Ben Grady
Dept. of Botany UW-Madison

• Poaceae
• Highly inconsistent taxonomy
•
Triticum and Aegilops separate genera
•
Triticum sensu lato
– Includes Aegilops
•
Triticum sensu stricto ~ 10 species
• Native to Mediterranean area
• Base n = 7

• Triticum monococcum L. (cultivated einkorn)
–
T. boeoticum (wild einkorn)
– Diploid - AA
• Triticum dicoccum Schübl. (emmer wheat)
–
T. dicoccoides (wild emmer)
– Tetraploid – AABB
•
Triticum aestivum L. (bread or common wheat)
– Hexaploid - AABBDD
–
T. dicoccoides (AABB) + Aegilops tauschii (DD)

• “
As soon as one begins to plant seed in a seedbed on a yearly basis and save seed for the following season, selection pressures are automatically set in motion, leading toward domestication” –J.R. Harlan
• Non-shattering rachis (two independent recessive loci) (Davies and Hillman, 1992)
• Seed dormancy periods
• Uniform ripening of seeds
• Seed size

Salamini et al., 2002

• HMW glutenin loci:
Glu-1-1 & Glu-1-2
• 9 alleles of the B chromosome
Glu- B1-1
( Glu-D1-1 outgroup)
• Wild and domesticated emmers
• Two well-supported clades a & b; divergence dated to 1.4-2.0 MYA
• Multiple domestication events?
• Domestication of mixed populations?
• Introgression?

NJ tree from Glu-B1-1 alleles in
T. aestivum a (black) b (white) from Brown et al., 2006

• a – black
• b - white a & b Glu-B1-1 frequencies in wild emmers
From Brown et al., 2006

Glu-B1-1 subclades in cult. emmers
Figure 9.2 (from Brown et al., 2006) Proportion of α (black) & β (white) alleles

Glu-B1-1
• a alleles more common than b alleles
• a alleles present in all accessions sampled
• b alleles present in Turkey and NW, through
Europe
• Do a alleles confer a selective advantage? – probably not
• Independent introductions of emmer into
Europe? – probably

Higher % of A alleles
Higher % of B alleles

Origins of Glu-B1-1 allele subclades
• Multiple domestications of emmer wheat?
– probably not
• Single domestication of diverse wild population?
– not bloody likely
• New alleles introduced after domestication via introgression with wild relatives?
– Yeah (supported by rDNA evidence)

Peterson et al., 2006
• Hybridization history of
T. aestivum
(allohexaploid)
– DD (
A. tauschii ) + AABB ( T. dicoccoides)
–
T. dicoccoides = A u A u ( T. urartu ) + BB ( A. speltoides

www.icarda.org

• Strict consensus tree from 8 equally parsimonious trees, sequences from two nuclear genes, DMC1 & EF-G, and plastid gene ndhF (Peterson et al., 2006)
• Triticum polyphyletic
• Aegilops polyphyletic

• Harlan, J.R. 1992. “Origins and Processes of Domestication”.
In Grass Evolution and Domestication. Ed: G.P. Chapman.
Cambridge U. Press, pgs: 159-166.
• Brown, T.A., S. Lindsay, & R.G. Allaby. 2006. “Using
Modern Landraces of Wheat to study the Origins of European
Agriculture”. In Darwin’s Harvest. Eds: T.J. Motley, N.
Zerega, & H. Cross. Columbia U. Press, pgs: 197-212.
• Peterson, G., O. Seberg, M. Yde, & K. Berthelsen. 2006.
Phylogenetic relationships of Triticum and Aegilops and evidence for the origin of the A, B, and D genomes of common wheat ( Triticum aestivum ). Molecular Phylogenetics and Evolution 39: 70-82
• Salamini, F., H. Ozkan, A. Brandolini, R. Schafer-Pregl, & W.
Martin. 2002. Genetics and geography of wild cereal domestication in the Near East. Nature Reviews Genetics Vol.
3 June 2002 429-441.