This presentation covers a brief description of Domestication, evolution, genetics, and genomics of wheat.

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2. INTRODUCTION TO TOPIC
• Domestication: The process of hereditary reorganization of
wild animals and plants into domestic and cultivated forms
according to the interests of people.
• Evolution is change in
the heritable traits of biological populations over
successive generations.
• Genetics is the study of genes, genetic variation, and heredity
in living organisms.
• Genomics is an area within genetics that concerns the
sequencing and analysis of an organism's genome.
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3. INTRODUCTION OF WHEAT
• Universal cereal of old world agriculture and world’s foremost crop
plant.
• Modern cultivar refers to two species:
Trititicum aestivum (2n=6x=42, AuAuBBDD) Bread Wheat
Trititicum turgidum (2n=4x=28, AuAuBB) Durum Wheat
• Bread wheat is 95% of total production and durum wheat is only 5 %.
• Wheat accounts for more than 20% of total humans food calories and
is grown on 17% of all type of crop areas.
• It is staple food of more than 40% world’s population.
• Wheat is a superb model organism for the evolutionary theory of
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4. DOMESTICATION OF WHEAT
• According to the history of wheat evolution, only wild
einkorn and wild emmer wheats were subjected to
domestication selection.
• There are two wild diploid Triticum species recognized: T.
boeoticum (AbAb) and T. urartu (AuAu) which have crossing
barriers between them.
• The diploid einkorn wheat T. monococcum was one of the
first crops domesticated.
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5. DOMESTICATION OF WHEAT CONT…..
• The other wild diploid Triticum species, T. urartu (AuAu) has played
an essential role in wheat evolution though it has never been
domesticated.
• Domesticated emmer appeared several hundred years later, i.e.,
9,500–9,000 BP and evolved as polymorphic populations rather
than as single genotypes .
• Domesticated emmer was once the main crop for bread-making in
ancient Egypt.
• Emmer cultivation has significantly declined and can be found only 5

6. SPEED OF WHEAT DOMESTICATION
• Conventionally, wheat domestication studies have focused on a few
qualitative traits (brittle rachis, tough glume and free-threshing)
controlled by single major genes.
• Hillman and Davies(1990) performed natural selection and concluded
that perhaps only 20–30 years would be enough to completely
domesticate these plants.
• Early farmers possibly did not focus only on indehiscence, but also on
other important quantitative traits—spike size, heading date/growth
duration, plant height, grain size, etc.—in the harvesting process of
wild wheat.
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7. EFFECT OF DOMESTICATION ON GENETIC
DIVERSITY
• Domestication of plants and animals usually results in a reduction of
genetic diversity involving the whole genome.
• The domesticate acquires improved fitness for human purpose often at
the expense of survival in nature, and a mutualistic relationship evolves
between humans and their crops .
• Several demographic and selective events occurred during the
domestication of wheat from T. dicoccoides.
• Haudry et al. (2007) analyzed nucleotide diversity at 21 loci in wild and
domesticated, cultivated durum and bread wheats.
• Low effective recombination resulting from self-pollination and a genetic
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8. EVOLUTION OF WHEAT
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9. GENETICS AND GENOMIC DISSECTION OF
QUALITATIVE DOMESTICATION TRAITS
Brittle
Rachis
• Transformation of brittle rachis to non brittle is first symbol
of domestication.
•Brittle rachis is controlled by Br2 & Br3 on short arms of
chromosome 3A &3B.
Glume
Tenacit
y
• Wild wheat floret is wrapped in tough glumes whereas cultivated has soft glumes
• At least 2 genes control glumes softness found on different positions on chromosome 2
Free
Threshing
•Thinner glumes and paleas allow an early release of naked
kernels.
• q induces non free-threshing & Q supports small square headed
ears with good threshability. 9

10. GENETICS AND GENOMIC ANALYSIS OF
QUANTITATIVE TRAITS
• The evolution from small-seeded wild plants with
natural seed dispersal to larger seeded non-shattering
plants.
• Seed size is complex polygenic trait under control of
7-8 chromosomes.
Seed size
• Short-day flowering wild grasses were transformed
into domesticates in which flowering time was
unaffected by day length.
• The heading date is controlled by photoperiod
response (Ppd) genes on the short arm of the group 2
chromosomes.
Flowering
Time
• Grain yield is most priority, minimizing labour inputs
and land needs.
• Yield is controlled by genes on 5 different
chromosomes and also have effects on other plant
characteristics.
Grain Yield &
other Traits
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11. DOMESTICATION SYNDROME FACTORS
INVOLVING QUANTITATIVE TRAITS AND GENE-
RICH REGIONS
• Domestication syndrome : Difference in domesticate and wild
relatives.
• Most domesticated traits(5-11) are clustered in chromosomes
1B,2A,3A &5A.
• Genes distribution is highly nonrandom in triticeae family
genes rich regions genes poor regions
• High pleiotropy and tight linkage suggest an important role
recombination both in consolidation of positive mutation and
reducing antagonism b/w selections.
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12. ROLE OF A & B GENOMES IN WHEAT
DOMESTICATION
• AFLPs show that molecular markers are non-randomly distributed
among A & B genome.
• B genome is more polymorphic than A genome
• Wild wheat domestication QTL mapping study shows that the numbers
of both QTL effects and domestication syndrome factors in the A
genome significantly exceeded those in the B genome.
• Extensive and intensive phylogenetic analyses are needed to explain the
fact that the A genome has played a stronger role than the B genome in
the domestication process. 12

13. IMPORTANCE OF TRITICUM DICOCCOIDES
IN WHEAT DOMESTICATION AND BREEDING
• The wheat domestication events mainly occurred in diploid wheat (T.
boeoticum) containing AbAb and tetraploid wheat (T. dicoccoides) containing
AuAuBB genomes.
• The wild emmer wheat, T. dicoccoides, actually is central to wheat
domestication Evolution
• T. dicoccoides possesses important beneficial traits, e.g., resistance to stripe
rust, stem rust, powdery mildew and soil born wheat mosaic virus, amino acid
composition etc.
• T. dicoccoides also shows agriculturally deleterious features such as brittle
rachis; no-free-threshing characteristic; few, small and light spikes; and small
grains. 13

14. CONCLUSION AND PROSPECT
• Domestication has genetically not only transformed the brittle rachis,
tenacious glume and non-free threshability, but also modified yield and
yield components.
• Wheat still has strong adaptability to diverse environments and end uses
due to the adaptive complexes that evolved in wild emmer.
• Germplasm collections are essential to conserve biodiversity and thus pay
big dividends to agriculture when used efficiently.
• It is essential to follow domestication processes and unravel many
functional and regulatory genes that were eliminated during domestication
.
• Whole genomes of several crops have been sequenced and this sequenced
data can be used to study the origin of genes and gene families. 14

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