Inhibitory effect of plant essential oils on controlling Alternaria species

Abstract

The use of natural products in the control of fungal diseases in plants is considered an alternative to synthetic fungicides due to their less negative effects on the environment. In this study, in vitro inhibitory effect of plant essential oils (PEOs) of black cumin, cumin, chamomile, cedarwood, and ginger were investigated for controlling two species of Alternaria, including Alternari solani and Alternaria alternata on tomato and cabbage under in vitro conditions, respectively. Aiming to evaluate the mycelial growth of the pathogen, mycelial discs were placed in Petri plates with 0, 500, 1000, 1500, 2000, and 2500 μL/L of PEOs. The experiment was carried out in a randomized plot design with three replications. Chemical analysis of PEO components were determined by Gas Chromatography and Mass Spectrometry methods. A total of 69 chemical compounds were determined in five different PEOs. As the main chemical compounds, Cuminaldehyde was detected in cumin PEO, Sesquithujene was found in ginger PEO, and Eucalyptol (1,8-cineole) was determined in black cumin, chamomile, and cedarwood PEOs. All five PEOs were found to inhibit the growth of Alternaria species in a dose-dependent manner, whereas cumin EO was determined more inhibitory effect against A. solani and A. alternata. Cumin PEO showed the highest effect against Alternaria species because it contains a Cuminaldehyde chemical compound. The lowest inhibition percentage was found in chamomile PEO compared to other PEOs. This study suggested that cumin PEO has the potential as an antifungal agent for controlling of Alternaria diseases.