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.

Stripe or yellow rust (YR) and leaf rust (LR) cause large losses in wheat production worldwide. Resistant cultivars curtail the levels of losses. The present study aimed to identify quantitative trait loci (QTL) for YR and LR resistance in 147 F_2:6 recombinant inbred lines (RIL) derived from the cross Fuyu 3/Zhengzhou 5389. The RIL population and parents were genotyped with the Wheat55K single nucleotide polymorphism (SNP) array and simple sequence repeat (SSR) markers. All materials were also phenotyped for YR severity at Mianyang in Sichuan province and Baoding in Hebei province in the 2015/2016, 2016/2017, and 2017/2018 cropping seasons, and LR severity at Zhoukou in Henan province and at Baoding in 2017/2018. Eleven QTL for YR resistance and five for LR resistance were detected using inclusive composite interval mapping (IciMapping). Four of these QTL on chromosomes 1BL, 2BS, 3AL, and 5AL conferred resistance to both YR and LR. The QTL on 1BL was Lr46/Yr29, and that on 7BL might be Lr68. The QTL on chromosome 2BS was detected at a similar position to previously detected loci. QYr.hebau-3AL/QLr.hebau-3AL, QYr.hebau-5AL/QLr.hebau-5AL, QYr.hebau-7DL, QYr.hebau-4BS, QYr.hebau-6DL, and QYr.hebau-2AS are likely to be new. An SSR marker for QYr.hebau-7DL was developed and validated in a diverse wheat panel from China, suggesting effectiveness in different genetic backgrounds. These QTL with closely linked SNP and SSR markers could be useful for marker-assisted selection in wheat breeding programs targeting durable resistance to both diseases.

Leaf rust (LR), caused by Puccinia triticina, is one of the most widespread diseases of common wheat (Triticum aestivum L.) worldwide. The LR resistance gene LrBi16 has been mapped on chromosome arm 7BL in Chinese wheat cultivar Bimai 16 and was closely linked to SSR loci Xcfa2257 and Xgwm344 with genetic distances of 2.8 cM and 2.9 cM, respectively. In the present study, a total of 304 AFLP primer pairs were used to screen Bimai 16 and Thatcher and resistant and susceptible DNA bulks. The polymorphic AFLP marker P-ATT/M-CGC_{173 bp} was used to genotype F₂ and F₃ populations to identify markers more closely linked to LrBi16. Marker P-ATT/M-CGC_{173 bp} was tightly linked to LrBi16 with a genetic distance of 0.5 cM. As LrBi16 was mapped near the Lr14a locus, 809 F₂ plants from the Bimai 16/RL6013 (Lr14a) cross were inoculated with the Pt pathotype FHNQ to test the allelism of Lr14a and LrBi16. All of the F₂ plants were resistant to FHNQ (IT between; and 2), suggesting that Lr14a and LrBi16 are allelic.