Host-Induced Gene Silencing Using BPMV on Soybean to Study Genes in the Soybean Rust Fungus Phakopsora pachyrhizi

To obtain direct evidence for the influence of an effector on the virulence or pathogenicity of a pathogen, it is necessary to knock out, knock down, or silence the respective gene. Since genetic transformation is not yet possible for rust fungi, silencing the gene is the only option. Posttranscriptional gene silencing uses RNAi. RNAi in plant pathogens can be accomplished by introducing dsRNA either by direct application of in vitro synthesized dsRNA or through positive-strand or double-strand RNA plant viruses. For studying effectors in Phakopsora pachyrhizi, we have implemented a host-induced silencing procedure based on virus-induced gene silencing using the bean pod mottle virus system. Here, procedures and interpretations of results are described and limitations of the system are discussed.