Abstract

Roots are a critical yet hidden part of plants, providing physical support and access to resources such as nutrients and water. The development of a plant’s root system across time and space is referred to as root system architecture, which influences the effectiveness of resource capture. In modern agriculture, applications of nitrogen fertilizers are critical to maintain high yield. However, up to 70% of applied nitrogen is not utilized by the plant and escapes into waterways and the atmosphere, causing environmental harm. Efficient nitrogen uptake is limited by the ability of the plant to access and absorb nitrogen through its roots. It has been proposed that modifying root system architecture could improve access to and uptake of nitrogen from the soil, for example, by modifying the postembryonic shoot borne root system comprised of nodal and lateral roots to increase soil exploration and grow deeper roots. But to test these theories and select for desirable root traits, a better understanding of the genetic basis of root system architecture is needed. In this dissertation, we identify a core regulator of nodal rooting from the classic maize mutant Rootless, which we name, Rootless1 (ZmRt1). We demonstrate that ZmRt1 quantitatively regulates nodal root primordia development across several maize backgrounds. We identified a Ds insertion allele, designated rt1-2, which results in a nodal rooting phenotype that we hypothesized would result in a root system architecture that improves nitrogen uptake in the field. To test this, we conducted nitrogen contrast experiments where we used advanced root phenomics tools to show changes in the root system architecture of rt1-2 plants leading to improved nitrogen uptake and yield. Additionally, we conducted the first study to measure the root system architecture diversity in the emerging cover crop pennycress. Adopting pennycress as a cover crop has the potential to improve the sustainability of the maize agroecosystem by catching residual nitrogen in fields. Together, this work advanced our understanding of the genetic regulation of RSA through ZmRt1 and natural variation in pennycress and maize RSA in the field, providing a valuable resource for future genetic studies.

Committee Chair

Christopher Topp

Committee Members

Ivan Baxter; Kenneth Olsen; Ram Dixit; Tao Ju

Degree

Doctor of Philosophy (PhD)

Author's Department

Biology & Biomedical Sciences (Plant & Microbial Biosciences)

Author's School

Graduate School of Arts and Sciences

Document Type

Dissertation

Date of Award

8-8-2025

Language

English (en)

Author's ORCID

https://orcid.org/0000-0002-3836-6556

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