Antifungal activity of essential oils emulsions, their bioactive compounds, and biological control of Fusarium wilt of Majorana hortensis

Abstract

This investigation was conducted to evaluate the activity of some essential oils emulsions and a biocide (Bio-Cure F) for controlling Fusarium wilt disease of marjoram ( Majorana hortensis ) caused by Fusarium oxysporum . The fungal filtrate of F. oxysporum isolated from the infected marjoram plants significantly decreased the marjoram seed germination and caused wilting of its seedlings. The essential oil emulsions of thyme; basil, and marjoram, inhibited the in vitro fungal growth of F. oxysporum , and significantly suppressed its sporulation and spore germination. However, thyme oil was the most effective one, which completely inhibited the fungal growth at a concentration of 2000 µg/ ml, and completely prevented its sporulation and spore germination. The tested essential oils were analysed for their bioactive components using Gas Chromatography (GC), which were recorded as follows: linalool and eugenol were detected in basil; terpinen-4-ol, β-phyllandrene, and sabinene in marjoram oil, and thymol, 1.8-cineole, ρ-cymene, and α-terpinene in thyme oil. In the greenhouse experiments, Actamyl 70 % wp (wettable powder) and Bio Cure F were the most effective treatments, which significantly decreased the disease incidence and increased the plant growth parameters, compared with the untreated control. On the other hand, all treatments increased the peroxidase and polyphenol oxidase antioxidant enzyme activities, compared with the control; however, Actamyl 70 % (wp) and Bio Cure F had the superiority; recording 1.27 and 1.23 (units/ ml enzyme) for peroxidase, and 0.57 and 0.51 (units/ ml enzyme) for polyphenol oxidase, respectively. The results of the present study indicated the strong antifungal potential of the thyme essential oil. Meanwhile, Bio-Cur F biocide can be effectively used as a potent biofungicide to controlling the marjoram wilt incited by F.