain proteins, i.e., gliadins and glutenins, have been widely studied using SDS-PAGE and other techniques. Sustainable production with little input of chemicals along with high nutritional quality for its precise ultimate uses in the human diet are major focus areas for wheat improvement. An expansion in the hereditary base of wheat varieties must be considered in the wheat breeding program. It may be accomplished in several ways, such as the use of plant genetic resources, comprising wild relatives and landraces, germplasm-assisted breeding through advanced genomic tools, and the application of modern methods, such as genome editing. In this review, we critically focus on phytochemical composition, reproduction growth, types, quality, seed storage protein, and recent challenges in wheat breeding and discuss possible ways forward to combat those issues.

Full text

Frontiers in Nutrition 01 frontiersin.org
Wheat quality: A review on
chemical composition, nutritional
attributes, grain anatomy, types,
classification, and function of seed
storage proteins in bread making
quality
AnamKhalid
1
*, AmjadHameed
2 and MuhammadFarrukhTahir
1
1 Department of Biochemistry, University of Jhang, Jhang, Pakistan, 2 Nuclear Institute for Agriculture
and Biology (NIAB), Faisalabad, Pakistan
Wheat (Triticum aestivum L.) belonging to one of the most diverse and substantial
families, Poaceae, is the principal cereal crop for the majority of the world’s
population. This cereal is polyploidy in nature and domestically grown worldwide.
Wheat is the source of approximately half of the food calories consumed
worldwide and is rich in proteins (gluten), minerals (Cu, Mg, Zn, P, and Fe), vitamins
(B-group and E), riboflavin, niacin, thiamine, and dietary fiber. Wheat seed-storage
proteins represent an important source of food and energy and play a major role
in the determination of bread-making quality. The two groups of wheat grain
proteins, i.e., gliadins and glutenins, have been widely studied using SDS-PAGE
and other techniques. Sustainable production with little input of chemicals along
with high nutritional quality for its precise ultimate uses in the human diet are
major focus areas for wheat improvement. An expansion in the hereditary base
of wheat varieties must be considered in the wheat breeding program. It may
be accomplished in several ways, such as the use of plant genetic resources,
comprising wild relatives and landraces, germplasm-assisted breeding through
advanced genomic tools, and the application of modern methods, such as
genome editing. In this review, wecritically focus on phytochemical composition,
reproduction growth, types, quality, seed storage protein, and recent challenges
in wheat breeding and discuss possible ways forward to combat those issues.
KEYWORDS
wheat, HMW-GS, LMW-GS, grain anatomy, nutritional quality
1. Overview
Wheat is the most extensively cultivated cereal grain around the globe and holds a crucial
place in agriculture (1–4). It is a principal nutriment for 36% of the world’s populace and is
propagated in 70% of the world’s cultivated regions. (5, 6). Internationally, wheat supplies
approximately 55% of the carbohydrates and 21% of food calories consumed worldwide (6–8).
It beats every other single grain crop (including rice, maize, etc.) in production and acreage and
is grown across a broad range of climatic situations (9); it is therefore the most signicant grain
crop on the entire planet (Table1).
OPEN ACCESS
EDITED BY
Khalid Gul,
University of Leeds,
UnitedKingdom
REVIEWED BY
Nisha Singh,
Gujarat Biotechnology University,
India
Agata Gadaleta,
University of Bari Aldo Moro,
Italy
*CORRESPONDENCE
Anam Khalid
invincible_me2@yahoo.com
SPECIALTY SECTION
This article was submitted to
Nutrition and Food Science Technology,
a section of the journal
Frontiers in Nutrition
RECEIVED 25 September 2022
ACCEPTED 26 January 2023
PUBLISHED 24 February 2023
CITATION
Khalid A, Hameed A and Tahir MF (2023) Wheat
quality: A review on chemical composition,
nutritional attributes, grain anatomy, types,
classification, and function of seed storage
proteins in bread making quality.
Front. Nutr. 10:1053196.
doi: 10.3389/fnut.2023.1053196
COPYRIGHT
© 2023 Khalid, Hameed and Tahir. This is an
open-access article distributed under the terms
of the Creative Commons Attribution License
(CC BY). The use, distribution or reproduction
in other forums is permitted, provided the
original author(s) and the copyright owner(s)
are credited and that the original publication in
this journal is cited, in accordance with
accepted academic practice. No use,
distribution or reproduction is permitted which
does not comply with these terms.
TYPE Review
PUBLISHED 24 February 2023
DOI 10.3389/fnut.2023.1053196

Khalid et al. 10.3389/fnut.2023.1053196
Frontiers in Nutrition 02 frontiersin.org
Wheat is of supreme importance among cereals mainly because of
its grains, which comprise protein with exclusive physical and chemical
attributes. It also encompasses other useful components, such as
minerals (Cu, Mg, Zn, Fe, and P), protein, and vitamins (riboavin,
thiamine, niacin, and alpha-tocopherol), and is also a valuable source
of carbohydrates (11). However, wheat proteins have been found to lack
vital amino acids; for example, lysine and threonine (12–14).
Wheat production and quality could possibly be enhanced
through the development of new and improved varieties that are able
to produce a superior yield and perform better under various agro-
climatic stresses and conditions (15). It is the common consensus that
the diversity of germplasm in breeding material is an essential
component in plant breeding (16, 17).
1.1. Wheat background
Wheat was rst cultivated approximately ten thousand years ago
during the ‘Neolithic Revolution’, which saw a shi from hunting and
collecting food to stable land management. Diploid, i.e., genome AA,
einkorn, and tetraploid, i.e., genome AABB, emmer, were the rst
types of wheat to be grown and, according to their hereditary
relationship, they originated in the southeastern regions of Turkey (18,
19). Cultivation expanded to the Nearby East almost nine thousand
years ago with the rst appearance of hexaploid wheat (20, 21). e
evolutionary and genome relationships between cultivated bread and
durum wheat and related wild diploid grasses, showing examples of
spikes and grain, are shown in Figure1 (20).
e previously grown forms of wheat were essentially landraces
from wild populations that were carefully chosen by farmers, probably
because of their higher yields. However, domestication is also linked
with the genetic trait selection of wheat, which is detached from that
of its wild ancestors. Two characteristics are of signicant importance,
the rst being spike-shattering loss at maturity, which causes a loss of
seeds at the time of harvest (22). It is a vital characteristic for certifying
the dissemination of seeds in genuine populations. e second is the
non-shattering characteristic, which has been deduced through
alterations at the brittle rachis (Br) locus (23) and the conversion from
husked to free-threshing nude forms, in which the outer sterile husk
attaches rmly to the seeds. e unrestricted congurations merge
from a deviant on the Q locus that alters the inuence of receding
mutations at the pertinacious grain husk (Tg) locus (18, 24, 25).
e haploid content of DNA regarding wheat’s six sets of
chromosomes (Triticum aestivum L. em ell, 2n = 42, AABBDD) is
almost 1.7 × 1,010 base pair. It is approximately 100× greater than that
of the genome of Arabidopsis, 40× that of rice, and nearly 6× that of
maize (20, 26). e majority of the DNA sequence of bread wheat is
derived from polyploidy, with substantial duplication, in which,
repetitive DNA sequences make up80% of the entire genome (27, 28).
e typical wheat chromosome is approximately 810 MB, 25× greater
than the usual rice chromosome. e developmental history of wheat
is illustrated in Figure2 (29).
At present, approximately 95% of wheat cultivated throughout
the world is hexaploid bread wheat, and the residual 5% is tetraploid
durum wheat (21). e latter is better adapted to the arid
Mediterranean environment than to bread wheat and is frequently
referred to as pasta wheat to manifest its ultimate specic usage (30).
Small quantities of other species of wheat, like emmer, spelt, and
einkorn, are cultivated in few areas, including the Balkans, Spain,
Turkey, and the Indian subcontinent (20, 31).
1.2. Taxonomic classification
See Table1.
1.3. Types of wheat
e genus name for wheat, i.e., Triticum , is derived from the Latin
word ‘tero’ (I thresh). e modern name, Triticum aestivum, represents
hexaploid bread wheat with genomes A, B, and D, dierentiating it
from tetraploid macaroni wheat, which is Triticum durum, comprising
genomes A and B, and is consumed predominantly for the production
of pasta. Nowadays, bread wheat (Triticum aestivum) is the most
extensively grown wheat. It is a hexaploid type of free-threshing wheat
(genome AABBDD). According to Nesbitt and Samuel, it stemmed
from the recent hybridization of the diploid (DD) Aegilops tauschii
var. strangulate and an allotetraploid wheat (AABB) no longer than
8,000 years ago (32).
Triticum aestivum and Triticum durum consist of seven
chromosome pairs (2n =14). Wheat has been cultivated in the form of
spring or winter crops. In extremely cold areas, spring varieties of
wheat have been propagated during spring so that they can grow and
ripen rapidly and can beharvested before the arrival of the autumn
snowfall. Within more temperate areas, winter wheat is propagated
prior to the onset of the winter snowfall that otherwise covers the
saplings, resulting in vernalization and allowing quick growth when
the snow thaws in the spring. In warm environments, peculiarity in
spring and winter wheat is almost futile. e point of signicant
dierence is early or delayed maturity (33). Types of wheat have been
frequently dierentiated according to endosperm texture, seed coat,
dough strength, color, and planting season. ese are concisely
explained as follows (34).
1.3.1. White and red wheat
Red wheat variants usually have greater latency than white variants
and have therefore been preferred in environments that are favorable
to harvesting before germination. White wheat variants are suitable for
growth in regions that are arid throughout the course of ripening and
harvesting and are ideal for manufacturing at noodles and bread (35).
TABLE1 Classification of Triticum aestivum (10).
Kingdom Plantae (Plants)
Sub-kingdom Tracheobionta (Vascular plants)
Super division Spermatophyta (Seed plants)
Division Magnoliophyta (Flowering plants)
Class Liliopsida (Monocotyledon)
Subclass Commelinidae
Order Cyperales
Family Poaceae/Gramineae (grass family)
Genus Triticum (wheat)
Species Triticum aestivum (common wheat)

