Antimicrobial Properties and Mechanism of Action of Peganum harmala Extract for Managing Bacterial Soft Rot in Potato (Solanum tuberosum) Associated with Pectobacterium carotovorum

Soft rot, primarily caused by Pectobacterium carotovorum infection, poses a significant threat to the postharvest storage of potato tubers. The overuse of chemical controls necessitates eco-friendly alternatives. This research investigates the antimicrobial efficacy of Peganum harmala seed extract against P. carotovorum and examines its potential for controlling soft rot disease. The antimicrobial effect of the extract was evaluated against P. carotovorum and Acinetobacter calcoaceticus using the agar well diffusion technique, and the minimum inhibitory concentration (MIC) was determined. Potato tubers were treated with the extract, inoculated with the bacteria, and evaluated for disease reduction over different storage durations (3, 6, and 9 days). The MIC of the extract was 25 mg/mL for P. carotovorum and 30mg/mL for A. calcoaceticus. Treating potato tubers with the MIC of the extract for 2h significantly reduced disease incidence by 79.72% for P. carotovorum and 74.63% for A. calcoaceticus after 3 days of storage. However, effectiveness decreased with extended storage periods. P. harmala extract demonstrates strong antimicrobial properties and provides a promising, natural approach for managing bacterial soft rot in potatoes.