A fictional field case study to understand the genetic basis of host-fungal pathogen interactions using the wheat powdery mildew-wheat pathosystem

Wheat powdery mildew is an important fungal pathogen of wheat with an obligatory biotrophic lifestyle (a parasite that can only develop on a living host). We investigated the genetics of this host-pathogen interaction by using phenotyping and PCR assays to detect genes in both wheat and powdery mildew, which are known determinants of the outcome of these interactions (resistance or susceptibility). The mildew genes increase or decrease the pathogen virulence, while the wheat genes provide specific immunity against the mildew isolates expressing the corresponding avirulence genes. Here, we describe the experiments performed to understand the genetic basis of race-specific resistance of wheat to powdery mildew, which is part of the course 'Mechanisms of Plant Disease Resistance against Fungal Pathogens' designed for advanced third-year students of biology at the University of Zurich, Switzerland. In this course, students learn how plants and their pathogenic fungi engage in an arms race against each other to survive.