Khalid et al. 10.3389/fnut.2023.1053196
Frontiers in Nutrition 03 frontiersin.org
1.3.2. Soft and hard wheat
Although there are several wheat varieties grown around the
world, they all fall into two essential categories (Table2) with distinct
properties: hard wheat and so wheat (37). Variety and seed stability
in hard and so wheat are related to resistance to being crushed (35).
1.3.3. Weak and strong wheat
e production of leavened bread is chiey restricted to the full DNA
sequence code for the proteins required for making a strong and elastic
dough that is appropriate for capturing gas bubbles during fermentation,
allowing the dough to upsurge. e exclusive pliable attributes of dough
are principally the result of the amount and type of gluten present.
Varieties with high gliadin glutenin contents are viscous and produce
expansible doughs, which are appropriate for preparing cookies, for
example, while varieties with a small gliadin glutenin content have greater
strength and elasticity, which is ideal for bread making.
e dierence in alleles in high-molecular-weight glutenins is
nearly associated with the quality of bread making and the ability of
the dough to withstand. Bread wheat varieties have three or ve main
high-molecular-weight glutenin subunits (38, 39). Glu-D1 genes
encode two of these subunits, one or two are encoded by Glu-B1, and
either none or one may beencoded by Glu-A1 (35, 40). More than
50% of the dierence in the baking potential and viscoelastic attributes
of dough depends on the wheat’s composition of high-molecular-
weight subunits of glutenin (35).
1.3.4. Spring and winter wheat
ese varieties are diverse in their need for a frozen phase to allow
normal development and reproductive growth. is need for
vernalization has been vigorously aected by changes at the Vrn-1
position (present on the long arms of group5 chromosomes), such as
Vrn-B1, Vrn-A1, and Vrn-D1, and their supercial adjustment by
negligible ower-inducing genes (41). Spring habits result from the
dominant Vrn-la on any of the three genomes of wheat and the presence
of the recessive, while winter habits result from alleles on Vrn-1b on all
three genomes. However, Vrn-1 genes have a close association with the
genes providing resistance to cold (42) and, thus, persist in winter (34).
Wheat development is largely determined by temperature, the
requirement of a cold phase, variety, and plant responses to the
corresponding lengths of dark and light periods during their
developmental phase. As previously stated, winter wheat variety
maturation was found to beaccelerated due to the owering process
in plants, i.e., with low-temperature exposure, usually 3–10°C, for 6
to 8 weeks. Growth has also been enhanced through long day
exposure which meaning growth is enhanced through longer period
of light as the days lengthen in spring. As the varieties dier in their
responses to vernalization, temperature, photoperiod, and the extent
of interaction between certain factors, they vary continuously in their
maturation rate and, therefore, contribute to the broader distribution
and adaptation of wheat in agriculture globally (34, 43).
1.4. Vegetative growth
1.4.1. Development of wheat seed
Wheat seeds require moisture levels of 35–45% for germination
(35, 44, 45). During propagation (Figure3) (46), the adventitious side
root outspreads earlier than the coleoptile. Seminal roots are generated
FIGURE1
The evolutionary and genome relationships between cultivated bread and durum wheat and related wild diploid grasses, showing examples of spikes
and grain.

Khalid et al. 10.3389/fnut.2023.1053196
Frontiers in Nutrition 04 frontiersin.org
in relation to the node of the coleoptile. When coleoptile arises from
the soil, its development halts and the rst true leaf propels to its end.
Seedlings rely on nutrients and energy supplied through the
endosperm until their rst leaf is photo-synthetically ecient (35).
1.4.2. Root growth
More than one node can grow in the soil based on sowing depth,
all exhibiting roots (47). e root axis grows during expected periods
in association with shoot growth, and the overall number of roots
generated is linked with the number of leaves present on lateral
branches and the extent of tillering (45). Roots emerging from lateral
branches usually spread once the tillers have developed three leaves.
A variety’s root development is analogous to its apex extension (35).
1.4.3. Leaf growth
Aer germination, the apex of a vegetative shoot gives rise to
secondary leaf primordia. Leaf primordial count can dier from seven
to een (35) and is inuenced by light strength, the nutritional level
of the plant, and temperature. Temperature imparts a signicant eect
on the emergence of leaves and expansion. e lowest temperature
withstood for the expansion of leaves is approximately 0°C, the
optimal temperature is 28°C, and the maximum is 38°C (35, 48).
1.4.4. Stem development
Stem elongation overlaps with the growth of tillers, leaves,
inorescence, and roots (49). Stem elongation initiates when the
maximum number of orets are present on the evolving spike,
FIGURE2
Evolutionary history of wheat.

Khalid et al. 10.3389/fnut.2023.1053196
Frontiers in Nutrition 05 frontiersin.org
introducing the stamen’s initial identiable stage, which resembles
almost terminal spikelet development. e fourth internode, with
nine leaves, is the rst to extend in spring wheat, whereas the stem’s
lower internodes remain short. Once an internode is extended partly
to its ultimate extent, the internode above it starts to extend. is
continues until the elongation of the stem is complete, generally close
to anthesis.
e peduncle is the last segment to extend. e height of the
wheat plant extends from 30 to 150 cm depending on the variety and
the propagating state. Alterations in plant stature are generally
TABLE2 Principal cultivars of soft and hard wheat cultivated in the world (36).
Hard wheat varieties
Durum Extremely hard, radiant, pale tinted grain used to form semolina our in order to make pasta & bulghur, rich in gluten protein,
high absorption of water
Hard red winter Hard, brown in color, protein-rich, used for hard-baked products and bread as well as pastry ours to elevate protein intended for
pie crusts
Hard red spring Hard, brown in color, protein-rich, used for bread and hard-baked products. Usually used in bread and gluten-rich ours
Hard white Hard, opaque, light in color, pale, medium protein content, planted in arid and temperate regions. Used for bread/brewing
So wheat varieties
So red winter So, low protein content, low water absorption, used for muns, pie crusts, biscuits, and cakes.
So white So, bran is decient in pigment, low protein content, low water absorption, grown in moderately humid regions. Used for
noodles, crackers, and wafers.
FIGURE3
Life cycle of wheat.

