The Origins of Triticum Domestication Ben Grady Dept. of Botany UW-Madison

The genus Triticum 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

Domesticated Wheats 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)

Domestication Traits “ As soon as one begins to plant seed in a seed- bed 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

Traits of Domestication Salamini et al., 2002

Glutenin Loci Study HMW glutenin loci: Glu-1-1 & Glu 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 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 & b Glu-B1-1 frequencies in wild emmers a – black b - white 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

Implications of Glu-B1-1 allele distributions 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

Allele expansion in Europe 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)

Phylogenetic Relationships… 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

Wild Triticum species

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

Selected References Harlan, J.R “Origins and Processes of Domestication”. In Grass Evolution and Domestication. Ed: G.P. Chapman. Cambridge U. Press, pgs: Brown, T.A., S. Lindsay, & R.G. Allaby “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: Peterson, G., O. Seberg, M. Yde, & K. Berthelsen 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: Salamini, F., H. Ozkan, A. Brandolini, R. Schafer-Pregl, & W. Martin Genetics and geography of wild cereal domestication in the Near East. Nature Reviews Genetics Vol. 3 June