Investigating Microbial Interactions in the Wheat Phyllosphere: Uncovering the Influence of Epiphytes on Zymoseptoria tritici Pathogenicity

This is one of the funded projects for our 2025 Undergraduate vacation bursary, click here to return to the list of 15 projects.

This project is going to be…	Experimental (lab/field based)
Institute	University of Exeter
Project supervisor	Dr. Graham Thomas
Title of Project	Investigating Microbial Interactions in the Wheat Phyllosphere: Uncovering the Influence of Epiphytes on Zymoseptoria tritici Pathogenicity
Date of Project Commencement	16 June 2025
Duration (weeks)	8
Brief Description of Project	Zymoseptoria tritici, the causal agent of Septoria tritici blotch (STB), is a major fungal pathogen of wheat, leading to significant global yield losses. While host resistance and environmental factors are well-studied, the role of microbial communities in the wheat phyllosphere in modulating Z. tritici pathogenicity remains poorly understood. This project investigates interactions between Z. tritici and co-occurring epiphytic bacteria and fungi isolated from UK field-grown wheat. Using in-vitro confrontation assays, the project aims to identify microbial strains that inhibit or promote Z. tritici growth, offering insights into potential biocontrol agents or microbial facilitators of infection.The leaf surface is an underexplored niche, where our understanding of the influence of microbial consortia on plant-pathogen interactions is currently limited. My research aims to change this (Thomas et al, 2024), and this project will explicitly address the relationships of epiphytic microbes with Z. tritici and thus STB disease. Identifying antagonistic microbes will contribute to sustainable disease management strategies, while discovering synergistic interactions may reveal novel mechanisms underlying Z. tritici’s adaptability. The project aims to advance understanding of a plant disease and it’s ecological contexts, with direct relevance to food security and agricultural sustainability. MethodsThe project combines in-vitro microbial interaction assays with functional and molecular characterisation of key isolates: Confrontation Assays:Dual-culture assays will assess interactions between Z. tritici and epiphytes. Fungal growth inhibition/promotion will be quantified using ImageJ for radial growth measurements, while hyphal morphology and spore germination will be analysed by light microscopy. Functional Characterisation:• Growth curves of selected strains will assess competitive advantage on different media e.g. carbon sources present on leaves, nitrogen sources, leaf waxes and leaf surface extracts. • Bacterial strains will be screened for siderophore production using chrome azurol S (CAS) agar assays.Molecular Identification and Phylogenetic Analysis: • Genomic DNA from bacterial/fungal isolates will be extracted, and 16S rRNA (bacteria) or ITS (fungi) regions amplified using universal primers.• PCR products will be sequenced and compared to NCBI databases for genus/species-level identification. • Phylogenetic trees will be generated to assess relationships between isolates with varying antagonistic/synergistic activity.This studentship offers interdisciplinary training in plant pathology, microbiology, and data science. The student will: • Gain hands-on experience in culturing plant pathogens and epiphytes.• Enhance analytical skills through quantitative data interpretation. • Contribute to high-impact research with real-world applications.• Present findings in a final report and lab meeting, building scientific communication skills Recommended reading for the projectThomas et al. (2024). Life on a Leaf: Critical review of phyllosphere microbial ecology and pathogen interactions. Francisco et al. (2023) [bioRxiv]: The apoplastic space of two wheat genotypes provide highly different environment for pathogen colonization: Insights from proteome and microbiome profiling.Seybold et al. (2020). A fungal pathogen induces systemic susceptibility and systemic shifts in wheat metabolome and microbiome composition. Vorholt et al. (2012). Microbial life in the phyllosphere.