Khalid et al. 10.3389/fnut.2023.1053196
Frontiers in Nutrition 06 frontiersin.org
attributed to the dierences in internode dimensions and not to the
internode number (35, 50).
1.4.5. Tiller growth
e rst lateral branches to arise are formed between the
coleoptile axils and the rst true leaf. Generally, three intervals
between two successive leaves divide the leaf emergence and its
subtended tiller. In winter wheat, small numbers of tillers develop in
winter or autumn if circumstances are moderate. e main shoot and
initially developed tillers fulll their growth and develop granules in
spring and winter wheat (51).
1.5. Reproduction
Wheat is principally an intra-oral pollinated crop. However, the
rate of outcrossing is up to 10% or greater on the basis of genotype,
population density, and environmental conditions. Cross-fertilization
due to wind depends greatly on physical aspects such as excessive
humidity and warm climates (52). Dry, warm climates give rise to
increased cross-fertilization rates, i.e., 3.7–9.7% in comparison to the
insignicant cross-fertilization rates of 0.1% under high-moisture
conditions (53). Allogamy in wheat has been observed as high as
1–2%. Flowering time and duration depend on geographical location.
Sunny climates and temperatures of at least 11–13°C are necessary for
blooming (54).
1.5.1. Spike growth prior to anthesis
e shi to propagative growth takes place close to apical cupola
elongation, once the core shoot has almost three complete leaves.
Floret division initiates in the crucial portion of the spike and
continues both up and down as spikelet induction is completed. It
creates a growth pyramid inside the prickle, which continues
throughout grain growth and anthesis. Terminal spikelet instigation
indicates the completion of spikelet formation (55).
During pre-anthesis, various developmental phases synchronize
with one another (46). Kirby identied a dierence of several weeks
in the instigation of numerous shoots on a plant, which is decreased
to just a few days in the period of spike appearance. Likewise,
variation in the spikelet initiation period between the two early
clusters in a fused ower could span 2 days; however, the dierence
in the duration of meiosis of these owerets is around 6 h (56). Once
the pollen-comprising stamen part elongates up to 1 mm and is
green, meiosis takes place instantaneously in the pistil and anthers
(55). e duration for which wheat owers remain open varies from
8 to 60 min depending on environmental conditions and
genotype (57).
1.5.2. Kernel growth
The ratio of multiplication of the endosperm cell is affected
by water stress, light intensity, genotype, and temperature (58, 59).
The accumulation of starch starts at 1 to 2 weeks following
anthesis and begins a 2 to 4-week period of direct rise in a dry
mass of kernel (60, 61). The development and ultimate mass of a
single kernel are determined by spikelet and floret site; grains that
are developed in proximal florets and middle spikelets are
generally very large (56, 60, 62). When rain coincides with
harvesting, germination takes place. Seeds ripened in cold
conditions are more latent compared to seeds matured in warm
environments (63).
1.6. Grain anatomy
Wheat grain is divided into three main segments, all structurally
and chemically distinguished from erstwhile. ese are: the germ, also
called the embryo, which is located at a single end of the grain in the
form of a tiny, yellow mound, simply dierentiated from the rest of the
kernel; the endosperm, which covers a larger part of the whole grain
and supplies nutrition to the developing plant as the kernel evolves;
and the external seed crust and cover lying underneath, which
contains protein cells that cover the whole kernel and protects the
embryo and the endosperm on or aer injury during the grain’s
subsistence (latent phase) (64). Regarding the unique roles of all three
parts, a signicant dierence exists in the chemical composition of
their constituents and, therefore, a broader variation is found in their
nutritional value (65).
Wheat kernels are usually elliptical, though dierent types of
wheat have kernels that vary from virtually long, trampled, slender,
and spherical in shape. e length and mass of the kernel are typically
around 5–9 mm and 35–50 mg. It features a crinkle below the lateral
side and it was therefore initially associated with the wheat ower. e
wheat kernel (Figure4) (65) encompasses 2–3% of the germ, 13–17%
of the bran, and 80–85% of the mealy endosperm (entire elements
altered to dehydrated material) (66).
Wheat ber is made up of several layers of cells which, when the
seed is dry, adhere so rmly to one another that they are removed by
the milling process in comparatively large pieces. By shiing and other
mechanical means, almost all the embryo and endosperm are
removed. However, as the separation is never perfect, even the purest
commercial bran always contains a little endosperm and possibly
traces of embryo (67). Chemically, as well as structurally, bran diers
signicantly from the embryo and endosperm and, consequently, its
nutritive value also diers. e longitudinal and transverse section of
the wheat grain is shown in Figure5 (68).
e bran, also known as the seed coat, which is present on the
external layers of the wheat kernel and composed of numerous layers,
is responsible for providing protection to the central part of the kernel.
e seed coat is enriched with minerals and vitamin B (14). e bran
is detached from the endosperm containing starch during the initial
step of milling. e bran consists of ber that is not soluble in water
so as to protect the kernel and endosperm. It contains 53% of the
cellulosic components.
Wheat ber has a complicated chemical conguration; however,
it comprises pentosans and cellulose, polymers founded on arabinose,
and xylose rmly attached to the proteins. ese elements are typical
polymers found in the cell layers, like the aleuronic layer and the
wheat cell wall. Carbohydrates and proteins both signify 16% of the
bran’s entire dry mass. e value of minerals is somewhat high, at 72%.
e two outer strata of the grain, the pericarp and the seed cover,
are composed of inactive hollow cells. e internal bran sheet, the
aleuronic sheet, is packed with active contents of plant cells (69). is
somewhat illustrates the elevated concentrations of carbohydrates and
protein in the bran. Signicant variation exists in the particular level
of amino acids that is present in the our and the aleurone layer. e
level of proline and glutamine is nearly half, whereas arginine is triple,

Khalid et al. 10.3389/fnut.2023.1053196
Frontiers in Nutrition 07 frontiersin.org
FIGURE4
Chemical constituents in dierent parts of wheat grain.
A
B
FIGURE5
Wheat grain structure in longitudinal and transverse section.

Khalid et al. 10.3389/fnut.2023.1053196
Frontiers in Nutrition 08 frontiersin.org
and histidine, asparagine, lysine, alanine, and glycine are double the
level in our (65).
e endosperm forms approximately 84% of the entire seed, its
proportions varying with the plumpness of the grain. is part of the
seed provides food for the growing embryo. Unlike the constituents
of the embryo, those of the endosperm are relatively stable substances,
designed by nature to remain unchanged until the germinating
embryo draws on them for its rst supply of food (21).
e endosperm is enclosed via the fused seed coat and the
pericarp. In the external endosperm, the aleuronic sheet holds a
unique conguration (70). It is made up of a single sheet of cubical
cells. Proteins and enzymes are abundant in the aleuronic sheet and
perform a critical role during propagation. e internal endosperm
lacking an aleuronic sheet is observed to bethe mealy endosperm.
In contrast to the other parts of the seed, the endosperm is
characterized by its very high starch content, which, together with
the protein, equals nearly 89% of its whole composition (71). e
endosperm largely encloses food assets required for the
development of seedlings and is full of starch. Besides carbohydrates,
the starchy endosperm consists of 15% fats and 13% proteins, such
as globulins, albumins, glutenins, and gliadins. e amount of
nutritional bers and minerals is low, at 0 or 5% and 1 or 5%,
respectively (66).
e germ on one side of the kernel is enriched with 25%
proteins and 8–13% lipids. e level of minerals is relatively high
(4–5%). Wheat germ is obtained as a by product during wheat
milling (65).
1.7. Chemical constituents of Triticum
aestivum
e main chemical components of wheat are given below.
1.7.1. Vitamins and minerals
Vitamin B5, B1, B6, B3, B8, B2, B12, K, E, and A; ascorbic acid;
boran; dry ascorbic acid; iodine; sodium; carotene; group2 metals of
the periodic table; magnesium; molybdenum; potassium; zinc;
aluminium; copper; phosphorus; sulfur; Iron; and selenium (72).
1.7.2. Enzymes
Superoxide dismutase, protease, amylase, lipase, transhydrogenase,
cytochrome oxidase (73).
1.7.3. Supplementary constituents
Amino acids, e.g., valine, asparagine, aspartic acid, alanine,
glutamine, proline, methionine, glycine, phenylalanine, threonine,
leucine, arginine, tryptophan, isoleucine, tyrosine, serine, histidine,
and lysine; mucopolysaccharides; chlorophyll; P4D1, i.e., glucoprotein;
bioavonoids, such as apigenin, luteolin, and quercitin; laetrile; indole
complexes; and choline, i.e., amygdalin (74–76).
1.8. Nutritional attributes of wheat
Wheat grains and their products are signicant constituents of our
daily diet. e average wheat consumption is 318 grams per person
each day, making up83% of the overall cereal consumption (72).
Wheat contributes a larger percentage of protein than energy to
the nutritional requirement of an adult male. Alone, it can fulll the
daily requirement of niacin and thiamine. e majority of the daily
riboavin and iron requirement is fullled by the quantity of wheat
recommended for an adult male (Table3).
Wheat is predominantly considered a source of protein, vitamins,
calories, and minerals. It is comparable with various cereals in
nutritional content. Its protein content is higher than sorghum, rice,
and maize and about equivalent to that of other cereals. e protein
content is inuenced by a variety of cultural and environmental
conditions, such as soil temperature, moisture, availability of nitrogen,
and method of cultivation. e percentage of protein in wheat can
beinuenced to a certain extent by the time of fertilizer application
and fertilizer type (72).
e nutritional content of protein is estimated not simply based
on the concentration of protein but also the amino acid equilibrium
within the protein. During human digestion, protein is broken down
into its constituents, absorbed by the bloodstream, and then assembled
again to form dierent types of protein required by the body for
growth, maintenance, and repair (21). Eight amino acids are vital for
humans as the body is unable to produce them and must take them
from food.
e biological signicance of wheat is determined by limiting
essential amino acids. ese amino acids become decient due to the
body’s increased requirements. Lysine is the decient amino acid in
wheat (64). During the process of milling, one-third of the total
protein is removed along with lysine as the majority of the protein and
lysine is present in the bran and the germ (14). ere is an inverse
relationship between the quantity of protein in grain and the quantity
of lysine/grams of protein (77).
1.9. Wheat quality
Wheat quality has two main characteristics: external quality and
internal quality. External quality involves freedom from foreign
material and weather damage, type, and purity of color. ese factors
are used to separate wheat into visual grades (72). Internal factors
involve parameters such as density, which is determined by evaluating
the test weight; chemical composition, which includes protein content;
moisture; and processing potential, which comprises milling quality,
end-use quality, and enzyme activity (5).
1.9.1. Classification and function of wheat
proteins
Protein is regarded as the most signicant nutrient for animals
and humans, as the name of its origin indicates (“proteios,” meaning
primary in Greek). e protein content varies from 10–18% of the
entire dry mass of the wheat grain (72). Proteins determine the
capability of wheat our, which can be dispensed into diverse
foodstus. Wheat proteins have an important role in carbon dioxide
retention, dough development, and baking quality due to their
quantitative qualitative and quantitative attributes (78). Mature wheat
grains contain 8–20% protein. e proteins in wheat display great
intricacy and diverse collaboration with one another, rendering them
hard to describe (79, 80).
Wheat proteins have been classied (Figure 6) (81) by their
enforceability and solubility in various diluents. Cataloging was

