Evolutionary History of Wheats—the Main Cereal of Mankind

Abstract

An attempt in integrating the results of different comparative-genetic analyses of wheats and their molecular taxonomy has been made; the correspondence of earlier evolutionary specifications to the phylogeny within the genus Triticum species has been estimated. The relationships have been established based on chloroplast and nuclear DNA sequence data. One phylogenetic tree has been constructed based on the chloroplast sequences, and several phylogenetic groups have been found within the genera Triticum and Aegilops. It has been shown that Aegilops speltoides was a donor of the plasmon for all polyploid wheat species, whereas the chloroplast genomes of the diploid Triticum species are close to other Aegilops species. Nuclear Acc-1 and Pgk-1 genes have been used as molecular markers for the A and B genomes of the Triticum species. No variability has been found in these genes within polyploid wheats. In contrast, three variants of these genes have been detected in diploid A genome Triticum. The detailed analysis showed that one of these variants was a progenitor for all A genomes of all polyploid Triticum species; the second variant is close to the B genomes of Ae. speltoides; and the third one is unique for wild diploid wheats. The inheritance of two domesticated and taxonomically important characters was studied in the ancient hexaploid wheat Triticum antiquorum. It was shown that the recessive gene controlling spherical grain was allelic to the s gene determining the same character in the endemic Indian species T. sphaerococcum. The dominant genes of T. antiquorum and T. sphaerococcum controlling compact ears were proved to be non-allelic to the corresponding T. compactum gene. Results of molecular analysis indicated the close relationship of all hexaploid wheat species.