Scientists studied two species of fungi called Arachnopeziza that are closely related to powdery mildew fungi but can grow independently on simple lab media. By analyzing their complete genomes and developing techniques to genetically modify these fungi, researchers created a new tool for understanding how powdery mildew fungi became dependent on plants. This breakthrough allows scientists to study these harmful plant pathogens more effectively without having to work directly with the difficult-to-cultivate powdery mildew fungi.