Genome-wide association study for septoria tritici blotch resistance reveals the occurrence and distribution of Stb6 in a historic Swiss landrace collection

Septoria tritici blotch (STB), caused by the fungus Zymoseptoria tritici, is a major constraint in global wheat production. The lack of genetic diversity modern elite cultivars largely hinders improvement STB resistance. Wheat landraces are reservoirs untapped diversity, which can be exploited to find novel resistance genes or alleles. Here, we characterized 188 Swiss for using four Z. isolates. We used genome-wide association study (GWAS) identify variants associated with amount lesion and pycnidia production fungus. majority were highly resistant both traits isolate 1E4, indicating gene-for-gene relationship, while higher phenotypic variability was observed against other GWAS detected significant SNP on chromosome 3A that 1E4. response 1E4 likely controlled Stb6 gene. Sanger sequencing revealed these ~ 100-year-old carry allele. This indicates importance this gene Switzerland during early 1900s disease control field. Our demonstrates characterizing historic landrace collections provide valuable information contributing will help breeders future make decisions integrating such germplasms breeding.