Genome-wide association studies reveal adaptation mechanisms in a major wheat pathogen

Human activity significantly influences the evolutionary dynamics of both crops and their pathogens, especially in agroecosystems. Zymoseptoria tritici, a major wheat pathogen, poses severe economic threats to wheat production worldwide. We utilize genome-wide association studies (GWAS) to uncover the genetic mechanisms behind Z. tritici adaptation to environmental and host factors. We identified candidate genes associated with thermal and host adaptation by integrating population sequencing, bioclimatic, and host genotype metadata. We conducted a high-throughput phenotyping approach, assessed the thermal response of over 400 Z. tritici strains at multiple growth temperatures, and used GWAS to identify candidate genes associated with climatic adaptation1. Additionally, we applied a genome-host association (GHA) approach, correlating 800 pathogen genotypes with natural infection phenotypes across various wheat cultivars2. These approaches identified multiple gene candidates, 20 of which were selected for functional validation, revealing that over half of the validated genes significantly affect the virulence of Z. tritici when deleted. Our study provides a novel application of GWAS in plant pathogens that transcends the limitations imposed by traditional phenotyping methods. By enhancing GWAS with environmental and host metadata, we gain insights into the evolutionary mechanisms driving pathogen adaptation