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Iowa State University

Plant Sciences

Graduate Theses and Dissertations

Breeding

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Genetic Architecture Of Antibiosis And Antixenosis Aphid Resistance In Soybean And Elucidation Of The Molecular Effect Of Pyramiding Rag1 And Rag2 Resistance Genes, Martha Ibore Jan 2017

Genetic Architecture Of Antibiosis And Antixenosis Aphid Resistance In Soybean And Elucidation Of The Molecular Effect Of Pyramiding Rag1 And Rag2 Resistance Genes, Martha Ibore

Graduate Theses and Dissertations

Soybean aphids are a major problem to soybean growers worldwide and they cause great yield losses. In the United States, soybean aphids can cause yield losses of up to 50% especially on susceptible varieties. Yield losses attributed to feeding by soybean aphids can be reduced by cultivating resistant soybean varieties. In recent years, certain biotypes of soybean aphids that can colonize resistant soybean plants have been reported, suggesting the continued need for identification of novel sources of aphid resistance to include in plant breeding programs. While gene pyramiding, in which certain resistant soybean genotypes carry more than one aphid resistance ...


Breeding For Cob Traits In Maize, Constantin Jansen Jan 2012

Breeding For Cob Traits In Maize, Constantin Jansen

Graduate Theses and Dissertations

The advantages of maize cobs as cellulosic feedstock are based on their compact architecture and high fraction of cellulose and hemicellulose. Cobs are low in ash content, nutrients, and minerals and their harvest will likely not deplete the soil. Dual-purpose maize, with larger cob biomass and high tissue density, could reduce transport costs providing more farmers with additional income from cob sales. The objective of this study was to lay the foundation for developing dual-purpose maize, combining high cob biomass and grain yield. This included a morphological and genetic analysis of cob characters under varying environments, as well as their ...


Novel Approaches To Improving Qualities Of Maize Endosperm, Anastasia Lorellen Bodnar Jan 2011

Novel Approaches To Improving Qualities Of Maize Endosperm, Anastasia Lorellen Bodnar

Graduate Theses and Dissertations

Maize is a high yielding crop that provides a relatively high calorie source of food and feed, but focus on yield has not improved nutritional qualities. Some nutrients that are lacking in maize are iron and essential amino acids. In this dissertation some ways that genes from maize might be used to improve nutritional quality of maize are discussed, including improvement of bioavailable iron with maize globin and exploration of maize seed storage proteins. In addition, strategies to improve maize are explored, including breeding with mutations and transgenes and investigation of the effects of selection on transgenes.

Maize globin was ...


Environmental Analyses And Candidate Gene Expression Of Ms9 Male-Sterility Locus And Computational Identification Of Candidate Genes For Male-Sterility Loci In Soybean, Christiana Wiebbecke Jan 2011

Environmental Analyses And Candidate Gene Expression Of Ms9 Male-Sterility Locus And Computational Identification Of Candidate Genes For Male-Sterility Loci In Soybean, Christiana Wiebbecke

Graduate Theses and Dissertations

Rapid growth rate of the human population is driving the increased demand for cultivated soybean [Glycine max (L.) Merrill], a major source of protein and oil in global food, feed, and biofuel production. Increasing yield at a pace faster than traditional breeding methods presently achieve has become a need and future commitment. In soybean, a self-pollinated crop, a possibility to increase yield may result from the development of hybrid cultivars. Researchers have been interested in floral development and pollination, as these factors have a direct impact on maintaining and enhancing crop yields. Soybean breeders also need to understand phenotypic differences ...


Did Recurrent Selection For Yield Affect Iowa Stiff Stalk Synthetic Maize Population Grain Fill Characteristics?, Steve James Eichenberger Jan 2011

Did Recurrent Selection For Yield Affect Iowa Stiff Stalk Synthetic Maize Population Grain Fill Characteristics?, Steve James Eichenberger

Graduate Theses and Dissertations

Hybrid maize yield increases, new product development, and increased stress tolerance can be more easily achieved with a better understanding of the physiological and genetic basis for phenotypic changes in response to recurrent selection for yield. The purpose of this study was to identify changes in grain fill characteristics and their interaction with plant density in a closed population and identify a model that accurately predicts grain fill in this population. We hypothesize that recurrent selection for increased yield indirectly impacted the grain fill characteristics of maize including final kernel weight, kernel fill duration, and kernel fill rate in the ...


Pleiotropic Effects Of Genes Involved In Cell Wall Lignification On Agronomic Characters, Yongsheng Chen Jan 2011

Pleiotropic Effects Of Genes Involved In Cell Wall Lignification On Agronomic Characters, Yongsheng Chen

Graduate Theses and Dissertations

Brown midrib (bm) mutants in maize, which are characterized with altered lignin composition, reduced lignin content and thus with enhanced cell wall digestibility (CWD), are often associated with inferior agronomic traits. To understand how the undesirable associations happen would help us better design strategies to manipulate the cell wall lignification for CWD enhancement without sacrificing biomass yield. First, I reviewed the current knowledge and approaches to study the nature of trait correlations. We proposed that dissection of the trait correlations into DNA polymorphism level is beneficial for plant breeding as intergenic, intragenic, or true pleiotropy will have different impact. Secondly ...