Bilateral BBSRC-EMBRAPA: Using Disease Risk Forecasting, NGS and HIGS to Explore and Control Fusarium Head Blight (FHB) Disease in Wheat Fields

Fusarium head blight (FHB), caused the fungus Fusarium graminearum and related species, is one of the most serious and hazardous crop diseases worldwide. The main consequence of FHB is that fungal trichothecene mycotoxins, such as deoxynivalenol (DON), accumulate in the grain, presenting a health risk to humans, farmed animals and natural ecosystems. In Southern Brazil, the UK and elsewhere, severe FHB epidemic years occur in cereal crops at a minimum of every 4 or 5 years, when wet weather prevails during crop flowering. Current control strategies are inadequate and leave crops and the harvested grain at risk.  

For the effective and sustainable control of FHB disease, a new multifaceted approach is required. Here we describe a recently funded bilateral UK-Brazil project in which we intend to take a novel whole fungal genome and disease risk modelling guided biotechnology approach (HIGS), in which we will engineer wheat plants to produce double stranded RNA molecules, which enter into the fungal cells early during plant infection and silence or switch off essential fungal genes. This should perturb the infection process and minimise disease establishment. We also intend to determine the plant and fungal mechanisms that control the HIGS phenomenon. Potentially, genome sequence guided HIGS could be developed to control multiple pathogens.

The following five research objectives will be pursued in this project:

• To explore the genomes of FHB causing species in Southern Brazil. Define the core and species-specific proteome of the FHB species complex (FGSC) for the development of molecular diagnostic tools and the selection of genes from those species that can be used as a target for HIGS. 
• To enhance FHB risk forecasting, establish a spore sampler network that can detect and quantify Fusarium species. Airborne Fusarium spore population will be determined using stored tapes from an air suction trap and various species and gene specific qPCR analyses. We will Incorporate data on the dynamics of airborne Fusarium spore populations into the existing FHB model, improving the framework for assessing pathogen-host-environment interactions.
• To develop various T-DNA based constructs to silence F. graminearum gene expression by HIGS and thereby control Fusarium infection.  Evaluate single gene HIGS constructs using stable transformation into Arabidopsis. Two lead HIGS constructs will be developed to silence simultaneously three F. graminearum gene and transform these into the moderately FHB resistance Brazilian wheat cultivar Guamirim. FHB resistance will be characterised in the resulting transgenic plant populations.
• To understand the underlying mechanisms to achieve HIGS in F. graminearum and the related species F. culmorum.  Our hypothesis is that distinct plant and fungal mechanisms regulate HIGS, and to confirm that, we will use Arabidopsis lines harbouring specific constructs/ single gene mutations and evaluate a F. graminearum strain that lacks functional dicer genes. 
• To perform two years of GM wheat trial in two locations in Brazil. Each trial will include the best four transgenic BRS Guamirim wheat lines at the T3 or T4 generation harbouring a different multi-target HIGS construct. Assessments will include in-field FHB symptom quantification, temporal quantification of airborne Fusarium inoculum, grain quality analyses, DON contamination quantification and subsequently sexual fungal spore production from grain samples. In addition, Fusarium isolates able to cause any disease on the HIGS lines will be collected and a full genome analyse completed.

This new approach should help to further optimise the construction, deployment and re-use of HIGS multi-gene cassette for the sustainable control of various plant diseases.