ABSTRACT

Increasing the yield and sustainability of crop production in a changing climate is one of the foremost challenges of our time. Corn is the most important crop in the United States, but despite steady increases in corn production, projected yields fall short of demands. Furthermore, petroleum-based nitrogen fertilizers have been identified as a primary driver of pollution of major waterways in the U.S. and globally. This project focuses on root systems, the "hidden-half" of plants, that are responsible for all of the water, nitrogen, and other nutrient acquisition. It leverages advanced imaging techniques, some of which were developed in the medical and industrial research sectors, to analyze the structure of root systems. Root structures from corn varieties that are known to be superior in nitrogen acquisition will be compared those that are inferior, and the genes that control root-nitrogen interactions will be identified. This will directly benefit corn and other crop breeders, and thus a major sector of U.S. agriculture, through identification of genes that control root growth and efficient nitrogen acquisition. An additional objective is to train the next generation of scientists by establishing after-school and summer educational programs for middle-school to undergraduate students. These trainees will gain first-hand experience building, programming, and employing plant imaging systems using 3D printers and affordable microprocessors.

Realizing the enormous potential of root systems to boost and stabilize crop yields under stress and to reduce unsustainable levels of fertilizer use will require a thorough understanding of their genetics and physiology. Image-based phenotyping has enabled high-throughput and accurate measurements of roots, but despite many new and promising methods, each has inherent tradeoffs that limit their individual power. This project employs an integrated root phenomic and physiological profiling approach to resolve the genetic basis and functional consequences of maize root architecture. It will profile the root architecture of two maize populations in four complementary ways: 3D/4D imaging of young plants in a gel based system, optical and X-ray based imaging of root crowns excavated from the field, and minirhizotron imaging of roots growing across the soil profile in the field. Quantitative genetic analyses from each of these methods will allow identification of the genes controlling these traits. Additionally, this integrated analysis of identical genotypes will generate the most comprehensive comparison of root phenotyping methods to date. One population will be selected from screening of the NAM parent lines in the first two years of the project, the other population will be the Illinois Protein Strain Recombinant Inbreds (IPSRIs). Over five years, this approach will address the following aims: 1. Identify genes driving phenotypic variation of root architecture, 2. Identify genes controlling phenotypic plasticity of root architecture to nitrogen supply, 3. Determine the functional impacts of root architecture on plant nitrogen status, elemental content and seed quality.

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