Uncovering genetic determinants of disease resistance in durum wheat against causative agents of Yellow Rust and Septoria Tritici Blotch and, environmental adaptation of Zymoseptoria tritici: insights from multi-environment GWAS and pathogen thermal adaptation

This thesis investigates the genetic basis of disease resistance and environmental adaptation in durum wheat and Zymoseptoria tritici, aiming to support sustainable crop management. Chapter 1 explores genetic resistance to Yellow rust (Puccinia striiformis f. sp. tritici) in a panel of 1324 Triticum turgidum landraces from the Mediterranean (Italy, Turkey, Tunisia, Lebanon). Genome-Wide Association Studies (GWAS) using four models (MLM, MLMM, FarmCPU, BLINK) identified 11 significant QTLs on chromosomes 1B, 2A, 2B, 5B, 7A, and 7B. Haplotype analysis revealed allelic diversity, origins, and phenotypic effects, improving knowledge of resistant variants. Subpopulation-specific GWAS further dissected rare alleles and QTL origins. Chapter 2 examines genetic resistance to Septoria tritici blotch (Zymoseptoria tritici) in a panel of 510 durum wheat landraces from the CEREALMED collection, assessed in Cadriano (Bologna) under artificial inoculation. Disease severity was scored at two timepoints to estimate the Area Under the Disease Progression Curve (AUDPC). GWAS identified eight QTLs across the panel and 16 within subpopulations, including novel loci expanding breeding targets for Stb resistance. Chapter 3 investigates genetic determinants of thermal adaptation in Z. tritici using 238 isolates from eight Euro-Mediterranean countries. GWAS linked key genes—heat shock proteins, chaperones, and zinc finger proteins—to optimal growth temperature (Topt), thermal performance breadth (TPB80), and pathogenicity metrics (PLACL, PycLes) assessed via high-throughput phenotyping. These findings highlight essential genetic targets for breeding programs aimed at disease resistance and climate resilience. By enhancing knowledge of host-pathogen interactions and adaptation, this study contributes to sustainable agriculture and supports Green Deal goals to reduce chemical inputs while improving environmental resilience.