DISSERTATION RESEARCH: The role of phyllosphere microbiomes in plant species coexistence and plant-pathogen interactions

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Microorganisms are species that are so small that you cannot see them with the naked eye. Microorganisms live all over the surfaces and inside of every type of larger organism on the planet, forming what is known as the "microbiome" of the larger hosts. This research will focus on the microbiomes of plants, which have profound impacts on plant health and performance. This research will focus on how microbiomes affect resistance of a host to another microorganism: a disease-causing fungus. By experimentally manipulating combinations of microbiomes, host species, and whether or not the disease-causing fungus is present, the researchers will be able to find out how microbiomes affect the ability of different plant species to compete with one another and to resist disease. By growing microbes found in natural microbiomes and by using state-of-the-art DNA sequencing approaches, they will begin to identify how important microbial players affect plant health. This project will involve the training of a graduate student in cutting-edge bioinformatics techniques. Because one outcome of this work will be to identify how and whether inoculating plants with the right microbiome protects against disease, the results from this work will also contribute to the development of new approaches to fighting costly pathogens in crops, and to helping land managers promote biodiversity in natural systems. In the past three decades, the plant-soil feedback framework has been used to achieve theoretical and empirical breakthroughs. Phyllosphere microbial communities, which reside in or on aboveground plant tissues, are similarly diverse, but current research suffers from an inability to connect presence and identity of phyllosphere microbes to larger ecological questions. In this project, researchers will test how pathogen infection alters the fitness and growth outcomes of con- vs. heterospecific phyllosphere microbial communities, with a focus on the fungal constituents of these microbiomes. Next-generation sequencing technologies will be combined with culture-dependent approaches to study the mechanisms of fungal community assembly in the phyllosphere. Functional trait data will be collected on select fungal cultures as metrics of plant-fungal and pathogen-fungal interactions. This trait-based approach will then be used to determine whether specific traits of the fungi measured in the lab can be used to understand their abundance and role on plants. This body of work has the potential to expand the scientific community's understanding of phyllosphere community assembly, and the mechanisms by which different phyllosphere communities inhibit or facilitate plant-species coexistence on their own or in conjunction with pathogens.