Exploitation of the 5BS Physical Map to Complete the SKr Crossability Locus

Most elite wheat varieties cannot be crossed with related species thereby restricting greatly the germplasm that can be used for alien introgression in breeding programs. Inhibition to crossability is controlled genetically and a number of QTL have been identified to date, including SKr, a strong QTL affecting crossability between wheat and rye located at the distal end of chromosome 5BS. We started the positional cloning of this gene and we elaborated a first draft of a physical map in both the crossable and non-crossable lines. We used the newly developed physical map of the 5BS chromosome arm to partly fill in the gaps and complete the sequence. Sequence was made of three main contigs and covered ~1 Mb. The sequence was used to develop several tens of markers useful for the screening of a mutant population derived from irradiated seeds of the cultivar Renan. This led to the identification of seven mutants showing crossability while Renan is a non-crossable variety. This allowed the refining of the positional cloning of the gene and reduced the number of candidate genes. Validation of these genes will be done through transgenesis (overexpression and knock-out) and through EMS mutant screening.