Genome-assisted identification of wheat leaf rust resistance gene Lr.ace-4A/Lr30.

Leaf rust is a devastating disease of wheat. Growing rust-resistant wheat varieties is the best strategy to mitigate this threat. Here, we generate a 10.51-gigabase chromosome-scale assembly of the durum wheat landrace PI 192051. Using mutagenesis and transcriptome sequencing, we identify the leaf rust resistance gene Lr.ace-4A within a recombination-sparse region of PI 192051 and demonstrate that Lr.ace-4A is identical to the previously designated Lr30 gene in hexaploid wheat. Lr.ace-4A/Lr30 encodes a non-canonical coiled-coil nucleotide-binding leucine-rich repeat receptor, featuring tandem nucleotide-binding domains. This gene is both necessary and sufficient to confer resistance to leaf rust, as demonstrated by CRISPR/Cas9-induced mutations and transgenic complementation. Lr.ace-4A provides near-immunity resistance in durum wheat, though its effectiveness is diminished in hexaploid wheat. Two amino acid polymorphisms differentiate the resistant and susceptible Lr.ace-4A haplotypes, with transgenic plants carrying either susceptible variant showing susceptibility. The cloning of Lr.ace-4A will accelerate its deployment in wheat breeding programs.