Physical mapping of Agropyron cristatum chromosome 6P using deletion lines in common wheat background

Genetically stable deletion lines of Agropyron cristatum chromosome 6P in common wheat background were generated, which allowed for physical mapping of 255 6P-specific STS markers and leaf rust resistance gene(s). Chromosomal deletion lines are valuable tools for gene discovery and localization. The chromosome 6P of Agropyron cristatum (2n = 4x = 28, PPPP) confers many desirable agronomic traits to common wheat, such as higher grain number per spike, multiple fertile tiller number, and enhanced resistance to certain diseases. Although many elite genes from A. cristatum have been identified, their chromosomal locations were largely undetermined due to the lack of A. cristatum 6P deletion lines. In this study, various A. cristatum 6P deletion lines were developed using a wheat-A. cristatum 6P disomic addition line 4844-12 subjected to (60)Co-γ irradiation as well as an Aegilops cylindrica gametocidal chromosome. Twenty-six genetically stable A. cristatum 6P deletion lines in the genetic background of common wheat were obtained, and their genetic constitutions were elucidated by genomic in situ hybridization (GISH) and sequence-tagged site (STS) markers specific to A. cristatum chromosome 6P. Moreover, 255 novel chromosome 6P-specific STS markers were physically mapped to 14 regions of chromosome 6P. Field evaluation of leaf rust resistance of various deletion lines and BC1F2 populations indicated that the A.cristatum chromosome 6P-originated leaf rust resistance gene(s) was located in the region 6PS-0.81-1.00. This study will provide not only useful tools for characterization and utilization of wheat materials with alien chromosomal segments, but also novel wheat germplasms potentially valuable in wheat breeding and improvement.