Doctoral Dissertations
Date of Award
5-2024
Degree Type
Dissertation
Degree Name
Doctor of Philosophy
Major
Entomology, Plant Pathology and Nematology
Major Professor
Heather M. Kelly
Committee Members
Larry L. Steckel, James Holloway, Sebe Brown
Abstract
Ear rots are a group of fungal diseases that affect maize during its growth and storage phases. These diseases can significantly impact crop yield, grain quality, and economic returns for farmers. Maize ear rots are caused by various fungal pathogens, including species from the genera Fusarium, Aspergillus, Penicillium, and Diplodia. These fungi often enter the maize ears through wounds or openings, such as insect damage or improper handling. Effective management of maize ear rots is crucial to mitigate their detrimental effects on maize production and ensure a healthy and marketable crop. Implementing integrated management strategies that combine cultural, genetic, chemical, and biological control measures can help minimize the occurrence and severity of maize ear rots, ultimately safeguarding the overall yield and quality of the crop. The studies presented in this dissertation aim to evaluate integrated management strategies to mitigate the impact of ear rots and associated mycotoxins.
Field trials were conducted in Tennessee for three years to evaluate commercially available Non-Bt and Bt hybrids with dual or triple insect traits to reduce ear rot incidence and mycotoxin contamination. The findings of this study contribute to the current body of literature that plant-incorporated insect traits reduce fumonisin contamination in maize compared to Non-Bt hybrids, though we did not consistently observe a difference between hybrids with two traits vs three traits. Moreover, a bioassay was performed to evaluate the direct relationship insecticidal proteins, Cry1F and Vip3A, may have on Fusarium vertillioides and fumonisin production. Our findings provide evidence of a direct influence of insect proteins on reduction of F. vertillioides growth and fumonisin production.
An artificially inoculated field study evaluated the use of Bt hybrids and the biological control Afla-Guard® to reduce ear rots and mitigate mycotoxin contamination. Our results demonstrated that the utilization of Bt hybrids and Afla-Guard® effectively decreased the incidence and severity of ear rots in the field. However, this study observed an increase in aflatoxin production when Afla-Guard® was applied. In this study, we inoculated the field with three strains of toxigenic Aspergillus flavus two weeks before the application of Afla-Guard®. This may have given the toxigenic isolates an unfair advantage to develop and outcompete the Afla-Guard® atoxigenic isolate.
Additionally, we evaluated Aspergillus and Fusarium as a biological control for Palmer amaranth (Amaranthus palmeri). A germination bioassay was conducted to evaluate pathogenicity and virulence of these pathogens on Palmer amaranth. The bioassay also incorporated soybean and cotton to assess potential pathogenicity/crop safety of the pathogens towards common crops. In this study, we observed that Fusarium and Aspergillus significantly reduced the germination of Palmer amaranth, while germination of soybean and cotton were relatively unaffected. The Fusarium species that was used in this study seems to be pathogenic to Palmer amaranth, with damping off symptoms observed. Damage caused by the pathogens in this study suggests that all three plant species are affected by Aspergillus and Fusarium, however the severity was lower in soybean and cotton compared to the Palmer amaranth. The Aspergillus species used in this study exhibited more phytotoxicity rather than pathogenicity, resulting in increased damage ratings. The confirmation of pathogenicity of the Fusarium species used in this study towards Palmer amaranth suggests that it could be a potential candidate for a biological control. Further research is needed to evaluate both pathogens and their ability to manage Palmer pigweed.
Recommended Citation
McLaughlin, Autumn, "Evaluation of Pre-Harvest Management Strategies for Corn Ear Rots and Associated Mycotoxins. " PhD diss., University of Tennessee, 2024.
https://trace.tennessee.edu/utk_graddiss/10073