COTTON
COTTON IS A SOFT, FLUFFY STAPLE FIBER THAT
GROWS IN A BOLL, OR PROTECTIVE CASE, AROUND
THE SEEDS OF THE COTTON PLANTS OF THE
GENUS GOSSYPIUM IN THE MALLOW
FAMILY MALVACEAE. THE FIBER IS ALMOST
PURE CELLULOSE. UNDER NATURAL CONDITIONS,
THE COTTON BOLLS WILL INCREASE THE DISPERSAL
OF THE SEEDS.
“THE FABRIC OF OUR LIVES”
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Oils, Balls, Q-tips ™,
Bandages, Tissue,
Paper, Napkins, Socks,
Shirts, Shorts,
Sweaters, Pants, Coats,
Towels, Linen, Cushions,
Drapery, Upholstery,
Rugs, Carpet,
Comforters, Mattresses,
Insulation, Filtration
GOSSYPIUM
Phylum Magnoliophyta
Class Magnoliopsida
Order Malvales
Family Malvaceae
Tribe Gossypieae
Lysigenous glands contain
sesquiterpenes
collectively called gossypol
n = 26
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DIVERSITY
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Annual, biennial or
perennial
Herbaceous, short shrub
or small tree
Primary axis, alternate
Leaves have varying
texture, shape, hairiness
Showy cream, yellow, red
or purple flowers axilary,
terminal or solitary with
typically 5 petals
SEED HAIRS
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Unicellular
outgrowths of the
epidermis of the
seed or seed coat
Unique
convolutions and
spiral twists causes
the fibers to cling
together when spun
FOUR INDEPENDENTLY DOMESTICATED
SPECIES!!
African-Asian diploids:
G. herbaceum
G. arboreum
New World tetraploids:
G. barbadense
G. hirsutum
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Annualized
Longer, stronger fiber
Higher yield, abundant fiber
Ease of harvest
Time of maturity
Day length neutral
Disease resistance
Glandless seed
MODERN MECHANIZED PRODUCTION
Modern Cotton Gin Stand
USDA
IOWA STATE UNIVERSITY
ECOLOGY, EVOLUTION, AND ORGANISMAL
BIOLOGY
Jonathan Wendel
Gene
expression
 Genome size
evolution
 Phylogenetics
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WENDEL AND CRONN, 2003: FIGURE 1
From Chapter 70:
Figure 70.1
6-11 mya
“Line of Domestication”
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CRETACEOUS HYPOTHESIS:
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Based on the observation of global distribution and impressive
morphological variation within the tribe
Evidence points to progenitor diploid species lines which are in
currently in different hemispheres
The continents where the progenitors may have originated have
shifted due to the movements of tectonic plates separating the
African and South American continents
Rationally suggests that allopolyploidy must be ancient!
Hybridization must have occurred before the splitting of the
supercontinents and therefore can be dated back to the
Cretaceous or early Tertiary
HYPOTHESES FOR RECENT ORIGIN OF
ALLOPOLYPLOIDY IN COTTON:
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Agronomically advanced fiber probably only developed
once
Origin must have involved human transfer of the A
genome cultigen to the New World
Followed by hybridization of the A genome cultigen
with a New World D genome species
So…allopolyploid cotton formed during agricultural
times, within the last 6 millennia!
OTHER PROPOSALS:
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Endrezzi et al.
Thermal stability measurements and hybridization
experiments:
 Argue for Miocene origin (5-18 mya)
 Calculations based on an early Cretaceous divergence of
parental diploid groups
Phillips 1963
Review of cytogenetic evidence
 Argues for mid-Pleistocene
 Two germinal lines of anciently diverging tribes recently
combined to form tetraploids
A PLEISTOCENE ORIGIN
Evolutionary implications of a recent origin of
allopolyploidy:
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Divergence and speciation of Gossypium tetraploids
Diploid parentage of the tetraploids
Biogeography
How can the progenitors have dispersed?
RAPID DIVERSIFICATION AND SPECIATION
Phylogenetic analyses demonstrate radiation
into 3 lineages involving 5 tetraploid species
 Supported by low levels of interspecific
divergence in nuclear genes
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-Island endemics
must have
originated after
additional
dispersal events
CONCERNING DIPLOID PARENTAGE
Cytogenetic studies indicate G. raimondii as the closest living relative of D
genome parental donor
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Hutchinson et al., 1947
 used 5 D-genome species in crosses with G. hirsutum or
G. barbadense
 Indicated G. raimondii as closer to the D-genome than
other species tested
 Innovative approach involving comparative analysis of
diverse synthetic allohexaploids
Liu et al., 2001b
 G. raimondii is the sister group to clade of all 5
allopolyploid species
A-GENOME PERSPECTIVES
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A-genome of allopolyploid cotton is more similar to the
A-genome diploids than the D-genome of the
allopolyploid is to that of the D-genome diploids!
G. arboreum and G. herbaceum better models of the
progenitor A-genome diploid than G. raimondii is of
the D-genome diploid
G. herbaceum more likely the A-genome donor than G.
arboreum
BIOGEOGRAPHICAL THEORIES
Theories, based on cytogenetic data, suggested that
polyploidization occurred after a Trans-Atlantic dispersal
of a species similar to G. herbaceum
Wendel and Albert, 1992:
Suggest pre-Pleistocene A-genome radiation into Asia,
followed by trans-Pacific dispersal to the Americas
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Supported by biogeography of D-genome species
Recent arrival of G. raimondii in Peru
ALLOPOLYPLOIDIZATION OF COTTON
OCCURRED ONLY ONCE
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All New World
tetraploid cottons
contain Old World
Cytoplasm
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Must have been one
single seed plant in the
initial hybridization
event
TRANSOCEANIC
VOYAGES
•Long distance dispersals are
characteristic of Gossypieae
•Important in diversification and
speciation
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But How!?
Seeds of many species of Gossypium are tolerant to long
periods of immersion in salt water
Capable of germination after many years of immersion
But, only retain their buoyancy for a couple months
 Stephens, 1966 suggested long distance dispersal may
have been accomplished on naturally floating debris.
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The test
1. Caravan a road, the binding force East Asia with Mediterranean in an antiquity:
а) Great silk way +
b) Great silk road
c) Commodity road
2. First of all route was used for export:
а) bamboo from China
b) Silk from China +
c) Tea from China
3. The great Silk way has arisen:
а) V-IV вв. Up to AD.
b) In II-I вв. Up to AD +
c) I-II вв. AD.
4. Where the Great Silk way came to an end:
а) In Romania
b) In Otare
c) In Rome +
5. Long time China stored(kept) as fiduciary manufacture:
а) Rice
b) Silk +
c) calico
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6. Where took the beginning a Great Silk way:
а) In a valley р. Инд
b) In the bottom current Сырдарьи
c) In area р. Хуанхэ in China +
7. What extent of a Great Silk way:
а) 9 thousand Km
b) 7 thousand Km +
c) 3 thousand Km
8. For transportation were used mainly:
а) Camels +
b) Horse
c) мамонты
9. Main subject of trade on a Great Silk Way
а) Silk +
b) Cotton
c) Rice
10. The term " a Great silk way " was entered with who?
а) Alexander the Great
b) Li Ji
c) Ferdinand Paul Wilhelm von Richthofen +
THANK YOU!