Khalid et al. 10.3389/fnut.2023.1053196
Frontiers in Nutrition 09 frontiersin.org
conducted on the basis of omas. D. Osborne’s work from the shi
of the previous era (82). According to his method, serial withdrawal
of crushed wheat kernels gives rise to protein properties as follows:
➢ Water soluble albumins
➢ Globulins, not soluble in natural water but soluble in diluted
solution of sodium chloride while
➢ insoluble at high NaCl concentrations
➢ Gliadins, soluble in 70% ethanol
➢ Glutenins, soluble in diluted NaOH or acid solutions
Albumins and globulins are the smallest wheat proteins. e
partition of globulins and albumins was not clear as originally
recommended by Osborne. Gliadins and glutenins represent complex
proteins of high molecular weight (83). e maximum number of
wheat kernel proteins that are physiologically active has been found
in globulin and albumin sets. In mueslis, they are stored in the germ,
seed coverings, and aleuronic cells, with a low concentration in the
starchy endosperm. Globulin and albumin constitute nearly 25% of all
kernel proteins (79).
Traditionally, protein in wheat grains has been divided into
prolamins and non-prolamins. e prolamins consist of gliadins and
glutenins, while the non-prolamins include salt and water-soluble
globulins. Albumin and globulin proteins concentrate during the
initial phase of grain development, aer which, the content of these
proteins remains constant from 10–15days aer owering (DAF)
onwards, the albumins and globulins tend to accumulate in the
emerging starchy endosperm from 10 to 15 DAF, involving primarily
trypsin inhibitors, α, β-amylase, and triticins. e characteristics of
wheat our quality depend on the prolamin content and composition
in the endosperm, whereas the role of albumins and globulins in the
development of our quality is not dened as well as that of
prolamins (66).
Albumins and globulins are primarily metabolic enzymes, which
have a role in numerous metabolic events during the course of grain
lling, comprising starch synthesis, protein synthesis, folding, and
energy metabolism. Storage proteins (gliadins and glutenins)
constitute approximately 75% of the overall protein content. Wheat
crops accumulate proteins in this way for seedling usage in advance.
ey are usually found in the starchy endosperm, not in the germ or
seed coat sheet. Wheat storage proteins are technically dynamic. ey
lack enzyme action, but they perform a role in dough development;
for example, these proteins are able to hold gas, generating so baked
foodstu (66).
Albumins and the wheat endosperm’s globulin cover 20–25% of
the total grain protein. Globulins and albumins have an excellent
amino acid equilibrium with regard to nutrition. Several of these such
proteins (enzymes) are involved in metabolic actions (79).
Wheat is exclusive among the palatable kernels, as its our
possesses a complex protein known as gluten, which, when prepared
as dough, has viscous and elastic characteristics and is essential for
manufacturing leavened bread. e rheological characteristics of
gluten are required not merely for bread manufacture but for a broad
range of foodstu that is only prepared using wheat, like cookies,
pastries, pitta bread, pasta, noodles, etc. e proteins in gluten include
monomeric and polymeric gliadins and glutenins. Glutenins and
gliadins are considered the main storing proteins of wheat,
representing around 75–85% of the overall seed proteins, with a ratio
of nearly 1:1in bread and common wheat. ey are enriched with
proline, glutamine, asparagine, and arginine, but nutritionally
signicant amino acids, like tryptophan, lysine, and methionine, are
present in small amounts (84).
TABLE3 Nutrients and calories supplied by the wheat as % of suggested daily allowance for adult male (77).
Calories(kcal) Thiamin Protein Niacin Riboflavin Iron
% of RDA 42 168 79 95 54 56
FIGURE6
Types of wheat proteins.

Khalid et al. 10.3389/fnut.2023.1053196
Frontiers in Nutrition 10 frontiersin.org
e gliadins, which represent 30–40% of all total proteins in our,
are a polymorphic blend of proteins that are soluble in 70% alcohol.
ey are separated into alpha, beta, gamma, and omega gliadins, with
an MW of 30–80 kilo Daltons, as dened by sodium dodecyl sulfate-
polyacrylamide gel electrophoresis. e omega gliadin MW is in the
range of 46–74 kilo Daltons, while alpha, beta, and gamma are low
molecular weight gliadins, ranging from 30–45kDa by amino acid
sequencing and SDS-PAGE. Recent methodology has revealed a close
link between alpha and beta gliadins and, thus, these are frequently
called alpha-type gliadins (82).
Gliadins are freely soluble in dilute alcohols, except glutenin
polymers; however, their subunits have the ability to bedissolved in a
similar way to the gliadins. e subunits of glutenin can beacquired
through the treatment of glutenin using a disulde reducing agent; for
example, β-mercapto-ethanol or dithiothreitol. Gliadins and glutenin
subunits both have unexpectedly high levels of glutamine and proline.
Hence, it has been suggested that these storing proteins becalled
‘prolamins’, as they display strong similarities with most storage
proteins in associated cereals, such as rye or barley. Residues of
cysteine have an important role in the structure of gliadins and
glutenin subunits. ese residues have a role in either disulde bonds
inside similar or dierent polypeptides, i.e., intra-chain disulde
bonds, or inter-chain disulde bonds (85).
Gliadins have shown an extremely varied fusion of a monomeric
form of gluten proteins. ree anatomically dierent gliadins, alpha,
gamma, and omega, can beillustrated. e evaluation of amino acid
sequences has shown that α-and γ-gliadins are linked to
low-molecular-weight glutenin subunits. For that reason, they have
been categorized as ‘prolamins enriched with sulfur’. Residues of
cysteines are situated at alpha type six remains of cysteine, and gamma
type eight remains of cysteine gliadins have been found at extremely
preserved sites and have a role in preserved intra-chain bonds of
disulde. Conversely, cysteine residues are absent in ω-type gliadins
and possess a very small amount of methionine. So, these gliadins
have been termed ‘sulfur-poor prolamins’ (73).
Polymers of glutenin are composed only of polypeptides related
through the disulde bonds present between the molecules, which
account for approximately 45% of the total protein inside the kernel
endosperm. Wheat protein consists of two types of subunits, the
LMW 10,000–70,000 Da and the HMW subunits of glutenin 80,000
to 130,000 Da. Studies on glutenin genetics of wheat have shown the
presence of high-molecular-weight glutenin subunit genes on the 1A,
1B, and 1D (extended chromosome arm) at the Glu-B1, Glu-D1, and
Glu-A1 positions, respectively. Tightly linked genes (two) are found
in each Glu-1 locus encoding x or y subunit types. In Triticum
aestivum, the Glu-A1 locus encodes null (N) subunit and 1Ax, while
the Glu-B1 locus commonly codes for 1Bx and 1By. Occasionally,
Glu-B1 codes for 1Bx or 1By subunits, whereas the Glu-D1 locus
codes for 1Dx and 1Dy subunits (85). As a result, for hexaploid wheat,
three to ve HMW-GS are usually produced by each genotype (85).
Electrophoretic studies have shown a signicant alteration in
mobility and the number of HMW-G subunits in pasta and bread
wheat. LMW-GS constitutes around one-third of all the protein in the
seeds and 60% of all the gluten protein (86). e LMW-S looks like
gamma gliadins in sequence and consists of roughly 20–30% of the
total protein, whereas the high-molecular-weight subunits constitute
around 5–10% of the total protein (85).
Low molecular weight proteins that are abundant in cysteine
might aect the viscoelastic characteristics of dough through
disulde or sulydryl exchange reactions with the proteins of
gluten. Proteins capable of binding lipids can inuence gluten-
lipid protein interactions, and consequently, the functionality of
protein in gluten (87). According to the evidence, stowage
globulins that are polymeric in nature are related to few bread-
making functions. In contrast to non-gluten proteins, gluten
proteins are sparingly soluble in water or dilute salt solutions (85).
A low quantity of ionizable side chain amino acids and an elevated
level of non-polar amino acids and glutamine are the factors that
contribute to its low solubility. e latter has better hydrogen
bonding capabilities (73).
1.9.2. Gluten proteins and wheat flour’s
bread-making function
Proteins of gluten principally dene the bread-making
capability of wheat our. A gluten protein allows the formation of
cohesive viscoelastic dough when the our is mixed with water and
is able to retain gas produced in the process of fermentation or
baking, forming bread’s exposed form conguration aer baking.
e viscoelastic attributes of dough that are crucial for bread
manufacture are mainly regulated by the gluten proteins of wheat,
but the collaboration between the gluten protein medium and the
additional constituents of our, such as lipids in our (88),
arabinoxylans (89), and non-gluten proteins, also have an inuence
on its viscoelastic properties. ese properties of wheat gluten are
altered further by the addition of oxidants, proteases, and reducing
agents, which immediately modies the gluten proteins, or by the
addition of emulsiers, lipids, and hemicelluloses, which alters
gluten protein interactions.
e bread manufacturing ability of wheat our is directly
associated with the protein content in our (90) and, therefore, with
the gluten protein content, as this type of protein rises more than
non-gluten protein due to its increased grain protein content.
erefore, an increased ‘amount’ of proteins in gluten is crucial.
Nevertheless, the direct correlation between breadmaking
performance and protein content relies on the genotype of the wheat,
indicating that the quality of ‘gluten’ protein is also of signicance in
the overall quality of the wheat (82, 85).
A sucient viscoelasticity equilibrium or the potential thereof is
mandatory for excellent breadmaking. Inadequately exible gluten
will lead to decreased loaf size. Improved elasticity indicates increased
loaf volume; however, excessively elastic gluten inhibits gas cell
expansion (91), also causing decreased loaf size. Glutenin polymers
are responsible for the strength and elasticity of dough (85). e
glutenin elasticity is thought to beinuenced by exible stretching of
actively and more favorably folded conformation of glutenin. Belton
(92) suggested that gluten elasticity is due to non- covalent interaction
mediate gluten elasticity primarily hydrogen bonds, inside and
between single glutenin chains. Conversely, gliadins are plasticizers
that deteriorate glutenin chain interaction (93), thus increasing the
viscosity of dough. erefore, the proportion of monomeric gliadin-
polymeric glutenin denes the equilibrium in the viscoelasticity of
dough and consequently inuences the gluten protein value. Today, it
is usually thought that quality dierences are strongly inuenced by
alterations in the quality of glutenin (85).

