Date of Award
5-2026
Document Type
Thesis
Degree Name
Master of Science (MS)
Department
Plant and Environmental Science
Committee Chair/Advisor
Dr. Julia L. Kerrigan
Committee Member
Dr. Guido Schnabel
Committee Member
Dr. James E. Faust
Abstract
Petal diseases significantly affect gerbera cut flower production, as minor visual damage renders flowers unmarketable. Among those pathogens causing petal spots, Itersonilia perplexans affects some Asteraceae plants. However, this pathogen's impact on Colombian gerbera remains poorly studied. This study was designed to fill four gaps: molecular identification of Colombian isolates, confirmation of pathogenicity, standardized culture media, and fungicide sensitivity data. Four objectives were pursued: (i) isolate and identify the causal agent through sequencing the Internal Transcribed Spacer, Small Subunit and Large Subunit from the rDNA; (ii) evaluate pathogenicity on detached gerbera petals; (iii) identify optimal culture media for I. perplexans mycelium growth; (iv) assess fungicide-sensitivity to major ornamental fungicides. Isolates obtained from symptomatic Colombian gerbera cut flowers were identified as I. perplexans through phylogenetic analysis. Pathogenicity tests confirmed that isolates produced lesions on detached gerbera petals, primarily on mechanically wounded tissue, but not restricted to it. Culture media screening revealed differences in growth rates between nutrient sources, with Potato Dextrose Agar supporting the fastest mycelial growth. Fungicide sensitivity assays showed distinct sensitivities among isolates, with one showing reduced sensitivity to Demethylation Inhibitor (DMI) fungicides. Difenoconazole (Inspire®, FRAC 3) was the only effective active ingredient with measurable EC50 values for all isolates. In contrast, dose-response relationships could not be established for seven other fungicides within the tested concentrations, due to insufficient dose-response. These results offer essential fungicide-sensitivity data that can guide disease management and resistance monitoring in Colombian gerbera production systems.
Recommended Citation
Beger, Matheus, "Identification, Pathogenicity, and Fungicide Sensitivity of Itersonilia Perplexans Associated With Petal Spot of Gerbera Cut Flowers in Colombia" (2026). All Theses. 4792.
https://open.clemson.edu/all_theses/4792
Author ORCID Identifier
https://orcid.org/0000-0002-3158-1632