Wheat stem rust is a devastating disease caused by the fungus Puccinia graminis f. sp. tritici.
Recent epidemics in Africa, Europe and Asia threaten regional and global food security.
Resistance is often conferred by just a single gene in a certain wheat cultivar; this facilitates the evolution of resistance-breaking pathogen strains. Deployment of cultivars carrying multiple (stacked) resistance genes would delay the evolution of pathogen virulence.
During infection, the pathogen secretes proteins called effectors which suppress host immune responses and modify various host cell processes to enable host colonisation.
However, when the host carries an immune receptor that recognises one of the fungal effector proteins this can trigger a defence response that halts pathogen spread. These effectors recognised by host immune receptors are called avirulence effectors.
Ngoni’s research is focused on cloning avirulence effectors corresponding to broad-spectrum immune receptor genes. Such effectors could be used as tools to confirm the function of individual genes in multi-gene stacks, and to generate molecular probes for studying effector diversity and population dynamics, thus allowing more judicious deployment of the corresponding resistance genes in breeding programmes.