Khalid et al. 10.3389/fnut.2023.1053196
Frontiers in Nutrition 11 frontiersin.org
1.10. Current challenges in wheat breeding
programs and improvement approaches
An increase in the world’s population of almost 10 billion is
expected by 2050, which will result in an increase in wheat demand at
a rate of approximately 1.7 annually (94). erefore, creating a
sucient supply response will persist as a policy challenge throughout
the 21st century. Wheat breeders’ responsibility and their role in
developing better varieties of wheat are becoming more signicant in
the improvement of crop production (95). Wheat productivity is
vulnerable to newly developed diseases and pests, inadequate water
resources, limited arable land, and quickly altering climatic situations
(94, 96).
Numerous diseases, like rusts (stripe, leaf and stem rust, powdery
mildew, spot blotch, Karnal bunt, and Fusarium head blight) severely
hamper wheat productivity (97). Several researchers have described
rusts as a major biotic stress in wheat, causing a wheat loss of 10–100%,
depending upon virulence factor, resistant/susceptible cultivar
genotype, initial time of infection, environment, pathogenesis ratio,
and disease duration (98).
Puccinia graminis f. sp. tritici (stem rust) can result in a yield loss
of up to 100%, and the sudden rise and spread of stem rust in Africa,
known as Ug99, to Iran, the Middle East, and other countries is a
severe concern for wheat production worldwide. Tilletia indica
(Karnal bunt) disease is not only responsible for yield loss but also
aects the quality of grain due to the infection of kernels. is disease
was detected in various other countries, such as Mexico, Pakistan,
India, Iran, Nepal, Afghanistan, Iraq, South Africa, and the
UnitedStates (94).
e Fusarium culmorum and Fusarium graminearum species of
Fusarium Head Blight/head scab cause grain to become infected with
mycotoxins, such as nivalenol (NIV), deoxynivalenol (DON), and
zearalenone (ZON). Yield losses occur due to shriveled grain, low test
weight, and failure of seed formation (99). Spot blotch (SB), a vicious
wheat leaf disease initiated by Cochliobolus sativus can cause a 70%
yield loss. Composite quantitative inheritance of SB resistance has
reduced breeding progress (100). Another harmful disease is the
biotrophic fungus Blumeria graminis, a powdery mildew (PM), which
is a universally occurring wheat foliar disease responsible for terrible
yield loss (101).
In contrast to biotic stress resistance, the resistance gene plays a
small role in defending wheat against insects due to the substantial
eect of temperature and light on the existence and performance of
the insects (94). Continuous damage to crop production caused by
pests and diseases is one of the key limitations in wheat breeding and,
therefore, food suciency globally. Aphids, termites, wheat midges,
wheat weevil armyworms, Hessian ies, and cereal cyst nematodes
(CCN) are the main arthropods feeding on wheat among various pests
(102), making it essential to recognize novel genes and know their
interactions and functions in resistance to CCN (103).
Abiotic stresses like drought, salt, and terminal heat stress are
important as they limit wheat production and pose a substantial
challenge to wheat breeding programs internationally (104). Climate
change is another factor that has resulted in a wheat loss of 33%
globally because of temperature increases and water shortages in
wheat-growing areas (105, 106). e induction of chromosome
restitution in meiosis at the time of male gamete development is a
major problem caused by climate variation. Heat stress at the terminal
stage of the wheat crop halts plant growth and the accumulation of
starch, causing yield ckleness (94). On the other hand, global
warming brutally disturbs weather patterns, ensuing temperature
extremes, frequent frost, drought, and snowfall (94). Complex
interactions of cellular and molecular mechanisms with whole-plant
adaptation have limited breeding approaches to heat resistance (104).
e complex wheat genome and barriers in hybridization pose
major challenges in identifying and understanding various gene
functions, thus making the manipulation and characterization of traits
of concern very dicult in the development of better varieties (107).
erefore, in order to understand several networks of genes and their
jobs in the wheat genome, the continued characterization of traits of
landraces and wild relatives is still needed for rapid progress in the
improved development of cultivars (98).
Plant breeders need to nd new resistance genes by manipulating
wheat germplasm, which is essential in combatting such insect/pest
diseases. Genome-wide association studies (GWAS) or QTL mapping
can beemployed to nd genes with drought resistance in unexplored
germplasm. e use of genes/transcription factors from wheat
germplasm like DREB, NHX2, AVP1, and SHN1 and their associated
markers is a viable method for producing salt-tolerant wheat
genotypes (104). QTLs in combination with R-specic resistant genes
provide eective and durable resistance in dierent environments
(108). Both approaches are suggested to deal with climate change.
Precise pre-breeding and selection approaches need to becarefully
designed and followed for the identication and exploitation of the
most eective and resilient loci, pyramiding, and partially tolerant
gene accumulation. Identication, cloning and modication, and
transfer of various R genes to diverse crop species through
conventional breeding methods, molecular Marker Assisted Selection
(MAS), and biotechnological tools, such as OMICS (genomics,
transcriptomics, proteomics, metabolomics, etc.), can be used to
combat pests and diseases and achieve long-lasting resistance (108).
Tools in tissue culture techniques, like micropropagation, gametic
embryogenesis (103, 109), somatic embryogenesis, cell suspension,
and protoplast fusion facilitate the fast, large scale-cloning of high-
value plants to produce pure lines (109). Apart from plant breeding
technologies, some abiotic factors can be reversed through
environmental management practices and developing microbe linkage
to plants to biologically control pathogens (110, 111). Diethyl
aminoethyl hexanoate application is found to increase plant tolerance
to abiotic stress, such as cold (112) and salt stress, (113) whereas
applying proline amino acid during plant adaptation increases
tolerance to salinity stress (114).
e incorporation of in vitro approaches, like protoplast fusion
(109), gametic embryogenesis (103), somatic embryogenesis,
mutagenesis, and plant cell/tissue culture, and the current
biotechnology practices, like synthetic biology, transgenic plants, gene
editing (115), OMICS technologies, and interference RNAs (116, 117),
can enhance tolerance to biotic and abiotic factors and control the
depth of plant roots (103). Another way to increase resistance is by
using microbial biotechnology to enhance plant nutrition and/or
promote biocontrol against pathogens (110), applying diethyl
aminoethyl hexanoate to achieve resistance to abiotic stress (116, 118),
and using proline to increase salt tolerance (119) and improve poor
water conditions (114).
Gene stacking can be used to combat disease-resistant genes and
inherit them as a sole trait (120). e incorporation of even more

