TaRLK-1B: A novel wheat gene conferring resistance to leaf rust revealed by a genome-wide association study

Leaf rust is a highly destructive foliar disease in wheat which causes major constraints in wheat production worldwide. In this study, we conducted a comprehensive assessment of adult plant resistance to leaf rust in 590 accessions from the advanced backcross-nested association mapping plus inter-crossed (AB-NAMIC) population. We used 660K genotype data to perform a genome-wide association study (GWAS), which identified significant quantitative trait loci (QTLs) on chromosomes 1B, 2A, 2B, and 7D, and then focused on the candidate gene TaRLK-1B on chromosome 1B. A cleaved amplified polymorphic sequence (CAPS) marker developed based on TaRLK-1B haplotypes could effectively differentiate between resistant and susceptible varieties. This gene encodes a membrane-localized leucine-rich repeat receptor-like kinase (LRR-RLK) that is upregulated in response to the fungal infection that causes leaf rust. Targeted knockout of TaRLK-1B in wheat led to reduced resistance to leaf rust, underscoring its essential role as a positive regulator of the defense against this disease. We propose that TaRLK-1B interacts with the receptor-like cytoplasmic kinase TaRLCK1B, potentially facilitating immune signal transduction. Our findings also demonstrate that pyramiding minor effect QTLs significantly increases resistance to leaf rust. This study provides novel insights into rust resistance genes and valuable QTL information, which can improve marker-assisted wheat breeding efforts.