Inhibitory effect of selective plant extracts against pathogenic fungi associated with wilting disease in sesame (Sesamum indicum L.)

A laboratory experiment was conducted to evaluate the inhibitory effect of ethanomethanolic extracts of wildly grown Cichorium intybus, Portulaca oleracea, Cakile arabica and Celosia argentea against wilting disease pathogens in sesame. Sesame plants exhibiting ideal disease symptoms, including chlorosis, wilting, root and stem base necrosis were collected from different regions of Anbar province (Ramadi, Haditha and Qa’im). Morphological and molecular characterization identified eight fungal isolates belonging to three fungal genera; Rhizoctonia solani, Macrophomina phaseolina, and Fusarium solani. Pathogenicity analysis in vitro and in planta showed that all isolates were pathogenic to sesame; however, R. solani (Rs-R1) and M. phaseolina (Mp-Q2) isolates were the most virulent, significantly inhibiting seed germination with a 100% infection rate compared to 73.33% for F. solani (Fs-R). Phytochemical analysis through gas chromatography-mass spectrometry (GC-MS) indicated the presence of various bioactive compounds mainly heterocyclic compounds, alkanes, fatty acids, ketones, terpenes and terpenoids. The ethanomethanolic plant extracts, especially P. oleracea showed a superior inhibitory effect against the three fungal isolates in vitro and in planta. Statistical analysis revealed a significant effect of P. oleracea extract concentrations on the pathogenicity of the three selected isolates and growth variables. However, the maximum concentration of 8 mg/mL successfully reduced the fungal pathogenicity and enhanced the sesame germination, plant height, stem diameter, leaf area, fresh weight, dry weight, chlorophyll and PPO activity, respectively. This study highlights the diversity of pathogenic fungi affecting sesame in Iraq and demonstrates the potential of selected plant extracts as natural alternatives for integrated disease management.