Wheat blast symptoms: the fungal disease attacks the spikes or heads of wheat plants, causing them to become blighted and turn a whitish-brown colour.
The team found that the wheat resistance genes Rwt3 and Rwt4 regulate defence molecules that recognize the fungal proteins PWT3 and PWT4 respectively.
Further experiments showed that wheat plants in which the function of one of these resistance genes was lost were susceptible to wheat blast, confirming the hypothesis that the first wheat blast epidemics in Brazil occurred due to the widespread cultivation of wheat varieties lacking Rwt3.
The scientists were able to use their analyses to learn more about the evolution of the interactions between different pathogens and wheat genes. For example, they found that Rwt4 is related to another gene, called Pm24, which confers resistance against another wheat disease called powdery mildew.
“The mechanism by which Rwt3 and Rwt4 recognise PWT3 and PWT4 is not known, but we have initiated research to establish how the fungal and host components interact with one another. The technologies are being used to identify genes that confer resistance against pathogens present in Bangladesh and Zambia,” says Paul Nicholson from the John Innes Centre in the United Kingdom, who co-authored this study, with Brande Wulff from King Abdullah University of Science and Technology, in Saudi Arabia.
“The discovery of two wheat resistance genes is hugely significant in light of our limited understanding of the genetic basis of wheat blast specificity. The potential for the emergence of highly virulent and aggressive blast strains is unknown and requires further study," says plant pathologist, Md. Motaher Hossain from the Bangabandhu Sheikh Mujibur Rahman Agricultural University in Bangladesh, who was not involved in this study.
Arora, S. et al. A wheat kinase and immune receptor form the host-specificity barrier against the blast fungus. Nat. Plantshttps://doi.org/10.1038/s41477-023-01357-5 (2023).