Genetic analysis of nitrogen remobilization and kernel composition in Zea mays L. and Sorghum bicolor (L.) Moench

ABSTRACT.;Lindsey, Raymond S. Ph.D., Purdue University, May 2015. Genetic Analysis of Nitrogen.;Remobilization and Kernel Composition in Zea Mays L. and Sorghum Bicolor (L.).;Moench. Major Professor: Mitchell Tuinstra.;Modern maize (Zea mays L.) production relies heavily on nitrogen fertilization for high.;productivity. Over-application of nitrogen fertilizers in cropping systems can have.;detrimental economic and environmental effects. For this reason, improving Nitrogen.;Use Efficiency (NUE) is a major goal of breeders and producers. Nitrogen Utilization.;Efficiency (NUtE) is one component of NUE, and the most important component under.;N-limited conditions. In this study we examined the genetic controls of the timing and.;preferential canopy position of leaf N remobilization during reproductive growth stages.;Utilizing a diversity panel of over 2,400 lines, genome wide association mapping was.;conducted in 2012 and 2013 to examine leaf chlorophyll content at different growth.;stages and kernel composition at maturity. Chlorophyll content meters were utilized for.;measurements of leaf chlorophyll content on two different leaves at VT, R2, and R4.;sampling times. Near infrared reflectance spectroscopy (NIRS) was utilized for analysis.;of kernel composition on whole kernels. NIRS was also utilized for analysis of kernel.;composition on whole kernels of sorghum (Sorghum bicolor L. Moench) in a diverse.;panel of 840 accessions; with the goal of applying known genetic controls of maize.;kernel composition to gain a greater understanding of the controls of sorghum grain.;composition. Results from the maize leaf chlorophyll analysis and sorghum kernel.;composition analysis suggest a role for NADH - Glutamate Synthase as a sink control of.;N remobilization from the leaves. Genes identified in these analyses suggest that genetic.;controls at both the source and sink level affect the timing and rate of N remobilization.;from the leaves. Knowledge of these genetic controls may be utilized in breeding.;programs to select lines with improved NUE and NUtE characteristics.