Exploitation of Aegilops species of section Sitopsis for wheat improvement

Section Sitopsis of the genus Aegilops is comprised of five diploid species sharing the S genome, which is closely related to the B genome of durum and bread wheat. Species of this section are a rich source of economically valuable traits for wheat improvement and, especially, resistance to different wheat diseases, The most exploitable species is Ae. speltoides, which is genetically the closest to the B genome and contains a variety of disease-resistance genes. Many lines of Aegilops speltoides carry a gene that promotes homoeologous pairing between Ae. speltoides and wheat chromosomes. This gene, casing the transfer of genes to wheat, was extensively used in the exploitation of Ae. speltoides genes. Transferring of desired genes from other Sitopsis species is facilitated by the use of the mutant ph1 gene, which allows for pairing between homoeologous chromosomes of these species and those of wheat. Gametocidal genes, interfering with successful gene transfer, are present in Ae. sharonensis, Ae. longissima, and Ae. speltoides, but their negative effect ill gene transfer from Ae. sharonensis may be overcome by an "anti-gametocidal" mutant wheat line. Particular cases of gene transfer from species of section Sitopsis into durum and bread wheat are described.