Agronomy and Horticulture, Department of


First Advisor

Brandi Sigmon

Second Advisor

James C. Schnable

Date of this Version

Summer 5-2023

Document Type



K. M. Linders, Plasticity of Sorghum Biomass and Inflorescence Traits in Response to Nitrogen Application. MS Thesis, Department of Agronomy and Horticulture, University of Nebraska-Lincoln, 2023.


A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfilment of Requirements For the Degree of Master of Science, Major: Agronomy, Under the Supervision of Brandi Sigmon and James C. Schnable. Lincoln, Nebraska: May, 2023

Copyright 2023 Kyle M. Linders


Nitrogen is an essential nutrient required for growth and development in plants. Insufficient nitrogen availability can reduce vegetative growth and grain yield. However, nitrogen is a costly input for farmers, is energy intensive to manufacture, and runoff of excess nitrogen fertilizer impacts water quality. Compared to its close relative, maize, sorghum has much greater resilience to nitrogen and water deficit, and heat stress, allowing sorghum to be grown with fewer inputs and on marginal land. Variation in total biomass accumulation and grain yield between sorghum accessions, as well as between nitrogen conditions, can be largely explained by differences in vegetative growth and inflorescence architecture traits. Previous genome-wide association studies (GWAS) in sorghum have identified genetic markers associated with genes known to play roles in controlling growth and development. However, these studies have typically been conducted using field trials with “optimal” nitrogen application conditions. A set of 345 diverse inbred lines from the Sorghum Association Panel (SAP) were grown under both standard nitrogen application (N+) and no nitrogen application (N-) treatments, and a range of biomass and inflorescence-related traits were phenotyped, including plant height, lower and upper stem diameter, rachis length, lower and upper rachis diameter, and primary branch number. Stem volume, an approximation of biomass, was calculated from the directly measured traits. Stem volume was, on average, 10.48% higher for genotypes in nitrogen fertilized blocks, than for genetically identical plants in no nitrogen application blocks. Within individual treatment conditions, between 58.1% and 90.7% of the total variation for the measured and calculated traits could be explained by genetic factors. Genome-wide association studies were conducted to identify genetic markers associated with these traits in order to better understand the genetic factors involved in nitrogen stress response for potential use in breeding improved sorghum varieties.

Co-Advisers: Brandi Sigmon and James C. Schanble