Necrotrophic Pathogens of Wheat

Abstract

Wheat diseases are caused by a wide range of organisms. Among the economically most significant are the necrotrophic pathogens from the order Pleosporales: Pyrenophora tritici-repentis and Parastagonospora nodorum. They cause the diseases tan spot and Septoria nodorum blotch, respectively. They are the top two diseases in Western Australia and probably underreported in other parts of the world. Recent molecular research has developed a novel understanding of these pathogens. They produce secreted effectors (mostly proteins) that induce necrotic symptoms on sensitive genotypes of wheat. Recognition in wheat is encoded by specific sensitivity loci. The amount of disease is a function of the number of effectors produced by the pathogen for which matching recognition alleles are expressed in the wheat cultivar. This understanding has opened up a new rationale for wheat disease breeding that relies on the removal of sensitivity alleles from wheat germplasm.