Genetic Variability of Btr1 Genes in Tetraploid Wheat Species and Aegilops speltoides Tausch

The Btr1 ( Brittle rachis 1 ) genes are involved in the control of important domestication-related trait—brittle rachis in wheat. In the current study, we investigated the Btr1 genes from two accessions of Aegilops speltoides Tausch and 29 accessions of 11 tetraploid wheat species, including previously unstudied Triticum karamyschevii Nevski, T. turanicum Jakubz., and T. turgidum L. of the section Dicoccoides Flaksb. and T. timopheevii (Zhuk.) Zhuk. of the section Timopheevii A. Flat. et Dorof. Two novel alleles Btr1-A a and Btr1-A t were described for the wheat species of the section Timopheevii . Several new alleles of Btr1-B were described for the studied tetraploid wheat species. Simple sequence repeats (SSRs) were detected in the 5'UTR of Btr1 genes. Wheat species with non-brittle rachises were characterized by perfect SSRs (GA) n , while in most of the wheat accessions with brittle rachises and Ae. speltoides, we defined the SSRs as being of an imperfect type. The relationship between the Btr1 alleles and the formation of non-brittle rachises vs . brittle rachises phenotype, as well as the possible origin of various Btr1 alleles are discussed.