Khalid et al. 10.3389/fnut.2023.1053196
Frontiers in Nutrition 12 frontiersin.org
disciplines is needed for breeding to reach the ultimate ‘deterministic’
phase and catch up with the situation in genomics, in silico breeding
and phenomics, etc. erefore, public sectors must incorporate novel
technologies into Mendelian genetics and the principles of
quantitative genetics in order to make dynamic alterations in crop
production (94).
Author contributions
AK: write-up and revision of manuscript. AH: planning,
nalization of basic idea, and revision. MT: revision of manuscript.
All authors contributed to the article and approved the
submitted version.
Conflict of interest
e authors declare that the research was conducted in the
absence of any commercial or nancial relationships that could
beconstrued as a potential conict of interest.
Publisher’s note
All claims expressed in this article are solely those of the authors
and do not necessarily represent those of their aliated organizations,
or those of the publisher, the editors and the reviewers. Any product
that may be evaluated in this article, or claim that may be made by its
manufacturer, is not guaranteed or endorsed by the publisher.
References
1. Kumar, S, Kumari, P, Kumar, U, Grover, M, Singh, AK, Singh, R, et al. Molecular
approaches for designing heat tolerant Wheat. J Plant Biochem Biotechnol. (2013)
22:359–71. doi: 10.1007/s13562-013-0229-3
2. Nawaz, R, Inamullah, HA, Ud Din, S, Iqbal, MS, Gürsoy, S, Kutbay, HG, et al.
Agromorphological studies of local Wheat varieties for variability and their association
with yield related traits. Pak J Bot. (2013) 45:1701–6.
3. Kizilgeci, F, Yildirim, M, Islam, MS, Ratnasekera, D, Iqbal, MA, and Sabagh, AE.
Normalized dierence vegetation index and chlorophyll content for precision nitrogen
Management in Durum wheat cultivars under semi-arid conditions. Sustainability.
(2021) 13:3725. doi: 10.3390/su13073725
4. Anam Khalid, AH, Shamim, S, and Ahmad, J. Divergence in single kernel
characteristics and grain nutritional proles of wheat genetic resource and association
among traits. Front Nutr . (2022) 8:805446. doi: 10.3389/fnut.2021.805446
5. Khan, MNN, Ahmad, Z, and Ghafoor, A. Genetic diversity and disease response of
rust in bread Wheat collected from Waziristan agency, Pakistan. Int J Biodivers Conserv.
(2011) 3:10–8. doi: 10.5897/IJBC.9000067
6 . Riaz, MW, Yang, L, Yousaf, MI, Sami, A, Mei, XD, Shah, L, et al. Eects of heat stress
on growth, physiology of plants, yield and grain quality of dierent spring wheat
(Triticum Aestivum L.) genotypes. Sustainability. (2021) 13:2972. doi: 10.3390/
su13052972
7. Breiman, A, and Graur, D. Wheat evolution. Israel J Plant Sci. (1995) 43:85–98. doi:
10.1080/07929978.1995.10676595
8. Ali, A, Khaliq, T, Ahmad, A, Ahmad, S, Malik, A, and Rasul, F. How Wheat
responses to nitrogen in the eld. Crop Environ. (2012) 3:71–6.
9. Erenstein, O, Jaleta, M, Mottaleb, KA, Sonder, K, Donovan, J, and Braun, H-J.
Global trends in Wheat production, consumption and trade In: Reynolds MP, Braun HJ,
editors. Wheat Improvement. Midtown Manhattan, NY: Springer (2022). 47–66.
10. Sharma, S, Shrivastav, VK, Shrivastav, A, and Shrivastav, B. erapeutic potential
of Wheat grass (Triticum Aestivum L.) for the Treatmentof chronic diseases. South
Asian. J Exp Biol. (2013) 3:308–13. doi: 10.38150/sajeb.3(6).p308-313
11. Garg, M, Sharma, A, Vats, S, Tiwari, V, Kumari, A, Mishra, V, et al. Vitamins in
cereals: a critical review of content, health eects, processing losses, bioaccessibility,
fortication, and biofortication strategies for their improvement. Front Nutr. (2021)
8:586815. doi: 10.3389/fnut.2021.586815
12. Ikhtiar, K, and Alam, Z. Nutritional composition of Pakistani wheat varieties. J
Zhejiang Univ Sci B. (2007) 8:555–9. doi: 10.1631/jzus.2007.B0555
13 . Urade, R, Sato, N, and Sugiyama, M. Gliadins from wheat grain: an overview, from
primary structure to nanostructures of aggregates. Biophys Rev. (2018) 10:435–43. doi:
10.1007/s12551-017-0367-2
14. Siddiqi, RA, Singh, TP, Rani, M, Sogi, DS, and Bhat, MA. Diversity in grain, our,
amino acid composition, protein proling, and proportion of Total our proteins of
dierent Wheat cultivars of North India. Front Nu tr. (2020) 7:141. doi: 10.3389/
fnut.2020.00141
15. Hassan, G, and Gul, R. Diallel analysis of the inheritance pattern of agronomic
traits of bread Wheat. Pak J Bot. (2006) 38:1169–75.
16. Bibi, K, Inamullah, HA, Din, S, Muhammad, F, and Iqbal, MS. Characterization of
Wheat genotypes using randomly amplied polymorphic DNA markers. Pak J Bot.
(2012) 44:1509–12.
17. Khalid, A, Hameed, A, and Tahir, MF. Estimation of genetic divergence in Wheat
genotypes based on agro-morphological traits through agglomerative hierarchical
clustering and principal component analysis. Cereal Res Commun. (2022) 50:1–8. doi:
10.1007/s42976-022-00287-w
18. Dubcovsky, J, and Dvorak, J. Genome plasticity a key factor in the success of
Polyploid Wheat under domestication. Science. (2007) 316:1862–6. doi: 10.1126/
science.1143986
19. Hawkesford, MJ, Araus, JL, Park, R, Calderini, D, Miralles, D, Shen, T, et al.
Prospects of doubling global Wheat yields. Food and Energy Security. (2013) 2:34–48.
doi: 10.1002/fes3.15
20. Shewry, P. Wheat. J Exp Botany. (2009) 60:1537–53. doi: 10.1093/jxb/erp058
21. de Sousa, T, Ribeiro, M, Sabença, C, and Igrejas, G. e 10, 000-year success story
of Wheat! Foods. (2021) 10:2124. doi: 10.3390/foods10092124
22. Pour-Aboughadareh, A, Kianersi, F, Poczai, P, and Moradkhani, H. Potential of
wild relatives of Wheat: ideal genetic resources for future breeding programs. Agronomy.
(2021) 11:1656. doi: 10.3390/agronomy11081656
23. Nalam, VJ, Vales, MI, Watson, CJ, Kianian, SF, and Riera-Lizarazu, O. Map-based
analysis of genes aecting the brittle rachis character in tetraploid wheat (Triticum
Turgidum L.). eor Appl Genet. (2006) 112:373–81. doi: 10.1007/s00122-005-0140-y
24. Simons, KJ, Fellers, JP, Trick, HN, Zhang, Z, Tai, Y-S, Gill, BS, et al. Molecular
characterization of the major wheat domestication gene Q. Genetics. (2006) 172:547–55.
doi: 10.1534/genetics.105.044727
25. Abdulkadir, AR. Dpph antioxidant activity, Total phenolic and Total avonoid
content of dierent part of Drumstic tree (Moringa Oleifera lam.). J Chem Pharm Res.
(2015) 7:1423–8.
26. Gohar, S, Sajjad, M, Zulqar, S, Liu, J, and Wu, J. Domestication of newly evolved
Hexaploid Wheat—a journey of wild grass to cultivated Wheat. Front Genet. (2022)
13:2931. doi: 10.3389/fgene.2022.1022931
27. Flavell, R, Bennett, M, Smith, J, and Smith, D. Genome size and the proportion of
repeated nucleotide sequence DNA in plants. Biochem Genet. (1974) 12:257–69. doi:
10.1007/BF00485947
28. Pourkheirandish, M, Dai, F, Sakuma, S, Kanamori, H, Distelfeld, A, Willcox, G,
et al. On the origin of the non-brittle rachis trait of domesticated einkorn Wheat. Front
Plant Sci. (2018) 8:2031. doi: 10.3389/fpls.2017.02031
29. Gupta, P, Mir, R, Mohan, A, and Kumar, J. Wheat genomics: present status and
future prospects. Int J Plant Genom. (2008) 2008:1–36. doi: 10.1155/2008/896451
30. Xynias, IN, Mylonas, I, Korpetis, EG, Ninou, E, Tsaballa, A, Avdikos, ID, et al.
Durum Wheat breeding in the Mediterranean region: current status and future
prospects. Agronomy. (2020) 10:432. doi: 10.3390/agronomy10030432
31. Kumar, A, Singh, A, Singh, V, Verma, R, and Singh, K. Inuence of moisture
regimes and fertility level on root and qualitative studies of Wheat (Triticum Aestivum
L.) under late sown condition. Biol Forum. (2022) 14:1559–62.
32. Haudry, A, Cenci, A, Ravel, C, Bataillon, T, Brunel, D, Poncet, C, et al. Grinding
up Wheat: a massive loss of nucleotide diversity since domestication. Mol Biol Evol.
(2007) 24:1506–17. doi: 10.1093/molbev/msm077
33. Wrigley, C. Wheat: a unique grain for the world In: K Khan and PR Shewry,
editors. Wheat: Chemistry and Technology. St. Paul, MN: American Association of Cereal
Chemists (2009). 1–17.
34. Gooding, M, Khan, K, and Shewry, P. e Wheat crop. Wheat: Chemistry and
Tec hn ol o gy . (2009). 4th Edn: Amsterdam: Elsevier, 19–49.
3 5. Edwards, MA. (2010). Morphological features of Wheat grain and genotype aecting
our yield. PhD thesis. Lismore, NSW: Southern Cross University.
36. Atwell, W, and Finnie, S. Wheat Flour. 2nd ed. Amsterdam: Elsevier (2016).
37. Katyal, M, Singh, N, Virdi, AS, Kaur, A, Chopra, N, Ahlawat, AK, et al.
Extraordinarily so, medium-hard and hard Indian wheat varieties: composition,

