The article reports the map-based cloning of the wheat powdery mildew resistance gene Pm13 from the wild wheat species Aegilops longissima. Pm13 encodes a mixed lineage kinase domain-like (MLKL) protein with an N-terminal-domain of MLKL (MLKL_NTD) and a C-terminal serine/threonine kinase (STK) domain. The resistance function of Pm13 was validated through mutagenesis, gene silencing, transgenic assays, and allelic association analyses. The development of introgression lines with reduced chromosome segments of Ae. longissima encompassing Pm13 enables its deployment in wheat cultivars. The cloning of Pm13 provides insights into the molecular mechanisms of powdery mildew resistance and highlights the role of kinase fusion proteins (KFPs) in wheat immunity. Wheat powdery mildew, caused by Blumeria graminis f. sp. tritici, is a devastating disease affecting wheat yield and quality. Resistance genes cloned to date primarily encode NLR immune receptors, but race-specific resistance genes have become ineffective due to pathogen evolution. Recent research has identified diverse kinase domains in Triticeae, suggesting new players in plant immunity. Cloning novel Pm genes could facilitate their use in breeding programs. Over 60 Pm resistance genes have been identified in wheat and its wild relatives, but only 16 have been cloned. Most of these genes encode NLR immune receptors. Only a few partial resistance genes have been identified, including Pm38/Yr18/Lr34/Sr57 and Pm46/Yr46/Lr67/Sr55, which encode ABC and hexose transporters. Recently cloned genes, such as Pm24 (WTK3) and WTK4, encode tandem kinase proteins, while Pm4 encodes a chimeric protein with a serine/threonine kinase and multiple C2 domains. The genetic bottlenecks of wheat polyploidization and domestication have reduced genetic diversity and increased vulnerability to stresses. Wild relatives of wheat, such as Aegilops longissima, are important sources of genetic diversity for disease resistance. Pm13, along with Pm66 and Pm6Sl, have been reported in Ae. longissima. Previous studies identified Pm13 on chromosome 3S from Ae. longissima accessions, and other resistance genes on different chromosomes were temporarily designated Pm13a and Pm13b. Recent introgression of Pm66 and Pm6Sl from Ae. longissima into wheat has been achieved. In this study, Pm13 was cloned using a combination of classical map-based cloning and ph1b-induced homoeologous recombination. Pm13 encodes a MLKL protein withThe article reports the map-based cloning of the wheat powdery mildew resistance gene Pm13 from the wild wheat species Aegilops longissima. Pm13 encodes a mixed lineage kinase domain-like (MLKL) protein with an N-terminal-domain of MLKL (MLKL_NTD) and a C-terminal serine/threonine kinase (STK) domain. The resistance function of Pm13 was validated through mutagenesis, gene silencing, transgenic assays, and allelic association analyses. The development of introgression lines with reduced chromosome segments of Ae. longissima encompassing Pm13 enables its deployment in wheat cultivars. The cloning of Pm13 provides insights into the molecular mechanisms of powdery mildew resistance and highlights the role of kinase fusion proteins (KFPs) in wheat immunity. Wheat powdery mildew, caused by Blumeria graminis f. sp. tritici, is a devastating disease affecting wheat yield and quality. Resistance genes cloned to date primarily encode NLR immune receptors, but race-specific resistance genes have become ineffective due to pathogen evolution. Recent research has identified diverse kinase domains in Triticeae, suggesting new players in plant immunity. Cloning novel Pm genes could facilitate their use in breeding programs. Over 60 Pm resistance genes have been identified in wheat and its wild relatives, but only 16 have been cloned. Most of these genes encode NLR immune receptors. Only a few partial resistance genes have been identified, including Pm38/Yr18/Lr34/Sr57 and Pm46/Yr46/Lr67/Sr55, which encode ABC and hexose transporters. Recently cloned genes, such as Pm24 (WTK3) and WTK4, encode tandem kinase proteins, while Pm4 encodes a chimeric protein with a serine/threonine kinase and multiple C2 domains. The genetic bottlenecks of wheat polyploidization and domestication have reduced genetic diversity and increased vulnerability to stresses. Wild relatives of wheat, such as Aegilops longissima, are important sources of genetic diversity for disease resistance. Pm13, along with Pm66 and Pm6Sl, have been reported in Ae. longissima. Previous studies identified Pm13 on chromosome 3S from Ae. longissima accessions, and other resistance genes on different chromosomes were temporarily designated Pm13a and Pm13b. Recent introgression of Pm66 and Pm6Sl from Ae. longissima into wheat has been achieved. In this study, Pm13 was cloned using a combination of classical map-based cloning and ph1b-induced homoeologous recombination. Pm13 encodes a MLKL protein with