Discovery of Fusarium Graminearum Resistance in Aegilops tauschii Germplasm and Introgression into Wheat.

Discovery of genetic resistance to fusarium head blight (Fhb), caused by Fusarium graminearum, is vital for the continued improvement of modern wheat. In this study, 109 accessions of the wheat D-genome progenitor species Aegilops tauschii Coss. were screened for Fhb resistance. Greenhouse grown Ae. tauschii were infected with F. graminearum by single-floret inoculation (SFI) and disease severity was rated as the percentage of infected spikelets at 21 day post-inoculation. An apparent relationship was identified between the geographical origins of Ae. tauschii accessions and Fhb resistance. Higher levels of Fhb resistance were observed in accessions collected from regions bordering the Caspian Sea that receive higher levels of annual rainfall. In total, 12 resistant to moderately resistant Ae. tauschii accessions were identified. One accession, TA1662, with moderate resistance to Fhb was crossed directly with the hexaploid wheat line KS05HW14 and backcrossed to restore typical D genome segregation. A population of 141 BC₂F_4:7 introgression lines (ILs) was planted in a replicated headrow nursery in Mason, MI, in 2015, and Fhb incidence and severity were recorded. DNA was isolated from the ILs, genotyping-by-sequencing was performed, and linkage maps of introgressed loci were constructed. QTL analysis identified a QTL for Fhb severity on the proximal portion of 7DL. Lines fixed for the Ae. tauschii allele at the 7DL QTL had lower average Fhb severity than those fixed for the wheat allele. Then, using SFI under greenhouse conditions, three lines fixed for the Ae. tauschii allele at the 7DL QTL were compared to three lines fixed for the wheat allele. Those fixed for the Ae. tauschii allele had lower disease severity and fewer fusarium damaged kernels (P-value < 0.05). The resistant germplasm identified and developed in this study will support long-term Fhb resistance breeding efforts.