Essential Oil of Foeniculum vulgare Mill. as a Green Fungicide and Defense-Inducing Agent against Fusarium Root Rot Disease in Vicia faba L.

Abstract

<i>Fusarium solani</i>, the causative agent of root rot disease is one of the major constraints of faba bean (<i>Vicia faba</i> L.) yield worldwide. Essential oils have become excellent plant growth stimulators besides their antifungal properties. <i>Foeniculum vulgare</i> Mill. (fennel) is a familiar medicinal plant that has inhibitory effects against phytopathogenic fungi. Herein, different concentrations of fennel seed essential oil (FSEO) (12.5, 25, 50, 100, 200 and 400 μL/mL) were examined against <i>F. solani</i> KHA10 (accession number MW444555) isolated from rotted roots of faba bean in vitro and in vivo. The chemical composition of FSEO, through gas chromatography/mass spectroscopy, revealed 10 major compounds. In vitro, FSEO inhibited <i>F. solani</i> with a minimum inhibitory concentration (MIC) of 25 µL/mL. In vivo, FSEO suppressed <i>Fusarium</i> root rot disease in <i>Vicia faba</i> L. by decreasing the disease severity (61.2%) and disease incidence (50%), and acted as protective agent (32.5%) of <i>Vicia faba</i> L. Improvements in morphological and biochemical parameters were recorded in FSEO-treated faba seeds. Moreover, the expression level of the defense-related genes defensin and chitinase was noticeably enhanced in treated plants. This study suggested using FSEO as a promising antifungal agent against <i>F. solani</i> not only to control root rot disease but also to enhance plant growth and activate plant defense.