Genetic factors for resistance to yellow rust, septoria tritici blotch, leaf rust, and stem rust in durum wheat, and environmental resistance, revealed by multi-environment genome-wide association study

This thesis explores the genetic basis of resistance to yellow rust (YR), septoria tritici blotch (STB), leaf rust (LR) and stem rust (SR) in durum wheat in order to provide a basis for the development of sustainable genetic research on disease resistance. Chapter 2 focuses on a genetic survey for loci controlling resistance for yellow rust (YR) in tetraploid wheat germplasm that was carried out based on the Global Durum Panel and Tetraploid Global Collection. Panels were evaluated in a multi-environmental field survey for infection type and disease severity, including 12 different environments across the Mediterranean area and Argentina (2019-2021). In GDP, GWAS identified eight main YR resistance loci in cultivars on different chromosomes, which overlapped with significant regions detected in TGC landraces as well. KASP® markers are used to functionally characterize genes within the identified QTL intervals. Chapter 3 evaluates the genetic resistance to Septoria tritici blotch in a panel of 506 durum wheat landraces and related subspecies from the CEREALMED collection, which were phenotyped in Cadriano and Fiorenzuola. Disease severity and vertical disease progression were systematically investigated on the flag leaf and canopy of wheat at key time points. GWAS results successfully revealed 18 loci significantly associated with resistance, including 14 in Cadriano and 4 in Fiorenzuola, all of which were stably expressed. Chapter 4 evaluated resistance to multiple races of three rust diseases in a global core population of durum wheat in India and the United States. Phenotypic data obtained through artificial inoculation revealed significant resistance variation and high heritability, confirming robust results. Subsequently, genome-wide association analysis using a 90K SNP array and multiple models identified a number of QTLs significantly associated with resistance across multiple chromosomes. Stable association loci that were significant in at least two models revealed novel genomic regions with potential for disease resistance.