Comparative pathogenomics in the ascomycete plant pathogens Zymoseptoria tritici and Verticillium dahliae

During host colonization, plant pathogens secrete molecules that enable host colonization —so called— effectors. Over the last decade, considerable attention in research on plant-microbe interactions has focused on understanding how pathogens adapt their effector gene repertoires to their host plants. In this thesis, the adaptation of the fungal pathogen Zymoseptoria tritici that is specialized on wheat plants is described and compared to the fungal pathogen Verticillium dahliae that is able to colonize a broad range of host plants. For V. dahliae, the core and lineage-specific (LS) effector genes were determined showing that strains that are able to infect the same host plant harbour highly divergent LS effector repertoires. Of the identified LS effectors, the Sun1 effector gene was shown to contribute to V. dahliae 85S virulence on sunflower. For Z. tritici, genome-wide assessment of bread and durum wheat isolates has showed extensive genetic diversity amongst Z. tritici isolates and revealed four effector candidates in bread wheat isolates. Moreover, genome-wide assessment of virulent and avirulent Z. tritici isolates on the bread wheat cultivar Shafir has led to the identification of the avirulence effector gene AvrStb6. Thus, pathogens adapt their effector gene repertoires to their host plants, which can subsequently be utilized to establish durable and broad-spectrum resistance.