Physiology Characterization of Nitrogen Use in Maize: Opportunities for Improvement

100 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2007.Nitrogen supply plays a key role in yield determination of the maize crop. An adequate supply of N is vital for the proper establishment and maintenance of the photosynthetic capacity, and for the determination of sink capacity and maintenance of that sink throughout seed development. Since N is one of the main factors powering yield, annual applications of fertilizer N are the norm. However, growing concerns about the environmental impact of crop productivity, together with increasing costs of fertilizer N necessitates a better understanding of processes associated with the efficiency of N use (NUE) and their importance in designing crop management strategies and in developing breeding programs for improved N use. The overall objective of this work was to identify and characterize physiological N response traits that are under genetic control and that can be used to improve NUE. Specific objectives included: (1) gaining a better understanding of how N is utilized by the plant to produce yield, (2) characterizing the genetic diversity for N use in maize hybrids; and (3) determining if N use traits can be identified and improved in maize inbreds. The overall approach was to evaluate maize genotypes (commercial and experimental hybrids and inbreds) under various levels of N supply ranging from deficient to excessive under field conditions. Results within each specific objective suggest that: (1) PEPc may serve as a storage sink for excess leaf N, and that a better allocation of N into Rubisco could improve maize photosynthesis, (2) No hybrid (commercial or experimental) was optimized for both N uptake and N utilization which suggests room for improvement in NUE for maize; and (3) Introgression of exotic germplasm, nearly always improved NUE of the hybrids, which was largely due to improved uptake efficiency. Overall, results presented in this work, provide a better understanding on how N is utilized for yield generation in the maize plant, and provides useful information on possible strategies to be incorporated in breeding programs aimed at N use improvement.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD