Genetic Analysis of Nitrogen Use Efficiency and Related Traits in the IBMRIL X IHP1 Population of Maize

Nitrogen (N) is often the limiting factor in the production of maize grain and most maize hybrids exhibit a strong response to supplemental N in the form of increased grain yield. Despite the economical and environmental importance of the N-response of maize, little is known about the specific genes involved in mediating the response. The objectives of this research were to identify genomic regions controlling N use efficiency (NUE) and related traits in maize and to associate candidate genes with the regions in an effort to elucidate the genetic mechanisms controlling the N-response. The high resolution Intermated B73 X Mo17 Recombinant Inbred Line (IBMRIL) population was test-crossed to Illinois High Protein 1 (IHP1), the known genetic extreme for grain protein concentration and N uptake ability, and the resulting hybrids were grown with and without 252 kg ha-1 supplemental N in an N-responsive environment for two years and evaluated for NUE traits. A strong N-response was observed for most NUE traits measured, including a nearly two-fold increase in grain yield with the addition of supplemental N, though stover biomass was shown to be largely unresponsive to supplemental N. Composite interval mapping identified genomic regions controlling the NUE related traits analyzed, including the identification of several regions which pleiotropically control several NUE traits. The QTL for stover biomass at low N and kernel composition traits were shown to be the most environmentally stable. Candidate genes, including genes involved in cytokinin signaling and storage protein synthesis, among others, could be assigned to a portion of the QTL identified, suggesting those pathways are involved in mediating the N-response in maize. Analysis of various metabolites in vegetative and early reproductive tissues suggested that asparagine concentration in developing earshoots is most highly correlated with NUE and may be a valuable tool for predicting maize hybrid performance in high and low N environments. Expression QTL analysis identified a QTL on chromosome 6 which controls the mRNA abundance of several N-responsive genes, suggesting that a gene in the QTL interval may be an important upstream regulator which mediates the N-response in maize. This study combining agronomic, physiological, metabolomic, and expression profiling of the IBMRIL X IHP1 population for NUE traits has led to several important discoveries concerning the regulation of NUE in maize and has added to the body of knowledge concerning the traits.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Biology

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2015

Author dc:creator

• Nichols, Devin M.

Contributors dc:contributor

• Stephen Patrick Moose

• Agriculture, Agronomy

Language dc:language

eng

Identifier

(MiAaPQ)AAI3337871

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/85378