Discovery and characterisation of a new leaf rust resistance gene introgressed in wheat from wild wheat Aegilops peregrina.

Wild wheat species Aegilops peregrina (UpUpSpSp), harbours resistance to various diseases including leaf rust and stripe rust. Inheritance studies in a recombinant inbred line population of wheat-Ae. peregrina introgression line IL pau16061 revealed the transfer of a single major dominant gene conditioning all stage resistance, herein temporarily designated as LrAp. Genomic in situ hybridisation of IL pau16061, resistant and susceptible RILs with U- and S-genome DNA probes confirmed that the introgression with leaf rust resistance is from the Up genome of Ae. peregrina. Fluorescence in situ hybridisation using chromosome specific probes identified Up genome introgression to be on the long arm of wheat chromosome 6B. To genetically map LrAp, bulked segregant analysis was combined with resistance gene enrichment sequencing (MapRenSeq). Five nucleotide binding leucine-rich repeat contigs distinguished resistant and susceptible bulks and single nucleotide polymorphism (SNP) markers from these contigs co-segregated with LrAp. All five RenSeq NB_ARC contigs showed identity with the long arm of wheat chromosome 6B confirming the introgression on 6BL which we propose is a compensating translocation from Ae. peregrina chromosome 6UpL due to homoeology between the alien and wheat chromosomes. The SNP markers developed in this study will aid in cloning and marker assisted gene pyramiding of LrAp.

Fine mapping of Aegilops peregrina co-segregating leaf and stripe rust resistance genes to distal-most end of 5DS.

KEY MESSAGE: Novel rust resistance genes LrP and YrP from Ae. peregrina identified on chromosome 5D and the linked markers will aid deployment of these genes in combination with other major/minor genes. Aegilops peregrina, a wild tetraploid relative of wheat with genome constitution UUSS, displays genetic variation for resistance to leaf and stripe (yellow) rust. The wheat Ae. peregrina introgression line, IL pau16058, harbouring leaf and stripe rust resistance, was crossed with wheat cv. WL711 to generate an F2:3 mapping population. Inheritance studies on this population indicated the transfer of dominant co-segregating resistance to leaf and stripe rust. Ethyl methane sulphonate mutagenesis of IL pau16058 identified independent loss-of-function mutants for leaf and stripe rust resistance, indicating that the leaf and stripe rust resistance is controlled by independent genes, herein designated LrP and YrP, respectively. A high-resolution genetic map of LrP and YrP was constructed using the Illumina Infinium iSelect 90K wheat array and resistance gene enrichment sequencing (RenSeq) markers. The map spans 4.19 cM on the distal-most region of the short arm of chromosome 5D, consisting of eight SNP markers and one microsatellite marker. LrP and YrP co-segregated with markers BS00163889 and 5DS44573_snp and was flanked distally by the SNP marker BS00129707 and proximally by 5DS149010, defining a 15.71 Mb region in the RefSeq v1.0 genome assembly.