Theses and Dissertations


Seval Ozkan

Issuing Body

Mississippi State University


Brown-Johnson, Ashli

Committee Member

Peterson, Daniel G.

Committee Member

Ma, Din-Pow

Committee Member

Williams, W. Paul

Committee Member

Shan, Xueyan

Date of Degree


Document Type

Dissertation - Open Access


Molecular Biology

Degree Name

Doctor of Philosophy


College of Agriculture and Life Sciences


Department of Biochemistry, Molecular Biology, Entomology and Plant Pathology


Understanding the role of phytohormone auxin in defense responses is one of the vital tools for plant breeders to develop maize germplasm lines that exhibit high resistance to Aspergillus flavus and subsequent aflatoxin accumulation. Besides its critical role in different developmental processes throughout the life cycle of plants, auxin is also involved in the network of plant-pathogen interaction as demonstrated in previous studies. However, the actual mechanism for the auxin signaling pathway leading to resistance is unknown. Therefore, the critical gap in the knowledge base is a lack of understanding of the role of auxin signaling in pathogen resistance in maize. Continuation of this gap is an important problem because fungal resistance is a highly quantitative trait and breeding for resistance is a challenge. A complete understanding of the auxin mechanism in resistance could lead the production of corn hybrids with resistance to A. flavus and aflatoxin accumulation. The focus of this research was to determine the effect of exogenous auxin on A. flavus growth and production of aflatoxin in growth media. In addition, auxin levels, the amount of aflatoxin, and fungal growth in three resistant (Mp313E, Mp715, and Mp719) and one susceptible (B73) germplasm line were determined. As a result, auxin significantly increased mycelium growth and significantly decreased aflatoxin at a high concentration in potato dextrose broth under the lab conditions. Under the field conditions, auxin levels were low in resistant lines but did not change in response to A. flavus infection. Susceptible line had high auxin levels and auxin levels significantly decreased in response to A. flavus infection.