"Soybean sudden death syndrome, caused by Fusarium virguliforme, is a key limitation in reaching soybean (Glycine max) yield potential, stemming from limited disease management through cultural practices and partial host resistance. The research within this thesis reveals the economic potential of fungicide seed treatment SDS fluopyram to alleviate yield loss, provides insights into field management of F. virguliforme and highlights transcriptomic plasticity of diverse host-fungal interactions. Previously, farm level studies have found the fungicide seed treatment of fluopyram profitable, yet the benefit across an aggregate level of soybean production at risk to SDS yield loss is unknown. To estimate economic benefits of fluopyram adoption in SDS at risk acres, in the light of U.S public research and outreach costs, an economic surplus approach was applied to calculate ex ante net benefits from 2018 to 2032. Through this framework of fluopyram adoption for alleviation of SDS associated yield losses, we estimated a net benefit of $5,829 million over 15 years, considering public seed treatment research costs from 2014 to present and future extension communication. While chemical seed treatments aid disease management of SDS, the ability of this pathogen to colonize asymptomatic hosts may increase the prevalence of F. virguliforme. Thus, the impact of cultural tactics upon F. virguliforme colonization of an asymptomatic host, and the ability of this colonization to alter subsequent SDS symptoms when rotated to soybean were explored. The exploration of tillage, and residue management across four U.S. states provided clarity to variable reports, revealing that no-tillage inconsistently enhances F. virguliforme colonization of corn and soybean roots, while corn residue did not alter pathogen colonization. Alternatively, an asymptomatic host provides a unique application to discover genetic factors facilitating soybean sudden death syndrome through investigation host-fungal interactions. Exploring this plant disease through a comparative orthologous mRNA-Seq on soybean and corn hosts under colonization of F. virguliforme uncovered transcriptional responses enabling a robust defense response in corn, and delayed immune induction within soybean permitting pathogenic colonization and susceptibility. To colonize both hosts, F. virguliforme exhibited a massive transcriptional rewiring of an infection program. Transcriptomic responses suggest, F. virguliforme is less suited for colonization of monocots by delayed colonization, and lower induction of CAZymes and effector proteins. Integration of the data generated through the mRNA-Seq experiments, including a micro-like RNA-Seq analysis of soybean host during colonization by F. virguliforme revealed an intimate communication between the plant and fungal pathogen; we posit that a micro-like RNA cross-talk potentially regulates host susceptibility. Overall, several hypotheses were generated surrounding hemibiotrophic enhancement of host senescence, and fungal ecological plasticity through transcriptomic reprogramming, which will deliver transparency upon a currently difficult and enigmatic syndrome."--Pages ii-iii.
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