Model for the evolution of groups of gamma-gliadins in Aegilops/Triticum. The six groups proposed are based on the ML tree (Figure 2, Additional file 4) and occur in genomes as summarised in Figure 3. Note that in this model the order of the groups on the chromosome is arbitrary, and duplications of genes within each group are ignored. The occurrence of pseudogenes is only indicated when it affected complete groups, but some pseudogenes may occur in all groups. Note that each genome has either group 6 gliadins or group 5 gliadins with nine cysteines and constant length.