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Abstract
Soybean is one of the most widely grown crops in the world. The advent of genetic engineering in soybean has allowed genetic manipulation of soybean for a variety of modifications. Development of transgenic soybean plants is primarily through the use of particle bombardment to deliver DNA. This is because soybean is recalcitrant to the most commonly used method for genetic engineering, Agrobacterium-mediated transformation. Resistance to the microbe Agrobacterium by almost all soybean genotypes implicates the soybean immune system. A single line has been previously identified as extremely susceptible to Agrobacterium, the soybean accession Peking, identified as PI 548402. This accession is important for understanding how Agrobacterium susceptibility is controlled in most soybean varieties, thus opening the door to genetic engineering of more soybean varieties. Chapter one contains a brief history of soybeans in plant breeding and plant immunity, with a focus on previous work characterizing Agrobacterium and soybean interactions. Chapter two describes an identified candidate gene for susceptibility in soybean and subsequent testing with Agrobacterium, modified strains, and candidate gene knockouts. Chapter three details the development of a mapping population derived from a Peking x Century inbred line and a resistant line, Jack or PI 540556, to determine the regions of the genome responsible for susceptibility, with further analysis of candidate genes identified within this region using RNA-Seq. Collectively, these chapters address finding the genomic regions in soybean that control susceptibility to Agrobacterium, using this knowledge to identify what changes could be implemented in the future to make transformation of all soybean genotypes possible. With these goals in mind, the objective of expanding Agrobacterium susceptibility to previously restricted soybean genotypes can be accomplished.