"Soybean (Glycine max) is the world's leading oilseed crop and is a critical source of protein for poultry and swine production. Soybean production is limited by many biotic factors including soybean sudden death syndrome (SDS) which is caused by a soil-borne fungal pathogen, Fusarium virguliforme. Effective management methods for soybean sudden death syndrome include long-term rotations, fluopyram seed treatment, and planting SDS resistant varieties. Host resistance to F. virguliforme is a quantitative resistance, as it is controlled by many genes, largely of small effect. To more efficiently breed SDS resistant soybean varieties, researchers have sought to identify the loci on the soybean genome responsible for SDS-resistance. Three recombinant inbred line (RIL) populations were evaluated for foliar SDS resistance at a naturally infested field site in Decatur, MI during the 2014 and 2015 growing seasons. These populations segregated for SDS resistance, as they were derived from a parent resistant to SDS and a parent susceptible to SDS. The parents and a subset of RILs from each population were genotyped with the SoySNP6K Illumina Infinium BeadChip. Linkage maps unique to each population were constructed using JoinMap ver. 2. Composite interval mapping was done using WinQTLCartographer (ver. 2.5). Six quantitative trait loci (QTL) were identified to be associated with SDS resistance. Three of the QTL associated with SDS resistance were identified across multiple years and/or populations. While biotic factors, such as SDS, work to limit soybean production, soybean quality factors, such as oil quality, can offer new production opportunities. Soybean oil is predominantly composed of five fatty acids: palmitic acid (11%), stearic acid (4%), oleic acid (25%), linoleic acid (52%), and linolenic acid (8%). While there is little variability in most commodity soybean varieties for fatty acid content, soybean breeders have been able to introduce oil quality traits into the soybean germplasm. Oil quality traits for soybean oil include high oleic acid content (>75%), low linolenic acid content (<3%), and low saturated fat content (palmitic + stearic < 8%). A RIL population was developed by crossing a high oleic acid, low linolenic acid, and low saturated fat content public variety (E16831) with a high yielding line with a commodity soybean fatty acid profile (E12076T). The parents, the RIL population, and bulked pools representing extreme phenotypes were genotyped with the SoySNP6K Illumina Infinium BeadChip, a linkage map was developed using JoinMap (v.2), and QTLs were detected using WinQTLCartographer (v 2.5). The study confirmed the effects of many known fatty acid biosynthesis genes including GmFAD2-1B, GmFAD3A, GmFAD3B, GMFAD3C, and GmFATB-1A. The study was also able to dissect possible strategies and limitations of marker assisted selection (MAS) for the development of soybean varieties with high oleic acid, low linolenic acid, and low saturated fat content."--Pages ii-iii.
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