Decoding the enigma of the wheat resistance locus Fhb1

Fusarium head blight (FHB) is one of the most destructive diseases of wheat leading to severe losses in both yield and crop quality. Moreover, the causative fungi of the genus Fusarium produce toxins that accumulate in the grains and constitute a serious threat to food and feed safety. Hence, controlling this disease is of pivotal importance and growing resistant varieties is a sustainable, environmentally friendly and cost-effective approach. Fusarium head blight: State of research and challenges Although FHB resistance loci have been localized in the wheat genome more than 20 years ago, the genes controlling this disease are largely unknown. In wheat, gene isolation and functional validation are especially challenging due to the huge genome size and polyploidy, comprising of three genomes derived from einkorn and two goat grasses. The FHB resistance locus Fhb1 in particular The most prominent FHB resistance locus is Fhb1. It is highly effective, widely deployed in practical wheat breeding and present in current cultivars on the farmers fields. Fhb1 confers resistance to fungal spread in the wheat spike as well as to the major Fusarium toxin Deoxynivalenol by conjugation into a non-toxic glucoside. While the causal gene controlling fungal spread at this locus is under discussion, the regulation of the concomitant detoxification is completely unknown. Research focus of the project We aim to resolve this Fusarium resistance locus via genome editing and extensive gene expression analysis. The recent advent of CRISPR/Cas as a genome-editing tool also known as gene scissors has radically changed mutagenesis and enables targeted candidate gene screens with higher specificity compared to random mutagenesis induced by chemicals or irradiation. We will generate defined mutations via CRISPR/Cas in the candidate region and evaluate edited individuals for FHB and toxin resistance by infiltrating Fusarium spores or Deoxynivalenol directly in wheat florets. Mutations, which are leading to susceptibility and reduced toxin glycosylation will determine the hub of Fhb1-mediated resistance and unravel the underlying mechanism. Findings may be applicable to other crops such as barley or maize, also affected by the fungus and may result in major benefits for crop protection.