Analysis of genetic diversity and evolutionary relationships among hexaploid wheats Triticum L. using LTR-retrotransposon-based molecular markers

The origin, diversity and distribution of hexaploid wheat still remain somewhat unclear. In this study we examined the patterns of genetic diversity and phylogenetic relationships of seven hexaploid wheat species using integration site polymorphism of the LTR retrotransposons. Forty-eight accessions (most of them aboriginal) of seven wheat species from different geographical regions were studied using sequence-specific amplification polymorphisms. Phylogenetic relationships among species were constructed with SplitsTree 4.10 based on Dice’s matrices. Genetic distances between the accessions clustered with PAST software were estimated by principal component analysis. All the accessions differentiated into two main groups, one including European spelt and the other combining common, club and Indian dwarf (shot) wheat with the Asian spelt. The spelt species T. macha , T. vavilovii and spelt spike (speltoid) free-threshing T. petropavlovskyi were intermediate between the two groups. The separation of these spelt species from all other accessions was determined by differences in the A genome. European spelt was subdivided into Central European and Spanish branches. As different genetic pools were characteristic of European and Asian spelt, European spelt could not originate directly from the Asian one. Supposedly, the A genome mostly harbors the species-forming or taxonomically important genes that distinguish spelt species from free-threshing ones, which group together with Asian spelt. Grouping of Asian spelt with free-threshing wheat suggests their close relatedness and confirms the hypothesis that free-threshing hexaploid wheats originated from the Asian spelt ancestor.