Introduction and persistence of arbuscular mycorrhizal fungal inoculum

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Worldwide, there is increasing use of biofertilizers, in particular arbuscular mycorrhizal (AM) fungal inoculants. In nature, these root-dwelling fungi are essential, providing their host plants with a benefits such as improved nutrient uptake, water relations and pathogen defense. Because of these benefits, there is a global industry for AM fungal biofertilizers, and they are marketed for use in agriculture, gardening and landscape restoration. ***Despite the increased uptake by growers around the world, there is little to indicate that these inoculants promote plant or soil health. Further, these inoculants have not been properly vetted, so evidence for their efficacy is scant, incomplete, or lacking altogether. Basic questions about their performance remain to be answered: What are the factors that determine establishment success? Can growers ensure a positive outcome? Currently, there are no recommendations for growers on best practices, nor can they monitor inoculation success. ***Perhaps more troubling is that the scientific community has almost no idea of the consequences of biofertilizer use. Only a small number of AM fungal genotypes are commercially produced. These isolates have undergone intense selection for aggressive growth and generalist growth habit. These traits render them an invasion threat, but there is no information on the fate of these inoculants in natural systems.***My research looks at factors affecting inoculant establishment and persistence in a novel system. Using greenhouse and field studies, I will use plant and fungal traits to predict which fungi are most likely to establish and persist in the field. Specifically, I will track the inoculation for commercial and local fungi using molecular probes under different host and soil scenarios. I will test for invasion risk by surveying dispersal vectors in real-world agricultural settings, using molecular probes to track the inoculants. Additionally, in a global survey, I will establish baseline occurrence for the world's most widely used AM fungal biofertilizer. Finally, using Next Generation Sequencing, I will evaluate how these introductions affect the local fungal communities.***Currently, the use of AM fungal biofertilizers represents at best a financial risk for growers. At worst, these inoculants may perturb local soil and plant communities, possibly disrupting ecosystem functioning. This is a clear case where industrial practices are not supported by scientific knowledge. The ethical, and economic implications of such oversight are profound, ranging from customer quality assurance to soil biodiversity and ecosystem functioning. ***The products of this research will help inform both practitioners and policy makers about the use of AM fungal inoculum. It will also help form the basis of a best practices tool for growers wishing to use AM fungal inoculum.