Evolutionary and molecular basis of host adaptation in fungal plant pathogens: insights from Zymoseptoria pathosystems
Host adaptation is considered a strong driver of pathogen evolution. With the ongoing development of modern agriculture, it is clear the importance in applying evolutionary analyses to access the risk of potential future pathogens, particularly in pathosystems that transition between wild and agricultural environments. Implementing population and functional genomics, transcriptome and infection assay approaches, we aimed to identify evolutionary and phenotypic patterns of host adaptation in fungal plant pathogens using the fungal pathogen Zymoseptoria tritici as a model of study. Unique collections of Z. tritici were isolated from wild (Aegilops spp.) and domesticated (Triticum aestivum) grass hosts, and different genomic and virulence-related aspects have been studied to identify key genomic traits playing a role in host adaptation of Z. tritici specimens in these different hosts. In Chapter 1, I describe methods to handle Z. tritici in laboratory and greenhouse conditions that are used throughout different experiments in the scope of this thesis. In Chapter 2, I focus on population genomics and virulence analyses of these host-diverging Z. tritici populations and reveal particular features of the Aegilops-infecting population that may have shaped its host adaptation and evolutionary history. In Chapter 3, I describe a new chromosome present in Aegilops-infecting Z. tritici isolates and propose its possible origin from introgression events with the closely related fungal species Zymoseptoria ardabiliae. Finally, in Chapter 4, I outline functional genetics analyses of candidate genes for host adaptation in the Aegilops-infecting Z. tritici population. As a foreseen impact, the results hereby generated are of relevance for translational evolutionary biology and plant pathology, highlighting the potential interaction between pathogens of wild and cultivated plants and a possible route of new pathogen lineages emergence.