Date of Graduation

8-2012

Document Type

Thesis

Degree Name

Master of Science in Crop, Soil & Environmental Sciences (MS)

Degree Level

Graduate

Department

Crop, Soil & Environmental Sciences

Advisor

Pengyin Chen

Committee Member

Kristofor Brye

Second Committee Member

Edward Gbur

Third Committee Member

Vibha Srivastava

Keywords

Biological sciences; QTL; Soybean; Stachyose; Sucrose

Abstract

Sucrose is a desirable sugar in soybean seed that affects the quality and taste of soyfoods, while stachyose is a non-digestible sugar that induces flatulence in non-ruminant animals. Therefore, soybean cultivars with high sucrose and/or low stachyose would be valuable for soyfood and meal markets. The objectives of this study were to identify quantitative trait loci (QTL) or genes associated with seed sucrose and stachyose content using simple sequence repeat (SSR) or single nucleotide polymorphism (SNP) markers. A low sucrose line, MFS-553, was crossed with a high sucrose plant introduction, PI 243545, to develop the sucrose QTL mapping population. A total of 626 random SSR plus 5361 SNP markers covering 20 soybean chromosomes were used to screen the parents MFS-553 and PI 243545, 209 SSR and 2016 SNP markers were polymorphic, of which, 97 SSR markers were used to screen the F2:3 population and 2016 SNP markers were used to screen the F3:4 population derived from MFS-553 x PI 243545. A normal stachyose cultivar, Osage, was crossed with a low stachyose line, V99-5089, to develop F3 mapping population for genetic study of stachyose content. A total of 34 SSR and 56 SNP markers on chromosome 10 and 11 were used to screen the parents Osage and V99-5089, 10 SSR and 18 SNP markers were polymorphic. Of these, 5 SSR and 16 SNP markers were used to screen the F3:4 lines derived from Osage x V99-5089. For phenotyping the sugar profile, seed of F2:3, F3:5 and F3:6 lines from MFS-553 x PI 243545 and seed of F3:5 and F3:6 lines from Osage x V99-5089 were analyzed for sucrose and stachyose using high performance liquid chromatography (HPLC). The sucrose content in MFS-553 x PI 243545 cross fitted to a normal distribution whereas stachyose content in Osage x V99-5089 appeared to fit to a bimodal distribution. Composite interval mapping (CIM) and multiple interval mapping (MIM) were performed to map the QTLs in the MFS-553 x PI 243545 population. Three QTLs for seed sucrose were mapped to chromosome 5, 9, and 16, explaining 46%, 10% and 8% of phenotypic variation for sucrose content, respectively. For the stachyose mapping, data revealed a major and a minor QTL on chromosome 11 and 10 explaining 81% and 11% of phenotypic variation for stachyose content, respectively. Chi-square tests further indicated that these two QTL represent two independent genes for stachyose content. Molecular markers and QTL/genes for sucrose or stachyose content identified from this study can be used for marker assisted selection in breeding soybean lines with desired sugar profile.

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