Theses and Dissertations

Issuing Body

Mississippi State University


Tomaso-Peterson, Maria

Committee Member

Allen, Thomas W.

Committee Member

Melanson, Rebecca A.

Date of Degree


Document Type

Graduate Thesis - Open Access


Plant Pathology

Degree Name

Master of Science (M.S.)


College of Agriculture and Life Sciences


Department of Biochemistry, Molecular Biology, Entomology and Plant Pathology


Frogeye leaf spot is a foliar disease of soybean caused by Cercospora sojina Hara, which until recently had been successfully managed by quinone outside inhibitor (QoI) fungicides. After widespread resistance to the QoI fungicides was reported throughout Mississippi, the next step in characterizing C. sojina was to study the fitness of selected isolates. Fitness measurements of resistance stability, colony growth, conidia production and germination, and virulence were assessed. A phylogenetic analysis was also conducted to assess the genetic similarity of the QoI-resistant and -sensitive C. sojina isolates. All isolates remained stable in terms of QoI resistance. Results of all fitness measurements indicated no significant differences between the QoI-resistant and -sensitive C. sojina isolates. The phylogenetic analysis supported these results revealing similarity between QoI-resistant and -sensitive C. sojina isolates. Based on these results no indication of a fitness cost is associated with QoI resistance in C. sojina isolates from Mississippi soybean.