Molecular and cytogenetic characterization of a common wheat-Agropyron cristatum chromosome translocation conferring resistance to leaf rust

Crested wheatgrass (Agropyron cristatum L. Gaertn.) is a perennial species of economic importance as forage that also displays potentially valuable traits for wheat improvement trough intergeneric hybridization. In order to incorporate resistance genes from A. cristatum against wheat leaf rust (Puccinia triticina Erikss.) into common wheat (Triticum aestivum L.) a breeding programme was carried out by crossing and backcrossing the self-fertile amphiploid AABBDDPP (2n = 8x = 56) with T. aestivum (2n = 6x = 42; AABBDD). The AABBDDPP amphiploid was previously obtained by crossing tetraploid wheat (Triticum turgidum L. conv. durum Desf. 2n = 4x = 28; AABB) with a self-fertile allotetraploid (2n = 4x = 28; DDPP) between diploid wheat (Aegilops tauschii Coss.) and crested wheatgrass (A. cristatum). After three backcrosses a fertile stable line (named TH4) was obtained with 42 chromosomes. The fluorescence in situ hybridization and GISH analysis confirmed that TH4 carries a compensating robertsonian translocation involving the long arm of wheat chromosome 1B and the short arm of an unidentified A. cristatum chromosome. Specific molecular markers from A. cristatum also demonstrated the presence of chromatin from this species in the TH4 line. Macroscopic and microscopic observations indicated that the A. cristatum fragment that has been transferred to common wheat contributed a substantial level of partial resistance to leaf rust. The A. cristatum translocation line in bread wheat makes the disease resistance gene(s) from A. cristatum accessible for wheat breeding programmes.Peer Reviewe