Stagonospora nodorum is a pathogenic fungus of wheat causing Stagonospora nodorum blotch disease, an important disease in western Canada. S. nodorum produces a multitude of host selective toxins (HSTs), which when recognized by corresponding sensitivity gene in wheat results in a compatible interaction. In this study, novel HST-host sensitivity gene interactions were investigated. Two different putative HSTs were identified. SnTox3 was likely one of the HSTs present in S. nodorum isolate Swift Current culture filtrate as the chromosomal location of the compatible sensitivity gene corresponded to that of Snn3 locus. Another putative HST interacting with Tsn1 or a tightly linked sensitivity gene was identified from S. nodorum isolate Langham. SNOG_15679, a candidate gene for production of this putative HST was heterologously expressed in Pichia pastoris which caused chlorosis on a sensitive host. Additional tests will be required to confirm the bioactivity of putative novel HST(s) produced by isolate Langham. / May 2015

Stagonospora nodorum is a necrotrophic fungal pathogen, and the causal agent of stagonospora nodorum blotch of wheat. Despite the economic importance of this disease, the molecular basis of the pathosystem is poorly understood. The aim of this study was to investigate the interaction between metabolism and infection in this pathosystem, with particular reference to the metabolism of mannitol. In common with many fungi, the main metabolite produced by S. nodorum is the acyclic hexitol mannitol. Among the previously suggested roles for this compound is a role in pathogenicity. The metabolism of mannitol has been hypothesised as occurring in a cycle involving the enzymes mannitol 2-dehydrogenase (Mdh1) and mannitol 1-phosphate 5 dehydrogenase (Mpd1). A strain was created harbouring disruption constructs for both of these genes. The double mutant was unable to synthesise or catabolise mannitol, and was unable to sporulate. Addition of exogenous mannitol completely restored in vitro sporulation, and partially restored in planta sporulation. This demonstrated an essential role for mannitol in asexual sporulation. This is the first demonstrated role for this compound. A 13C NMR study of the wild type strain, the mdh1 and mpd1 single mutants, and mpd1mdh1 double mutant was undertaken to investigate carbon utilisation and cycling. Disruption of Mpd1 significantly altered the metabolite profile with the mpd1 mutants producing trehalose and glycerol in place of mannitol. Labelling patterns in the double mutant showed that scrambling of label can be explained by the triosephosphate isomerase triangle and pentose phosphate pathway. This suggests the contribution of mannitol to label scrambling has been overstated in previous studies. The evidence did not support the metabolism of mannitol in S. nodorum as occurring in a cycle, but rather as two separate pathways. A GC-MS analysis of diseased and non-diseased tissue from infected leaves, compared to non-infected and mock-inoculated leaves, could not detect any metabolites associated with a systemic host reaction to pathogen attack.

Thesis (Ph.D.)--Murdoch University, 2008. / Thesis submitted to the Faculty of Health Sciences. Includes bibliographical references (leaves 243-296)

Stagonospora nodorum is a necrotrophic fungal pathogen that is the causal agent of leaf and glume blotch on wheat. Very little is currently known about the molecular mechanisms required for pathogenicity of S. nodorum, despite its major impact on Australian agriculture. S. nodorum is a polycyclic pathogen. Rain-splashed pycnidiospores attach to and colonise wheat tissue and subsequently sporulate within 2-3 weeks. Several cycles of infection are needed to build up inoculum for the damaging infection of flag leaves and heads, sporulation is therefore a critical component of the infection cycle of S. nodorum; our aim is to determine the genetic and biochemical requirements for sporulation for development of control of the pathogen. Disease progression of S. nodorum on wheat cv. Amery was monitored by light microscopy to determine the time point when pycnidia development began. Early pycnidia development was evident 12 days post-infection. This information was used to guide a genomics and a metabolomics based approach to determine the requirements for sporulation in S. nodorum. The genomics approach utilised two cDNA libraries created from sporulating and non-sporulating cultures. EST frequency was used to determine highly expressed genes under the two developmental states. Gene expression from the most highly represented genes during sporulation were confirmed using quantitative PCR. A gene encoding an arabitol 4-dehydrogenase (Abd1), was mutagenised, in its absence sporulation was reduced by approximately 20%. The metabolomics approach isolated metabolites from both in planta infection and in vitro growth. Rapid changes in the abundance of metabolites were detected during the onset of sporulation. Key fungal metabolites identified include mannitol and trehalose. The concentration of both mannitol and trehalose increased dramatically in concert with pycnidia formation. Both mannitol and trehalose have also been linked to pathogenicity in filamentous fungi. Creation of deletion mutants of the gene encoding trehalose 6-phosphate synthase showed the synthesis of trehalose is required for full sporulation of S. nodorum in planta and in vitro.

Thesis (Ph.D.)--Murdoch University, 2006. / Thesis submitted to the Division of Science and Engineering. Includes bibliographical references (leaves 330-343).

Thesis (Ph.D)--Murdoch University, 2007. / Thesis submitted to the Divsion of Health Sciences. Includes bibliographical references (leaves 215-250).

Thesis (Ph.D.)--Ohio State University, 2005. / Title from first page of PDF file. Document formatted into pages; contains xxi, 195 p.; also includes graphics. Includes bibliographical references (p. 184-195). Available online via OhioLINK's ETD Center

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The thesis deals with important pathogens affecting winter wheat, in particular the speckled glume and leaf blotch on wheat(Phaeosphaeria nodorum), septoria leaf blotch on wheat(Mycosphaerella graminicola)and tan spot on wheat(Pyrenophora trtici-repentis. It outlines the biology, symptoms that appear on wheat plants, and economic importance of these diseases and emphasizes the climatic conditions needed for their development and spread .The conclusion sumarizes the occurence data of the above-mentioned 3 diseases from 3 production(corn, beetroot and potato) areas and 4 districts (2 Moravian and 2 Bohemian districts per each production area) in the period of 1971 to 2010 and compares their frequency of occurrence. That work also includes the occurrence data of the diseases from 2012 when their occurrence on winter wheat was monitored at the training experimental station of the Mendel University in Brno in Žabčice.

T. aestivum ssp. spelta Iranian type has long been thought to potentially be the direct non-free threshing hexaploid progenitor. I evaluated a RIL population derived from a cross between CS and Iranian spelta accession P503 to identify loci suppressing free-threshabilty in P503. Identification of QTL associated with threshability in region known to harbor the Tg2A gene, and an inactive tg2D allele supported the hypothesis of Iranian spelta being derived from a more recent hybridization between free-threshing hexaploid and emmer wheat. Parastagonospora nodorum is an important fungal pathogen and secretes necrotrophic effectors that evoke cell death. In this research, a DH population segregating for Snn5 was used to saturate Snn5 region of chromosome 4B with molecular markers. The physical distance between Snn5 flanking markers was narrowed to 1.38 Mb with genetic distance of 2.8 cM. The markers developed in this study will provide a strong foundation for map-based cloning of Snn5.