Stable transformation of Erysiphe graminis an obligate biotrophic pathogen of barley

Barley powdery mildew, Erysiphe graminis f.sp. hordei , is an obligate biotrophic pathogen and as such cannot complete its life cycle without a living host. The inability to transform this fungus and manipulate its genome has constrained research towards understanding its life cycle and pathogenicity. Here we describe an in planta transformation system based on delivery of DNA using a gold-particle gun and selection using benomyl or bialaphos. Using this method, we consistently obtained stable transformants with efficiencies comparable to other filamentous fungi. Stable expression of the β-glucuronidase in E. graminis was demonstrated by co-transforming the uidA gene with the selectable markers.