Khalid et al. 10.3389/fnut.2023.1053196
Frontiers in Nutrition 13 frontiersin.org
protein prole, dough and baking properties. Food Res Int. (2017) 100:306–17. doi:
10.1016/j.foodres.2017.08.050
38 . Gadaleta, A, Giancaspro, A, Blechl, AE, and Blanco, A. A transgenic durum Wheat
line that is free of marker genes and expresses 1dy10. J Cereal Sci. (2008) 48:439–45. doi:
10.1016/j.jcs.2007.11.005
39. Gadaleta, A, Blechl, A, Nguyen, S, Cardone, M, Ventura, M, Quick, J, et al. Stably
expressed D-genome-derived Hmw Glutenin subunit genes transformed into dierent
durum Wheat genotypes change dough mixing properties. Mol Breed. (2008) 22:267–79.
doi: 10.1007/s11032-008-9172-8
40. Payne, PI. Genetics of Wheat storage proteins and the eect of allelic variation on
bread-making quality. Annu Rev Plant Physiol. (1987) 38:141–53. doi: 10.1146/annurev.
pp.38.060187.001041
41. Loukoianov, A, Yan, L, Blechl, A, Sanchez, A, and Dubcovsky, J. Regulation of
Vrn-1 Vernalization genes in Normal and transgenic Polyploid Wheat. Plant Physiol.
(2005) 138:2364–73. doi: 10.1104/pp.105.064287
42. Reddy, L, Allan, R, and Campbell, K. Evaluation of cold hardiness in two sets of
near isogenic lines of Wheat (Triticum Aestivum ) with polymorphic vernalization alleles.
Plant Breed. (2006) 125:448–56. doi: 10.1111/j.1439-0523.2006.01255.x
43. Carson, G, Edwards, N, Khan, K, and Shewry, P. Criteria of Wheat and our
quality. Wheat: Chemistry and Technology (2009) 4th Edn: Amsterdam: Elsevier, 97–118.
44. Evans, LT, Wardlaw, IF, Fischer, RA. Wheat. In: Evans LT, editor. Crop Physiology.
London, New York and Melbourne: Cambridge University Press (1975). p. 101–149.
45. Feng, T, Xi, Y, Zhu, Y-H, Chai, N, Zhang, X-T, Jin, Y, et al. Reduced vegetative
growth increases grain yield in spring Wheat genotypes in the dryland farming region
of north-West China. Agronomy. (2021) 11:663. doi: 10.3390/agronomy11040663
46. Kirby, EM, and Appleyard, M. Cereal Development Guide. 2nd ed. Stoneleigh,
Warwickshire: Arable Unit, National Agricultural Centre (1984).
47. Hadjichristodoulou, A, Della, A, and Photiades, J. Eect of sowing depth on plant
establishment, Tillering capacity and other agronomic characters of cereals. J Agric Sci.
(1977) 89:161–7. doi: 10.1017/S0021859600027337
48 . Kronenberg, L, Yu, K, Walter, A, and Hund, A. Monitoring the dynamics of Wheat
stem elongation: genotypes dier at critical stages. Euphytica. (2017) 213:1–13. doi:
10.1007/s10681-017-1940-2
49. Patrick, J. Vascular system of the stem of the Wheat plant II development.
Australian J Botany. (1972) 20:65–78.
50. Johnson, JW, Austin, KL, Jones, GS, Davis, GH, and King, TM. Ecacy of
17α-Hydroxyprogesterone Caproate in the prevention of premature labor. N Engl J Med.
(1975) 293:675–80. doi: 10.1056/NEJM197510022931401
51. Shang, Q, Wang, Y, Tang, H, Sui, N, Zhang, X, and Wang, F. Genetic, hormonal,
and environmental control of Tillering in Wheat. Crop J. (2021) 9:986–91. doi: 10.1016/j.
cj.2021.03.002
52. Russell, K, and Van Sanford, DA. Breeding Wheat for resilience to increasing
nighttime temperatures. Agronomy. (2020) 10:531. doi: 10.3390/agronomy10040531
53. Poehlman, JM. Breeding Field Crops. New York: Henry Holt and Company Inc
(1959). 427 p.
54. Mandy, G. Panzenzuechtung, Kurz Und Bundig. Budapest: Deutscher
Landwirtschasverlag (1970).
55. Kirby, E, and Appleyard, M. Development of the Cereal Plant. e Yield of Cereals
Royal Agriculture Society of England, London (1983): 1–3.
56. Kirby, E. Ear development in spring Wheat. J Agric Sci. (1974) 82:437–47. doi:
10.1017/S0021859600051339
57. De Vries, AP. Flowering biology of Wheat, particularly in view of hybrid seed
production—a review. Euphytica. (1971) 20:152–70. doi: 10.1007/BF00056076
58. Brocklehurst, P, Moss, J, and Williams, W. Eects of irradiance and water supply
on grain development in Wheat. Ann Appl Biol. (1978) 90:265–76. doi:
10.1111/j.1744-7348.1978.tb02635.x
59. Impa, SM, Vennapusa, AR, Bheemanahalli, R, Sabela, D, Boyle, D, Walia, H, et al.
High night temperature induced changes in grain starch metabolism alters starch,
protein, and lipid accumulation in winter Wheat. Plant Cell Environ. (2020) 43:431–47.
doi: 10.1111/pce.13671
60. Simmons, SR. Growth, development, and physiology In: EG Heyne, editor. Wheat
and Wheat Improvement. Madison, WI: American Society of Agronomy, Inc (1987).
77–113.
61. Huang, J, Wang, Z, Fan, L, and Ma, S. A Review of Wheat Starch Analyses:
Methods, Techniques, Structure and Function. Int J Biol Macromol. (2022) 203:149. doi:
10.1016/j.ijbiomac.2022.01.149
62. Ferrante, A, Savin, R, and Slafer, GA. Floret development and grain setting
dierences between modern durum wheats under contrasting nitrogen availability. J Exp
Bot. (2013) 64:169–84. doi: 10.1093/jxb/ers320
63. Austin, R, and Jones, H. e Physiology of Wheat, Part III. Cambridge, UK: Plant
Breeding Institute (1975).
64. Poutanen, KS, Kårlund, AO, Gómez-Gallego, C, Johansson, DP, Scheers, NM,
Marklinder, IM, et al. Grains–a major source of sustainable protein for health. Nutr R ev.
(2022) 80:1648–63. doi: 10.1093/nutrit/nuab084
65. Sramkova, Z, Gregova, E, and Sturdík, E. Chemical composition and nutritional
quality of Wheat grain. Acta Chimica Slovaca. (2009) 2:115–38.
66. Belderok, B, Mesdag, J, and Donner, DA. Bread-Making Quality of Wheat: A
Century of Breeding in Europe. Berlin: Springer Science & Business Media (2000).
67. Onipe, OO, Jideani, AI, and Beswa, D. Composition and functionality of Wheat
bran and its application in some cereal food products. Int J Food Sci Technol. (2015)
50:2509–18. doi: 10.1111/ijfs.12935
68. Rathjen, JR, Strounina, EV, and Mares, DJ. Water movement into dormant and
non-dormant Wheat (Triticum Aestivum L.) grains. J Exp Bot. (2009) 60:1619–31. doi:
10.1093/jxb/erp037
69. Beres, BL, Rahmani, E, Clarke, JM, Grassini, P, Pozniak, CJ, Geddes, CM, et al. A
systematic review of durum Wheat: enhancing production systems by exploring
genotype, environment, and management (G× E× M) synergies. Front Plant Sci. (1665)
2020:568657. doi: 10.3389/fpls.2020.568657
70. Bao, J, and Malunga, LN. Compositional diversity in cereals in relation to their
nutritional quality and health benets. Front Nutr. (2021):8. doi: 10.3389/
fnut.2021.819923
71. Osborne, TB, and Mendel, LB. e nutritive value of the Wheat kernel and its
milling products. J Biol Chem. (1919) 37:557–601. doi: 10.1016/
S0021-9258(18)87394-X
72. Iqbal, MJ, Shams, N, and Fatima, K. Nutritional quality of wheat In: Ansari MR,
editor. Wheat. London: Intech Open (2022)
73. Wieser, H, Koehler, P, and Scherf, KA. e two faces of Wheat. Front Nut r. (2020)
7:517313. doi: 10.3389/fnut.2020.517313
74. Kulkarni, S, Acharya, R, Nair, A, Rajurkar, N, and Reddy, A. Determination of
elemental concentration proles in tender wheatgrass (Triticum Aestivum L.) using
instrumental neutron activation analysis. Food Chem. (2006) 95:699–707. doi: 10.1016/j.
foodchem.2005.04.006
75. Padalia, S, Drabu, S, Raheja, I, Gupta, A, and Dhamija, M. Multitude potential of
wheatgrass juice (green blood): an overview. Chronicles Young Scientists. (2010) 1:23.
76. Singh, N, Verma, P, and Pandey, B. erapeutic potential of organic Triticum
Aestivum Linn. (Wheat grass) in prevention and treatment of chronic diseases: an
overview. Int J Pharm Sci Drug Res. (2012) 4:10–4.
77. Khan, M. Nutritional Attributes of Wheat. Birmingham, AL: Progressive Farming
(1984).
78. Irshad, M, Idrees, M, Saeed, A, Muhammad, BR, Ahmad, S, Naeem, R, et al.
Physiochemical trace elements and protein proling of dierent Wheat varieties of
Pakistani origin. Golden Res oughts. (2013) 3:1–8.
79. Zilic, S, Barac, M, Pesic, M, Dodig, D, and Ignjatovic-Micic, D. Characterization
of proteins from grain of dierent bread and durum Wheat genotypes. Int J Mol Sci.
(2011) 12:5878–94. doi: 10.3390/ijms12095878
80. Khalid, A, and Hameed, A. Characterization of Pakistani Wheat germplasm for
high and low molecular weight Glutenin subunits using Sds-Page. Cereal Res Commun.
(2019) 1:1–11. doi: 10.1556/0806.47.2019.013
81. Chinuki, Y, and Morita, E. Wheat-dependent exercise-induced anaphylaxis
sensitized with hydrolyzed Wheat protein in soap. Allergol Int. (2012) 61:529–37. doi:
10.2332/allergolint.12-RAI-0494
8 2. Shewry, P. What is gluten—why is it special? Front Nutr . (2019) 6:101. doi: 10.3389/
fnut.2019.00101
83. Sharma, A, Garg, S, Sheikh, I, Vyas, P, and Dhaliwal, H. Eect of Wheat grain
protein composition on end-use quality. J Food Sci Technol. (2020) 57:2771–85. doi:
10.1007/s13197-019-04222-6
84. Rosa-Sibakov, N, Poutanen, K, and Micard, V. How does Wheat grain, bran and
Aleurone structure impact their nutritional and technological properties? Trends Food
Sci Technol. (2015) 41:118–34. doi: 10.1016/j.tifs.2014.10.003
85. Veraverbeke, WS, and Delcour, JA. Wheat protein composition and properties of
Wheat Glutenin in relation to Breadmaking functionality. Crit Rev Food Sci Nutr. (2002)
42:179–208. doi: 10.1080/10408690290825510
8 6. Sharma, D, Saharan, V, Joshi, A, and Jain, D. Biochemical characterization of bread
Wheat (Triticum Aestivum L.) genotypes based on Sds-Page. Triticeae Genom Gene.
(2015):6.
87. Mac Ritchie, F, Du Cros, D, and Wrigley, C. (1990). Flour polypeptides related to
Wheat quality. Adv Cereal Sci Technol, Y. Pomeranz, St Paul, MN: American Association
of Cereal Chemists, Inc.) 79–145.
88. Scherf, KA. Immunoreactive cereal proteins in Wheat allergy, non-celiac gluten/
Wheat sensitivity (Ncgs) and celiac disease. Curr Opin Food Sci. (2019) 25:35–41. doi:
10.1016/j.cofs.2019.02.003
89. Roels, S. Factors Governing Wheat and Wheat Gluten Functionality in Breadmaking
and Gluten/Starch Separation. Belgium: Dissertationes de Agricultura (1998).
90. Hoseney, RC. Principles of Cereal Science and Technology. St. Paul, MN: American
Association of Cereal Chemists (AACC) (1994).
91. Andersson, AA, Andersson, R, Piironen, V, Lampi, A-M, Nyström, L, Boros, D,
et al. Contents of dietary bre components and their relation to associated bioactive
components in whole grain Wheat samples from the Healthgrain diversity screen. Food
Chem. (2013) 136:1243–8. doi: 10.1016/j.foodchem.2012.09.074

