Entomology, Department of
Department of Entomology: Dissertations, Theses, and Student Research
First Advisor
Joe Louis
Committee Members
Jeffrey D. Bradshaw, Tom Weissling
Date of this Version
5-2025
Document Type
Thesis
Citation
A thesis presented to the faculty of the Graduate College at the University of Nebraska in partial fulfillment of requirements for the degree of Master of Science
Major: Entomology
Under the supervision of Professor Joe Louis
Lincoln, Nebraska, May 2025
Abstract
Sorghum, Sorghum bicolor (L.) Moench, the fifth most-grown cereal crop in the world, is a versatile crop, grown across different agro-ecological regions. Sorghum has numerous uses ranging from food and forage purposes to biofuel production. Sugarcane aphid (SCA; Melanaphis sacchari) is a major threat to sorghum production, accounting for 50% to 100% yield loss under heavy infestations. Perennial sorghum can be a sustainable and climate-resilient alternative to the current cereal farming systems. The development of perennial sorghum offers numerous benefits, such as reduced economic inputs, more carbon sequestration, better soil health, and sustainable yields. We employed host plant resistance (HPR) to screen forty-three perennial sorghum genotypes for their response to SCA infestation, aiming to identify resistant and susceptible genotypes. The no-choice assay (antibiosis levels) results divided the genotypes into four clusters (highly susceptible, moderately susceptible, moderately resistant, and highly resistant), based on aphid count and plant damage. We selected two genotypes, X999>R485 (SCA-resistant) and PR376~Tift241 (SCA-susceptible), and tested their antixenosis levels of resistance using choice assay and electrical penetration graph (EPG). The SCA-resistant genotype is highly resistant to SCA infestation, while the SCA-susceptible genotype has weak resistance. To better understand the factors modulating the resistance in these two genotypes, we used transcriptomics to identify the molecular and genetic mechanisms underlying perennial sorghum’s response to SCA infestation. Transcriptional response of perennial sorghum to SCA feeding at early and late time points showed that aphid feeding induces plant defenses by regulating the expression of genes related to reactive oxygen species (ROS) production, death acids, cell wall-related modifications, and callose synthesis in the SCA-resistant perennial sorghum genotype. Overall, transcriptomic results indicate that the SCA-resistant perennial sorghum genotype rapidly triggered plant defenses against SCA infestation. The identification of SCA-resistant perennial sorghum genotypes and the specific pathways and genetic mechanisms dominating this interaction will guide future perennial sorghum breeding programs.
Advisor: Joe Louis
Comments
Copyright 2025, Esha Kaler. Used by permission