Evolutionary Phytopathology
Producing food sufficient in quality and quantity remains paramount for sustaining quality of life. Inadvertent introductions of phytopathogenic fungi have had dire consequences to nature and to cultivated crops on various continents in the past. The economic impact of such introductions can be seen in yield loss and in increased input costs for cultivation and disease control, as well as in social impact. To combat these diseases on an international scale, it is important to clarify whether the same species and genotypes occur in various countries, since each different species and genotype can be expected to have different patterns of attack, as well as different responses to fungicides and to climatological conditions. With such pathogens, it is also important to know what their host ranges and mating strategies are, and how this relates to different disease control mechanisms. The global movement of agricultural and forestry produce is inextricably cross-linked, and will continue to be so in future. Knowing which pathogens occur where and on what crops facilitates trade in agricultural produce. In this programme, we address these economically vital matters by investigating the speciation and host adaptation of various important phytopathogenic fungi.
A central theme of this programme concerns species concepts, host specificity, and the mechanisms underlying the process of speciation. The genomic variation within a fungal species is generally poorly understood. For instance, many important phytopathogenic fungi consist of numerous different phylogenetic lineages, which may represent different species that share the same morphotype. Fungal species evolve rapidly due to their short generation time. As a consequence of this rapid evolution new fungal species emerge. Such species may have acquired common or specific traits to enable them to be pathogenic on humans, animals or plants. Important research questions relate to mechanisms driving speciation. Mutating mating types and effectors governing pathogenicity/virulence represent some important mechanisms by which new species can evolve. These mutations will result in the (in)ability to mate and reproduce, which will affect gene flow between strains and pathogenicity on different host species. Knowledge about mechanisms of speciation and the impact of this on gene flow and variation in the fungal population will contribute to novel disease management strategies.
Our group studies the factors that drive speciation and evolution of novel fungal lineages, especially in the Dothideomycetes, a class of fungi that contains thousands of important plant pathogenic fungi. In fungi with a sexual phase in their life cycle, evolution of mating type and effector genes play an important role in speciation and host specialization. Sex and recombination, via the mating types, play an important role in generating variation, leading to novel lineages and speciation. Another aspect of research focuses on comparative genomics. Our group is actively participating in international consortia interested in comparative genomics of fungi belonging to the Dothideomycetes.