Khalid et al. 10.3389/fnut.2023.1053196
Frontiers in Nutrition 14 frontiersin.org
92. Belton, P. Mini review: on the elasticity of Wheat gluten. J Cereal Sci. (1999)
29:103–7. doi: 10.1006/jcrs.1998.0227
93. Khatkar, B, Bell, A, and Schoeld, J. e dynamic rheological properties of glutens
and gluten sub-fractions from wheats of good and poor bread making quality. J Cereal
Sci. (1995) 22:29–44. doi: 10.1016/S0733-5210(05)80005-0
94. Kumar, S, Jacob, SR, Mir, RR, Vikas, V, Kulwal, P, Chandra, T, et al. Indian Wheat
genomics initiative for harnessing the potential of Wheat germplasm resources for
breeding disease-resistant, nutrient-dense, and climate-resilient cultivars. Front Genet.
(2022) 13:834366. doi: 10.3389/fgene.2022.834366
95. Vitale, J, Adam, B, and Vitale, P. Economics of wheat breeding strategies: focusing on
Oklahoma hard red winter Wheat. Agronomy. (2020) 10:238. doi: 10.3390/agronomy10020238
96 . Beres, BL, Hateld, JL, Kirkegaard, JA, Eigenbrode, SD, Pan, WL, Lollato, RP, et al.
Toward a better understanding of genotype× environment× management interactions—a
global Wheat initiative agronomic research strategy. Front Plant Sci. (2020) 11:828. doi:
10.3389/fpls.2020.00828
97. Roy, C, Juliana, P, Kabir, MR, Roy, KK, Gahtyari, NC, Marza, F, et al. New
genotypes and genomic regions for resistance to wheat blast in south Asian germplasm.
Plan eory. (2021) 10:2693. doi: 10.3390/plants10122693
98. Bhardwaj, SC, Singh, GP, Gangwar, OP, Prasad, P, and Kumar, S. Status of Wheat
rust research and Progress in rust management-Indian context. Agronomy. (2019) 9:892.
doi: 10.3390/agronomy9120892
99. Brar, GS, Brûlé-Babel, AL, Ruan, Y, Henriquez, MA, Pozniak, CJ, Kutcher, HR,
et al. Genetic factors aecting fusarium head blight resistance improvement from
introgression of exotic Sumai 3 alleles (including Fhb1, Fhb2, and Fhb5) in hard red
spring Wheat. BMC Plant Biol. (2019) 19:1–19. doi: 10.1186/s12870-019-1782-2
100. Ayana, GT, Ali, S, Sidhu, JS, Gonzalez Hernandez, JL, Turnipseed, B, and
Sehgal, SK. Genome-wide association study for spot blotch resistance in hard winter
Wheat. Front Plant Sci. (2018) 9:926. doi: 10.3389/fpls.2018.00926
101. Mwale, VM, Tang, X, and Chilembwe, E. Molecular detection of disease
resistance genes to powdery mildew (Blumeria Graminis F. Sp. Tritici) in Wheat
(Triticum Aestivum) cultivars. Afr J Biotechnol. (2017) 16:22–31. doi: 10.5897/
AJB2016.15720
102. Smiley, RW, Dababat, AA, Iqbal, S, Jones, MG, Maa, ZT, Peng, D, et al. Cereal
cyst nematodes: a complex and destructive Group of Heterodera Species. Plant Dis.
(2017) 101:1692–720. doi: 10.1094/PDIS-03-17-0355-FE
103. Marli, GKM. Current challenges in plant breeding to achieve zero hunger and
overcome biotic and abiotic stresses induced by the global climate changes: a review. J
Plant Sci Phytopathol. (2021) 5:053–7. doi: 10.29328/journal.jpsp.1001060
104. Choudhary, A, Kaur, N, Sharma, A, and Kumar, A. Evaluation and screening of
elite Wheat germplasm for salinity stress at the seedling phase. Physiol Plant. (2021)
173:2207–15. doi: 10.1111/ppl.13571
105. Dormatey, R, Sun, C, Ali, K, Coulter, JA, Bi, Z, and Bai, J. Gene pyramiding for
sustainable crop improvement against biotic and abiotic stresses. Agronomy. (2020)
10:1255. doi: 10.3390/agronomy10091255
106. Malhi, GS, Kaur, M, and Kaushik, P. Impact of climate change on agriculture and its
mitigation strategies: a review. Sustainability. (2021) 13:1318. doi: 10.3390/su13031318
107. Bekeko, Z, and Mulualem, T. Genetics of plant–pathogen interactions and
resistance. J Gene Environ Resour Conservat. (2016) 4:123–34.
108. Kaur, B, Bhatia, D, and Mavi, G. Eighty years of gene-for-gene relationship and
its applications in identication and utilization of R genes. J Genet. (2021) 100:1–17.
109. Gniech Karasawa, MM, and Embryogenesis, Gametic, Somatic Embryogenesis,
plant cell cultures, and protoplast fusion: Progress and opportunities in biofuel
production. NascimentoDD do and WA Pickering Plant-Based Genetic Tools for Biofuels
Production, Netherlands: Bentham Science Publishers. (2017). 15.
110. Yadav, AN, Kour, D, Kaur, T, Devi, R, Guleria, G, Rana, KL, et al. Microbial
biotechnology for sustainable agriculture: current research and future challenges. New
and Future Developments in Microbial Biotechnology and Bioengineering, Amsterdam:
Elsevier. (2020): 331–344.
111. Okungbowa, FI, Shittu, HO, and Obiazikwor, HO. Endophytic bacteria: hidden
protective Associates of Plants against biotic and abiotic stresses. Notulae Scientia
Biologicae. (2019) 11:167–74. doi: 10.15835/nsb11210423
11 2. Lu, J, Guan, P, Gu, J, Yang, X, Wang, F, Qi, M, et al. Exogenous Da-6 improves the
low night temperature tolerance of tomato through regulating Cytokinin. Front Plant
Sci. (2021) 11:599111. doi: 10.3389/fpls.2020.599111
113 . Zhang, C, He, P, Li, Y, Li, Y, Yao, H, Duan, J, et al. Exogenous diethyl Aminoethyl
Hexanoate, a plant growth regulator, highly improved the salinity tolerance of important
medicinal plant Cassia Obtusifolia L. J Plant Growth Regul. (2016) 35:330–44. doi:
10.1007/s00344-015-9536-3
114. Ghaari, H, Tadayon, MR, Bahador, M, and Razmjoo, J. Investigation of the
proline role in controlling traits related to sugar and root yield of sugar beet under water
decit conditions. Agric Water Manag. (2021) 243:106448. doi: 10.1016/j.
agwat.2020.106448
115. Steinwand, MA, and Ronald, PC. Crop biotechnology and the future of food.
Nature Food. (2020) 1:273–83. doi: 10.1038/s43016-020-0072-3
116. Liu, S, Geng, S, Li, A, Mao, Y, and Mao, L. Rnai Technology for Plant Protection
and its Application in Wheat. aBIOTECH. (2021) 2:365–74. doi: 10.1007/
s42994-021-00036-3
117. Dalakouras, A, Wassenegger, M, Dadami, E, Ganopoulos, I, Pappas, ML, and
Papadopoulou, K. Genetically modied organism-free RNA interference: exogenous
application of RNA molecules in plants. Plant Physiol. (2020) 182:38–50. doi: 10.1104/
pp.19.00570
118. Zhang, J, Li, S, Cai, Q, Wang, Z, Cao, J, Yu, T, et al. Exogenous diethyl
Aminoethyl Hexanoate ameliorates low temperature stress by improving nitrogen
metabolism in maize seedlings. PloS One. (2020) 15:e0232294. doi: 10.1371/journal.
pone.0232294
119. Naliwajski, M, and Skłodowska, M. e relationship between the antioxidant
system and proline metabolism in the leaves of cucumber plants acclimated to salt stress.
Cells. (2021) 10:609. doi: 10.3390/cells10030609
120. Chang, YN, Zhu, C, Jiang, J, Zhang, H, Zhu, JK, and Duan, CG. Epigenetic
regulation in plant abiotic stress responses. J Integr Plant Biol. (2020) 62:563–80. doi:
10.1111/jipb.12901