Pubblicazioni

Yellow rust (YR) is one of the most important foliar diseases in wheat leading to significant yield losses. The use of resistant varieties is a cheap, efficient and environmentally sound method to control wheat YR. Modern wheat varieties often harbor major resistance genes, which confer full protection against specific races of wheat rusts, and quantitative resistance conferring partial but durable resistance to mostly all the races of the pathogen. Although major resistance is easy-to-use in breeding programs, it tends to be short-lived against new compatible wheat rust races. Thus, the frequent emergence of new P. triticina virulent races requires a constant search of new source of resistance. The objectives of this study are to identify putative novel sources of effective resistance against YR with quantitative trait loci (QTL) or genes from an extensive series of Swiss modern varieties and landraces and to map genomic loci associated with YR resistance by combining high-quality disease phenotyping tools and genome-wide association study (GWAS) approach. A set of 539 wheat genotypes (320 landraces and 220 improved cultivars) was scored for adult plant YR response variation under field conditions in three different Swiss sites from 2019 to 2021. The panel was genotyped with either 15K or 25K Illumina iSelect SNP array providing information of 12’408 markers covering all 21 wheat chromosomes and subjected to genetic analysis using four statistical models. Preliminary results allowed identifying of an important number of markers associated to YR resistance, depending on the statistical model performed. Among those, six significant marker-LR resistance associations (with − log10 (p) > 5.0), located on chromosomes 1A, 1D and 7A, were detected with all statistical models, representing strong QTLs for resistance to LR. The next step will be to compare the location of the most significant markers and QTLs, identified here, with that of previously mapped QTLs and genes for YR resistance on a wheat consensus map and sort-out novel QTLs for durable yR resistance. The encouraging results obtained in the present study should be highly useful for identifying new QTLs for durable resistance using existing natural genetic resources. The newly identified markers provide important genomic information to initiate marker-assisted selection as well as fine mapping and cloning of the underlying genes and QTLs.