Crop Science Seminar: Dissection of Wheat-Septoria Interactions

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• Dr Kostya Kanyuka, Head of Pest & Pathogen Research, NIAB
• Wednesday 16 March 2022, 10:30-11:30
• Online.

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Septoria tritici blotch (STB), is one the most important foliar diseases of wheat in the UK and globally. This disease is caused by the ascomycete fungus Zymoseptoria tritici (also known as Septoria tritici), a pathogen with a very interesting infection biology which includes penetration of leaves exclusively through stomata followed by colonisation of the extracellular spaces (apoplast). Moreover, Z. tritici could be described as a “latent necrotroph”. That is, this fungus behaves as a biotroph during the first prolonged asymptomatic infection phase lasting >10-14 days and then rapidly transitions to necrotrophy killing the infected wheat leaf cells, which release the nutrients required for the fungus to proliferate and sporulate. What induces the transition to necrotrophy is an important big question in the biology of this pathogen, which currently remains unanswered. In the first part of my talk, I will pose hypotheses to explain this phenomenon and present and discuss data from the experiments addressing these hypotheses. I will also describe the plant virus-based functional genomics tools and resources we established and/or developed to aid the experimentation, which incidentally helped accelerate the pace of gene discovery in the wheat – Z. tritici pathosystem (and beyond).

Management of STB in wheat traditionally relies on fungicides that are typically applied thrice during the growing season. This repeated application has led to the fungus evolving resistance to all major classes of fungicides. With the additional problem of some of the potent chemistries being phased out due to the changes in regulations, significant efforts were put on breeding for disease resistance to Z. tritici in recent years. Understanding the mechanisms of natural disease resistance operating in wheat against this important fungal pathogen, both at mechanistic and molecular levels, is also very important as this knowledge could help develop new, effective STB disease control strategies. In the second part of my talk, I will focus on Stb6 – the wheat disease resistance gene that has been deployed by breeders for several decades. Interestingly, by contrast to the many known intracellular NLR -type disease resistance genes, Stb6 controls resistance without cell death. We have recently isolated this gene and showed that it encodes a cell wall-associated receptor-like kinase (WAK) protein resembling extracellular immunity receptors that often recognise conserved pathogen derived molecules, and this fits well with the pathogen’s apoplastic lifestyle. However, Stb6 somehow or rather recognises the highly variable small, secreted protein produced by Z. tritici. I will present our latest experimental data that has led us to propose a speculative hypothesis regarding the molecular mechanism of Stb6-mediated resistance.

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This talk is part of the Plant Sciences Departmental Seminars series.

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