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Aegilops tauschii, the diploid wild progenitor of the D subgenome of bread wheat, is a reservoir of genetic diversity for improving bread wheat performance and environmental resilience. Here we sequenced 242 Ae. tauschii accessions and compared them to the wheat D subgenome to characterize genomic diversity. We found that a rare lineage of Ae. tauschii geographically restricted to present-day Georgia contributed to the wheat D subgenome in the independent hybridizations that gave rise to modern bread wheat. Through k-mer-based association mapping, we identified discrete genomic regions with candidate genes for disease and pest resistance and demonstrated their functional transfer into wheat by transgenesis and wide crossing, including the generation of a library of hexaploids incorporating diverse Ae. tauschii genomes. Exploiting the genomic diversity of the Ae. tauschii ancestral diploid genome permits rapid trait discovery and functional genetic validation in a hexaploid background amenable to breeding.

Wheat powdery mildew is an important fungal pathogen of wheat with an obligatory biotrophic lifestyle (a parasite that can only develop on a living host). We investigated the genetics of this host-pathogen interaction by using phenotyping and PCR assays to detect genes in both wheat and powdery mildew, which are known determinants of the outcome of these interactions (resistance or susceptibility). The mildew genes increase or decrease the pathogen virulence, while the wheat genes provide specific immunity against the mildew isolates expressing the corresponding avirulence genes. Here, we describe the experiments performed to understand the genetic basis of race-specific resistance of wheat to powdery mildew, which is part of the course 'Mechanisms of Plant Disease Resistance against Fungal Pathogens' designed for advanced third-year students of biology at the University of Zurich, Switzerland. In this course, students learn how plants and their pathogenic fungi engage in an arms race against each other to survive. [ABSTRACT FROM AUTHOR]

Plant genomes have evolved several evolutionary mechanisms to tolerate and make use of transposable elements (TEs). Of these, transposon domestication into cis-regulatory and microRNA (miRNA) sequences is proposed to contribute to abiotic/biotic stress adaptation in plants. The wheat genome is derived at 85% from TEs, and contains thousands of miniature inverted-repeat transposable elements (MITEs), whose sequences are particularly prone for domestication into miRNA precursors. In this study, we investigate the contribution of TEs to the wheat small RNA immune response to the lineage-specific, obligate powdery mildew pathogen. We show that MITEs of the Mariner superfamily contribute the largest diversity of miRNAs to the wheat immune response. In particular, MITE precursors of miRNAs are wide-spread over the wheat genome, and highly conserved copies are found in the Lr34 and QPm.tut-4A mildew resistance loci. Our work suggests that transposon domestication is an important evolutionary force driving miRNA functional innovation in wheat immunity. [ABSTRACT FROM AUTHOR]