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

Deepika Narang,Burkhard Steuernagel,Jianbo Li,Satinder Kaur,Cristobal Uauy,Subhash Bhardwaj,Peng Zhang,Sreya Ghosh,Urmil Bansal,Brande B H Wulff,Parveen Chhuneja

doi:10.1038/s41598-020-64166-2

Abstract

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.

Highlights

Wild wheat species Aegilops peregrina (UpUpSpSp), harbours resistance to various diseases including leaf rust and stripe rust
All the seedlings in 69 families showed resistant infection type (;) and these RILs were classified as homozygous resistant, while all the seedlings in 81 families showed infection type 33+ and these RILs were classified as homozygous susceptible (Fig. 1)[22]
We identified five contigs with single nucleotide polymorphism (SNP) with an allele frequency indicative of linkage to LrAp, i.e. a majority of SNPs derived from the susceptible parent were detected in the susceptible bulk (SB) and a majority of SNPs derived from the resistant parent were detected in the resistant bulk (RB) (Supplementary Fig. 2)

Summary

Introduction

Wild wheat species Aegilops peregrina (UpUpSpSp), harbours resistance to various diseases including leaf rust and stripe rust. Difficulties associated with genetic characterisation of alien genes include low throughput and physical resolution of cytogenetic techniques[10,13,14] and limited transferability of microsatellite markers to the tertiary gene pool[15]. A leaf rust resistant introgression line (IL) pau16061, was developed previously from the hybridisation of the wild species Ae. peregrina (UpUpSpSp) with the wheat line WL711 (vulnerable to rust)[21]. The wheat-Ae. peregrina IL pau16061 was characterised cytogenetically to identify the donor genome of the introgression with leaf rust resistance, and the resistance was mapped with SNP markers designed directly from NLRs identified through MapRenSeq

Methods

Results

Conclusion