Stripe rust is a devastating disease in wheat that causes substantial yield loss around the world. The most effective strategy for mitigating yield loss is to develop resistant cultivars. The wild relatives of wheat are good sources of resistance to fungal pathogens. Here, we used a genome-wide association study (GWAS) to identify loci associated with stripe rust (causal agent: Puccinia striiformis f. sp. tritici) resistance in wild emmer (Triticum dicoccoides) at the seedling stage, in the greenhouse, and at the adult plant stage, in the field. We found that the two major loci contributing to resistance in our wild emmer panel were the previously cloned seedling-stage resistance gene, Yr15, and the adult-plant-stage resistance gene, Yr36. Nevertheless, we detected 12 additional minor QTLs that additionally contribute to adult plant resistance and mapped a locus on chromosome 3AS that tentatively harbors a novel seedling resistance gene. The genotype and phenotype data generated for the wild emmer panel, together with the detected SNPs associated with resistance to stripe rust, provide a valuable resource for disease-resistance breeding in durum and bread wheat.

Quantitative trait loci (QTL) for barley stripe rust resistance were mapped in recombinant inbred lines (RILs) from a Lenetah x Grannelose Zweizeilige (GZ) cross. GZ is known for a major seedling resistance QTL on chromosome 4H, but linked markers suitable for marker assisted selection have not been developed. This study identified the 4H QTL (LOD = 15.94 at 97.19 cM), and additional QTL on chromosomes 4H and 6H (LOD = 5.39 at 72.7 cM and 4.24 at 34.46 cM, respectively). A QTL on chromosome 7H (LOD=2.04 at 81.07 cM) was suggested. All resistance alleles were derived from GZ. Evaluations of adult plant response in Corvallis, OR in 2013 and 2015 provided evidence of QTL at the same positions. However, the minor QTL on 4H was not statistically significant in either location/year, while the 7H QTL was significant in both. The SNP markers flanking the resistance QTL were validated in RILs from a 95SR316A x GZ cross for their ability to predict seedling resistance. In 95SR316A x GZ, 91-92% of RILs with GZ alleles at the major 4H QTL and at least one other were resistant to moderate in reaction. In these populations, at least two QTL were required to transfer the barley stripe rust resistance from GZ.

The genus Avena consists of approximately 30 wild and cultivated oat species. Cultivated oat is an important food crop, yet the broader genetic diversity within the Avena gene pool remains underexplored and underexploited. Here, we characterize over 9000 wild and cultivated hexaploid oat accessions of global origin using genotyping-by-sequencing and explore population structure using multidimensional scaling and population-based clustering methods. We also conduct analyses to reveal chromosome regions associated with local adaptation, sometimes resulting from large-scale chromosome rearrangements. We report four distinct genetic populations within the wild species A. sterilis , a distinct population of cultivated A. byzantina , and multiple populations within cultivated A. sativa . Some chromosome regions associated with local adaptation are also associated with confirmed structural rearrangements on chromosomes 1A, 1C, 3C, 4C, and 7D. This work provides evidence suggesting multiple polyploid origins, multiple domestications, and/or reproductive barriers amongst Avena populations caused by differential chromosome structure.

Stripe rust (incited by Puccinia striiformis f. sp. hordei) and stem rust (incited by P. graminis f. sp. tritici) are two of the most important diseases affecting barley. Building on prior work involving the introgression of the resistance genes rpg4/Rpg5 into diverse genetic backgrounds and the discovery of additional quantitative trait locus (QTLs) for stem rust resistance, we generated an array of germplasm in which we mapped resistance to stripe rust and stem rust. Stem rust races TTKSK and QCCJB were used for resistance mapping at the seedling and adult plant stages, respectively. Resistance to stripe rust, at the adult plant stage, was determined by QTLs on chromosomes 1H, 4H, and 5H that were previously reported in the literature. The rpg4/Rpg5 complex was validated as a source of resistance to stem rust at the seedling stage. Some parental germplasm, selected as potentially resistant to stem rust or susceptible but having other positive attributes, showed resistance at the seedling stage, which appears to be allelic to rpg4/Rpg5. The rpg4/Rpg5 complex, and this new allele, were not sufficient for adult plant resistance to stem rust in one environment. A QTL on 5H, distinct from Rpg5 and a previously reported resistance QTL, was required for resistance at the adult plant stage in all environments. This QTL is coincident with the QTL for stripe rust resistance. Germplasm with mapped genes/QTLs conferring resistance to stripe and stem rust was identified and is available as a resource to the research and breeding communities.