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Abstract
Increasing grain yield in soybean (Glycine max (L.) Merrill) is the primary objective of soybean breeding but increasing yield has been a challenge due to its complex, quantitative nature and interaction with environments. This research focuses on utilization of genomic tools to identify genomic regions under breeding selection; develop a methodology for selection of yield and seed composition traits; and development of a high yielding germplasm line with diverse pedigree. PI 416937 is a Japanese plant introduction which has been utilized in the development of many high yielding lines over the past ~20 years. Nine genomic regions were identified from this PI under positive selection while 17 genomic regions were identified under negative selection. These genomic regions were not significantly associated with yield across replicated yield trials, but a methodology was illustrated for identifying regions under selection for yield and utilizing these regions for incorporation of beneficial diversity. Genomic selection is a strategy for modeling allelic effects across an entire genome to increase the rate of genetic gain for quantitative traits. Implementation of genomic selection for prediction of yield as well as higher heritability traits such as protein and oil content was investigated in soybean. There appeared to be an inflation in predictive ability due to population structure when performing cross-validation. Larger training sets, higher heritability traits, and closer genetic relationships between training and validation sets improved prediction while marker density had little effect.Light-tawny pubescence has been hypothesized to be related to improving yield as this phenotype has been hypothesized to increases light reflectance in the leaf canopy which reduces canopy temperature and plant stress, thus increasing yield potential. QTL mapping and GWAS were used to map and pinpoint the Td locus, but yield trials failed to validate a significant yield advantage associated with the light-tawny phenotype. G13-6299 is a recently released germplasm line from the UGA Soybean Breeding Program which contains 19% exotic pedigree, possesses nematode resistance and desirable agronomic characteristics, and is high yielding. This line was developed for utilization by breeders in order to increase grain yield via the incorporation of beneficial exotic yield alleles.