Chapter Four - The Genomics of Powdery Mildew Fungi: Past Achievements, Present Status and Future Prospects

Abstract

Abstract Powdery mildew fungi (Ascomycota phylum) are obligate biotrophic plant pathogens that can only grow and reproduce on living host cells. They infect a wide range of plants, including many crops and the diseases they cause are common, easily recognizable and widespread. Although functional investigations in these genetically intractable organisms have been hampered by their obligate biotrophic nature, recent advances in genomics and transcriptomics have contributed tremendously to our understanding of powdery mildew biology. Comparative genomics was a powerful tool to pinpoint what distinguishes powdery mildew fungi from other filamentous plant pathogens and helped us to better understand how obligate biotrophy evolved. Comparative genome analyses among isolates in both the wheat and the barley powdery mildew lineages revealed isolate-specific mosaic genome structures of evolutionary young and old haplogroups. In addition to providing hints into the evolutionary origin of powdery mildew fungi, the observed mosaic genome structure also reflects the reproductive mode of these pathogens and explains how the large standing genetic variation is generated in powdery mildew populations. In this chapter, I discuss how the revolution in genomics has contributed and will contribute in the future to better understand the obligate biotrophic lifestyle, the virulence arsenal, the reproductive mode and the evolutionary history of powdery mildew fungi.