Cotton
J. E.(Jed) and Bonnie McClellan
© 2005 California Academy of Sciences
http://calphotos.berkeley.edu
http://www.georgiacottoncommission.org/
© 2006 Matt Below
Katie Konchar – UW Department of Botany
http://calphotos.berkeley.edu
“The fabric of our Lives”
www.absorbentcotton.com/
• 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
Southern Illonois University
Ethnobotanical Leaflet
http://www.kbcottonpillows.com
www.goodhumans.com
Gossypium
Phylum Magnoliophyta
Class Magnoliopsida
Order Malvales
Family Malvaceae
Tribe Gossypieae
Lysigenous glands contain
sesquiterpenes
collectively called gossypol
www.algieri-images.co.uk
© 2006 Matt Below
http://calphotos.berkeley.edu
n = 26
Diversity
• 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
www.malvaceae.info
www.biologie.uni-hamburg.de
www.invasive.org
Seed Hairs
Steve Hurst. Provided by ARS Systematic
Botany and Mycology Laboratory. Cyprus.
• Unicellular
outgrowths of the
epidermis of the
seed or seed coat
• Unique
convolutions and
spiral twists
causes the fibers
to cling together
when spun
African-Asian diploids:
G. herbaceum
G. arboreum
New World tetraploids:
G. barbadense
G. hirsutum
• Annualized
• Longer, stronger fiber
• Higher yield, abundant
fiber
• Ease of harvest
• Time of maturity
• Day length neutral
• Disease resistance
• Glandless seed
http://www.classbrain.com
Four Independently Domesticated
Species!!
Modern Mechanized Production
http://entweb.clemson.edu
http://content.answers.com
Modern Cotton Gin Stand
USDA
Iowa State University
Ecology, Evolution, and Organismal Biology
Jonathan Wendel
• Gene
expression
• Genome size
evolution
• Phylogenetics
www.eeob.iastate.edu/faculty/WendelJ/research.htm
Wendel and Cronn, 2003: Figure 1
From Chapter 70:
Figure 70.1
6-11 mya
“Line of Domestication”
www.prosnea.nl
Two parental diploid groups on
opposite sides of the world!
How did Gossypium disperse over such a long
distance? Where humans involved?
When did the divergence of A and D genomes
occur?
And, when did the chance recombination of these
genomes
lead to
allopolyploidization?
Cretaceous Hypothesis:
• 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
www.public.iastate.edu
http://www.rocksandminerals.com/geotime/geotime.htm
Hypotheses for Recent Origin of
Allopolyploidy in Cotton:
• 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:
• 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:
• 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
-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
• 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
• 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
• Supported by biogeography of D-genome species
• Recent arrival of G. raimondii in Peru
Allopolyploidization of Cotton
Occurred Only Once
• All New World
tetraploid cottons
contain Old World
Cytoplasm
• Must have been one
single seed plant in
the initial hybridization
event
By Evert at http://davesgarden.com
So, how did it get there?
www.ferdinando.org.uk
Transoceanic
Voyages
•Long distance dispersals are
characteristic of Gossypieae
•Important in diversification and
speciation
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.