My main research interests are in the area of host-parasite interactions, particularly in the role of host-specific toxins in fungal pathogenicity and plant disease development. Our work has focused on the purification, characterization and mode of action of Ptr ToxB, a host-specific toxin produced by Pyrenophora tritici-repentis, the causal agent of tan spot of wheat. We have recently also began exploring the basic pathogenic ability of virulent and avirulent isolates of the pathogen, and its relationship to toxin production. Furthermore, since my arrival at the University of Alberta, my interests have expanded beyond the tan spot pathosystem to include a number of other areas in plant pathology. Of particular importance has been our work on clubroot of crucifers, caused by Plasmodiophora brassicae, which is an emerging disease of canola in Alberta. Given the recent occurrence of this disease in the province, the scope of our research on clubroot has ranged from the basic to the applied. We have examined questions related to pathotype composition and diversity in populations of the pathogen from Alberta and throughout Canada, and have initiated work on molecular changes induced in susceptible canola genotypes in response to infection. In addition, we have started field research aimed at developing an integrated management strategy for control of clubroot on canola. This latter component of the work is closely related to a third area of recent interest, the development of integrated management strategies for dealing with root diseases of field crops in general. In order to strengthen and complement our research capabilities, I have established collaborations with a number of researchers at this University and at other institutions, both at the provincial and national level.