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Title:Genetic improvement of aphid resistance, protein, and elemental composition in soybean
Author(s):Ward, Russell A
Director of Research:Diers, Brian
Doctoral Committee Chair(s):Diers, Brian
Doctoral Committee Member(s):Hartman, Glen L.; Kolb, Fred; Nelson, Randy
Department / Program:Crop Sciences
Discipline:Crop Sciences
Degree Granting Institution:University of Illinois at Urbana-Champaign
Degree:Ph.D.
Genre:Dissertation
Subject(s):Soybean, Soybean Aphid, Protein, Ionomics
Abstract:Yield Drag Associated with the Aphid Resistance Gene Rag2 from PI 200538 The soybean aphid (Aphis glycines Matsumura) is an important pest of soybean [Glycine max (L.) Merr.] that was first identified in North American during 2000. The pest can be controlled by the resistance genes Rag1 and Rag2, which have been introgressed into Midwestern adapted soybean lines. In previous studies, the Rag2 resistance allele was shown to be associated with a seed yield reduction. The objective of this study was to confirm the reduction in yield associated with Rag2 and determine its cause. This was done by testing a population of lines with all combinations of resistance and susceptibility alleles at Rag1 and Rag2 to further discern the effect of the Rag2 gene on agronomic traits, and by evaluating the introgressed genetic region surrounding Rag2 in populations of near isogenic lines to localize quantitative trait loci (QTL) causing yield drag associated with the Rag2 gene. The populations were tested in multiple environments across three years with little or no aphid infestation. Yield tests of the population segregating for Rag1 and Rag2 showed that Rag2 was associated with a yield reduction across environments, but Rag1 was not. Results from the tests of the Rag2 genetic region populations indicate that one or more QTL(s) causing yield drag are located within a 6.5 Mbp region approximately 1.6 Mbp from Rag2. This information can be used to break the linkage between the yield reduction QTL(s) and Rag2, ultimately providing higher yielding aphid resistant cultivars. Fine Mapping of the Soybean Seed Protein QTL cqSeed protein-003 Soybean is a widely grown, important source of protein and oil for both animal and human consumption. In this study, the previously identified protein QTL cqSeed protein-003 on chromosome 20 (formerly linkage group I) was fine mapped to further delineate the candidate gene region of the QTL. Fine mapping was conducted using a population of near isogenic lines (NILs) segregating for cqSeed protein-003 developed through five backcrosses (BC5) using PI468916 as the donor parent and A81-356022 as a recurrent parent. Genetic marker analysis of the BC5 populations placed the QTL in a 77.8 kb region on chromosome 20, based on the Glyma.Wm82.a2 (Gmax2.0) map assembly. This narrowed candidate gene region can help facilitate gene cloning which ultimately can result in the identification of the causal gene(s) for one of the most widely studied, large effect protein QTL in soybean. Mapping of Ionomic QTL in a Soybean Nested Association Mapping Population It is estimated that nearly half of the world’s population suffers from nutrition deficiencies. With the world’s population projected to reach 9.3 billion people by 2050, there will be a need not only for more food, but also more nutritious food to alleviate nutritional deficiencies. More land will likely be used by agriculture to meet the increasing food demand, often coming from land contaminated with heavy metals or high levels of unwanted nutrients. To produce crops with increased concentration of beneficial nutrients and fewer toxic metals, one must have an understanding of the genetic control of mineral accumulation in plant tissue which can be studied through ionomic analysis. Therefore, the objective of this study was to map QTL controlling the elemental composition of soybean seed. The ionome of seed samples from two environments (Illinois 2012 and Nebraska 2012) of the soybean nested association mapping (NAM) project were analyzed for elemental concentration of 20 traits. These data were then analyzed with 4,312 SNPs in a joint linkage analysis to identify QTL from both growing environments. In total, 88 QTL were identified, including a previously identified QTL for calcium. This information can be used in additional studies to gain more knowledge of the genetic architecture of elemental accumulation in soybean, but also in marker-assisted selection and genomic prediction models. This study provides an important first step in that process which will ultimately result in biofortification of beneficial elements, and sequestration of heavy metals in crops.
Issue Date:2017-05-23
Type:Thesis
URI:http://hdl.handle.net/2142/98215
Rights Information:Copyright 2017 Russell Ward
Date Available in IDEALS:2017-09-29
Date Deposited:2017-08


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